I realised that I had not really done an update on progress. So where are we?
The insulating of the walls were completed week before last and since then the flooring has gone down on the first floor and the garage lined with ply to help seal it, provide some of the fire resistance and something to screw to. The flooring (as with everything) took longer on the steel frame. The joists do not fall on 600mm centres exactly so where the join was off the joist a gusset had to be glued and screwed in. We also glued the floor down with copious amounts of D4 so that will never move! The screws were Timco 50mm Self drilling but they really did not like going through the Egger 22mm chipboard so the needed a pilot hole (another process).
So with the windows on site, wind and water tight is in sight. The first windows went in today and I must say, after much work on getting the detailing right, I think we have come up with a great solution that really minimises the thermal bridges.
I am using a number of products from Soudal to try and make the windows as air-tight as possible and I will blog more on that another time.
So the detail is that the windows have a plywood box round the frame, sealed using Soudal Vapourseal. The ply is Malayan WBP EN636/3. The specification for ply has changed so just asking for ‘External Ply’ is just not good enough. This assembly is then slotted into the frame and pushed through so the 6mm Masterboard can be attached on the outside of the ply so it sticks out by about 20mm. The Masterboard is there at the insistence of the BCO for fire protection. If I had known about that before, I would have made the openings bigger to allow for it. The assembly is then slid back so that the window sits about 20mm back from the front edge of the insulation. The frame is then screwed to the steel opening using 50mm self drilling screws.
When the blockwork is built it will be returned back to close the cavity and the gap between the window frame and the blockwork will be filed with expanding foam tape.