panel handbook & grade glossary · aggregate-coated panel a panel coated with stone chips...

G L O S S A R Y

A P AThe Eng ine e r ed Wood As so c i a t i on

PANEL HANDBOOK &GRADE GLOSSARY

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Wood is good. It is the earth’s natural, energy efficient and renewable building material.

Engineered wood is a better use of wood. It uses less wood to make more wood products.

That’s why using APA trademarked plywood, oriented strand board and APA EWSglued laminated timbers is the right thing to do.

A few facts about wood.■ We’re not running out of trees. One-third of the United States land base –731 million acres – is covered by forests. About two-thirds of that 731 million acres issuitable for repeated planting and harvesting of timber. But only about half of the landsuitable for growing timber is open to logging. Most of that harvestable acreage also isopen to other uses, such as camping, hiking, hunting, etc.

■ We’re growing more wood every day. American landowners plant more thantwo billion trees every year. In addition, millions of trees seed naturally. The forestproducts industry, which comprises about 15 percent of forestland ownership, isresponsible for 41 percent of replanted forest acreage. That works out to more than onebillion trees a year, or about three million trees planted every day. This high rate ofreplanting accounts for the fact that each year, 27 percent more timber is grown than is harvested.

■ Manufacturing wood products isenergy efficient. Wood products madeup 47 percent of all industrial rawmaterials manufactured in the UnitedStates, yet consumed only 4 percent ofthe energy needed to manufacture allindustrial raw materials, according to a 1987 study.

■ Good news for a healthy planet. For every ton of wood grown, a young forestproduces 1.07 tons of oxygen and absorbs 1.47 tons of carbon dioxide.

Wood. It’s the right product for the environment.

D O T H E R I G H T T H I N G R I G H T ™


Percent of Percent ofMaterial Production Energy Use

Wood 47 4

Steel 23 48

Aluminum 2 8

NOTICE:The recommendations inthis guide apply only topanels that bear the APAtrademark. Only panelsbearing the APA trademarkare subject to theAssociation’s qualityauditing program.

RATED SHEATHING

EXPOSURE 1SIZED FOR SPACING32/16 15/32 INCH

000PS 1-95 C-D PRP-108

THE ENGINEERED

WOOD ASSOCIATIONAPA

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his glossary from APA – The Engineered Wood Association is designed as a

handy reference guide to wood structural panel products and common con-

struction terminology. It contains up-to-date information about APA

Performance Rated Panels, plywood siding, sanded grades, panel construction

systems, grading terminology, fasteners, finishing, and much more.

For more detailed information about APA panel products and construction sys-

tems, write for a free copy of the Publications Index, Form B300, P.O. Box 11700,

Tacoma, Washington 98411-0700.

The Association maintains a comprehensive inventory of publications for archi-

tects, builders, dealers, do-it-yourselfers and others who use and specify wood

structural panel products.

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A

A-AA sanded plywood panel with A-gradeface and back plies and D-grade innerplies. Bonded with interior or exteriorglue. Commonly used for cabinets,built-ins, furniture, partitions and otherinterior or protected applications wherea smooth surface or appearance qualityon both sides is important.

A-A ExteriorA sanded plywood panel with A-grade face and back plies and C-grade innerplies. Bonded with exterior glue.Commonly used for fences, built-ins,signs, boats, cabinets, commercial refrig-erators, shipping containers, tanks, toteboxes, ducts and other exterior or highmoisture applications where a smoothsurface or appearance quality on bothsides is important.

A-BA sanded plywood panel with A-gradeface, B-grade back and D-grade innerplies. Bonded with interior or exteriorglue. Commonly used as a substitute forA-A where the appearance of one side isless important.

A-B ExteriorA sanded plywood panel with A-gradeface, B-grade back and C-grade innerplies. Bonded with exterior glue.Commonly used as a substitute forA-A Exterior where the appearance ofone side is less important.

AFG-01A performance specification developedby APA – The Engineered WoodAssociation for glues recommended foruse in the APA Glued Floor System.AFG-01 requires that glues applied atthe job site be sunlight resistant, strongunder many moisture and temperatureconditions, and able to fill gaps.

Aggregate-Coated PanelA panel coated with stone chipsimbedded in a resin coating.

Air-DriedSee SEASONING.

APA – The Engineered Wood AssociationThe trade organization representingmost of the nation’s wood structuralpanel manufacturers. The Associationhas three main functions: 1) research toimprove plywood and other engineeredwood products and systems, 2) qualityinspection and testing to assure themanufacture of high quality panel products, and 3) promotion of panelproducts and building systems.

Anchor BoltBolts that tie the sill plate and thus theframe of a structure to its foundation.

APA Glued Floor SystemA floor system developed by APA inwhich a single layer of APA RATEDSTURD-I-FLOOR panels (or subflooringin the case of double-layer construction)is glue-nailed to wood joists. The bondis so strong that floor and joists behavelike an integral unit, increasing floorstiffness and greatly reducing floorsqueaks and nail popping. Only con-struction adhesives conforming to APAspecification AFG-01 are recommendedfor use with the system. See T-BEAM.

A-C ExteriorA sanded plywood panel with A-gradeface, C-grade back and C-grade innerplies. Bonded with exterior glue.Commonly used for soffits, fences,boxcar and truck linings, farm buildings,tanks, commercialrefrigerators and otherhigh-moisture applica-tions where theappearance orsmoothness of onlyone side is important.

Acrylic ResinAn ingredient of water-base (latex)paints and stains. Synthetic resin withexcellent weathering characteristics.Acrylics can be colorless and transpar-ent, or pigmented.

AdhesiveSee GLUE.

A-DA sanded plywood panel with A-gradeface, D-grade back and D-grade innerplies. Bonded with interior or exteriorglue. Commonly usedfor paneling, built-ins,shelving, partitionsand other interior orprotected applicationswhere the appearanceor smoothness of onlyone side is important.

4

EXTERIOR

A-C GROUP 1

000PS 1-95

THE ENGINEEREDWOOD ASSOCIATION

APA

EXPOSURE 1

A-D GROUP 1

000PS 1-95


APA

A-A • G-1 • EXPOSURE 1-APA • 000 • PS1-95

A-B • G-1 • EXPOSURE 1-APA • 000 • PS1-95

A-A • G-1 • EXT-APA • 000 • PS1-95

A-B • G-1 • EXT-APA • 000 • PS1-95

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5

APA Rated® SidingA grade designation covering APAproprietary siding products. Commonlyused, in addition to siding, for fencing,soffits, wind screens and other exteriorapplications. Can be used for interiorpaneling. Can be manufactured asconventional veneered plywood, as acomposite or as oriented strand boardsiding. Both panel and lap siding areavailable. Special surface treatment suchas V-groove, channel groove, deepgroove (such as APA Texture 1-11),brushed, rough sawn and texture-embossed (MDO). Span Rating (studspacing for siding qualified for APASturd-I-Wall applications) and face gradeclassification (for veneer-faced siding)indicated in trademark.

APA Performance Rated Panels®

Panel products developed by APA – TheEngineered Wood Association, such asAPA RATED SHEATHING, APA RATEDSTURD-I-FLOOR and APA RATEDSIDING, designed and manufactured tomeet performance criteria for specificend-use applications. APA PerformanceRated Panels can be manufactured asconventional veneered plywood, ascomposites (veneer faces bonded toreconstituted wood cores), or as mat-formed panels (including waferboardand oriented strand board.) The trade-marks on APA Performance Rated Panelsinclude a Span Rating denoting themaximum recommended spacing ofsupports over which the panel shouldbe placed for the designated end use, and the exposure durabilityclassification of the panel.

APA Rated® SheathingAn APA Performance Rated Paneldesigned and manufactured specificallyfor residential and other light frame wallsheathing, roof sheathing and subfloor-ing applications. APA RATED SHEATH-ING can be manufactured with SpanRatings of 12/0, 16/0, 20/0, 24/0,24/16, 32/16, 40/20and 48/24, in thick-nesses ranging from5/16 to 3/4 inches,and in three exposuredurability classifica-tions – Exterior,Exposure 1 andExposure 2.

RATED SHEATHING

EXPOSURE 1SIZED FOR SPACING

24/16 7/16 INCH

000PRP-108


APA

RATED SIDING

SIZED FOR SPACINGEXTERIOR

24 oc 15/32 INCH


APA

000PRP-108

RATED SIDING303-18-S/W

EXTERIOR000

PS 1-95 PRP-108FHA-UM-64


APA

11/32 INCHGROUP 1 16 oc

SIZED FOR SPACING

Brushed

Rough sawn

APA Texture One-Eleven®

Kerfed

Reverse board & batten

Channel groove

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Strength axis

.............................

.............................

.............................

