pryda trussed

7/24/2019 Pryda Trussed

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PRYDA FLOOR TRUSS SYSTEMS ................2

INTRODUCTION ............................................................................3

FACTORS AFFECTING FLOOR PERFORMANCE ........................4

PERMANENT LOADS....................................................................5

SERVICEABILITY...........................................................................6

SPAN TABLES ................................................................................7

RESIDENTIAL FLOORS ....................................................................7

COMMERCIAL FLOORS...................................................................8

INTERNAL WALLS.........................................................................9

INTERNAL NON-LOAD BEARING WALLS .......................................9

NON-LOAD BEARING WALLS UNDER ..........................................10

LOAD BEARING WALLS UNDER ...................................................10

EXTERNAL WALLS .....................................................................11

FLOOR OPENINGS......................................................................12

DUCTS FOR MECHANICAL SERVICES ..................................14

CANTILEVERS..............................................................................14

STRONGBACKS ..........................................................................15

STABILITY BRACING................... ..................................... ......17

SUPPORT AND CONNECTION DETAILS ................................17

FIXING AT SUPPORTS ...............................................................20

PRODUCT BENEFITS .................................................................20

PRYDA RAFTER TRUSS SYSTEMS.............21

INTRODUCTION ..........................................................................21

PRODUCT BENEFITS .................................................................21

LOADING.......................................................................................21

SPAN TABLES ..............................................................................22

SERVICES .....................................................................................23

TIE DOWN AND FIXING DETAILS ............................................23

FACTORS AFFECTING PERFORMANCE ................................23

BRACING ......................................................................................24

Information for designers on the principles behind the design of Pryda open web parallel

truss floor and rafter truss systems and to incorporate relevant details within their specifications.

CONTENTS

P R Y D A T R U S S S Y S T E M S

GUIDE TO SPECIFICATIONPRYDA FLOOR TRUSS & RAFTER TRUSS SYSTEMS

P R Y D A T R U S S S Y S T E M S

October 2004


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TOP CHORD SUPPORTEND DETAIL(Page 19)

END DETAIL

(Page 17)

STANDARDEND DETAIL

(Page 17)

STRONGBACKS

(Page 15)

STAIR OPENING DETAILS

(Page 12)

DUCTS/SERVICES

(Page 14)

EXTERNALCANTILEVERS

(Page 14)

STABILITY BRACING

(Page 17)

PRYDA LONGREACH TRUSS

(Page 3)

PRYDA SPAN TRUSS

(Page 3)

INTERNAL SUPPORTS

(Page 10)

INTERNALCANTILEVERS

(Page 14)

INTERNAL BRACING

WALLS (Page 9)PRYDA FLOOR TRUSS SYSTEMS

NOTE: Illustrations used in this gui de showing only Pryda Longreach details also apply to Pryda Span.Where Pryda Longreach and Pryda Span are shown together in the same illustration it signifies that thedetails apply to both products, but the two products should not be used together as il lustrated.


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Right Way Up Wrong Way Up

P R Y D A F L O O R T R U S S S Y S T E M S 3

Pryda Floor Truss Systems are a complete structural

system for timber floors made up of flooring material,

floor trusses, strongbacks, connections and bracing.

They have been proven over many years and provide

occupiers with floors that have an excellent andpredictably reliable performance.

The timber for these trusses is on flat, which provides a

stable platform during installation and minimises theoverall depth required. All trusses use commonly

available timber and most floor trusses in Australia are

made from 70 mm or 90 mm dry timber.

There are two different types of web systems for these

trusses. Both have timber chords but Pryda Longreach

uses all-timber webs, while Pryda Span uses metal webs

for the diagonals and timber webs for the verticals.

Both systems of Pryda floor trusses are generally made toorder by licenced fabricators. While there are standard end

details that allow trusses to be trimmed on site, this

practice is not common. This is not only because alltrusses are designed for an exact span for economic

reasons, but the interaction between the true span of the

trusses and the flooring should be considered for proper

dynamic performance assessment.

INTRODUCTION

Pryda Longreach TrussesLongreach trusses are a premium performance product

using nailplated, all-timber trusses of any depth, but

typically 300 mm deep for residential floors and 400mm deep for commercial floors.

Pryda Longreach trusses are referenced as FT200,FT250, FT300, FT350 and FT400, where FT means

Floor Truss, and 200 is the nominal overall depth

(mm). The actual depth dimensions are in nominal size

steps, or may be individually specified as required for

the particular project.

Right Way Up Wrong Way Up

Pryda Span TrussesPryda Span trusses have metal diagonal webs for lightweight and economy. They are ideal for shallower trusses

where there is more clearance room to accommodate the

plumbing than with timber webs, and for trusses where

the chord design has some reserve capacity, as is often

the case. In some instances, a few diagonal metal webs

may have to be replaced by timber webs in these trusses,

as load or geometry considerations dictate.

Webs may be on both sides of the truss, or just on

alternate sides, and in the latter case this allows for the

webs to overlap.

Pryda Span trusses are referenced as PS20, PS25,

PS30, and PS40, where PS means Pryda Span, and

20 is the nominal overall depth (cm). The overalldepths are in specific steps, but are nominally 200 to

400 mm deep in 50 mm increments. The actual depth

dimensions are in nominal size steps according to the

metal web used, and if required, the specific depth

should be obtained from the Pryda licenced fabricator.

Timber Webs

Metal Webs

PRYDA LONGREACH TRUSS

PRYDA SPAN TRUSS


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Floor liveliness, or bounce, has been an intermittent

issue over the years with lightweight residential floors -

for all forms of timber and steel construction. To

eliminate these problems, Pryda Floor Systems are

designed to stringent dynamic performance criteria.Pryda Floor Systems have three options for floor

performance that can be selected by the designer.

AS1684.1 as the minimum criteria

Pryda Normal is more stringent Extra Stiff criteria used for those who want a superior

performance overall, or for tiled areas where cracks in

the grouting due to floor movement is to be

minimised.

The floor truss is only one component that can affectthe floor performance. On-site conditions are always

important and proper attention to detail must be taken

at the time of installation.

Flooring MaterialThe flooring material has a significant effect on the

perceived bounciness of a floor. It has the ability to

spread human impact loads depending on the material

and the thickness. Plywood acts differently to

particleboard, and T&G acts differently to both. A simpleway to improve floor performance is to select flooring

that is stiffer (e.g. thicker) than the minimum for your

chosen application.

StrongbacksThese are timber members, e.g. 140 x 35 mm running

at right angles to the trusses. There is generally onerow down the centre, but there could be more with

larger spans. Their main function is to help the flooring

spread footfall impacts to adjacent trusses. They aremost effective with the thinner particleboard floors used

in residential construction and become unnecessary as

the flooring becomes more substantial for the higher

commercial loads. It is important that strongbacks be

properly attached to the truss vertical webs as detailed,

as poor fixing techniques, such as having large gaps

between the strongback and the web, can reduce the

strongback effectiveness considerably.

BearingTrusses must bear directly on their supports and not beheld above them by the flooring. This may sound odd,

but where the support top plate is not level, and the

flooring is nailed to the truss top chord, the flooring itself

can lift the lower truss(es) by a few millimetres and this

considerably worsens the perception of floor bounce.

