When starting out with the installation of your roof truss's its essential to ensure that you have all the correct information regarding the truss's supplied and ensure you have all the necessary design details and specifications for your roof. If you encounter any technical areas that need addressing when it comes to the design and manufacturing/ Installation of the truss's to the specific job then they are best addressed before installation of the Truss Roof, check that a Truss Layout is provided, that the design criteria is acknowledged, where support locations are and that you have the necessary fixings "specified" as well as any details of special bracing that may be required to install your truss roof .
Checklist:
Before you start to install the Truss roof it's essential that you go through and make sure you have a clear picture any problems you might encounter when physically installing the roof once you have a clear picture of what needs to be done in your head you always encounter on the job problems that will change or delay your installation process.
Go around the top plates and ensure they are all straight and make sure "all walls, supporting and non supporting" are plumb, fixed and secure, check to find out the level of your top plate and ensure all supporting walls are to the specification. Ensure all supporting walls have 12mm clearance over non load bearing walls, check all your Truss's for any damage and ensure you setup a scaffold.
Best Way to Erect a Truss Roof:
Find the Truss layout, find and mark the top plates and where all supported Truss's will sit in relation to them. Once you do this you should workout what order is best for the installation of Truss's, start with simple Girder or Gable end roofs with the smallest span where possible, start from and end using the gable and hips for support and then erect your nearest standard truss, ensuring you plumb and level your Truss's as you move along. If you leave Valley's and large blocks to last you will gain a full picture of your Truss roof more quickly.
Tips for Truss Installation: - Locate Supporting Truss's at the end of block, Ie: Girder Truss and Hips and Truncated Girder Truss for Standard Truss's.
- Erect Truss at the end of a roof block.
- Ensure you fully fix these as you go.
- When erecting Standard Truss's make sure you have all Girder truss's installed in that block.
- Saddle Truss's to be installed last when all adjacent blocks are installed.
Spacing and Bracing: When settining our your Truss's you will find youself fixing to to marks on your top plate but they need to be spaced at the apex and a spacer can be used to space them while you install your tempoary bracing. You can make a simple gig up to your desired centers.
Gable End and Eaves:
Gable ends are relitivly simple however when eves come into play you will find yourself using a raking truss to house your outrigers, your facia and barg board are then installed of this.
Saddles and Connecting Major and Minor Roofs:
Saddle truss's are used to connect major and minor roof blocks. They are fixed using braces and blocking as they are never housed. Sitting on the roofing pitch they must be plumbed. They are
Lining Installation and Truss "Settlement":
Truss's are designed with a camber on the bottom cord this allows for settlement of the truss once all loadings are places on the Truss, this includes air conditions units and ducting, roofing and linings ect... This means that when you go to install the linings you must account for the
Installation Tolerances:
The tolerance for the plumb of a Truss is The Lesser of 50 or the Truss height/ 50.
For the camber it is The Lesser of 50 or the Truss length/ 200.
Steps we used in installing our Truss Roof.
- First thing we did was to setup our top plate to the shape required, we then leveled and squared the Top plate ensuring that the roof we where about to put up was indeed level.
- Our Truss Roof was a gable end roof, so we started by installing our two standard Truss's at each end of the main roof. We fixed and plumbed one end.
- We than ran our String line down the ridge line from one apex to the other. This gave us a a point for the rest of our truss apexs to meet ensuring a straight ridge line.
- Next we started to install the rest of our standard Truss's from one end at 600mm centers.
- Once we got to the point where our two minor roof blocks met we then installed our Truncated Girder Truss. We ensured it was inline and level.
- Then the Girder Brackets go on, ensuring we retain our 600 centers when installing them. Making sure they are at the right heights to keep our ridge line straight.
- Before we could install of our Standard Truss's we needed to install our Ridge Truss's on each side to brace the truncated girder Truss.
-Once we finnished putting on all four Hip Truss's we installed the last of the standard truss's.
- Its important to note that we braced the standard Truss's as we moved along, keeping our roofline straight.
- One our main block with Gable ends was complete we then setout installing the rest of our Minor block roofs.
- We started this by first installing our Jack Truss's.
- Once this was done we ran a Stringline all the way through from one Apex to another from one side of the roof to the cemetric apex on the other side.
- This gave us a height for our saddle Truss's and we fixed them to keep our apex straight all the way through.
- Once this was done fixed our creepers using tempoary bracing.
- After this we installed our speed bracing in a diamond shape on our main block.
- We then went about installing our valley boards, we used a string line to find our true valley and marked out 200mm in each direction leaving us with a 90mm gap between our two valley boards.
- One group then went of and installed our facia and facia brackets, using pop rivets to fix the internal and external corners.
- At the same time another group could fix all of our roofing batterns down, we followed down our valley boards and maintainted a distance of 140mm from our ridgeline, facia and hip lines.