STURD-I-FLOOR16, 20, 24, 32, or 48 oc

Carpet

Tongue and Groove edges orblocking between supports

VERTICAL APPLICATION

Insulation as required

Rated Siding

HORIZONTAL APPLICATION

Building paper behind vertical joints ofgrooved panel siding

Vertical battens at panel butt joints

Rated Siding


Blocking athorizontaljoints

6

APA Rated Sturd-I-Floor®

An APA Performance Rated Paneldesigned and manufactured specificallyfor residential and other light framesingle-floor (combined subfloor-under-layment) applications for use undercarpet. APA RATED STURD-I-FLOORcan be manufactured with Span Ratingsof 16, 20, 24, 32 and 48 oc, in thick-nesses ranging from 19/32 to1-1/8 inch, and in three exposure dura-bility classifications – Exterior, Expo-sure 1 and Exposure 2. Panels areavailable with either square edges ortongue-and-grooveedges as specified.APA RATED STURD-I-FLOOR 48 oc ply-wood, commonlycalled 2-4-1, is alsoused in heavy timberroof construction.

RATED STURD-I-FLOOR

EXPOSURE 1

24 oc 23/32 INCH

000PS 1-95 UNDERLAYMENT

PRP-108


APA

SIZED FOR SPACINGT&G NET WIDTH 47-1/2

APA Sturd-I-Wall®

A construction system in which APARated Siding panels or lap are attacheddirectly to studs (single wall) or overnonstructural wall sheathing, such asfiberboard, gypsumboard or rigid foaminsulation. APA Siding bearing a SpanRating of 24 oc in the trademark can beapplied vertically direct to studs spaced24 inches on center. Siding with a SpanRating of 16 oc can be used verticallydirect to studs 16 inches on center.Panels with either Span Rating can beapplied direct to studs 24 inches oncenter with face grain horizontal pro-vided horizontal joints are blocked.

APA TrademarkAPA – The Engineered Wood Association isan approved quality supervision andtesting agency for softwood plywoodand wood structural panels. Typicaltrademarks of APA member-manufac-tured products are shown throughoutthis brochure. See QUALITYINSPECTION AND TESTING.

APA STURD-I-WALL®

APA STURD-I-FLOOR®

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B

Back-OutSee NAIL POPPING.

Back-PrimingApplication of a coat of primer to theback of a panel. Cabinet doors shouldbe back-primed to prevent warping.

BackstampThe approved agency mark on the backof a panel. All unsanded and touch-sanded panels, andpanels with A or Bfaces on one side only,carry the APA trade-mark on the panelback. See alsoAPA TRADEMARKand EDGEMARK.

BattenA thin, narrow strip of plywood orlumber used to conceal or protect ajoint between adjoining pieces of lumber or plywood.

B-C ExteriorA plywood panel with sanded B-gradeface, C-grade back and C-grade innerplies. Bonded with exterior glue. Utilitypanel for farm serviceand work buildings,boxcar and trucklinings, containers,tanks, agriculturalequipment, as a base for exterior coatings, etc.

B-DA plywood panel with sanded B-gradeface, D-grade back and D-grade innerplies. Bonded withinterior or exteriorglue. Utility panel forbacking, sides of built-ins, industry shelving,slip sheets, separatorboards, bins, etc.

BevelTo cut panel edges or ends at an angleto make smooth mating joints between panels.

B-BA sanded plywood panel with B-gradeface and back and D-grade inner plies.Bonded with interior or exterior glue.Utility panel for interior or protected applications.

B-B ExteriorA sanded plywood panel with B-gradeface and back and C-grade inner plies.Bonded with exterior glue. Utility panelwith solid paintable surface both sides.

B-B Plyform®

Concrete form grades with high reuse factor. Sanded both sides and mill-oiled unless otherwise specified. Specialrestrictions on species. Also available inHDO for very smooth concrete finish, in STRUCTURAL I (allplies limited to GroupI species), and withspecial overlays.EXPOSURE DURABILITYCLASSIFICATION:Exterior.

7

EXTERIOR

A-C GROUP 1

000PS 1-95


APA

B-B • G-2 • EXPOSURE 1-APA • 000 • PS1-95

B-B • G-2 • EXT-APA • 000 • PS1-95

PLYFORM

000PS 1-95


APA

EXTERIOR

B-B CLASS 1

EXTERIOR

B-C GROUP 2

000PS 1-95


APA

EXPOSURE 1

B-D GROUP 2

000PS 1-95


APA


Rated Siding

Batten

Bevel joint

BATTEN

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BlockingLight lumber strips nailed between majorframing members to support edges ofstructural panels where they meet.

BlowA localized delamination caused bysteam pressure buildup during the hotpressing operation. The steam mayresult from high moisture content of theveneer, excessive glue spread, or highpress temperatures.

Boat PatchSee REPAIRS.

BondTo glue together, as veneers are“bonded” to form a sheet of plywood.Pressure is applied to keep mating partsin proper alignment. Most glues used inpanel manufacture require both heatand pressure to cure properly.

BowDistortion of a wood structural panel sothat it is not flat lengthwise. See also CUP.

BundleA unit or stack of wood panels heldtogether for shipment with bands. Stacksize varies throughout the industry, withthe average stack running about 30 to33 inches high. A bundle 30 incheshigh, for example, contains 120 sheetsof 1/4-inch panels, 80 sheets of 3/8-inchpanels, or 60 sheets of 1/2-inch panels.

Butt JointThe joint formed when two parts arefastened together without overlapping.For end-to-end joints, use a nailingstrip. For corner joints, nail directly intopanel if it is at least 3/4-inch thick. Ifpanel is thinner than 3/4 inch, use areinforcing block.

Box BeamA beam built of lumber and wood structural panels in the form of a longhollow box which will support moreload across an opening than will itsindividual members alone. Lumbermembers form the top and bottom(flanges) of the beam, while the sides(webs) are panels.

BridgingShort wood or metal braces or strutsplaced crosswise between joists to helpkeep them in alignment. Bridging maybe solid or crossed struts. Most buildingcodes no longer require bridging of floor joists. See illustration underBLOCKING.

BrushedAn APA 303 Siding surface treatment.Brushed or relief-grain surfaces accentthe natural grain pattern to create strik-ing textures. Difficult to paint or stain.See APA RATED SIDING.

8

Full depth bridgingacts as blocking

Bridging

BlockingPanel websboth sides

Lumber flanges

Lumberstiffeners

CORNER JOINT

Nails intoreinforcing block

Reinforcingblocks

END-TO-END JOINT

Nail stripNails

Butt joint

BOW

BUTT JOINT

BOX BEAM

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C

CaulkWaterproof sealant used to fill joints orseams. Caulks are available as putties,ropes, or compounds extruded from cartridges.

C-C Plugged ExteriorA touch-sanded plywood panel withC-Plugged-grade face, C-grade back andinner plies. Bonded with exterior glue.Commonly used forsevere moisture condi-tions, exterior bal-conies and decks,refrigerated or con-trolled atmosphererooms, and boxcar and truck floors.

C-D PluggedA touch-sanded plywood panel withC-Plugged-grade face, D-grade back andinner plies. Bondedwith interior or exte-rior glue. Used forbuilt-ins, cable reelsand walkways.

Center (Centers)Inner ply or plies of a plywood panelwhose grain runs parallel with that ofthe face and back plies.

Center GapSee CORE GAP.

Center-To-CenterSee ON-CENTER and CLEAR SPAN.

Clear SpanDistance between inside faces of supports.

CodeSee MODEL CODE.

COM-PLY®

APA – The Engineered Wood Associationproprietary trade name for APAmember-produced composite panels.See APA PERFORMANCE RATEDPANELS and COMPOSITE PANEL.

ComponentA glued and/or nailed structural assem-bly of wood structural panels and lum-ber, such as a stressed-skin panel. Alsodescribes prefabricated building sections in panelized construction.

Composite PanelA veneer-faced panel with a reconstitutedwood core. See APA PERFORMANCERATED PANELS and COM-PLY.

ChamferThe flat surface created by slicing off thesquare edge or corner of a piece of wood or panel.

Channel GrooveAn APA 303 Siding texture consisting of shallow grooves cut into panel facesduring manufacture. See APA RATED SIDING.

CheckingWood exposed to alternating moist anddry conditions eventually develops opencracks or “checks.” Reduce checking bysealing panel edges before installation tominimize moisture absorption, and byusing a priming coat or resin sealer onthe surfaces.

ChordAny of the outside members of a trussconnected by web members. Also, mayrefer to perimeter members of a paneldiaphragm. See illustration under TRUSS.

Circular PlugSee REPAIRS.

Class ISee B-B PLYFORM.

9

C-C PLUGGED

GROUP 1

EXTERIOR000

PS 1-95


APA

C-D PLUGGED

GROUP 2

EXPOSURE 1000

PS 1-95


APA

Chamfersmitered

Chamfer

16" center-to-center

14-1/2" clear span

Framing

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CHAMFERCLEAR SPAN

COMPOSITE PANEL

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Cross CuttingSawing wood across the grain. Becausethe wood in wood structural panels iseither cross-laminated or randomlyoriented, any cut made in a wood struc-tural panel is a cross cut. Always use across-cut saw when hand- or power-sawing wood structural panels.