This situation is difficult to observe during the early

stages of construction and in any instance of potentialfloor performance complaint it should be checked using

a piece of card to see if there are any gaps between the

trusses and their supports.

Supporting BeamsIf any floor system is supported on beams e.g. steel ortimber lintels/beams the amount of floor bounce in that

area can become unacceptable if it is not properly

assessed at design time. The dynamics of anysupporting beam and the dynamics of the truss must be

considered simultaneously as they interact with each

other. Each can be satisfactory in its own right, but not

satisfactory in combination.

Pryda Longreach TrussesPryda Longreach can be designed for all common floor

loads, including commercial loadings up to 5 kPa orpoint loads up to 6.7 kN. These trusses are slightly

heavier than Pryda Span trusses and being all-timber

generally have a stiffer performance as they can

dissipate floor vibrations very well, and the nailplates

connecting the webs and chords are quite substantial.

Pryda Span TrussesPryda Span are manufactured using light gauge metal

webs and are lighter than Longreach, but this is

considered during the design process. The metal websystem can be very cost-effective, especially if the truss

chords have reserve capacity, as is often the case.

FACTORS AFFECTING FLOOR PERFORMANCE

P R Y D A F L O O R T R U S S S Y S T E M S4


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Permanent (dead) loads which are considered during the

design process include:

Self-weight of the truss

Flooring (particleboard, T&G, plywood, etc)

Floor covering (carpet, ceramic tiles, etc) Ceiling (plasterboard, battens, etc) Temporary (live) loads such as furniture which may be

in place for long periods of time. These are taken as

500 Pa irrespective of the magnitude of actual design

live load.

Typically, the flooring, floor covering, self-weight andceiling under amount to approximately 410 Pa for

residential floor truss designs.

Spa BathsThe load imposed by a standard bath can be ignored

when selecting floor trusses, but spa baths need special

attention due to the higher loads that can be imposed.The self-weight of the spa shell and the support base

also adds to the load on a floor truss. Reducing the floor

truss spacing may cause issues with plumbing and sothe alternative is to select a design span which is

greater than the actual span when estimating from the

span tables.

A large corner spa (1.5m x 1.5m x 0.5m) has a water

capacity of approximately 250 litres. A design span

that is 1.3 times longer than the actual span can be

adopted. A feature spa (1.5m x 1.5m x 0.6m) has a water

capacity of approximately 450 litres.

For actual spans of less than 3.0m - adopt adesign span equal to 2 times the length of the

actual span.

For actual spans between 3.0m and 4.5m - adopt

a design span equal to 1.7 times the length of the

actual span.

For actual spans greater than 4.5m - adopt a

design span equal to 1.4 times the length of theactual span.

These rules are illustrated by the following example:

Feature spa bath loaded on a FT300 floor truss

with a span of 3500 mm.

From Longreach Residential Span Table: Normally

the top and bottom chord sizes are 90 x 35

MGP10.

Using the design rule: 3500 mm x 1.7 = 5950 mm.

Refer to Table again: Chord sizes are increased to

90 x 35 MGP12 to allow for spa load.

If these rules for spa baths are not appropriate because

they require an increase in floor truss depth as well as

change in chord grade and size, then an alternative

method may be used. Spa bath loads may be allowed

for by simply reducing the spacing to a third of the

original spacing under normal conditions. Therefore, in a

floor truss layout with a spa bath over, the spacingshould be reduced to 150 mm (for 450 mm crs) or 200

mm (for 600 mm crs) for the width of the bath.

Water BedsA queen size waterbed is expected to weighapproximately 450 kg. For waterbeds with a holding

capacity of up to 600 litres adopt the same design rules

as for feature spas.

Other Heavy LoadsWhere special load cases are to be applied to the floor

trusses such as heavy ceramic tiles, extra stiffness may

be desired in the flooring system to minimise potential

cracking in the tile grout. This can be achieved by

adopting a design span equal to at least 25% greater

than the actual span of the truss.

Generally, other heavy furniture items, such as a grand

piano, could be allowed for in a similar manner, howevercheck with a Pryda design office first, as large point

loads can be critical.

Designers should advise the Pryda licensed fabricatoron the magnitude of these loads once they have

identified the size and capacity of the feature.

Temporary LoadsTemporary (live) loads are the transient loads that are

placed on the floor and are mainly due to construction

loads, people, furniture, storage, etc. These loads are an

estimation of the temporary occupancy and the

associated use of the room that the floor supports.

Typically, the trusses are designed for a distributed live

load and a concentrated load, taken separately whichever produces the most adverse effect.

Typical live loads in AS1170.1-1989 are:

Houses general areas: 1.5 kPa / 1.8 kN (see

span tables)

balconies: 3.0 kPa / 1.8 kN

Bedrooms and private rooms in apartment buildings:

2.0 kPa / 1.8 kN

Offices in retail or industrial premises: 3.0 kPa / 6.7

kN (see span table)

Public corridors in institutional buildings such as

schools: 4.0 kPa / 4.5 kN

Assembly areas without fixed seating in institutionalbuildings: 5.0 kPa / 3.6 kN

PERMANENT LOADS


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Deflection LimitsPryda floor trusses are designed to be within deflectionlimits set out in AS1684.1-1999. Further deflection limits

have been adopted based on research and experience

to produce trusses that exhibit greater stiffness than theminimum. It is believed that unsatisfactory floor vibration

issues can be minimised by designing trusses under a

normal or extra stiff classification in the Pryda Floor

software. The domestic live load span table is designed

according to AS1684.1-1999 criteria.

Load Condition AS1684.1 Normal Extra stiff

Design live load L/300 L/480 L/600

1500 Pa live load 9.0 mm 9.0 mm 7.0 mm

Dynamic CriteriaDynamic limits have been established to further ensure

that the floor trusses are acceptable with regard to

springiness or bounce. Along with the deflection

limits, these dynamic limits are based on extensive

research and scientific investigation in Australia and

overseas to ensure the comfort of the building

occupants.

Load Condition AS1684.1 Normal Extra stiff

300 Pa live load Freq > 8Hz Freq > 10Hz Freq > 12Hz

1 kN live load 2.0 mm 2.0 mm 1.5 mm

Special Note: The dynamics of a flooring system are

characterised by the perceived frequency of vibration in

the floor under a specific load. The rigidity of thesupporting structure can have a significant effect on the

dynamics of a flooring system. For example, a joist

supported by rigid walls will seem to exhibit less bounce

when walked upon than the same joist supported by

flexible beams that permit some level of support

movement.

It is the responsibility of the building designer to ensure

that the combined frequency of vibration of the flooring

system is adequate. The Span Tables assume a rigid

and adequately designed supporting structure. Providinga less than adequate supporting structure will have an

impact on the serviceability qualities of the flooring

system.

Pryda design offices use software that can check the

effect of trusses which are sitting on flexible supports,

and advice in this area is available to specifiers.

SPECIAL CONDITIONS

Residential, Commercial or Essential Building

Importance

The classification of building importance according toAS1720.1-1997 is a means of providing different

capacity factors for primary structural elements in

buildings other than houses. In most cases a floor joist

is not a primary structural element in any of these

building classifications, and this is the assumption usedin the span tables.

