Builders Breakfast Series

November 26-27, 2008

Presented by:

Dave Pasolli

Western Wood Truss

Association of Alberta

12 things you should know about

installing trusses properly and

safely

• The WWTA-Ab represents 35

truss manufacturers

throughout Alberta as well as

Associate members and

suppliers to the truss industry.

• Members agree to abide by the

Association’s Standard Code

of Practice.

• Agree to participate and

adhere to the WWTA Quality

Assurance Program.

Safely Handling and Erecting

Trusses

• Supplied with every

package by a WWTA

member. • Erection Procedure

• Mechanical Handling

• Alignment guidelines

• Temporary Bracing

• Permanent Bracing

#1 Site Storage

• Store trusses in a stable position and on

relatively smooth dry ground.

• Trusses stored horizontally, should be

blocked every 8 to 10 feet.

• Do not store bundles upright unless

properly braced.

#1 Site Storage

Trusses can not be used as a bulldozer to clear

the jobsite

#1 Site Storage

• Do not break banding until ready to install.

• Do not drag or push trusses along the

ground.

• Do not store on uneven ground.

#1 Site Storage

Excessive lateral bending can pop the connector plates off!

Damage should be addressed before installation of trusses

#2 Ensure Trusses are at the right

location

#2 Ensure Trusses are at the right

location

Pay close attention to symmetrical trusses with multiple bearings

Cantilever Trusses or

Trusses installed upside down

#3 Mechanical Handling

20’ or less a single pick up point

may be used

Trusses up to 30’ should be lifted

using 2 pick up points so that the

distance between them is about ½

the length of the truss

Trusses 30-60’ should be lifted

with a spreader bar and short

cable slings. Over 60’ they should

be lifted with a strongback which

is 2/3 to ¾ the length of the truss

Best Practice

Pre-assemble the roof truss system on the

ground when possible. Divide large heavy

roofs into smaller sections when necessary.

Web Bracing is NOT designed to hold a module of

trusses together for lifting

Web Bracing is NOT designed to hold a

module of trusses together for lifting

#4 Alignment of Trusses

Out of Plumb Installation Tolerance

Alignment Tolerance along Truss Length

#5 Permanent Lateral Bracing

• Is Specified on the Truss Design Drawings

• May also be Specified on the Building

Structural Drawings

Buckling due to compression force P

Required Continuous Lateral Bracing

+

Simple Beam Truss

+ indicates tension

- indicates compression

Tension and Compression

Forces in each Member

+ = Tension

- = Compression

No Lateral Bracing on

Compression Web

Broken Compression Webs

1x4 bracing bent to find webs

Permanent Continuous Lateral Bracing

Anchored by X-bracing at each end

Permanent Continuous Lateral

Bracing anchored by X-Bracing at

each end or every 20’

Brace the Braces-Look for Triangles

Permanent Continuous Lateral Bracing

Anchored by X-bracing at each end #6 Permanent Top Chord Bracing

• Plywood or OSB sheathing fastened

directly to the top chord

• Purlins

• Blocking

2x4 @ 24” o.c.

Insufficient Purlins on Piggyback Trusses

Blocking at Girder Trusses and Regular Hip Systems

Permanent Bracing of the Bottom

Chord Plane

• Maintains truss

spacing

• Keeps the bottom

chord in plane

• Prevents bottom

chord from buckling in

buildings where there

is internal pressure

Cantilever truss with Bottom Chord

in Compression

#7 Gable Wall Bracing

#7 Gable Wall Bracing

#7 Gable Wall Bracing

Tall Wall Bracing

• For walls over 11.9’ with a stacked gable

truss on top requires a design to

permanently brace the wall.

• It is the Builder/Designers responsibility to

design a Permanent Building Bracing

System to resist the lateral loads applied

for the wall and the gable.

• All walls must me looked at individually.

No Bracing for the Gable at a tall wall

#8 Correct Connections

• During the review of the installation make

sure all trusses have the proper connector

and that the correct nails for the hanger

are used

• Ensure that Girder Trusses are connected

properly according to instructions on the

truss design drawing.

Sloped Truss Bottom Chord in a Flat Hanger

Tie-Down for a Girder Truss

Hangers not properly installed

1 nail

installed

Girder Truss Bolted Together

Ledger Connection at ICF Wall

#9 Proper Bearing for Trusses

• Ensure Load is

transferred correctly

to foundation.

• Solid columns under

Girder Trusses.

• Look out for when a

Roof Girder is bearing

on a floor.

#10 Construction Loads

Stacking bundles of shingles as shown above may load

the middle of the top chord panel of the truss with a point

load exceeding 800 lbs.

Placement of Roofing Materials

Placement of materials

788(1) An employer must ensure that supplies and roofing

materials stored on a roof are located not less than

2 metres from a roof edge.

(2) An employer must ensure that the weight of

supplies and roofing materials stored on a roof is

uniformly distributed.