CupCrosswise distortion of a woodstructural panel from its flat plane. See also BOW.

Curved PanelStressed-skin or sandwich panels curvedto various degrees of arc. Used in roofconstruction.

Core Gap (Center Gap)An open veneer joint extendingthrough, or partially through, a plywoodpanel. Product Standard PS 1 specifiesthat the average of all gaps shall notexceed 1/2 inch, and that every effort be made to produce closely butted core joints.

Crawl SpaceA space often about two feet highbeneath a house floor allowing access toplumbing or wiring. See also PIRF.

CrippleAny vertical framing member cut lessthan full length, as in cripple studsunder a window opening.

Crossband (Cores)In plywood, the veneer layers with graindirection perpendicular to that of theface plies. See CORE.

Concentrated LoadSee LOADS.

Concrete FormMold into which fresh concrete isplaced to set. Plywood provides tough,durable, easy-to-handle, split-resistantand lightweight concrete forms. It canbe bent for curved forms and liners, andits natural insulating properties helpmoderate temperature variations formore consistent curing. Almost any APAtrademarked plywood can be used inconcrete formwork applications, butPLYFORM is specifically manufacturedfor that purpose. See also B-BPLYFORM.

Core (Cores)In conventional plywood, inner plieswhose grain runs perpendicular to thatof the outer plies. In composite panels,a layer of reconstituted wood. See also PLY.

10

3-PLY PANEL

Core

Plywood upper skin

Insulation

Plywood lower skin

Plywood orlumber ribs

Distortion across panel

CORE

CUP

CURVED PANEL

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D

Dado JointJoint formed by intersection of twoboards, one of which is notched with arectangular groove.

Dead Load (D.L.)See LOADS.

Decorative PanelA plywood panel grade with rough-sawn, brushed, grooved or striatedfaces. May be any exposure durability.Common uses include paneling, built-ins, accent walls, counter facings anddisplays. Exterior uses include siding,gable ends and fences.Check with manufac-turer for specificExterior applicationrecommendations,which vary with par-ticular products.

DeflectionBending of a wood structural panel orframing member between supportsunder an applied load.

DelaminationSeparation between plies or withinreconstituted wood due to adhesivebond failure. Separation in area immedi-ately over or around a permitted defectdoes not constitute delamination.

DiaphragmElements of a building that provideshear strength to withstand wind andearthquake loads.

Dogbone PlugSee REPAIRS.

11

Roof (horizontaldiaphragm) carriesload to end walls.

End wall (verticaldiaphragm) carriesload to foundation.

Side wall (vertical diaphragm)carries load to roofdiaphragm at top and tofoundation at bottom.

Wind load

SIDING OVER APA RATED SHEATHING

Sheathing (applied horizontally)

Sheathing (applied vertically)

Rated Siding

DECORATIVE

EXPOSURE 1GROUP 2

000PS 1-95


APA

Double WallA light frame wall construction systemconsisting of exterior finish siding, suchas APA RATED SIDING, applied overstructural wall sheathing – typically APA RATED SHEATHING. See APA STURD-I-WALL.

DIAPHRAGM

DOUBLE WALL

DADO JOINT

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E

EaveThe edge of a roof that extends beyondor overhangs a wall. The underside of aneave may form an “open soffit.” Texturedpanels, applied face down to eave raftersas roof sheathing, give open soffits adecorative finished surface. See SOFFIT.

EdgemarkAPA trademark stamped on the paneledge. Appears on sanded grades withB-grade or better veneer faces, PLYRON,MARINE, and panels with overlaidsurfaces on both sides.

Edge SealingApplication of a coating (e.g., sealant,paint) to the edges of a wood structuralpanel to reduce its water absorption.Edge seal before painting the panelsurface if panel edges will be exposed to repeated wetting and drying.

Edge SpacingSee PANEL SPACING.

Edge SupportSupport, such as panel clips or lumberblocking, installed between framingmembers at wood structural panel edgesto transfer loads from one panel to theother across the joint. Panels withtongue-and-groove edges can be used inmany applications without additionaledge support.

End SpacingSee PANEL SPACING.

Engineered 24" FramingA building system using wood structuralpanels over lumber framing spaced24 inches on center in walls, floors and roof. The system’s series of in-lineframes – trusses, studs and joists –provide cost-effective materials utiliza-tion and simpler, faster construction. It is recognized by major model codes and the FHA.

ExpansionMoisture absorption causes wood toexpand. Spacing between panel edgesand ends is recommended to allow forany possible panel swelling. See PANEL SPACING.

Exposure Durability ClassificationExposure ratings for APA woodstructural panels designated in APAtrademarks as Exterior, Exposure 1,Exposure 2, or Interior.

Exterior panels have a fully waterproofbond and are designed for applicationssubject to permanent exposure to theweather or to moisture.

Exposure 1 panels have a fully water-proof bond and are designed for appli-cations where long construction delaysmay be expected prior to providingprotection, or where high moistureconditions may be encountered inservice. Exposure 1 panels are madewith the same exterior adhesives used inExterior panels. However, because othercompositional factors may affect bondperformance, only Exterior panelsshould be used for permanent exposure to the weather.

Edge TreatmentEdge finishing method, such as bandingwith wood or plastic, or filling withputty or spackle.

Edge VoidA panel defect in which the edge or endof an inner ply has split or broken awayduring manufacture, leaving a gap in theedge of the plywood panel.

EmbossedA panel surface treatment. Heat andpressure against a master patternimpress a variety of textured effects into panel surfaces, which remainsmooth and paintable.

End GrainThe end of a piece of wood exposedwhen the wood fibers are cut across the grain. All wood structural paneledges are end grain, and should befinished accordingly.

12

Butt edging. Keep edges square; use matching strip of solid wood.

Butt edging. Keep edges square; use matching strip of solid wood.

“Mitered” butt edging. Use glue and brads to fasten strips.

A-B • G-1 • EXT-APA • 000 • PS1-95

EDGE TREATMENTS

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Exposure 2 panels (identified asInterior with intermediate glue underPS 1) are intended for protected con-struction applications where only mod-erate delays in providing protectionfrom moisture may be expected.

Interior panels or panels which lackfurther glueline information in theirtrademarks are manufactured with inte-rior glue and are intended for interiorapplications only.

Exposure 1See EXPOSURE DURABILITYCLASSIFICATION.

Exposure 2See EXPOSURE DURABILITYCLASSIFICATION.

ExteriorPS 1 exposure durability term forplywood manufactured for permanentoutdoor or marine use and bonded with100 percent waterproof adhesives. See INTERIOR and EXPOSURE DURABILITY CLASSIFICATION.

Exterior GlueA 100 percent waterproof adhesivebonding all Exterior, Exposure 1 andmost Interior panels. For applicationssubject to temporary exposure to mois-ture during construction, specifyExposure 1 or Exposure 2. Forpermanent exposure to weather ormoisture, use only Exterior panels. See also INTERIOR GLUE, INTER-MEDIATE GLUE and EXPOSUREDURABILITY CLASSIFICATION.

FasciaWood or plywood trim used along theeave or the gable end of a structure.

Fiberglass-Reinforced Plastic (FRP)A tough, nonscuff plywood coatingmade of glass fibers combined withresins. These coated panels (composite)are used in truck and trailer bodies,containers and concrete forms. Seamlesspanels 40 feet long and longer can beproduced as trailer sidewalls or roofs.

FillerA material for filling nail holes, checks,cracks or other blemishes in surfaces of wood before application of paint,varnish or other finishes.

F

FaceThe highest-grade side of any veneer-faced panel that has outer plies of differ-ent veneer grades. Also, either side of apanel where grading rules draw nodistinction between faces. For example,the face of an A-C panel is the side withthe A-grade outer ply. Both sides of anA-A or B-B panel are referred to as faces.

Face-CheckingPartial separation of wood fibers parallelto grain in the wood or veneer surfacesof panels caused chiefly by the strains of weathering and seasoning. See CHECKING.

Face GrainDirection of the grain of the outer ply(face) of a veneer-faced panel in relationto its supports. A panel’s greatest stiff-ness and strength is parallel to the facegrain. Therefore, in construction, runthe face grain or long dimension of thepanel across supports for greatest stiff-ness and strength.

13

Fascia

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FinishesStains, paints or sealers which protect,color or enhance the natural beauty ofwood structural panels.

Exterior finishes primarily protectsiding and maintain its appearance.They minimize the weathering actionwhich roughens and erodes the surfaceof unfinished wood. Different finishesgive varying degrees of protection so thetype, quality, quantity and applicationmust be considered to achieve thedesired performance. All exterior paneledges should be sealed if the panels willbe painted or stained. Sealing whilepanels are stacked is easiest. Exteriorfinishes recommended for wood struc-tural panels include semi-transparentstain, solid-color stain and acrylic latex paint.

Interior finishes: Preparation isminimal. Overlaid (MDO and HDO)plywood needs no preparation; sandedand textured grades require only touch-sanding. Recommended interior finishesinclude oil base paint, latex paint, stain and sealer.