Pryda Floor software utilises the different capacity

factors in cases where floor trusses support significantadditional roof and/or floor loads in a commercial or

essential services building. For example, a floor truss

supporting a concentrated girder load from an internal

loadbearing wall needs special consideration.

Bearing at SupportsIt is important that floor trusses bear over the support

wall plate or beam with a minimum of 30 mm for

residential floors and 40 mm for commercial floors.

This requirement is implemented to ensure that localisedcrushing of the top plate or bottom chord does not

occur. It also encourages suitable load transference

between upper loadbearing wall frames and lower wall

frames.

No Ceiling UnderneathIf there is no ceiling fixed directly underneath the

trusses, install 90 x 35 F5 (on flat) lateral ties to the

bottom chord, located approximately at the third points

of the span. This will prevent one type of undesirabledynamic response which is otherwise normally

prevented by the ceiling (if fixed directly to the truss

bottom chords) or ceiling battens.

SERVICEABILITY




These span tables are for indicative purposes and

represent only a small selection of the possibilities.

Specific designs can be prepared on request for different

timber choices or for different loading requirements.

FlooringThe span tables have been developed using a design

method that assumes the minimum flooring requirement

for the associated load criteria. Although the self-weight

of the flooring material contributes to the dead load onthe truss, it is the stiffness of the flooring that has a

significant effect on the performance of the trusses

under live loading. It is assumed that there is no

composite action between the floor and truss however

the floor fixings do offer lateral restraint to the top chord.

All the trusses shown are assumed to be bottom chord

supported. If the truss is required to be supported by

the top chord, select 45 mm minimum chord thickness

for the top chord to allow sufficient area to fit the end

vertical nailplates.

Australian StandardsThe span tables in this Guide to Specification and the

designs produced by the Pryda Floor software comply

with the following standards:

AS1170.1-1989 SAA Loading Code. Part 1: Dead and

live loads and load combinations

AS1684.1-1999 Residential timber-framed construction.

Part 1: Design criteria.

AS1720.1-1997 Timber Structures. Part 1: Design Methods

SPAN TABLES

PRYDA LONGREACH FLOOR TRUSSES - MAXIMUM SPANS

Residential loads (1.5 kPa / 1.8 kN)

Truss Chord size and grade (TC and BC) Clear depth Max. pipe dia O/A O/A

Reference90x35 P10 90x35 P12 90x45 F17

between within web depth depth

450 crs 600 crs 450 crs 600 crs 450 crs 600 crschords (mm) profile (mm) 35/35 45/45

FT200 4200 3300 4700 4200 5300 4800 120 80 190 210

FT250 5000 4100 5400 4900 6100 5500 170 130 240 260

FT300 5400 4400 6000 5400 6700 6100 220 180 290 310

FT350 5700 5200 6600 6000 7400 6600 270 230 340 360FT400 6400 5400 7100 6400 7900 7200 320 280 390 410

PRYDA SPAN FLOOR TRUSSES - MAXIMUM SPANS

Residential loads (1.5 kPa / 1.8 kN)


Reference90x35 P10 90x35 P12 90x45 F17


450 crs 600 crs 450 crs 600 crs 450 crs 600 crschords (mm) profile (mm) 35/35 45/45

PS25 4900 4200 5300 4800 6000 5200 170 150 240 260

PS30 5400 4500 5900 5300 6700 5800 220 190 290 310

PS40 N/S N/S N/S N/S 8000 7000 332 260 N/S 422

N/S = not suitable

RESIDENTIAL FLOORS

The trusses here have been designed to the followingcriteria:

1.5 kPa distributed load, or 1.8 kN concentrated load

applied over 19 mm x 19 mm

19 mm particleboard flooring (450 mm crs) and 22

mm (600 mm crs) with 10-13 mm plasterboard ceiling

Top chord panel lengths should not exceed 550 mm

for Longreach trusses. Panel lengths for Pryda Spantrusses are preset at about 600mm.

Deflection limits as for solid floor joists in AS1684.

A 10% reduction in maximum span will increase thefloor stiffness by 30%.

All timber webs are 35 mm thick. Metal webs are

generally as pairs at the truss ends, but are reduced

to singles on alternating faces if the force in the webs

is small enough to warrant it.

Any duct space must not exceed 500 mm in length,

and must be located within the centre half of the span.

Prefix P denotes MGP, e.g. P10 means MGP10 F17 and P15 chords of the same size are

interchangeable.


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COMMERCIAL FLOORS

The trusses here have been designed to the following

criteria:

3.0 kPa distributed load, or 6.7 kN concentratedload applied over 100 mm x 100 mm

25 mm F11 plywood flooring diaphragm. Any

substitute should have a similar or better stiffness. 10-13 mm plasterboard ceiling.

Top chord panel lengths should not exceed 550 mm

for Longreach trusses, except that for 90 x 35 P12

chords it must not exceed 450 mm. Panel lengths for

Pryda Span trusses are preset at about 600mm.

All diagonal timber webs are 45 mm thick. All metal

webs are in pairs.

Any duct space must not exceed 300 mm in length,

and be located within the centre half of the span.

Prefix P denotes MGP, e.g. P10 means MGP10

F17 and P15 chords of the same size areinterchangeable.

These trusses are inherently much stiffer than the

residential designs, and will not produce any perceived

bounce problems.


PRYDA LONGREACH FLOOR TRUSSES - MAXIMUM SPANS

Commercial loads (3.0 kPa / 6.7 kN); 450 mm centres


Reference90x35 P12 90x35 F17 90x45 P12 90x45 F17


chords (mm) profile (mm) 35/35 45/45

FT250/3 4500* 4600 4900 5200 170 130 240 260

FT300/3 5200* 5400 5600 6000 220 180 290 310

FT350/3 5800* 6100 6400 6700 270 230 340 360

FT400/3 6300* 6700 6900 7400 320 280 390 410

FT450/3 6900* 7300 7600 7900 370 330 440 460

* TC panel length not to exceed 450mm

PRYDA SPAN FLOOR TRUSSES - MAXIMUM SPANS

Commercial loads (3.0 kPa / 6.7 kN); 450 mm centres


Reference90x35 F17 90x45 P12 90x45 F17


chords (mm) profile (mm) 35/35 45/45

PS25/3 4400 4600 4800 170 150 240 260

PS30/3 5100 5300 5500 220 190 290 310

PS40/3 N/S N/S 7000 332 260 N/S 422

N/S = not suitable



INTERNAL WALLS

These details refer to all internal walls which are non-

loadbearing for gravity loads, but which may also be

wind bracing walls. If the floor is to carry loadbearing

internal walls, do not use these Span Tables and check

with a Pryda design office for a specific design.

The floor truss system requires no additional stiffening

when supporting non-loadbearing walls, however

special consideration is required for non-loadbearingwalls acting as wind bracing walls. Specifiers should

notify the Pryda licenced fabricator of wall bracing

positions and capacities.

