On-Site Insight Edition 2 - 2007 by Master Builders Association of the ACT

On-site Insight March 2007

In This Issue Company Fined Importance of Safety Checks Sunlight on Timber Floors Moisture on Timber Floors Roof Truss Collapses Coronor’s Findings Truss Installation Checklist Bridge Demolition Drum Lifter Production ACT Workcover Issues

Important Dates Saturday 31 March Auction of ‘The Jenolan’, the Master Builders, LDA & PBS Charity House Thursday 5 April BREAKFAST with Neil Savery Talk on Planning Reform Clifton Suits Canberra Thursday 19 April IAMA Conference Effectively Resolving Comercial Disputes

Company Fined over Compensation Policy in the ACT A Canberra based company has been fined $1250 dollars and could face further charges for offences under the Workers Compensation Act 1951. The company engaged a number of individuals to perform regular and systematic work for the business over a substantial period of time. It wasn’t until one of the workers was injured on the way to work that it was found that the business did not have appropriate cover for their workers. A personal injury received by a worker on an employment related journey is an injury arising out of, or in the course of, the workers employment and therefore can be claimed as workers compensation. When a worker is injured during the course of employment and the employer is not covered by a compulsory workers compensation insurance policy in the ACT, the worker can make a claim to the Default Insurance fund (DI fund) the safety net to meet costs of workers compensation claims. When a claim is made to the DI fund and an amount of compensation has been paid to the claimant by the fund, the DI fund may claim an amount equal to three times the amount of the payment that is a debt owing by the employer to the DI fund.

The Importance of Safety Checks on Air Compressors We bring to your attention the importance of safety checks and maintenance on air compressors to minimise the likelihood of the receiver vessel rupturing. It is also important that all safety checks and maintenance on the compressor is documented and kept on file. How can an air compressor explode? During operation, deposits of lubricating oil tend to build up in the line that supplies compressed air from the compressor cylinder to the air receiver. As the diameter of the supply line decreases, the already high temperature of the compressed air rises further to a point where it is possible for the contaminant to ignite.

Friday 1 June 2007 Excellence in Building Awards

Sparks are then carried into the air receiver where oil from the compressor, which is often present as a mixture with air in the air receiver, burns explosively. As the pressure relief valve is not designed for such an event, rupture of the air vessel is likely to occur. Static electricity has also been identified as a contributing factor during an explosion of an air compressor.

Wednesday 11 - 13 July Remodelling Conference Rydges Lakeside Canberra

To avoid such incidents and damage all air compressor equipment should be maintained in a safe operational condition and be regularly inspected. The standard AS/NZS 3788 should be used as a guide for carrying out these inspections.

A N I N D U S T R Y U P D AT E F R O M T H E M A S T E R B U I L D E R S A S S O C I AT I O N O F T H E A C T

On-site Insight Roof Truss Collapse

The Effect of Sunlight on Timber Floors

Summary of Coroner’s Findings

Sunlight and artificial light produce a range of issues for timber floors that should influence initial choice and on going performance and maintenance. Prolonged direct exposure to sunlight through glass such as northern and western facing doors or windows is likely to cause heat and excessive drying and movement in timber, Some sites tests show Moisture Content (MC) of timber as low as 6% in areas exposed to direct sunlight through glass compared to a typical moisture content of 10% to 12%. The drop in moisture content may result in shrinkage and gapping between boards of 1mm to 3mm. Wider boards are more prone to movement than narrow boards.

Following the editorial in Februarys Onsight Insight regarding the collapse of a truss roof in South Australia 2002. The Coroner’s observation in the executive summary of his findings highlighted: that “… neither the builder nor the architect, engineer, software designer, truss manufacturer, roof contractor, roof tiler or Local Government authority took any responsibility for the overall integrity of the roof structure”.

The recommended practice is to cover windows both internally and externally and to acclimatise the timber to the anticipated ongoing relative humidity of the location, known as the Equilibrium Moisture Content (EMC). EMC is usually lowered when extensive glass areas allow longer sunlight hours. Timber floors in these areas therefore require lower moisture content. Air conditioning is relevant to the MC in timber floors as it acts as a dehumidifier and can further lower the EMC in the room. This should be taken into account together with the effects of sunlight. The effects of prolonged sunlight on timber floors are not only a summer event as the windows also collect sun during the winter.

