FRAMES AND TRUSSES SYDNEY

One of the most critical things in roof building design in Sydney is making sure the wall frames and roof trusses are engineered to Australian standards (prefabricated timber trusses standard AS 4440 “Installation of NailPlated Timber Trusses”. All design details have to be provided by the engineer responsible for the building design. Using a certified frame and truss manufacturer will make sure the roof installation is safe and able to withstand ceiling and wind loads. The loads that are imposed on the building are finding a way to get transferred down through the timber frame structure into the foundation. Some of those loads that we are referring to start up on the roof (that could be snow loading, wind loading). On the windy days when you have a strong wind coming over the top of your house, it creates an uplift on your building. We also have to accommodate lateral forces from winds that act upon the walls. The main goal in this design is to transfer all the loading down into the foundation correctly and that all starts up in the timber roof trusses.

Additional loading, including hot water tanks and air conditioning, require special attention and they have to be considered before placing an order for prefabricated frames and trusses. Refer to Australian Standard AS 1684 for the correct design of wall frames and beams supporting trusses.

So how the load can be transferred across the building structure?

When designing the roof and frames and trusses in Sydney, what we need to do is to get our main roof loads to the outside timber walls. All of the timber roof trusses are typically intended to transfer loading from the roof down through the truss and out to each end of the truss, taking that through the timber wall system.
As the studs go down and into the timber floor system, we pick up that load with what’s called squash blocks. Underneath the wall and buried in the floor system there are LVL blocks.

How do you transfer loads on high, steeply-pitched roofs?
Parallel chord trusses are used when extreme pitch on the interior side is required for your ceiling. The roof system has the exact same pitch on the outside. That means that the ceiling is parallel with the roof plane. It is important to have enough heel height when designing a parallel chord truss. Heel height is a distance from the top of the wall vertically to where it meets the roof sheeting. With a parallel chord truss, it requires an extremely tall heel to get that truss to work.

What is a girder truss? A girder truss is simply a multi-truss member that supports other trusses
How point load blocking and beams transfer the load? The wall above point load blocking will typically have a one, two or three-ply stud in that wall transferring that roof load and floor load down. We must be able to transfer that load through that block into the beam, through the post, down into the foundation.

What is the role of drop beams?
A common item in any basement are drop beams. What are drop beams allow us to do is to support the floor system. Most floor systems, whether they’re dimensional floors: two by four, two by ten, two by twelve, an engineered floor systems needs some sort of center support. Most of the floor systems can not span through the front of the building to the back. In order to accomplish the load-bearing requirements, we use an engineered LVL beam. FHA posts are also required to transfer those loads from that beam. Majority of the beams cannot go from end to end without having a steel FHA post to transfer those critical loads. Once the loads hit the steel column, they’re not just hitting that basement slab. Beneath the basement slab is a built-up post pad. Those are the bearing members that carry all the loading that starts up on the roof system