Bracing walls parallel to thefloor trussesIf the wall is positioned between two floor trusses and is

a wind bracing element with a capacity of no more than1.5kN/m and does not exceed 2.7m high, fix noggings

at each end of the bracing element to transfer wind

forces to the adjacent trusses. Use 2/14gx100mm

Timberfixx screws to fix the bottom plate of the bracingelement into the nogging, and 12gx65mm Timberfixx

screws to fix the bottom plate to the flooring at 450mm

centres along the length of the bracing element. For

wind bracing wall capacities of up to 3.0kN/m fix a

120x45 MGP10 strongback to the vertical web nearest

the end of the bracing element. The strongback will

pass through two trusses either side of the wall and fixto the webs with 2/12gx65mm

Timberfixx screws. The flooring

material shall be nailed andglued to all floor trusses in the

flooring system.

If a bracing wall sits directly over

a floor truss then fix 14gx100mm

Timberfixx screws into the truss

at 450mm centres along the

length of the bracing elementalong with 2/14g x 100mm

screws at each end for 1.5kN/m

wind bracing capacities. Use 4

screws at each end with the

strongback detail as outlined

above for up to 3.0kN/m windbracing capacities.

Bracing walls perpendicular to thefloor trussesFor wind bracing walls of up to 1.5kN/m wind bracing

capacity with the element no higher than 2.7m, use

14gx100mm Timberfixx screws to fix the bottom plate of

the bracing element to each perpendicular floor truss. If

the end of the bracing element finishes directly above a

floor truss use 2/14gx100mm Timberfixx screws, and ifnot then use the same screws into the nogging as

previously mentioned. For wind bracing walls of up to

3.0kN/m capacity adopt the same details as for bracingwalls parallel to the floor trusses. The flooring material

shall be nailed and glued to all floor trusses in the

flooring system.

Platform FlooringWhere a structural platform floor has been constructed

over the trusses, any non-loadbearing wall parallel tothe trusses does not require additional support other

than that of the platform flooring.

INTERNAL NON-LOADBEARING WALLS

Max. Wind Brace

Capacity of 1.5kN/m

Internal Bracing Wall

Fix Bracing Wall to Nogging

Using 2/14g x 100mm

Timberfixx Screws at

Each Floor Truss Crossing

Under Bracing Element

3/3.75 x 90mm Nails Fixing

Nogging to Upright Member

3/3.75 x 90mm Nails

Fixing Upright to Top

And Bottom Chords2/12g x 65mmTimberfixx Screws

to Strongback120 x 45mm F5or

MGP Upright Member

End of

Bracing

Element

Fix Bracing Wall to Nogging Using 2/14g

x 100mm Timberfixx Screws

120 x 45mm F5orMGP Nogging

PARALLEL BRACING WALL

PERPENDICULAR BRACING WALL

Max. Wind Brace Capacity of 1.5kN/m

Internal Bracing Wall

Fix Bracing Wall to Nogging Using 2/14gx 100mm Timberfixx Screws

3/3.75 x 90mm Nails Fixing

Nogging to Upright Member3/3.75 x 90mm Nails Fixing

Nogging to Top And Bottom Chords

For wind bracing capacities of up to 3.0kN/m extend a 120 x 45mm

MGP10 strongback through two trusses either side of bracing wall

at the nearest vertical web. In the 3.0kN/m case adopt an M10 bolt

connection through nogging rather than screws and use 12g x

65mm Timberfixx screws elsewhere instead of 3.75 x 90mm nails.

2/12g x 65mm Timberfixx Screws

120 x 45mm F5orMGP

Upright Member

Length of

Bracing ElementMax.

2700mm

HighWall

75mm Nails @

150mm Centres

120 x 45mm F5orMGP10 Nogging


10/24

Important: Should an internal wall be required tosupport floor trusses, this intention should be made

abundantly clear on both the trusses and the truss

layout. The supporting structure, footings, etc. should

then be designed to cope with the high wall loads that

can result.

Internal lower storey walls can be used for support tocreate single length trusses across the width of the

building. Preferably, a double web with a gap will cater

for small deviations in support positions, while a block

insert of up to 600 mm in length will accommodate

larger deviations. Alternatively, if the exact location of

the support is known, then a vertical web can bedetailed at the support point.

P R Y D A F L O O R T R U S S S Y S T E M S1 0

NON-LOADBEARING WALLS UNDER

Floor trusses must be adequately supported on the

loadbearing supports nominated in the design. There

may be a detrimental effect on the walls and the flooringsystem if the trusses bear on a non-loadbearing wall.The tops of internal non-loadbearing walls need lateral

stabilising by fixing to the truss bottom chords. The

trusses must be allowed to deflect downwards, so

Pryda Partition Hitches have been developed for thispurpose, which should be nailed to the truss near thetop of the slots.

LOADBEARING WALLS UNDER

Internal Support Types

Fitted FlooringWhere a fitted floor is being used,

locate a double truss under each

wall to provide support to both the

wall and flooring. Alternatively, usesupplementary ledger plates fixed

to the side of the floor trusses.

Fitted Flooring

Non-Loadbearing Wall

Fitted Flooring

Non-Loadbearing Wall

FITTED FLOOR FIXING

DOUBLE TRUSS

FITTED FLOOR FIXING

SUPPLEMENTARY LEDGER PLATES

Single Web

Internal Support Wall

SINGLE WEB SUPPORT

Double Web

Internal Support Wall

DOUBLE WEB SUPPORT

45mm Thick Block

(Solid or Claw Joined)

250

or DeeperMax. 600mm

Internal

Support Wall

NAILED BLOCK SUPPORT


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These details are for floors that support external

walls loadbearing and non-loadbearing

WALL DETAILS

Fully Supported End TrussWhere the end floor truss is supported along

its full length by a lower storey wall or bycontinuous base brickwork or footing while

carrying an upper storey wall above, a

simplified floor truss, as shown, may be used.

End Truss Under Gable RoofWhere the end floor truss is located under a gable end

roof and is free spanning, it is appropriate to use a

single floor truss as it is carrying a non-loadbearing walland floor only.

End Truss Carrying RoofLoads OverWhere a free spanning end floor truss is carrying roof

loads along its length transferred from the wall above

then it is necessary to use one or more special floor

trusses under this wall. This will depend upon the RoofLoad Width (RLW) being carried and the weight of the

roof materials. A guide to floor truss requirements for

these conditions are in the following table, otherwisethese trusses must be specially designed and require

further consultation with a Pryda design office.

No. of floor trusses required

Maximum RLW Concrete Tiles Metal Roofing

1800* 2 1

* Refer to AS1684-1999 for RLW description

EXTERNAL WALLS

Offset Loadbearing WallsPryda floor trusses selected using this Guide are not

designed to support offset loadbearing walls. If these

walls supported by floor trusses are required to carry

roof or other loads, please refer to a Pryda licensedfabricator for an individual design.

Diagonal Webs at Max.

6000mm Centres

Additional Block Required

For Loadbearing Jamb Stud Above

Modified Floor Trusses

Jamb Studs With Lintel Over

FULLY SUPPORTED END TRUSS


12/24P R Y D A F L O O R T R U S S S Y S T E M S1 2

Pryda floor trusses can be

detailed to suit an opening

in a floor, eg as required to

accommodate stairways.