The Effect Of Moisture on Timber Floors Under constant conditions of temperature and humidity timber attains moisture content in equilibrium with these conditions. In actual use these factors may change by the minute so uncoated timber is constantly making slight adjustments to the restless environment and its equilibrium moisture content will vary between about 10% and 15% in Sydney and other central coast areas; it may fall to 6% in the dry inland summer and rise to 18% during the hot humid rainy season on the north coast. The moisture content of the timber in air conditioned buildings is about 7% to 10%. The lightweight timbers which dry quickly will also be more susceptible to sudden changes in humidity than the dense, slow drying species with the result that the seeming advantage that species with relatively low shrinkage values have, may be nullified to some extent in practice by their greater sensitivity. If the floor supplied is above the mean equilibrium moisture content level, then cramp the floor tightly and if below, cramp loosely. In this latter case it is dangerous to cramp very dry material to normal tightness because the return of damper conditions will cause the timber to expand and could result in buckling of the floor. The average amount of seasonal moisture movement is about 0.3mm per metre width of flooring for each 1% change in moisture content.

He also detailed the following: • Due to inadequate lateral bracing of the double girder truss, which was heavily loaded from the bottom chord rather than , as is more usually the case, on top chords, the top chord began buckling into an ‘S’ shape. • This buckling steadily increased over time (the process of ‘creep’) thereby progressively increasing the compressive forces on the top chords. • Because the bottom chord of the double girder truss was fixed by steel truss bolts where the other trusses met the double girder truss at right angles, it was prevented from rotating in sympathy with the distortion of the chords. • The top chord buckled so far that it twisted upwards from the heel joint and failed due to torsion (twisting) both in the area of the top chord where the brittle wood and high slope-of-grain were found, and also in the vicinity of the heel joint which was weakened by hidden gum veins; • The whole weight borne by the truss would have then been forced onto the small portion of bottom chord remaining which then failed in shear. It’s obvious from these findings that the collapse was not completely due to initial truss failure, but was a culmination of events that started with inadequate installation methods that contributed to ultimate truss failure and roof collapse. Areas still to be investigated according to some commentators are: • The area of heel joints and design software. • Reasons for the cause and how to stop nail plate liftout, ie moisture cycling effect, density layer changes in timber, the effect of lack of sarking ventilation, overloading etc. The Master Builders Association is in the process of developing a training programme for the installation of roof trusses. In the mean time we have attached a truss installation checklist that we recommend is used at the completion of the truss installation. Members will be provided with written information on draft recommendations and advisory notes when they are available.

On-site Insight TRUSS INSTALLATION CHECKLIST When installing roof trusses use the following checklist to ensure a quality job and to avoid overlooking any important aspects. Supporting Structure F

Check that all top plates that support trusses are level and straight. (Any misalignment of supporting structure will be reflected in the straightness of the roof)

Is the speedbrace apex fixing correct according to “Fixing & Bracing Guidelines”?

Is the speedbrace fixing to each truss top chord correct according to “Fixing & Bracing Guidelines”?

Check that the distance between supporting walls match the spans of the trusses.

Is the speedbrace to top plate fixing correct according to “Fixing & Bracing Guidelines”?

Are the tops of internal non-load bearing walls set down below that of external load bearing walls?

Is the speedbrace splice detail correct according to “Fixing & Bracing Guidelines”?

Are lintels in load bearing walls suitable for truss loading?

Is supporting structure fully braced, plumb and stable?

Has all cantilever and web bracing been installed as per design?

Have all the web ties been installed and braced back to a rigid part of the building with cross braces?

Are roof battens of correct size and grade?

Are roof battens fixed to each truss including to each ply of double & triple girders using the correct size nails?

Are roof battens spliced correctly:-

Roof Trusses F F

Have trusses been stored and lifted in accordance with the manufactures instructions? Are trusses free of any modifications, cut members or broken members? Does the truss design criteria on the documentation conform to the job specification for roof cladding and special loads, eg roof mounted hot water tanks, air conditioners, etc?

no more than 1 in 3 on any truss?

no 2 splices adjacent on any truss and none in unbraced zones of gable roof ends?

Are trusses correctly positioned according to truss layout plan?

Are intermediate top chord ties/battens fixed between saddle trusses (if applicable)?

Are trusses accurately spaced?

Have cantilever or internally supported trusses been orientated correctly ie. Are “support here” stickers located above bearing walls?

Are trusses installed within installation tolerances?

(a) Plumb – All sections of truss less than 50mm or height/50 out of vertical (b) Bow – All chord bows less than 50mm or chord length/200 F

BOTTOM CHORD BRACING F

Truss Connection Details F

Are all multiple ply trusses nailed/screwed/bolted together?

Are all walling plates fixed to truss as per design?

Do all trusses in corrosive environments have stainless steel plates and/or other suitable protection?

