One of the things that has slowed us down is the detailing that has had to be done. This has mostly been things that Brian Edwards has not done before so it has all had to be worked out. That and my attempts to remove as many thermal bridges as possible has added time to the build.
One of the key areas so far has been the rafter sprockets and fascia. There were discussions about how large the timber used needed to be to take both the uplift stress and the weight of the gutters etc. Firstly, we had to wait until the rafter panels were on the Oak frame so we could see where the roof line intersected so the fascia ran round level as these 2 areas are different pitches. Once that was sorted the rafter sprockets could all be cut from 89×38 timber. At the edge of the roof panels, some 38×50 was screwed to the steel and 40mm PIR insulation put between these. We are using some SOUDAL Fix & Bonds low expansion foam to help seal and fix the insulation.
The rafter sprockets are then screwed on through to the steel frame and more insulation inserted between these. Again copious amounts of expanding foam provide a well sealed detail. The gable end was done in much the same way. The SIPs were designed to come to the same height as the top surface of the steel rafter panels and the 38×50 used followed by the 89×38 both in-filled with insulation.
The next detail to be sorted out was the fascia and the over fascia protector. This is complicated by my decision to use the Nu-Lok tiling system that consists of a metal ‘Z’ batten and a clipped in tile. Partly because of this, and the fact these battens will be screwed to the counter battens rather than right through, the counter battens are 38×50.
Again the detail we have ended up with is very neat and does the job just fine.
The fascia itself is just 145×22 Dressed and Treated with 2 coats of Sadolins on both sides. A groove has been put on the back face to take 9mm ply for the soffit.
We also had long discussions over the use of a breathable membrane on the roof. I really fail to see why it is needed but it was an argument I was not going to win with the BCO so I reluctantly accepted this.
The other thing I should mention are the long fixings I am using. The first lot I got through ACS where I got some wall channel from (more on that another time) and they are not great. As you can see, the tips keep breaking.
I had been recommended a firm called CFT Ltd http://www.cftltd.net/stafix.html but had not used them. I have now found a local supplier Regis Roofing in Glasgow and started using them. They are far superior, Stainless Steel instead of BZP, and even cheaper for a longer screw.