A header beam is normallyrequired to support the

incoming trusses while adouble lamination standard

truss is often suitable to carry

each end of the header beam.

Block DetailAlternatively, a solid block (600 mm long) fixed to the

side of the trusses may support the header beam. The

header beam may be notched into the solid block or

fixed to the block using a Pryda Joist Hanger as shown.

FLOOR OPENINGS

Beam Pocket DetailThe trusses need to be detailed with a beam pocket wide enough

to fit the header beam as shown. The header beam should be

blocked hard up against the underside of the carrying floor trussesand nailed to each vertical web with 4/3.15 x 75 mm nails.

Stairway Parallelto TrussesUse the following charts to

determine header beam

specifications and also chordspecifications for the double

lamination floor truss for Load

Case 1 only. The header beam

(max. 2000mm span) supports

the curtailed floor trusses and

stair loadings from the upper

flight of stairs.

Curtailed Truss Span

Double Truss

Header Beam

Opening

FLOOR OPENINGS

Solid Packing Under

Header Beam

BEAM POCKET

Header Beam

35mm Solid Block Fixed To Side

of Truss With 75 x 3.75mm Dia.

Nails at 50mm Centres

Pryda Joist Hanger

PRYDA JOIST HANGER SUPPORT Header Beam

Pryda Triplegrip

35mm Solid Block Fixed

to Side of Truss With 75 x

3.75mm Dia. Nails at

50mm Centres

600mm

NOTCHED HEADER SUPPORT

Double Supporting Truss

Max. 2000mm

Header BeamSupported byDouble Floor Truss

Header Beam Carrying Curtailed

Floor Trusses And Stair Load From

Upper Flight of Stairs Only

Max. 3000mm

Max. 7500mm

LOAD CASE 1 STAIRWAY PARALLEL TO TRUSSES


13/24

StairwayPerpendicularto TrussesUse the following charts

to determine header

beam specifications

and also chord

specifications for the

double lamination floor

truss for Load Case 2only. The 900mm wide

stairway runsperpendicular to the

curtailed floor trusses

and the header beam

(max. 3500mm span)

supports the trusses.

P R Y D A F L O O R T R U S S S Y S T E M S 1 3

HEADER BEAM SELECTION CHART

Maximum floor truss span (mm) onto header beam

Maximum Header beam

Supported Floor (max. 3500mm)

Truss Span (mm)

1000 190 x 45 F17 or 200 x 45 Hyspan LVL

2000 240 x 45 F17 or 240 x 45 Hyspan LVL

3000 2/240 x 35 F17 or 240 x 63 Hyspan LVL

4000 2/240 x 45 F17 or 2/240 x 45 Hyspan LVL

5000 2/290 x 45 F17 or 2/300 x 45 Hyspan LVL

HEADER BEAM

SELECTION CHART

Maximum Header beam

Supported Floor (max. 2000 mm span)

Truss Span (mm)

1500 190x45 P12 or 200x45 Hyspan LVL

2500 190x45 F17 or 200x45 Hyspan LVL

3500 190x45 F17 or 240x45 Hyspan LVL

4500 240x45 F17 or 240x45 Hyspan LVL

5500 240x45 F17 or 240x45 Hyspan LVL

SUPPORTING FLOOR TRUSS SELECTION CHART

Chord selection requirements for double floor truss

Truss Supported floor truss span (mm)

depth1500 2500 3500

250 90 x 45 P12 N/A N/A

300 90 x 35 P12 90 x 45 F17 N/A

350 90 x 35 P12 90 x 45 F17 N/A

400 90 x 35 P12 90 x 45 P12 90 x 45 F17

Note: In this load case the header beam and the supporting floor trusses have been designed to support stair loadings

however the stairs must be self- supported at the mid-landing level. MGP15 may be used in place of F17 timber. These

tables are only applicable to load case 1.

SUPPORTING FLOOR TRUSS SELECTION CHART

Chord selection requirements for double floor truss

Truss

Supported floor truss span (mm)

depth 2000 3000 4000 5000

250 90x45 P12 90x45 P12 N/A N/A

300 90x35 P12 90x45 P12 90x45 F17 N/A

350 90x35 P10 90x45 P10 90x45 P12 90x45 F17

400 90x35 P10 90x45 P10 90x45 P12 90x45 F17

Note: Stair load on to double lamination floor truss is

considered. MGP15 may be used in place of F17 grade

timber. These tables are only applicable to Load Case 2.

(mm)

Double Trusses

Header Beam Supported

by Floor Trusses

Curtailed

Trusses

Max. 3500mm

900mm

Max. 6000mm

Beam Pocket

LOAD CASE 2 STAIRWAY PERPENDICULAR TO TRUSSES



External Cantilevered BalconiesThese details concern the cantilever which forms a

balcony generally outside the room. Cantilevered

balconies can be used with the standard floor trusses

under certain conditions. If these conditions cannot be

met, the trusses will need specific design. The live load

on balconies is twice as high (3 kPa) as the normal

residential floor loads (1.5 kPa).

Pryda floor trusses can be designed to cantilever as a

continuous truss, or alternatively a timber joist may be

fixed to the side on site as shown below. It is importantthat the fabricator is notified prior to manufacture.

Balcony cantilever joists should be sized according to

the framing manuals, but must be restricted to a length

of no more than one quarter of the internal truss span.

DUCTS FOR

MECHANICAL

SERVICES

The open web configuration of Pryda floor trussespermits ductwork and mechanical services to pass

through the depth of the truss. Under domestic loads,

Pryda Span and Longreach floor trusses may be

detailed with voids up to 500 mm long near the centre

of the span. The span tables show depth clearances

and the maximum pipe diameter that can beaccommodated without special designs being required.

Pryda Floor software permits duct spaces to be detailed

anywhere along the length of the truss, under specificdesign.

There are three common types of cantilevered balconies

internal, external, and those which support offset walls

above.

Internal CantileversFound in two-storey construction where the first floor

trusses are cantilevered only a small amount as an

architectural feature. These cantilevers are built as a

simple extension to the truss, with vertical webs

introduced at the point of support.

CANTILEVERS

Max. 500mm

Max. Pipe Dia. Permitted In-Between

Web Profiles (Refer Span Tables)

Max. Clear

Depth

CENTRE GAP FOR MECHANICAL SERVICES

Floor Truss

Span

Cantilever Length

INTERNAL CANTILEVER DETAIL

Cantilever Balcony

Beam to Suit75mm x 3.75mm Dia. Nails at Max. 200mm

Centres Along Chords and Webs

Floor Trusses

Balcony

Joists to Suit

Not Less Than

Balcony Cantilever

BalconyCantilever

EXTERNAL CANTILEVER



The cantilever balcony beam shall run a similar distance

back into the floor truss and at least to the next vertical

web past that distance. The cantilever joists are to be

fixed to the truss bottom chord and vertical webs with

3.75 mm dia nails (75 mm long into 35 mm joists and 90mm long into 45 mm joists) at maximum 200 mm centres.

Note: These cantilever details are not intended for

cantilevers carrying loadbearing walls over. In thisinstance, refer to a Pryda design office for special

design.