Fire-Rated SystemsWall, floor and roof construction ofspecific materials and designs that hasbeen tested and rated according to firesafety criteria (e.g., flame spread rateand fire resistance). Testing and approvalare performed by agencies such asUnderwriters Laboratories, Inc. A

Foam CoreCenter of a structural wood panel-faced“sandwich” panel. Liquid plasticfoamed into all spaces between thepanels serves to both insulate and sup-port the component skins. Or structuralwood panel skins are pressure-glued toboth sides of rigid plastic foam boardsor billets. See SANDWICH PANEL.

FootingThe base for foundation walls, posts,chimneys, etc. The footing is wider thanthe member it supports, and distributesthe weight of the structure to theground over a larger area to preventsettling.

Frame ConstructionConstruction in which the structuralparts are wood or dependent on a woodframework for support. Typically, lumberframing is sheathed with wood struc-tural panels for roofs, walls and floor.The classification of frame constructionremains the same in building codeseven when masonry covering is appliedon exterior walls.

FRPSee FIBERGLASS-REINFORCEDPLASTIC.

FRTSee FIRE-RETARDANT-TREATED.

FurringProcess of leveling parts of a ceiling, wallor floor by means of wood strips, calledfurring strips, before adding panel cover.

one-hour rating, for example, meansthat an assembly similar to that testedwill neither collapse nor transmit flameor high temperature for at least onehour after a fire starts. Structural woodpanels are an approved material in anumber of fire-rated designs. See FLAME SPREAD.

Fire-Retardant-Treated (FRT)Chemical treatment of wood and ply-wood to retard combustion. Plywood ispressure-impregnated with fire retardantchemicals mixed in water in accordancewith American Wood PreserversAssociation Standard AWPA C27.NOTE: Span Ratings and load capacitiesare based on untreated panels, and maynot apply following fire-retardant treat-ment. Obtain structural performancecharacteristics of FRT panels from thecompany providing the treatment andredrying service.

Flame SpreadThe spread of fire along the surface ofa material. Flame spread ratings areexpressed in numbers or letters andare used in building code interiorfinish requirements.

FlangeTop and bottom longitudinal membersof a beam. Box beams are fabricatedwith lumber flanges (top and bottom)and structural wood panel webs (sides).See BOX BEAM.

FlashingSee Z FLASHING.

14

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15

Fascia rafter

Cripples OutriggerRidge board

Collar beam

Roof rafter

Ceiling joist

Header joist

Anchor bolts

Sill plate

Bottom plate

Stud walls

Header

Top plate(doubled)

Plywood or lumber splice

Corner post (usually 3 posts)

APA panel subflooring or APA STURD-I-FLOOR

Floor joists

Glulam girder

Lumber post

Post footing Footing

Fascia

Foundation(concreteblock shown)

APA panel wallsheathing or APA Rated Siding

APA panelroof sheathingOutside bearing wall

Center bearing wallPartition wall (non-load bearing)

FRAME CONSTRUCTION

FRAME CONSTRUCTION

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GLUES

Type of Glue Description Recommended Use Precautions How to Use

Urea Comes as powder to be Good for general wood Needs well-fitted joints, Make sure joint fits tightly. Resin mixed with water and used gluing. For work that must tight clamping, and room Mix glue and apply thin coat.Glue within 4 hours. Light colored. stand some exposure to temperature 70° or warmer. Allow 16 hours drying time.

Very strong if joint fits well. dampness, but is not Some require heat to cure.completely waterproof.

Liquid Comes ready to use at any Good for indoor furniture Not sufficiently resistant to Use at any temperature Resin temperature. Clean-working, and cabinetwork. First moisture for outdoor but preferably above 60°. (White) quick-setting. Strong choice for small jobs where furniture or outdoor Spread on both surfaces, Glue enough for most work, tight clamping or good fit storage units. clamp at once.

though not quite as tough may be difficult. Sets in 1-1/2 hours.as urea resin glue.

Resorcinol Comes as powder plus This is the glue to use with Expense, mixing difficulty Use within 8 hours after (Waterproof) liquid, must be mixed each Exterior-type plywood for and dark color make it mixing. Work at temperatureGlue time used. Dark colored, work to be exposed to unsuited to jobs where above 70°. Apply thin coat

very strong, completely extreme dampness. Good waterproof glue is not to both surfaces; allow waterproof. for farm buildings, boats. required. Needs good fit, 16 hours drying time.

tight clamping.

G

GirderA large horizontal beam which supportsinterior walls or joists. Most wood framehouses have a lengthwise center girderthat supports the joists and floor panels.See FRAME CONSTRUCTION.

GlueMany adhesives, preferably inconjunction with nails or other fasten-ers, produce strong joints in structuralwood panel construction. Type dependson purpose and exposure of finishedproduct. The most common glues arelisted in the chart below.

16

Other available glues include: Hot melt glues – for relatively small parts.Remember they cool and set quickly.Epoxy glues – limited use; most are not formulated for wood. Expensive.Contact Cements – useful for applyinglaminates and edge stripping to ply-wood. Not recommended for structuraljoints. Wall panel adhesives – handyfor applying decorative paneling orfacing. May require a few nails per panelto position panels while glue sets.Casein glues – slow setting, permittingeasier construction of difficult assemblies.

Glue-Nailed (Nail-Glued)Gluing wood structural panel joints andconnections with pressure provided bynailing. For most effective fastening,

pieces should meet continuously alongtheir joint. Apply glue to one or bothsurfaces according to manufacturer’sdirections, then press surfaces togetherand nail in place. For work such as cabi-nets or drawers, or whenever possible,joint should be clamped as well as nailedto maintain pressure until glue sets.

Glued Floor SystemSee APA GLUED FLOOR SYSTEM.

GluelineThe adhesive joint formed betweenveneers in a plywood panel or betweenface veneers and core in a compositepanel (primary glueline), or betweenlumber and wood structural panel partsin an assembly such as a component(secondary glueline).

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GlulamShort for glued-laminated structuraltimber – large beams fabricated bybonding layers of specially selectedlumber with strong, durable adhesives.End and edge jointing permit produc-tion of longer and wider structural woodmembers than are normally available.Glulam timbers are used with woodstructural panels for many types of residential and commercial construction.

Grooving is available in a variety ofwidths and spacings on several surfacetextures. See also APA RATED SIDINGand TONGUE-AND-GROOVE JOINT.

Group NumberPlywood is manufactured from over70 species of softwood. These species areclassified according to strength and stiff-ness under manufacturing standard PS 1into Groups 1 through 5. Group 1 woodsare the strongest. The group number of aparticular panel is determined by theweakest (highest numbered) species usedin face and back (except for some thinpanels where strength parallel to facegrain is unimportant).

Growth RingA tree’s annual cross-sectional growthlayer, including springwood andsummerwood.

Gusset PlateA piece of plywood connecting lumbermembers of a truss or other frame struc-ture. Gussets may be applied to one orboth sides of the joint. Plywood is usedbecause of its great strength andsplit-resistance.

GradeRefers to the letter-graded quality ofveneers used in plywood manufacture (N,A, B, C-Plugged, C and D), or to particu-lar panels, e.g., A-A, Underlayment, etc.See also VENEER GRADE.

GrainThe natural growth pattern in wood.The grain runs lengthwise in the treeand is strongest in that direction.Similarly, grain usually runs the longdimension in the face and back veneersof a plywood panel, making it strongerin that direction. Wood structural pan-els should therefore usually be appliedwith the long dimension perpendicular to or across supports.

Grain RaiseThe condition on the surface of aplywood panel resulting from harder ordenser wood fibers swelling and risingabove softer surrounding wood.

GrooveOne of the surface treatments frequentlygiven to textured siding in which aseries of narrow, parallel channels arecut into the surface of the panel.

17

Gussets

GUSSET PLATES

GLULAM

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H

HardwoodWood of the deciduous or broadleavedtrees – oak, maple, ash, walnut – asdistinct from the softwood of the conif-erous or needleleaved trees – pine, fir,spruce, hemlock. The term has only ageneral reference to actual wood hard-ness. Construction and industrial ply-wood may use either variety. SeeSOFTWOOD.

HDOSee HIGH DENSITY OVERLAY.

HeaderA cross member placed between studsor joints to support loads over openingsfor stairways, chimneys, doors, etc. Seealso FRAME CONSTRUCTION.

HeartwoodThe nonactive core of a tree distinguish-able from the growing sapwood by itsusually darker color and greater resis-tance to rot and decay.

Heavy TimberA building code designation for a partic-ular type of construction with good fireendurance. Heavy Timber is widelyrecognized as comparable to one-hourconstruction. A panel roof deck of1-1/8-inch tongue-and-grooved ply-wood with exterior glue over 4-inch-wide supports meets the Heavy Timberrequirements and provides the same fireperformance as nominal 2-inch tongue-and-groove lumber decking.

Impact Insulation ClassValues which rate the capacity of floorassemblies to control impact noise suchas footfalls. FHA requirements (andsome local building codes) specifyminimum acceptable ratings.

