How to build a Pergola – Step Four

Step Four-Assemble Gable Frames

The next step in building your Softwoods pre cut gable pergola is to assemble your gable frames. It’s at this point that you might finally start to get the feeling that you are actually building something! However as with the previous steps, this step is also preparation for the building to come.

Gable frames consist of the internal rafters and collar ties, which are made into an A shaped frame to be lifted into the structure once the beams have been installed. Your gable frames will provide the internal shape to your structure, so it’s important to make sure that they are all of a uniform shape and size. Your frames will be made on the ground then lifted into place later. You will need to do this on a flat surface for the most accuracy.

Layout rafters with bottom chord and ridge block

Lay the bottom chord on timber blocks (rafter stiffeners) on a flat surface and then place 2 rafters with their ends on the inside of the mitre (see the diagram below for a clear picture). The rafter edge will line up with the vertical face of the notch as well as the angle of the rafter.

Using a ridge spacer (supplied in the hardware box) as a makeshift ridge, move the rafters so they meet the ridge spacer at the top. Make sure the rafters are still in the correct position against the bottom chord. The rafters and ridge should look like the diagram above, and need to be elevated on rafter stiffeners as described previously so that it is easy to drill through the rafters in the coming steps.

Place collar tie

Once rafters are in position, place the collar tie on top of the pair of rafters with the cut edge following the angle of the rafters. The rafters and collar tie should form an A shape.

To establish the exact position on the rafters that the collar tie should sit, measure from the edge of the rafter to the edge point of the collar tie on both sides and check if they are about the same. If you are unsure, have a look at the diagram below for the point that you should be measuring.

You may need to move the collar tie a few times until your measurements are the same or similar.

Drill and bolt collar ties

Drill 10mm holes for your bolts through the collar tie and rafter using the table and diagram below to determine their quantity and placement. You can clamp the collar tie to the rafters as you drill to make sure that there’s no movement of the frame as you drill.

Once the holes are drilled insert the bolts through the rafter and collar tie. You will need to knock the bolts in with a hammer. Because of the tight holes, the frame will be held firmly in place. There is no need to fix with washers and nuts at this stage.

Now your first gable frame is almost done. To continue with the next frame, place another set of rafters and a collar tie above the frame you’ve just made (see example below)

Line up the rafters and the collar ties so they are parallel with the first frames components. This should allow you to easily and accurately recreate the first frame, using the ridge block and the angle of the previous gable frame as a guide.

To make sure your collar ties all line up when the frames are installed, measure the distance between the two at both ends. If it is the same, the collar ties should all be straight.

Once you are confident that your new frame is in the correct shape, mark and drill the holes for your bolts through the collar tie and rafters as before, inserting the bolts once you are done. Repeat this process until all of your gable frames are assembled with bolts inserted on the ground, and then stand the frames up one by one and fit them with washers and nuts and tighten.

All of your gable frames should now be finished. Store them in a dry safe place until they are needed.

You can now move onto the next step, Installing Fascia Brackets.


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