Part 38

CONSTRUCTION LOADS

Construction loads (lifts of sheathing, bundles of

shingles, lifts of drywall etc) should be placed only

on fully braced & sheathed structures

WARNING! Trusses are very unstable and have

NO CAPACITY to carry load until they are

properly braced and sheathed. Placing loads on

unbraced truss assemblies is a hazardous act and

can cause property damage, or worse, severe

personal injury or death.

CONSTRUCTION LOADS

Use extreme caution when placing construction

loads and only stack reasonable amounts of

materials.

Distribute loads over as many trusses as possible.

Position sheets or bundles with the longest edge

perpendicular to the trusses.

WARNING! Stacking excessive construction loads

on roof or floor trusses is an unsafe act and can

cause property damage, or worse, severe personal

injury or death.

CONSTRUCTION LOADS

Make every attempt to stack materials along

outside supports or directly over inside supports.

If bundles of asphalt shingles must be placed along

the roof ridge lines, distribute the bundles along

both sides of ALL ridge lines to avoid high stacks

and over loading in one area. Do not stack shingles

more than two bundles high.

CONSTRUCTION LOADS

If stacks of plywood or OSB must be placed on

trusses, distribute the stacks along the outside

supports with no stack exceeding 16 inches in

height. Distribute the stacks over as many trusses

as possible. Position sheets flat with the longest

edge perpendicular to the trusses.

Take every precaution to secure the sheets to

prevent them from sliding or being blown off the

roof.

WARNING! Stacking excessive construction loads

on roof or floor trusses is an unsafe act and can

cause property damage, or worse, severe personal

injury or death.

Trusses Collapsed Under Load of Roof

Sheathing

#11 Safely Installing Trusses

Placing Trusses

Hazards:

• Falling.

• Being struck.

Control Measures:

• Workers placing trusses MUST be protected from falling and

from being struck by the trusses.

Options may include the use of:

- scaffolding, ladders, a fall protection system or

mechanical means.

Placing Trusses

Control Measures:

• Workers must NOT walk on walls where there is the

potential of falling 3 m (10 ft) or more without adequate fall

protection.

• If the employer’s written fall protection plan for roofers

includes a travel restraint system and requires the installation

of anchors to specific trusses, the anchors must be installed as

shown and specified on the house plans and should be

installed on the designated trusses prior to lifting. Workers

installing trusses or applying sheathing must not use these

“roofer anchors” as these anchors require all trusses be

completely installed including bracing and sheathing.

#12 Fall Protection

• A Fall Protection system may Include:

– Guardrails

– Travel restraint or fall arrest system

– Safety net

– Control zone, or

– Some other equally effective means that

protects the worker from falling.

Travel Restraint System

A travel restraint system prevents a worker from

traveling to an edge or position from which the worker

could fall.

Personal Fall Arrest System

• A fall arrest system

arrests a worker’s fall

to prevent injuries; it

does not prevent a

worker from falling.

• An Engineered

system must be used.

Anchors for personal fall arrest

systems or a travel restraint system

attached to trusses must not be

used until the trusses are

completely installed including all

bracing and sheathing.

Fall Protection and Roof Trusses

A falling worker attached to a single truss

can cause all the trusses on the structure to

collapse in a domino effect

Types of Permanent Travel Restraint

Anchors

OH&S Code 2008 Changes

• It was proposed that an owner must ensure that permanent anchorages meeting the requirements of section 149 are installed or designated on all structures after September 1, 2008.The anchorage is capable or sagely withstanding the impact forces applied by a personal fall arrest system that has a minimum breaking strength per attached worker of 16 kilonewtons.

OH&S Code 2008 Changes

• It is the position of the WWTA that when

permanent fall protection anchors are

specified it is the Building Designer’s

responsibility to design a bracing system

to resist these lateral loads.

OH&S Code 2008 Changes

• This change was opposed by the

Homebuilders of Alberta and is currently

being reviewed.

Repairs and Damage

• Report all damage to the truss

manufacturer immediately.

• Not all repairs are the same

• Inspect trusses prior to unloading and

installing

Modified Trusses

CAN NOT

MODIFY PLATED

TRUSSES TO

MAKE AN ATTIC

Broken Roof Truss

• Most likely broken before installation

• Requires Engineers Repair

Floor Truss Damage

The Assurance of Quality

• Management commitment to quality

• Agreement to abide by the WWTA Code of Practices

• Design drawing requirements

• Documentation requirements

• Lumber handling and storing requirements

• Continuous inspections of metal plate placements

• Continuous inspections of truss dimensions

• A process of continuously improving quality

• Pass the WWTA quality assurance audit

The Assurance of Quality

• What is the big deal with sealed truss

design drawings?

• What do they tell you?

• Don’t trusses have a big safety factor?

What is wrong

with the picture?

Plate deformation due to

gap in compression

member

Metal plate not placed

properly

Missing Truss Plate

The Assurance of Quality

The Western Wood Truss

Association of Alberta

Questions? Dave Pasolli

WWTA

(403) 279-3385

dave@wwta.ab.ca

Thank You for Attending!

See you at the next

BUILDER BREAKFAST