Impact Noise RatingValues for floor assembly impact sound transmission, now replaced by IIC classification.

Inner PliesAll plies of a plywood panel except face and back.

INRSee IMPACT NOISE RATING.

Interior GlueA moisture-resistant, but not waterproof, adhesive used in the manufacture of some plywood panels.See also EXTERIOR GLUE, INTER-MEDIATE GLUE and EXPOSUREDURABILITY CLASSIFICATION.

InteriorPS 1 exposure durability term forplywood manufactured for indoor use or construction subjected to onlytemporary moisture. See EXTERIOR and EXPOSURE DURABILITYCLASSIFICATION.

Intermediate GlueAn adhesive bonding some PS 1 panelswhich has a moisture resistance midwaybetween interior and exterior glues.Panels bonded with intermediate glueare comparable with those designatedunder APA performance standards as Exposure 2. See EXPOSUREDURABILITY CLASSIFICATION.

High Density Overlay (HDO)Plywood finished with a resin-impregnated fiber overlay to provideextremely smooth hard surfaces thatneed no additional finishing and havehigh resistance to chemicals and abra-sion. The overlay material is bonded toboth sides of the plywood as an integralpart of the panel faces. Used for con-crete forms, cabinets, highway signs,counter-tops and other punishingapplications. See also MEDIUMDENSITY OVERLAY (MDO).

I

I-BeamSee I-Joist.

Identification IndexFormer term for Span Rating. See SPAN RATING.

IICSee IMPACT INSULATION CLASS.

I-JoistJoist whose cross section resembles the letter “I”. The flanges of an I-joist arecomposed of lumber or laminatedveneer lumber (LVL), and the web iscomposed of plywood or orientedstrand board.

18

I-JOIST

Web

Flanges

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L

LapTo position adjacent objects so that one surface extends over the other. Termmay designate a lap siding technique,in which each panel or piece overlapsthe edge of the next lower panel. Ashiplap joint unites two panels whenhalf the thickness of each is cut away so that the two pieces fit together with outer faces flush.

LayerIn plywood a layer consists of one or more adjacent plies having the wood grain in the same direction.For instance, four ply panels always havethree layers with both core plies at rightangles to the faces. These two plies areone layer and each face is another. Incomposite panels, the reconstitutedwood portion is one layer and each face is another. See PLY.

J

Jointed CoreCore veneer that has had edges machined square. Gaps between piecesof core shall not exceed 3/8 inch, andthe average of all gaps in the panel shall not exceed 3/16 inch.

JoistHorizontal framing member of a floor,ceiling or flat roof. Wood structuralpanels are commonly used for subfloor-ing and underlayment or single-layerflooring (APA RATED STURD-I-FLOOR)over floor joists. APA RATED SHEATH-ING is typically used over roof joists.

K

KerfA slot made by a saw; the width of a saw cut.

Kiln-DriedWood dried in ovens (kilns) bycontrolled heat and humidity to speci-fied limits of moisture content. Veneersare kiln dried before lay-up. See also SEASONING.

KnotNatural growth characteristic of woodcaused by a branch base imbedded inthe tree trunk.

KnotholeVoid produced when a knot dropsout of veneer.

Lay-UpThe step in wood structural panelmanufacture in which veneers or reconstituted wood layers are “stacked”in complete panel “press loads” aftergluing and before pressing. Also theconstruction of the panel.

Live Loads (L.L.)See LOADS.

LoadsThe weight or pressure a structure carries or sustains, which must be con-sidered in planning a building. Uniformloads are evenly distributed over a largearea, usually the entire surface of a panel.Concentrated loads are applied over avery small area (for example, by a pianoleg). Dead loads are stationary, perma-nent loads; that is, the weight of all thematerial used in construction of thebuilding (or section). Live loads areplanned loads the structure must carryunder normal conditions, such as peopleor furniture and equipment, that wouldbe moved across the structure’s surface.These loads are generally assigned by thebuilding code for the type of structure;for example, a heavy-equipment storagewarehouse, a house or an office building.Live loads are generally considered to be uniform loads.

Lumber CorePlywood manufactured with a corecomposed of lumber strips. The faceand back (outer) plies are veneer.

19

HORIZONTAL JOINTS

Full lap

Shiplap

LAP

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M

Marine GradePlywood panels manufactured with thesame glueline durability requirements asother Exterior panels but with morerestrictive veneer quality and manufac-turing requirements. The grade is partic-ularly suitable for marine applicationswhere bending is required, as in boat hulls.

MDOSee MEDIUM DENSITY OVERLAY.

Medium Density OverlayPlywood finished with an opaqueresin-treated fiber overlay to provide asmooth surface ideal as a paint base.Recommended for siding and otheroutdoor applications, and for built-ins,signs and displays, furniture, etc.Available without grooving, withV-grooves, or in T 1-11 or reverse board-and-batten grooving. See alsoHIGH DENSITY OVERLAY (HDO) and APA RATED SIDING.

Miter JointA joint formed by fitting together twopieces of lumber or panels that havebeen cut off at a 45° angle.

Model CodeA building code developed by a regionalfederation of building officials. These arecontinually reviewed and updated bycommittees of building officials. Modelcodes in the United States are theUniform Building Code (UBC), pub-lished by the International Conferenceof Building Officials; the StandardBuilding Code (SBC), published by the Southern Building Code CongressInternational; and the National BuildingCode (NBC), published by the BuildingOfficials and Code AdministratorsInternational. Members of these threecode organizations comprise theNational Evaluation Service. SeeNATIONAL EVALUATION SERVICE.

Moisture RetarderSee VAPOR RETARDER.

N

NailsNails commonly used for residentialconstruction include:

Common and box nails: 16 penny (d)common and box, for general framing.8d and 10d common and box nails, fortoenailing. 6d and 8d common and boxnails, for subfloor, wall and roof sheath-ing. Size depends on thickness of woodstructural panel sheathing.

Scaffold nails: 8d and 10d mostcommon, for scaffolds, bracing and any temporary fastening that must later be removed.

Siding nails: Nonstaining nails of sizespecified for siding thickness.

Casing and finish nails: 4d, 6d and 8dmost common, for exterior and interiortrim and installation of siding andpaneling where large nailheads should not show.

Roofing nails: A special type,commonly available. Size depends onthickness of roofing and deck material.

Drywall nails: 4d to 6d size dependson drywall thickness; for 1/2-inch dry-wall use 4d drywall nails.

20

Common

Box

Casing

Finishing

Mitered joint

MARINE • A-A • EXT-APA • 000 • PS 1-95

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For underlayment and finish floor:Special nail types with greater holdingpower than ordinary varieties are alsoavailable. For hardwood strip flooring,use either 8d hardwood nails or2-1/2-inch hardened, spiral-threaded(screw-shank) nails. For 1/2-inch andthinner Underlayment grade plywood(over subflooring), use 3d ring-shanks.For 19/32 through 3/4-inch Sturd-I-Floor panels, use any of the 4ddeformed-shank nails illustrated below.

For 1/4-inch panels use 3/4-inch or1-inch brads, 3d finish nails, or (if noobjection to heads showing) 1-inch bluelath nails. For exterior application, usegalvanized or coated nonstaining nails or fasteners.

Predrilling is occasionally necessary incareful work where nails must be veryclose to panel edges. Select a drill bit ofslightly smaller diameter than the nail to be used.

Space nails about 6 inches apart formost work. Closer spacing is necessaryonly with thin panels which mightotherwise buckle slightly between nails.

National Evaluation Service (NES)An arm of the Council of AmericanBuilding Officials sponsored jointly bythe three major American model codeorganizations – the InternationalConference of Building Officials (ICBO);the Southern Building Code CongressInternational (SBCCI); and the BuildingOfficials and Code Administrators Inter-national (BOCA). NES studies applica-tions for new products, and publishesevaluation reports recommendingapproval by its three constituentmembers. See MODEL CODE.

NESSee NATIONAL EVALUATION SERVICE.

Noise-Rated SystemsConstruction designed to reduce sound transmission. Various plywoodconstruction systems tested both inlaboratories and buildings meet orexceed requirements.

Nominal DimensionFull “designated” dimension. Forexample, a nominal 2 inch by 4 inchstud may measure 1-1/2 inch x3-1/2 inch when surfaced. It is acommercial size designation, subject to acceptable tolerances. See also SIZED FOR SPACING.

NoncertifiedStructural panels not included inProduct Standard PS 1, or coveredunder various Performance Standards,and which may bear the mark of themanufacturer rather than a recognizedtesting agency, such as APA.

Nail-GluedSee GLUE-NAILED.

Nail PoppingFlooring nails occasionally appear to“pop” up so that nail head impressionsare visible on the surface of the finishedfloor covering. Shrinkage of floor joistaway from the nail shank after installa-tion exposes the head. When floormembers are dry, make sure fastenersare flush with or below floor surface justprior to installation of thin floor cover-ing such as tile, linoleum or vinyl.Fasteners should be set if green framingwill present nail popping problemsupon drying. Do not fill nail holes.

