The changing weather conditions can have an adverse affect on roof trusses if they are left exposed to the elements for any extended length of time. In the following paragraphs, MiTek Australia discuss effects of weather exposure on roof frames and trusses.

An example of such a situation is one where the trusses and frames have been left uncovered on site during construction delays, sometimes for many weeks and possibly months. When the job recommences, the builder commonly neglects to have the trusses and wall frames checked by the truss manufacturer or engineer.

When a house frame is subjected to excessive and prolonged exposure to sun and rain, any or all of the following may occur: the timber components may distort, split and suffer fungal damage, the nailplates in trusses may corrode and back out, the trusses may lose their shape and camber and may suffer greater creep deflection under service than expected. Cladding and lining a defective structure is akin to sweeping dirt under the carpet. It is a disaster waiting to happen.

A fabricator recently noticed during an unscheduled visit to a building site that some of their trusses, which were delivered about four months earlier, had just been installed after having been left exposed to the elements for that entire period. The fabricator conveyed his concerns to the builder and advised that the trusses should be inspected by an engineer since there was evidence of severe weathering.

A full and detailed report of the truss condition and any recommendations for rectification would be required. In essence, roof trusses in a weathered state should not have been installed in the first place without appropriate examination.

The builder risked forfeiting his truss warranty automatically had he simply finished off the house without sourcing any professional help to rectify this issue.

Fortunately, as part of their normal operating procedure, the fabricator’s manufacturing and delivery quality control system safeguarded his reputation by documenting all inspection checks in the production process, as well as photographing the completed packs along with the date of despatch from the yard. In the event of any dispute, the fabricator had all the systems in place to ensure his protection. The message for builders and fabricators is twofold.

For builders, it is imperative that when trusses or frames are delivered on site, immediate action is taken to cover and protect them if they are not going to be installed soon after. A tarpaulin or other similar weather proof material is suitable provided allowance is made for adequate ventilation. For fabricators, it is important to ensure that the documentation and quality control systems are up to date and can withstand scrutiny if the need arises.

It is essential that everyone understands the destructive effect prolonged weather exposure has on frames and trusses so that appropriate preventative measures are taken before undesirable and costly damage occurs.

Architecture & Design Team

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MiTek Australia

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