In light of the increased use of engineered timber products on building sites, many problems can arise following the frame completion stage. Kevin Ezard explains how to avoid any costly rectifications after the building is completed.

Every residential builder and tradesman would be very familiar with the range of engineered timber products such as I-joists, glulam and laminated veneer lumber (LVL) beams that are now being used on most building sites in Australia. But would you believe there is still a continuing major problem with installation faults occurring on construction sites?

This has been brought to the attention of engineered timber suppliers and often requires expensive rectification after building completion.

The engineered beam suppliers all provide comprehensive installation guides with detailed instructions, and copies are usually sent to the building site with the timber delivery. These guides contain examples of correct fixing and fasteners for floor and roof framing, plus hole cutting charts and a range of do’s and don’ts for guidance.

Whilst there are occasional difficulties with site installation it seems that most carpenters understand the onsite procedures and get to the frame completion stage without problems due to their many years of experience.

However, based on the feedback from suppliers regarding site problems experienced, it seems that most of the major issues develop following the frame completion inspection by the building surveyor. At this next stage of building the installation of services such as plumbing, electrical, and ducting for air conditioning are undertaken, and this is where the problems start occurring.

The most frequent source of these problems is in the creation of access for the building services, which often generates significant damage to engineered beams from inappropriate cutting of holes and even complete removal of beam sections to create a pathway for services.

Typically these issues arise in wet areas with toilet and shower positioning not aligning between joists for plumbing access, or lack of provision in the floor space for ducting and other services that need to run across the joists.

What this means is that the fully inspected and approved timber frame has now been structurally altered after the inspection, with potential for the floor performance to be compromised from damage inflicted by following trades.

And to make it worse any structural damage may not be observed and corrected before the next inspection (after the plaster has been installed), meaning problems may not emerge until there is a defect showing some time after building completion.
Recent examples onsite show I-joists severely damaged by use of hammers to smash holes through the webs, cutting notches in flanges or saw cutting of complete sections to virtually destroy the joist as a structural member. Often this damage is not picked up until the owner discovers a floor movement after a period of use, leading to a claim that can be expensive for the builder to rectify.

One of the largest national distributors of engineered timber products, Tilling Timber, has many years of experience. According to national product manager Craig Kay, pre-planning of floor space services is the solution.

“The key is to consolidate the services and create a pathway for access to minimise installation time and eliminate potential problems due to the amount of floor depth available and need for large penetrations such as ducting,” he says.

“Most house plans don’t include consideration of services installation, particularly for air conditioning ducts, which if pre-planned can save builders time and money onsite.

“With a house plan layout for all major services such as wet area plumbing for toilets and showers, electrical outlets, and ductwork for heating and cooling, the floor system can then be detailed and suitable size holes located and pre-cut in the I-joist webs.

“Even a single row of holes lined up in each joist for basic services will consolidate runs to save time and ensure trouble-free installation. Tilling Timber has many builder customers that are now utilising this additional service at no extra cost with all I-joist holes and penetrations pre-cut before delivery to site, ensuring following trades activity is smoother, faster and does not have any problems down the track.”

During construction if a repair is needed where a large hole or oversize penetration has been cut in an I-joist or LVL beam there are some options for rectification onsite to restore the beam.

One product available for I-joist repair is SmartFrame WebFix® which utilises a V-shaped floor truss web to overlay the penetration hole and to support the joist section in that area, allowing the duct to pass through the truss web.

For LVL beam repair when an oversize hole requires reinforcement onsite, the SmartFrame HoleFix has a pair of steel brackets which are screwed onto the beam face surrounding the hole. These are ideal when plumbing drainpipes need to be accessed through LVL joists, however they require design and certification for each application.

From the feedback received it seems that more care and attention is needed onsite to ensure engineered timber products do not suffer damage that may cause problems after building completion. Given the importance of these issues, more on the topic of common problems onsite will be covered in future articles.