21

“Popped” nail

Screw-shank

Ring-shank

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O

O & ESOiled and edge-sealed. Surfaces ofconcrete form panels are lightly coatedwith oil and the edges sealed if specified.

On-Center (O.C.)On-center spacing, meaning thedistance from the center of one struc-tural member to the center of the adja-cent member, as in the spacing ofstudding, joists, rafters, nails, etc. See also CLEAR SPAN.

Open DefectsIrregularities such as splits, open jointsand knotholes that interrupt the smoothcontinuity of veneer.

P

P & TSPlugged and touch-sanded face of aplywood or composite panel.

PaintsSee FINISHES.

Panel ClipSpecially shaped metal device for sup-porting panel edges to reduce differ-ential deflection in roof construction.

Panel SpacingThe gap left between installed panels ina structure. Panels in floor, wall or roofdeck construction should be spaced toallow for any possible expansion due tochanging moisture absorption levels.Proper spacing helps prevent bucklingand warping. APA spacingrecommendations are:

See also SIZED FOR SPACING.

Oriented Strand Board (OSB)Wood structural panels manufacturedfrom reconstituted, mechanicallyoriented wood strands bonded withresins under heat and pressure.Oriented strand material may be pro-duced as the center layer of compositepanels, or may be cross-laminated in layered panels. See also APAPERFORMANCE RATED PANELS.

Overlaid PlywoodPlywood panels with factory-applied,resin-treated fiber faces on one or bothsides. Term may also apply to metal andother overlaid panels. See HIGH DEN-SITY OVERLAY (HDO) and MEDIUMDENSITY OVERLAY (MDO).

22

Panel Type Edge End

APA Rated Sheathing 1/8 1/8

APA Rated Siding 1/8 1/8

APA Rated Sturd-I-Floor 1/8 1/8

Underlayment 1/32 1/32

ORIENTED STRAND BOARD (OSB)

PANEL CLIP

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PanelingWood panels joined in a continuoussurface, especially decorative panels forinterior wall finish. Textured plywood inmany varieties is often used as interiorpaneling either in full wall sections oraccent walls. See APA RATED SIDINGfor textured plywood used as paneling.

Panelized ConstructionBuilding components fabricated in wall,floor, or roof sections, etc., to be assem-bled into a completed structure at thebuilding site. Panelized constructionspeeds erection and cuts on-site laborcosts. It offers the high quality availablethrough controlled factory productionand inspection procedures.

PatchSee REPAIRS.

PCUFSee PLUGGED CROSSBAND UNDER FACE.

Peeler LogA specially selected softwood log usedto produce veneer. Peelers are debarked,then lathe-turned against a long knifeblade which slices off a thin, continu-ously unwinding sheet of veneer thenclipped to size, dried, graded, repairedand laminated into plywood panels.

Plugged CoreInner ply construction of solidC-Plugged veneer pieces. Gaps between pieces of core should notexceed 1/2-inch per Product Standard PS 1. See JOINTED CORE.

Plugged Crossbands Under Face (PCUF)A designation denoting a SANDED PANEL of special construction, making it suitable for use as an UNDERLAYMENT, for example A-C (PCUF).

PlyA single veneer in a panel.

PlyformSee B-B PLYFORM.

Performance Rated Panels®

See APA PERFORMANCE RATED PANELS.

Performance StandardA standard applying to panels such asAPA RATED SHEATHING, APA RATEDSTURD-I-FLOOR and APA RATEDSIDING. Panels manufactured to meetAPA performance standards must satisfyrigorous, exacting performance criteria.See also PRODUCT STANDARD andAPA PERFORMANCE RATED PANELS.

Permanent Wood FoundationSee WOOD FOUNDATION.

PIRF (Perimeter-Insulated Raised Floor System)Crawl space foundation-floor systemwhere insulation is applied only to theinside of the perimeter foundation stemwall. The resulting system saves con-struction costs and gives superior energy performance.

Pitch StreakA localized accumulation of pitch inwood cells in a more or less regular streak.

Plastic OverlaidSee MEDIUM DENSITY OVERLAY andHIGH DENSITY OVERLAY.

PlateIn wood frame construction, thehorizontal lumber member on topand/or bottom of the wall studs whichties them together and supports the studs or rafters.

PlugSee REPAIRS.

23

Peeler log

Pressure bar

Veneer

KnifeLathe chuck

3 ply3 layer panel

4 ply3 layer panel

5 ply5 layer panel

PLIES

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Plyron®

A plywood panel manufactured with ahardboard face for an extra-smoothpainting and tough wearing surface.May be Exposure 1 or Exterior.Exposure 1 PLYRON is available with astandard, tempered or treated hard-board surface and is manufactured ofD-grade veneer except the ply directlyunder the hardboard surface, whichmust be C-grade. Exterior PLYRON isavailable with a tempered or treatedsurface and is manufactured withC-grade plies throughout. PLYRON isideal for work surfaces, fixtures, built-ins, cabinets and doors, underlaymentand industrial uses.

PoppingSee NAIL POPPING.

PrefabricatedIn housing, all parts constructed orfabricated at the factory so that finalconstruction only involves assemblingand uniting standard parts at the jobsite. Commonly abbreviated as “prefab.”See PANELIZED CONSTRUCTION.

PrefinishedA ready-to-use panel withfactory-applied finish – paint, overlays or coatings.

PreframedPanelized building in which wall, flooror roof sections are framed and sheathed at the factory.

PreprimedA panel with a factory-applied primer orundercoat needing only final finish after installation.

PRP®

See APA PERFORMANCE RATED PANELS.

PurlinSubframing which supports roofdecking where larger beams are main structural supports.

PWFAbbreviation for Permanent WoodFoundation. See WOODFOUNDATION.

Q

Quality Inspection And TestingTesting program administered by APA toensure quality levels in member millsequal to or exceeding those prescribedby U.S. Product Standard PS 1, PS 2 orAPA’s own performance standards. Theprogram is based on scientific randomsampling. If quality levels are not main-tained, APA trademark privileges may bewithdrawn until compliance is restored.

PreservativesProducts which prevent wooddeterioration due to weather exposure,excessive moisture or insect attack.Treatments range from chemical pres-sure-impregnation, as for woodfoundations, to application of paints or sealers.

Pressure-Preservative TreatedWood treated with preservative bypressure-injecting treating solutions into wood cells. See WOOD FOUNDATION.

PrimerAn undercoat applied to bare wood as asealer and base for paint. See FINISHES.

Product StandardAn industry product manufacturing orperformance specification. APA trade-marks carrying the PS 1 or PS 2 mark areidentification by the manufacturer thatthe panel has been produced in confor-mance with U.S. Product Standard PS 1for Construction and Industrial Plywoodor Voluntary Product Standard PS 2,Performance Standard for Wood-basedStructural-Use Panels. PS 1 is a detailedmanufacturing specification and alternateperformance standard developedcooperatively by the softwood plywoodindustry and the U.S. Department ofCommerce. PS 1 requirements and asupplementary set of APA specificationshelp ensure that plywood manufacturedby APA member mills maintains its con-sistently high quality. PS 2 is a similarstandard, without the detailed manufac-turing specification, that relies on perfor-mance testing to assure that thestructural panels meet realistic, rigorous standards.

24

Roof purlins

PLYRON • EXT • APA • 000

PLYRON • EXPOSURE 1 • APA • 000

PURLIN

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R

R ValueA measurement of thermal resistance, orability to retard heat transmission. Usedto compute insulating effectiveness.

Rabbet JointA joint formed by cutting a groove inthe surface or along the edge of a board,plank or panel to receive another piece.

Racking ResistanceThe ability of a panel to resist forces inthe panel’s plane tending to distort itfrom its rectangular shape.

RafterSloping supporting member of a roofimmediately beneath the sheathing.

Raised GrainSee GRAIN RAISE.

Rated SheathingSee APA RATED SHEATHING.

Rated SidingSee APA RATED SIDING.

RepairsAny patch, plug or shim in a veneer. Apatch is a sound wood insert to replacea defect in veneer. “Boat” patches are

ResawnSee ROUGH SAWN.

Resilient Floor CoveringAny of the vinyl or asphalt-base floorcoverings (tile or sheet) with enough“give” to resist deformation or dentingfrom dropped objects. Resilient floorcoverings installed over APA STURD-I-FLOOR or UNDERLAYMENT panelswith “sanded face” provide smooth, stifffloors for comfortable walking.

Reverse Board And BattenAn APA 303 Siding surface treatment.Deep, wide grooves cut into texturedsiding surfaces during manufacturecreate striking, sharp shadow lines. See APA RATED SIDING.

Ridge BeamThe top horizontal member of a slopingroof, against which the ends of therafters are fixed or supported.

Rigid FrameStructural member functioning like anarch, comprised of studs and raftersfastened with plywood gussets. Rigidframe construction eliminates the needfor ceiling or tie members.

