Preservation of Historic WoodStructures

Ron AnthonyAnthony & AssociatesAnthony & Associates

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© The Wood Products Council 2014© The Wood Products Council 2014

The Wood Products Council isa Registered Provider with TheAmerican Institute of Architects

This course is registered withAIA CES for continuingprofessional education. As

Continuing Education Systems(AIA/CES), Provider #G516.

such, it does not includecontent that may be deemedor construed to be anapproval or endorsement by

Credit(s) earned on completionof this course will be reported toAIA CES for AIA members

the AIA of any material ofconstruction or any method ormanner ofhandling, using, distributing,AIA CES for AIA members.

Certificates of Completion forboth AIA members and non AIAmembers are available uponrequest

or dealing in any material orproduct.___________________________________________request.Questions related to specific materials,methods, and services will be addressedat the conclusion of this presentation.

Course Description

Wood structures are often historically significant and provide asense of place to local communities, creating an impetus forrenovation or adaptation providing the structure remainssound. Where good construction practices and appropriatemaintenance have been made a priority, wood structures maylast for generations, a testament to wood's potential long termdurability. This presentation will focus on considerations related

h i f d T i ill i l dto the preservation of wood structures. Topics will includefactors that affect wood performance, the basics of conductinga condition assessment and how to maximize the retention ofhi t i f b i hil t di th lif f th t t R ihistoric fabric while extending the life of the structure. Repairand replacement materials and considerations related tospecifications will also be discussed.

Learning Objectives

1. Review the science behind wood as a constructionmaterialmaterial.2. Understand how to determine the condition of woodstructural elements in an existing structure by learningabout factors that affect performance and the basics of aabout factors that affect performance and the basics of astructural assessment. This will enable the designer tounderstand the structure s ability to perform to currentcodes and regulations.

3. Discuss ways to extend the life of an existing structure,which is a crucial element in effective historicpreservation.4. Learn about considerations for repair and replacementof wood elements and ideas for better specifications.

ContextContext

Frank Lloyd Wright and Wood• Believed wood should be allowed to be

wood, not painted to look like , psomething else

• Believed in simple rather than detailedBelieved in simple rather than detailed millwork

Frank Lloyd Wright and Wood• Grew to think of wood as more of an

architectural than structural material because of perception of shrinking forests

• Not necessarily driven by durability issuesissues

Material Properties andMaterial Properties and Behavior

• Variability

• Durability

Factors Affecting WoodFactors Affecting Wood Performance

• Moisture content

• Durabilityy

Equilibrium Moisture qContent

• Depends upon relativeDepends upon relative humidity

• Is always changing• Affects wood performance• Affects wood performance

DurabilityDurability

•Natural durability due toNatural durability due to extractives

•Chemical preservatives•Remedial treatments•Remedial treatments•Finishes•Detailing

Decay Fungi

•Food

•Moisture

•Oxygen

•Temperature

InsectsInsects

•Borers tunnel through wood but d t t itdo not eat it• Bore holes contain frass

•Termites digest wood•Termites digest wood• Bore holes are clean

W h i f W dWeathering of Wood

•Moisture

•Ultraviolet light

•Abrasion

Why do we investigate wood structures?structures?

Primary reasons:

• Concerns about moistureConcerns about moisture• Concerns about deterioration• Questions about material properties• Catastrophic failure has occurredCatastrophic failure has occurred• Performance failure has occurred

Wood Assessment

• Visual• Visual• Probingg• Moisture content• Nondestructive testing

Visual Inspection, Probing andMoisture Diagnostics

Resistance DrillingResistance Drilling

Decayed Wood

Digital RadioscopyDigital Radioscopy

P 8 P 7 P6

7 84 11

1 69

53 2

11131415 12

10

B tt j i tButt jointbetweenblocking

Fracture Bolt Strength of lumber and gtimber

O ti F G diOptions For Grading

• Use current grading rules

U hi t i d t• Use historic data

• Destructive testing• Destructive testing

D i V lDesign Values

• Based on species and gradep g• Grade based on defects and

isize• Includes end-use conditionsIncludes end use conditions• Includes factor of safety

Specifications

Why write specifications?Why write specifications?To communicate between parties what is needed toparties what is needed to

minimize waste and expensep

Wood SpeciesWood Species

• Softwoods Pinus strobus• Softwoods – Pinus strobus

• Hardwoods – Quercus spp.

Di iDimensions

• Actual• Actual

• Nominal

M i t C t tMoisture Content

• Deterioration• Deterioration

• Shrinkage and swelling

Structural ConsiderationsStructural Considerations

M t i l P tiMaterial Properties

B di• Bending• CompressionCompression• Shear• Tension

Stiff• Stiffness• ConnectionsConnections

Non structural ConsiderationsNon-structural Considerations

Type of CutType of Cut

• Vertical grain or quarter g qsawn

• Flat grain or plain sawng

• Rift sawn• Rift sawn

AestheticsAesthetics Reclaimed vs NewReclaimed vs. New

TreatmentTreatment

• Wood preservatives

• Fire retardant treatment

• Stains and paints• Stains and paints

What Goes In A Specification?What Goes In A Specification?

• SpeciesDi i• Dimensions

• Moisture content• Grade

T f t• Type of cut• Treatment• Aesthetics

Repairs

P A Y E T T ERPBW +32 Quincy Street Expansion and Renovation

Q ti ?Questions?

This concludes TheThis concludes TheAmerican Institute ofArchitects ContinuingEd i SEducation SystemsCourse Ron Anthony

A th & A i t IAnthony & Associates, Inc.woodguy@anthony associates.com

P A Y E T T ERPBW +32 Quincy Street Expansion and Renovation