Offset Wall CantileverA common cantilever issue encountered is one in which

the timber clad second storey frame is offset 150 mm

outside the lower storey frame. This permits the upper

storey external wall cladding to finish flush with the

lower storey brickwork. As a result, the floor trusses are

cantilevered to support the upper storey roof loads andtransfer these down to the foundations via the lower

storey walls. Often this issue occurs parallel and

perpendicular to the span of the floor trusses.

Strongback beams run perpendicular to the trusses and

are used to spread footfall impact loads to adjacent

trusses. They are required for all residential floors and

some of the lighter commercial floors.

Strongbacks are not required for trusses up to 3.5m inspan. For trusses 3.6m to 7m span, use one row of

strongbacks located close to midspan. For trusses

above 7m span use 3 rows of strongbacks located onerow at midspan, and two further rows located at each of

the quarter points.

Strongbacks should be fixed hard up against the vertical

web, but may be fixed up against the top chord or the

bottom chord to suit. Fixings may be hand hammered

75 x 3.75 nails, or power driven 75 x 2.9 nails, or 12g

11 x 65 Timberfixx screws. While screws are more

expensive, they provide the best performance as theyare more rigid, they clamp the timber components

together, and they prevent squeaks due to various floor

components loosening over time.

Where Pryda Span trusses have been used, and there is

no vertical web close to the desired location of the

strongback, a supplementary vertical web may be nailed

to the side of the truss instead with 2 nails to the top

chord and to the bottom chord, to provide a fixing for

the strongback.

STRONGBACKS

Upper Storey

Loadbearing Wall

Min.

250mm

150mm

Solid Blocking

(Min. F5)

Min.300mm

CANTILEVER PERPENDICULAR OFFSET

UPPER LOADBEARING WALL

Solid Block to Suit Truss

Depth (Min. F5) Trimmer Plate

Upper Storey

Loadbearing Wall

- Max.5000mm RLW

- Conc.Tile Roof

600mm

Skew Nail

Pryda Triple Grips

Floor Truss

90 x 35mm F5 Pole Plate

Fixed to Top Chord And

Vertical Webs With 75 x

3.75mm Dia. Nails (200mm

Centres Into Chord)

Lower Storey

Loadbearing Wall

150mm

Min.

250mm

CANTILEVER PARALLEL OFFSET UPPER LOADBEARING WALL

Strongback Size

as Per Table

LONGREACH STRONGBACK

Strongback Size

as Per Table

PRYDA SPAN STRONGBACK


16/24

Strongback Size Selection

STRONGBACK BEAM SELECTION

Nominal truss Strongback depth and No. of fixingsdepth (mm) grade (all 35 mm thick) per connection

200 90 F5/P10 or 70 F17 2/nails or 1/screw

250 120 F5/P10 or 90 F17 3/nails or 2/screws




In locations where the strongback needs to be joined,

either of the following methods may be used:

Non-aligned StrongbacksIn cases where different adjacent spans cause thestrongbacks to be out of alignment, the following detail

may be adopted. Vertical blocks of 90 x 35 mm are fixed

with 2/3.75 dia x 75 mm nails to both top and bottomchords. Strongbacks are then fixed into the side of the

block and the preceding vertical web with the number of

nails specified in the table.

Strongbacks Not Required

Strongbacks may be omitted from floors when:

The floor has been designed for live load of 3000 Pa

and 4.5 kN, or greater.

Either 25 mm F11 plywood, or 2 layers of 19 mm F11

plywood (or better) has been used

In these situations, either the truss will be very stiff dueto the high design load, or the flooring itself is capable

of dissipating human footfall impacts.

Instead, use 90 x 35 F5 (on flat) lateral ties fixed to thebottom chord, located 3000 mm apart (max.).


Overlap

Strongback at

Vertical Webs

STRONGBACK SPLICE

Min. 5/3.75mm Nails

Each Side of Joint

Splice Strongback Together

With Cleat on Side

ALTERNATE STRONGBACK SPLICE

Additional Block

Max. 600mm

Vertical Web

NON-ALIGNED STRONGBACKS


17/24

Pryda floor trusses must be braced back to their

supporting structure for stability in a similar manner to the

bracing stipulated by AS1684-1999 for solid deep joists.

Use diagonally placed Pryda Strapbrace or timber braces

(minimum thickness of 25 mm) at 2700 mm centresmaximum at the ends of trusses and at any internal wall

supports. Alternatively, a continuous trimming beam maybe used at the end of each truss see End Type 3 - with

diagonal bracing at the end bays only. This bracing does

not substitute for wind bracing.

Pryda floor trusses are braced laterally at the top chordlevel by the flooring material and at the bottom chord level

by the ceiling lining. If there is no ceiling fixed directly (or

by battens) then 90 x 35 binders must be provided on thebottom chord at 3000 mm centres maximum.

Pryda floor trusses have the advantage of adapting to

a range of different on-site support conditions.

The dimensions of the 12 standard end types can varyto meet most detailing requirements. The joint details

shown in this manual are intended as a guide only.

Variations to these may be required and should be

verified.

End Type Details

End Type 1

Most common end type for bottom chord bearing on

wall plate or steel section while also permitting upper

wall frame to bear directly above. May also be used for

connection to framing brackets.

End Type 2

Similar purpose as End Type 1, however permits timber

end bracing trimmers to provide lateral stability. It also

accommodates minor site variations by allowing the

setbacks to be curtailed if need be.

P R Y D A F L O O R T R U S S S Y S T E M S 1 7

STABILITY BRACING SUPPORT AND

CONNECTION DETAILS

Length of Pryda Strapbrace to Suit Height of Trusses

Min. 2/3.15mm x 30mm Pryda Nails

Into Side of Top Wall Plate

and 2 Nails to Underside

Max. 2700mm Centres

90 x 35mm F5

2/75mm Nails

Into Vertical

Web

Max. 1800mm Centres

Fix Trimmer to Ends of Floor Trusses With

2/3.15mm Dia. x 75mm Nails

End Trimmer

Note: End Brace Requires Diagonal

Bracing Down to Wall at Each End

of a Bay of Trusses

Min. Bearing 30mmWall Plate

CANTILEVER SUPPORT



Block

Supporting

Trimmer

End TrimmerLoadbearing Wall

Top Chord Extension of Any

Length to Maintain Floor Level

Primary Bearing

Point Min. 30mm

End Type 3

Accommodates ease of installation of timber end

bracing trimmers while also supporting upper

loadbearing wall frame. It acts as an additional bottom

plate and supports the edge of the sheet flooring.

End Type 4

Suitable for bottom chord bearing on the bottom flange

of a steel channel or universal beam while also

maintaining floor level above top flange.

End Type 5-1

Flexible end type that comprises of a solid block insert

nailed into position through top and bottom chords. The

resulting I-beam end is bottom chord supported and

can be cut back on an angle to suit steel sections.

End Type 5-2

This version of End Type 5 has a full width end block

that is cut back to accommodate an upper storey

loadbearing wall set back from the lower storey.

End Type 5-3

Alternatively, End Type 5 with a full width end block is

suitable for cantilevering over lower storey walls and

carrying upper storey load bearing walls.