RippingSawing wood in the direction of thegrain. See CROSS CUTTING.

Rotary PeelSee PEELER LOG.

Rough SawnA decorative APA Siding treatmentimparting a rough, rustic appearance by saw-scoring the surface of a panelduring manufacture. Same as resawn.See APA RATED SIDING.

Router PatchSee REPAIRS.

oval shaped with sides tapering topoints or small rounded ends. “Router”patches have parallel sides and roundedends. “Sled” patches are rectangularwith feathered ends.

A plug may be a circular or dogboneshaped wood patch, or a synthetic fillerof fiber and resin to fill openings andprovide a smooth, level, durable surface.A shim is a long narrow wood or syn-thetic repair not more than 3/16 inchwide. Various other shapes of plugs or patches may be encountered. PS 1 specifies sizes, shapes and numbers of allowable patches in given veneer grades.

25

Boat patch

Router patch

Circular plug

Sled patch

Dogbone plug

Shim

RABBET JOINT

REPAIRS

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S

Sanded PanelsInterior, Exposure 1 or Exterior plywood panels factory-sanded forapplications where smoothness andappearance are important. These panels– with N, A or B-grade faces – are idealfor furniture, cabinets, doors, fences,signs, etc. Sanded panels save timebecause they may be finished with little or no preparation.

Sandwich PanelSee Structural Insulated Panel.

SapwoodLiving wood of pale color near theoutside of a log. Under most conditions,sapwood is more susceptible to decay than heartwood.

Scarf JointAn angled or beveled joint in plywoodsplicing pieces together. The length ofthe scarf is 5 to 12 times the thickness.

ShimSee REPAIRS.

ShiplapJointing in which ends or edges arenotch-milled to overlap and form a rabbet joint.

ScrewsUse flat head wood screws for attachingwood structural panels where nails willnot provide sufficient holding power.Sizes shown below are minimum; uselonger screws where work permits.Lubricate screws with soap if they arehard to drive. If used for sheathing, usesame spacing as recommended for nails.

SeasoningRemoval of moisture from wood toimprove its serviceability, usually by airdrying – drying by air exposure withoutartificial heat – or kiln drying – dryingin a kiln with artificial heat. Plywoodveneers are seasoned before lay-up andgluing into panels.

Shear WallSee DIAPHRAGM.

SheathingThe structural covering, usually of wood panels or boards, on the outsidesurfaces of framing. It provides supportfor construction, snow and wind loadsand backing for attaching exterior facingmaterials such as wall siding, roofshingles or underlayment in double-layer floors. APA RATED SHEATHING is recommended for conventionalapplications. See APA RATEDSHEATHING.

26

Countersink

Shank

Thread root

Shiplap jointStud

SidingPanel

Length

Thickness

SCREW SIZES

Plywood Screw Screw Drill Size Drill Size forThickness Length Size for Shank Root of Thread

(in.) (in.) (in.) (in.)

23/32 1-1/2#8 11/64 1/8

19/32 1-1/4

15/32 1-1/4#6 9/64 3/32

3/8 1

1/4 1 #4 7/64 1/16

SCARF JOINT

SHIPLAP

SCREWS

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Shop Cutting PanelPanel rejected as not conforming tograde requirements defined in theProduct Standard. Panel identification, a separate mark that does not mentionthe Standard, reads: “Shop CuttingPanel – All Other Marks Void.”Normally a “shop” panel’s defect maybe eliminated by cutting the panel intosmaller pieces for applications notgoverned by building codes.

SidingSee APA RATED SIDING.

Sill PlateThe lowest framing member of a struc-ture, resting on the foundation andsupporting the floor system and theuprights of the frame.

Single FloorA single-layer wood structural panelflooring system combining subflooringand underlayment. See APA RATEDSTURD-I-FLOOR.

Single WallSee APA STURD-I-WALL.

Sized For SpacingA notation in APA RATED SHEATHINGand RATED STURD-I-FLOOR trade-marks indicating panels may betrimmed during manufacture to lengthand width tolerances of +0, –1/8 inch.This trimming is designed to encourageproper panel spacing. See PANEL SPACING.

Sled PatchSee REPAIRS.

wood and other panel products may useeither variety, but are more commonlymanufactured of softwoods. See HARDWOOD.

Solid CoreSee PLUGGED CORE.

Sound Transmission ClassSee STC.

SpacingSee PANEL SPACING.

SoffitThe underside of the roof overhang.Wood structural panels are often usedas finishing materials for soffits.

SoftwoodWood of the coniferous or needleleavedtrees – pine, fir, spruce, hemlock – asdistinct from the hardwood of thedeciduous or broadleaved trees – oak,ash, maple, walnut. The term has only ageneral reference to actual wood hard-ness. Construction and industrial ply-

27

Closed soffit

Open soffit

Strength axis

Strength axis

SOFFITS

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Span RatingThe number that appears in the trade-mark on APA RATED STURD-I-FLOOR,APA RATED SHEATHING and APARATED SIDING panels. Two numbersseparated by a slash (e.g., 24/0, 32/16,48/24) appear on APA RATEDSHEATHING. The left-hand number isthe maximum recommended center-to-center spacing of supports in incheswhen the panel is used for roof sheath-ing with long dimension across supports(unless the strength axis is otherwiseidentified). The right-hand number isthe maximum center-to-center spacingof supports in inches when the panel isused for subflooring with long dimen-sion across supports. When a panel isapplied as wall sheathing, a rating of24 or more means the panel can beapplied to studs spaced 24 inches oncenter. A rating less than 24 means thepanel can be applied to studs spaced16 inches on center. APA RATEDSHEATHING panels may be applied aswall sheathing either vertically or hori-zontally. In all cases the panel should beapplied continuous over three or moresupports.

The single-number Span Ratings on APARATED STURD-I-FLOOR panels (16,20, 24, 32 or 48 oc) denote maximumrecommended center-to-center spacingbetween floor joists with panels laidwith long dimension across three ormore supports.

Similarly, the single-number SpanRatings on APA RATED SIDING panelsare the maximum recommended center-to-center spacings of studs (16 or24 o.c.) when the panel is applied verti-cally direct to studs (or over nonstruc-tural wall sheathing such as fiberboard,gypsum or rigid foam insulation sheath-ing). All RATED SIDING panels may be

testing. Manufactured with Exterior orExposure 1 durability classifications. Seealso APA RATED SHEATHING.

Structural Insulated PanelA section of layered construction made up of high-strength structuralwood panel faces, or “skins,” attachedto both sides of low-density core materi-als such as plastic foam or honeycombpaper fillers. Sometimes referred to assandwich panel or stress-skin panel.

StudThe basic vertical framing members ofwalls, usually 2x4s. Studs are tradition-ally spaced 16 inches on center,sometimes 24 inches as in theEngineered 24" Framing System. See SPAN RATING.

Sturd-I-FloorSee APA RATED STURD-I-FLOOR.

Sturd-I-WallSee APA STURD-I-WALL.

applied horizontally direct to studsspaced 16 or 24 inches on center, pro-vided horizontal joints are blocked.When RATED SIDING is used over APARATED SHEATHING or lumber, theSpan Rating refers to the maximumrecommended spacing of vertical rowsof nails rather than studs.

Panels with a given Span Rating may bemanufactured in more than one thick-ness, and vice versa, because of varyingpanel compositions and configurations.

Species GroupSee GROUP NUMBER.

StainsSee FINISHES.

STCSound Transmission Class. A measure ofthe ability of a wall or floor assembly toreduce noise transmission.

Stressed-Skin PanelAn engineered structural panel assemblyfor roof deck or floor applications builtof plywood sheets glued to framingmembers. The quick-covering assemblyhas greater load carrying capacity thanwould its individual members ifinstalled separately.

StringerA lumber member supporting a series of cross members. Frequently applied to stair supports.

Structural IUnsanded grade for use where shearand cross-panel strength properties areof maximum importance, such as panel-ized roofs and diaphragms. All plies inStructural I plywood panels are specialimproved grades and panels markedPS 1 are limited to Group 1 species.Other panels marked Structural I Ratedqualify through special performance

28

RATED SHEATHING


32/16 15/32 INCH

000STRUCTURAL I RATEDDIAPHRAGMS-SHEAR WALLS

PANELIZED ROOFSPRP-108 HUD-UM-40C


APA

RATED SHEATHINGSTRUCTURAL I


32/16 15/32 INCH

000PS 1-95 C-D PRP-108


APA

STRUCTURAL INSULATEDPANEL

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SubflooringAPA RATED SHEATHING panelsapplied directly over floor joists whichwill receive an additional underlaymentlayer. Wood structural panels providestrength and stiffness. They also reducethe number of floor joints as comparedwith board sheathing. See alsoUNDERLAYMENT.

SwellingSee EXPANSION and PANEL SPACING.

Synthetic RepairsSee REPAIRS.

T

T-BeamBeam resembling a “T” in cross section.Several side-by-side T-beams acting as aunit may form a floor. This principleaccounts for the increased stiffness of glued floors.