For suspended ceilings or where furring channels are “clipped” to bottom chords:- have bottom chords ties and diagonal bracing been installed in accordance with AS4440?

Temporary Bracing

Have the trusses been fixed to top plates correctly at:a)

load bearing wall i.e. Trip-L-Grip

Internal non-brace wall i.e. internal wall bracket

Internal braced wall i.e. blocking pieces fixed in accordance with AS4440?

Have hip end components been fixed correctly at:a)

jack truss to hip truss – small stations i.e. nailed

jack truss to hip truss – large station i.e. Creeper Connector

Are top chord temporary ties no greater than 3000mm spacing?

Hip truss & jack trusses to truncated girder and to truncated standard truss as per AS4440

Are bottom chord temporary ties no greater than 4000mm spacing?

Structural fascia and/or strutted overhangs?

Permanent Bracing TOP CHORD BRACING F

Is the Speedbrace configuration correct according to “Fixing & Bracing Guidelines”?

Are saddle trusses fixed in accordance with AS4440?

Are standard truss to girder truss fixing type according to approved plans and are all nails/bolts installed and tight?

Has all strengthening been completed for guard rail systems – (if applicable)?

A N I N D U S T R Y U P D AT E F R O M T H E M A S T E R B U I L D E R S A S S O C I AT I O N O F T H E A C T

241 Northbourne Ave, Lyneham Canberra ACT 2602 Tel: (02) 6247 2099 Fax: (02) 6249 8374 www.mba.org.au

Bridge Demolition At approximately 14:00 hrs on February 22nd 2007, the Acacia Inlet Bridge on Parkes Way was partly demolished, as part of the works currently in progress on the Gungahlin Drive Extension. To assist the demolition, a small amount of explosives were used that would bring the deck of the bridge towards the ground, and to distress cabling within the bridge structure. To use explosives as part of the demolition process, the applicant was required to meet the Dangerous Substances [explosives] Regulation 2004. The Dangerous Substances [explosives] Regulation 2004 set the foundations and safety duties necessary for any use of explosives in the ACT. These regulations are strictly adhered to in the issuing of any license or permit. It must also be noted that this partial demolition was carried out with minimal quantities of explosives. The application was aided by a blasting consultants report, that identified the reasoning for using explosives, the exclusion zones, the amount of explosives required, and how the bridge would fall. This article was taken from act workcovers e-news March 2007

Drum Lifter goes into Production The Drum Grab, designed by Matthew Schaeffer and Ian McClenaghan, which won first prize in the National Farm Invention of the Year, has gone into production and is now for sale. CAST IN DUCTILE IRON by White Industries, and treated with lanolin to prevent rust, it has a safe load of 1.5t certified by an independent testing laboratory in accordance with Australian Standards. It works with any 200L drum that has a rim and fits open top and closed head, plastic and steel drums preventing injuries and spillages. Usable with any lifting device it will lift and lower drums on their side but will not release the drum until you want it to. The device costs $319 including handling, freight and GST. For more info ph: (02) 6772 7551 or email info@ drumgrab.com.au This was taken from the earthmover and civil contractor magazine February 2007

ACT WorkCover Tackles Manual Handling Issues Injuries and disease resulting from heavy lifting, repetitive tasks, and sustained awkward posture are the focus of a Trans-Tasman workplace safety campaign targeting manufacturing. ACT WorkCover has joined other jurisdictions in the national campaign to reduce bodystressing injuries in the manufacturing industry. ACT WorkCover announced its Manual Tasks Intervention Program in October 2006 and this national campaign will compliment and run parallel with that program. Body stressing is the term given to muscular stress due to hazardous manual handling or repetitive movement, and is a major social and economic burden to the manufacturing industry. It accounted for 44% of all the industry’s workers compensation claims in 2003/2004 across Australia. ACT WorkCover will be targeting businesses that manufacture structural metal products, such as those that produce garage doors, roof trusses and aluminium gates. In 2005/2006 the ACT paid out over $379,000 in workers compensation payments in the structural metal products industry. The campaign will focus on educating employers to work together with their employees to effectively identify and manage manual handling risks. ACT WorkCover Inspectors will visit approximately 30 businesses between March and June and provide practical guidance and information on how to identify and manage risks associated with manual handling in this industry and to measure compliance with the ACT Occupational Health and Safety Act 1989. A letter outlining details and the intent of the planned inspection program will be sent to businesses prior to the audit, and to assist businesses in preparing for the visits. Any member requiring a copy of ACT WorkCover’s publication ‘A Guide to Manual Tasks’ should contact Lorraine at MBA on 6247 2099 or lorraine@mba.org.au