End Type 6-1

Standard bottom chord bearing with the capacity totransfer high loads from upper loadbearing walls.

High Load Wall

Max. 300mm

Min. 100mm

Max. 80mm

Max.

150mm

Max.

300mm

Max. 300mm

Max. 200mm



Skew Nails Preferable Into

Beam to Restrain Bottom Chord

Min. Bearing 30mm

Min. Top Chord Bearing 30mm

Max. 110mm

Max. 35mm

Min. Bearing 30mm on

Primary Bearing Point

Min. Bearing 30mm on

Primary Bearing Point

Overhang Any Length

End Type 6-2

End Type 6 also provides extra timber nailing area when

supporting trusses in Pryda joist hangers.

End Type 7-1

Top chord support on wall frames, floor beams andwaling plates. Promotes easy installation. It is advised

that bottom chord should be restrained (skew nailsminimum) to obtain best results.

End Type 7-2

Top chord support on wall frames, floor beams and

waling plates. Promotes easy installation. It is advisedthat bottom chord should be restrained (skew nails

minimum) to obtain best results.

End Type 8

Similar purpose to End Type 7 however the level ofthis truss is not governed by the supporting member.

This end type also permits the floor trusses to support

higher loads.

End Type 9

Permits the floor trusses to be supported on the top

chord while also housing the supporting beam within the

depth of the truss. Encourages continuous ceiling lines

under trusses.

End Type 10

This end type is suitable for short internal cantilevers

alongside stair openings.

End Type 11Permits support into steel channels and universal beams

while maintaining a floor and ceiling level that finishes

flush with the top and bottom flange.

End Type 12

Permits bottom chord support into steel channels and

universal beams with the bottom chord finishing flush

with the bottom flange while also maintaining a floor

level above the top flange.

Waling Plate

Min. Bearing 30mm

on Waling Plate

Timber Beam

Pryda Joist

Hanger Supporting Truss

End Web Should be Max. 5mm

From Edge of Supporting Member


20/24

Each truss shall be held onto its supporting plate/bearer

by a minimum of 2/75 x 3.15 mm dia nails. If preferred,

a better fixing may be achieved by using one Pryda

Minigrip with 3/35 x 3.15 mm dia Pryda nails per tab.

When supporting trusses on steel or timber beams via

top chords it is preferable to restrain the bottom chord

using skew nails while the top chord should be fixed to

the supporting beam using screws or Pryda Triplegrips.

This practice improves the stiffness of the floor by

minimising movement and vibration at the supports.

FIXINGS AT SUPPORTS


2/75mm x 3.15mm Dia.Skewed Nails

75mm x 3.15mmDia. Skewed Nails

Preferred

Pryda fully engineered open-web timber floor truss

systems with timber webs (Pryda Longreach) or metal

webs (Pryda Span) have many advantages:

Designed to eliminate the problem of bouncy floors

commonly found with some solid timber joists andprovide a floor that feels and acts rock-solid.

The open webs allow easy fixing of electrical,

plumbing, ducts and energy services. There is no

need for drilling or notching, saving time on site.

Greater design flexibility. Extra long spans and large

cantilevers can be provided, with the ability to

support high loads. Can also eliminate the need forsome interior support walls and beams, giving more

scope to architects and designers thus reducing the

cost of the support structure.

Eliminates uneven ceiling levels or complex ceilingsupport systems and allows a consistent depth

throughout the job at no extra cost.

Lightweight compared to solid timber, making

handling and lifting on site much easier. Computer designed for optimum strength and accuracy.

Fully kiln dried timber ensures stability, free from

movement due to shrinkage

Manufactured to size and ready to install, eliminating

the need to trim on site. No material or labour wastage.

Each truss is job specific, minimising waste

More end types for fast fixing to steel, concrete,masonry or timber.

Wide and stable surface for fixing floor and ceiling

materials. Provides a stable surface for tradesmenmoving around the elevated areas of a job

More efficient use of natural resources than solid

timber joists

Standard data and design details available on CAD

PRODUCT BENEFITS

OPTION 2

Pryda Minigrip With Min. 3/35 x

3.15mm Dia. Pryda Nails Per Tab

OPTION 1

2/75 x 3.15mm

Dia. Skewed Nails

TYPICAL PLATE SUPPORT FIXING

75mm x 3.15mm

Dia. Skewed Nails

Preferred

Screw, Bolt orDrive Pin Fixing

TYPICAL BEAM SUPPORT FIXING OPTION 1

TYPICAL BEAM SUPPORT FIXING OPTION 2

Service PipesBetween Webs

Void Used For Service Duct

VOIDS ACCOMMODATING SERVICES

CANTILEVER SUPPORT


21/24P R Y D A R A F T E R T R U S S S Y S T E M S 2 1

PRYDA RAFTER TRUSS SYSTEMSPRYDA LONGREACH OR

PRYDA SPAN TRUSSES

AS ROOF PURLINSINTRODUCTION

Pryda Longreach and Pryda Span trusses are alsoavailable for use as part of the Pryda Roof Truss

System. The design and manufacturing principles use

similar standards to the floor trusses and therefore the

benefits associated with Longreach and Pryda Span can

be also be attained in roof construction.

Longreach and Pryda Span trusses are suitable as roof

purlins or rafters for all roof materials. Pryda roof trusses

are generally made to order with special fixingrequirements for stability and tie-down against wind

uplift.

LOADING

Permanent LoadsPermanent loads which are considered during the

design process include:

Self-weight of truss

Roof material (sheet steel, slate, tile, battens etc)

Ceiling material (plasterboard, battens)

Temporary LoadsTemporary (live) loads are those associated with non-trafficable roofs and are the result of stacked materials

or equipment used in repair and maintenance

operations. The minimum live load level stipulated inAS1170.1-1989 is 250 Pa on the plan projection of the

roof. However, the intensity of the load on a truss willincrease when the area supported by the truss is less

than 14 square metres. The design also considers the

concentrated load of a single person standing on the

cladding.

Wind LoadsCalculated in accordance with the Loading Code Part 2:

Wind Loads 1989 for the ultimate limit state.

Pryda Longreach or Pryda Span trusses are lightweight

and easy to handle compared to solid purlins/rafters and

this is an advantage when lifting into hard-to-get roofpositions.

Longreach can be manufactured to any depth to meet

height restrictions or match existing roof features.

The open web truss profile allows mechanical services

to pass through while special duct spaces may beincorporated into the profile for larger service pipes and

ducts.

Pryda trusses can be manufactured to suit any on-siteconfiguration using the numerous truss end-type details.

They may also be designed to incorporate box gutters.

Pryda roof trusses are manufactured in 70mm and

90mm wide timber which improves resistance to

buckling under wind loads and reduces the number ofrequired lateral restraints to the bottom chord.

In the same manner as floor trusses, the Pryda RoofSystem eliminates uneven ceiling levels or complex

ceiling support systems and allows a consistent depth

throughout the job.

PRODUCT BENEFITS


22/24P R Y D A R A F T E R T R U S S S Y S T E M S2 2

SPAN TABLES

There are two types of roof truss designs shown here Purlin trusses and Rafter trusses. The criteria for overall

heights, clear heights and construction is the same as for floor trusses.