TelegraphingShow-through on a smooth overlaidplywood panel surface of underlyinggrain or defects.

edge joint is particularly efficient intransferring the load across the joint.Some APA RATED STURD-I-FLOORT&G panels measure 47-1/2 inchesacross the face.

Touch-Sanded PanelsWood structural panels “sized” to uni-form thickness by light surface sandingduring manufacture. Sander skips areadmissible. Normally applied to C-Plugged faces.

TrademarkSee APA TRADEMARK.

TrussA combination of members usuallyarranged in triangular units to form arigid framework for supporting loadsover a span. Parallel chord trusses arealso used for floor and roof supports.

Testing AgencySee APA – The Engineered WoodAssociation and QUALITY INSPECTIONAND TESTING.

Texture 1-11®

APA trade name for a special RATEDSIDING panel 19/32 inch or thickerwith 3/8-inch-wide vertical groovestypically spaced 4 or 8 inches on center.Shiplapped edges maintain patterncontinuity when installed. See APARATED SIDING.

Textured PlywoodPanels with a variety of machined sur-face textures. Available as Exterior withfully waterproof glueline for siding andother outdoor uses and for interior wallpaneling. See APA RATED SIDING.

303® Specialty SidingSee APA RATED SIDING.

Tongue-And-Groove JointA system of jointing in which the rib ortongue of one member fits exactly intothe groove of another. A speciallydesigned APA – The Engineered WoodAssociation tongue-and-groove panel

29

Gusset

Upper orcompression chord

GussetLower or tension chord

Gusset

Web membersTRUSS

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2-4-1®

Synonymous with APA RATEDSTURD-I-FLOOR 48 oc. 2-4-1 is a1-1/8-inch-thick all-veneer panel withan Exposure 1 durability classification.It’s designed for single-floor applicationsover 2x supports spaced 32 inches oncenter or over 4x supports 48 inches oncenter. 2-4-1 may alsobe used in HeavyTimber roof construc-tion. Available as specified withsquare edge ortongue-and-groovejoint. See APA RATEDSTURD-I-FLOOR.

U

UnderlaymentA material applied over subflooring anddirectly beneath nonstructural finishflooring, such as tile or carpeting. Woodpanel underlayment provides a smoothsurface for finish flooring and excellentpuncture and indentation resistance.See also SUBFLOORING, PLUGGEDCROSSBAND UNDER FACE andUNDERLAYMENT GRADE.

Underlayment C-C Plugged ExteriorAn Exterior underlayment panel with atouch-sanded C-Plugged face ply.Common uses include underlayment inconditions of severe moisture or humid-ity (bathrooms, kitchens), refrigerator orcontrolled atmospherestorage rooms, exteriorbalconies and decks,pallet bins, tanks,boxcar and truckfloors and linings, andopen soffits.

combined with insulation to controlcondensation. A vapor retarder shouldbe installed on the warm side of walls.

VeneerA thin sheet of wood laminated withothers under heat and pressure to formplywood, or used for faces of compositepanels. Also called ply.

Veneer GradeThe standard grade designations of softwood veneer used in panelmanufacture. The six grades are:

N Special order “natural finish”veneer. Select all heartwood or allsapwood. Free of open defects. Allows some repairs.

A Smooth and paintable. Neatly made repairs permissible. Also used for natural finish in lessdemanding applications.

B Solid surface veneer. Router or sledrepairs and tight knots permitted.

C Improved C veneer with splits Plugged

limited to 1/8 inch in width andknotholes and borer holes limited to1/4 inch by 1/2 inch.

C Knotholes to 1 inch. Occasionalknotholes 1/2 inch larger permittedproviding total width of all knots andknotholes within a specified sectiondoes not exceed certain limits. Limitedsplits permitted. Minimum veneer gradepermitted in Exterior plywood.

D Permits knots and knotholes to3 inches in width, and 1/2 inch largerunder certain specified limits. Limited splits permitted.

VoidSee CORE GAP.

Underlayment GradePS 1-designated, touch-sanded panelsdesigned as a base for finish flooringsuch as carpeting (and tile or linoleumwhen specified with a sanded face) andinstalled over structural subflooringsuch as APA RATED SHEATHING.These panels are manufactured witheither interior or exte-rior glue – the latterdesigned for applica-tions subject to longconstruction delays orsimilar moisture expo-sure. Underlaymentpanels are identifiedby Group number.

Unsanded PanelsInterior, Exposure 1 or Exteriorsheathing grade panels designed forutility applications and left unsanded forgreater stiffness, strength and economy.

V

Vapor RetarderA material (such as plastic film) whichcontrols moisture transmission throughwalls and other building elements. Often

30

Gypsumwallboard

Warm-side vapor retarder

Plywoodsiding

Insulation

C-C PLUGGED

GROUP 1

EXTERIOR000

PS 1-95


APA

UNDERLAYMENT

GROUP 1

EXPOSURE 1000

PS 1-95


APA

RATED STURD-I-FLOOR

EXPOSURE 1

1-1/8 INCH2-4-1

000PS 1-95 UNDERLAYMENT


APA

48ocSIZED FOR SPACING

T&G

VAPOR RETARDER

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W

WaferboardPanels manufactured from reconstitutedwood wafers, as opposed to strands,bonded with resins under heat andpressure. See also ORIENTED STRAND BOARD.

WainscotThe wooden lining of the lower part ofan interior wall.

WalerHorizontal timbers used to braceconcrete form sections.

Z

Z FlashingA Z-shaped piece of galvanized steel,aluminum or plastic installed at hori-zontal joints of panel siding to preventwater from entering wall cavity.

WarpingBending or twisting from a straight line.An improperly seasoned piece of lumbermay warp when exposed to heat ormoisture. To reduce the possibility ofwarping, protect wood panels fromdampness or moisture and follow APAspacing recommendations. Painting andwater-repellent dips will minimize mois-ture absorption. Sealing all edges andback-priming also reduces the chancesof warping in cabinet doors. See PANEL SPACING.

Water RepellentsWood preservatives with water-resistantproperties.

WebSee BOX BEAM and TRUSS.

WickingThe tendency of wood to draw moistureup through its cells by capillary actionin the direction of the grain.

Wood FoundationA residential and light frame foundationsystem utilizing pressure-preservative-treated plywood panels and wood fram-ing in place of poured concrete footingsand masonry or poured concrete walls.The system is commonly known as thePermanent Wood Foundation (PWF).The system can often be installed on aprepared site in less than half a day innearly any weather, speeding construc-tion and reducing costs. The PWF isalso applicable to crawl-space founda-tion construction.

31

Plywood concrete form

Waler

Vertical bracing

Snap tie shoe

Snap tie

Blockingbetween studs

Aluminum, plastic or galvanized steel flashing

The product use recommendations in this publi-cation are based on APA – The Engineered WoodAssociation’s continuing programs of laboratorytesting, product research, and comprehensive fieldexperience. However, because the Association hasno control over quality of workmanship or theconditions under which engineered wood prod-ucts are used, it cannot accept responsibility forproduct performance or designs as actually con-structed. Because engineered wood productperformance requirements vary geographically,consult your local architect, engineer or designprofessional to assure compliance with code,construction, and performance requirements.

FLASHED JOINT – HORIZONTAL

WALER

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P A N E L H A N D B O O K &G R A D E G L O S S A R YG L O S S A R Y

We have field representatives in most major U.S. cities and in Canada who can helpanswer questions involving APA trademarked

products. For additional assistance in specifyingAPA engineered wood products, get in touch with

your nearest APA regional office. Call or write:

WESTERN REGION7011 So. 19th St. ■ P.O. Box 11700Tacoma, Washington 98411-0700

(253) 565-6600 ■ Fax: (253) 565-7265

EASTERN REGION2130 Barrett Park Drive, Suite 102Kennesaw, Georgia 30144-3681

(770) 427-9371 ■ Fax: (770) 423-1703

U.S. HEADQUARTERS AND INTERNATIONAL MARKETING DIVISION

7011 So. 19th St. ■ P.O. Box 11700Tacoma, Washington 98411-0700

(253) 565-6600 ■ Fax: (253) 565-7265

PRODUCT SUPPORT HELP DESK(253) 620-7400

E-mail Address: [email protected]

(Offices: Antwerp, Belgium; Bournemouth,United Kingdom; Hamburg, Germany; Mexico City,

Mexico; Tokyo, Japan.) For Caribbean/LatinAmerica, contact headquarters in Tacoma.

The product use recommendations in this publica-tion are based on APA – The Engineered WoodAssociation’s continuing programs of laboratorytesting, product research, and comprehensive fieldexperience. However, because the Association hasno control over quality of workmanship or the con-ditions under which engineered wood products areused, it cannot accept responsibility for productperformance or designs as actually constructed.Because engineered wood product performancerequirements vary geographically, consult yourlocal architect, engineer or design professional toassure compliance with code, construction, andperformance requirements.

Form No. X505R/Revised April 1997/0300

www.apawood.org@Web Address:

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