Purlin Trusses

Purlin trusses run parallel to the ridge and are perpendicular to the plane of the roof. The steel sheeting is fixed directlyto the top of the chord, and a ceiling is assumed to be attached directly (or with battens) to the bottom chord.

PRYDA LONGREACH PURLIN TRUSSES - MAXIMUM SPANS

Steel roofing @ 900mm CRS; roof pitch 10 - 30 degrees

Truss Chord Size (TC and BC)

Reference 90x35 P10 90x35 P12 90x45 F17

Wind N1, N2 Wind N3 Wind N1, N2 Wind N3 Wind N1, N2 Wind N3

FT200P 5200 4200 5700 5000 6300 5900

FT250P 6500 4800 6600 6100 8200 7000

FT300P 6600 5500 7600 7000 9400 8100

FT350P 7500 6000 8500 8000 10500 9000

FT400P 8300 6600 9000 8800 11600 10000

PRYDA SPAN PURLIN TRUSSES - MAXIMUM SPANS





PS25P 6900 6000 7700 6600 8200 7900

PS30P 7600 6700 8900 7700 9400 9000

PS40P N/S N/S N/S N/S 13000 10500

N/S = not suitable

Rafter TrussesRafter trusses are often laid horizontally (like floor trusses), and are overlaid with graded purlins which provide a fall to

the roofing material. However, a small pitch may also be given to the rafter trusses with battens overlaid in the normal

manner. The steel sheeting is fixed to the purlins, and a ceiling is assumed to be attached directly (or with battens) to

the bottom chord.

PRYDA LONGREACH RAFTER TRUSSES - MAXIMUM SPANS





FT200R 5300 4700 6400 5400 7600 6500

FT250R 7000 5700 7700 6600 9100 7800

FT300R 7700 6300 8900 6700 10500 9000FT350R 8800 6600 9800 7500 11800 10100

FT400R 9500 7100 10800 8200 13100 11100

PRYDA SPAN RAFTER TRUSSES - MAXIMUM SPANSSteel roofing @ 900mm CRS; roof pitch 0 - 10 degrees




PS25R 7300 5800 7800 6700 9200 7900

PS30R 8300 6500 9000 7700 10000 9000

PS40R N/S N/S N/S N/S 12500 10500

N/S = not suitable

Note: For design specifications outside the scope of these tables (e.g. cyclonic wind zones) contact a Pryda design office.


23/24P R Y D A R A F T E R T R U S S S Y S T E M S 2 3

FACTORS AFFECTING

PERFORMANCE

The performance of Pryda Roof Trusses may be limitedby a number of factors including deflection under dead

load and timber strength capacity under a dead, live or

wind load case.

Deflection limitsLongreach and Pryda Span Roof Trusses are designed

according to deflection limits set out in AS1684.1.

Load Condition Max. Deflection Ratio

Permanent load span/300

Temporary live load span/250

Ultimate wind load span/150

Special loading conditionsAir conditioning units and other mechanical equipment

can add significant loads to roof trusses. Theintroduction of an increased truss spacing to incorporate

a skylight will also produce a special loading condition.The truss fabricator should be informed of these

conditions to accommodate special designs.

SERVICES

The span tables list the clear depth between chords if a

duct space is made available within the web profile,

while also indicating the maximum pipe diameter that

may be passed through the webs.

ALLOWABLE SPACE FOR SERVICES

End ConfigurationsThe full range of end configurations available tofloor trusses may also be incorporated into

Longreach and Pryda Span roof trusses. In

addition to this the end configuration may be

designed to fit a box gutter. This option is

available to all truss depths however the

dimensions of the box gutter may be limited.

BOX GUTTER OPTIONS

Pryda roof trusses must be fixed down to the supporting

structure using connections that match or exceed the

magnitude of the wind uplift forces on each truss. Eachtruss shall be held onto its supporting plate/bearer by a

minimum of 2/75x3.15mm skew nails, or one PrydaMinigrip or Multigrip with 3/35x3.15mm nails per tab.

Refer to AS1684-1999 for further guidance on fixings

and tie down requirements.

Pryda roof trusses shall also be braced laterally at the

ends of the trusses using Pryda Strap Braces at each

end of a run of trusses.

TIE DOWN AND

FIXING DETAILS

END BRACING AND TIE DOWN

Block Insert Option

On Site Construction Option

Max. 500mm

Max. Pipe Dia. Permitted In-Between

Web Profiles (Refer Span Tables)

Max. Clear

Depth

Minimum Tie Down 2/75 x 3.15mm

Skew Nails or Minigrip/Multigrip

With 3/35 x 3.15mm Nails in Each

Tab. Refer AS1684 For Minimum

Tie Down Requirements.Bend Steel Brace Over And

Fix With 3/35 x 3.15mm Nails

to Side And 2 Nails Over

Lateral Bracing at Ends of Trusses

Using Pryda Strap Brace or

Equivalent. Cross Brace at Each

End of a Run of Trusses.


24/24

Roof Battens Continuousin This Area

Roof Battens

Continuous in This Area

OBracing Between 30And 45O to Top Plate

When Viewed in Plan

Steel Brace

Box Gutter

End Type 1

Loadbearing

Wall Frame

Brick Parapet

Wall

30O-45O

Bottom chord bracingStrongbacks are not required forLongreach or Pryda Span roof trusses.

For suspended ceilings, or exposedbottom chords, or where ceiling battensdo not provide restraint to bottom

chords under wind uplift conditions,

it is recommended that bottom chord

ties are introduced in accordance

with AS4440 1999: Installation of

Nailplated Timber Roof Trusses. In

addition to this, Pryda Speed or StrapBraces shall be fixed to the truss

bottom chords to transfer bracing

loads back to the supporting structure

according to AS4440-1999: Installation

of Nailplated Timber Roof Trusses.

In circumstances where the ceilingmaterial and battens do provide effective

restraint then bottom chord ties shall not

be required.

BRACING

BRACING REQUIREMENTS FOR SUSPENDED CEILINGS AND

UNRESTRAINED BOTTOM CHORDS

TOP CHORD BRACING REQUIREMENTS

Top chord bracingThe forces generated by resistance to buckling of thetop chord and wind loading perpendicular to the span of

the trusses must also be transferred back to the

supporting structure by steel braces. It is recommended

that Pryda Speed Brace or Strap Brace be applied to

the top chord in conjunction with adequately spacedroof battens in accordance with AS4440 1999:

Installation of Nailplated Timber Trusses. The steel brace

shall be continuous over the ends of the trusses and be

anchored down to the top plate.

Steel Brace to Underside

of Bottom Chord to

Transfer Bracing Loads to

Structure

Longreach orPryda Span as

Roof TrussesBottom Chord Ties

Suspended

Ceiling

Note: Refer AS4440 -1947 Installation of

Nailplated Timber Trusses For Further Guidanceon Bottom Chord Restraint Requirements

45O

PRYDA AUSTRALIA

Head Office: 29 Healey Road, Dandenong, Vic 3175Tel: (03) 9706 5488 Fax: (03) 9706 5499

Website: www.pryda.com.au

Offices in Sydney Brisbane and Perth

pryda trussed

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