Crofter Posted July 22, 2016 Share Posted July 22, 2016 After a couple of weeks away from the build, I'm going to install my windows next week. I *think* I know what I'm doing, but thought it would be worth asking those with a bit more knowledge than myself to confirm... Wall buildup is (from inside out) 12.5mm plasterboard, 25mm battened service void, plastic vcb, 50mm PIR, 145mm studs fully filled with rock wool, 11mm OSB, breather membrane, 25mm counter batten (vertical), 50x50 batten (horizontal), then final element is vertical larch cladding laid board on board- thickness tbd. As built, I have only got the studs/osb and breather in place just now. The breather is trimmed and lapped into the openings. The windows are 3G alu-clad with a frame depth of about 95mm. My plan is to install the windows so that they are flush with the outer face of the OSB. I have left a 15mm gap all round and will screw through the frames, with treated softwood packers to make up the gap. Where sashes are fixed I will use angle brackets. Low expansion foam to fill the gaps. On the outside, the reveal (ingo?) will be made from the same wood as the cladding, with a bead of sealant at the join. On the inside, the vcb will be fixed to the window frame using airtightness tape. My only real concerns are 1- should I use plastic rather than softwood for the packers? 2- any reason to use e.g. torx screws rather than ordinary pozi ones? 3- forming the weather seal. Should I close up the 15mm gap all around with sealant, then the timber reveal pieces butt up to that? Is there a risk of trapping moisture and if so what sort of sealant could I use? 4- forming the airtightness seal on the inside. Would it be best to tape a strip of VCB material around the frame edge before installation, or is it OK to just tape the vcb onto the window later in the build? 5- do I need to think about the 25+50mm cavity between the timber cladding and the OSB, and some way of closing it, other than what would be needed to support the reveals anyway? Hope all of that makes sense. I have tried googling all of this but 99% of info seems to be about houses with masonry outer skins. Link to comment Share on other sites More sharing options...
Crofter Posted July 23, 2016 Author Share Posted July 23, 2016 Anyone? Another question- the through-frame fixings, I am thinking of using stainless for this as they will be visible whenever the window is open, and I could see some moisture being trapped inside the window mechanism between the seals. 1 Link to comment Share on other sites More sharing options...
Tennentslager Posted July 23, 2016 Share Posted July 23, 2016 This help? http://www.gov.scot/Publications/2002/03/15098/8744 Link to comment Share on other sites More sharing options...
Crofter Posted July 23, 2016 Author Share Posted July 23, 2016 Yes have digested that one already! Also found a useful guide from NorDan. Just trying to nail (screw?) down the last few details. Link to comment Share on other sites More sharing options...
Tennentslager Posted July 23, 2016 Share Posted July 23, 2016 Don't know if this will help re Q3 and 5 but what I did was make a frame from 4*2 that was 10mm smaller all around than the window. The cill and the head were at a 22.5 degree angle for rain run off. I cheek screwed this from the inner face through to the studs around the window. Long decking screws as they were angled about 45 degrees. This meant the window/OSB join was covered by this frame and was also the external reveal. The cladding was butted up to this frame . Sealed it using bog standard mastic. There's a decent pic on my blog if you zoom in on the gable windows. There was no need for a head on the other windows as they were tucked up under the eaves and never going to get wet. Hope this makes sense Link to comment Share on other sites More sharing options...
Crofter Posted July 23, 2016 Author Share Posted July 23, 2016 Yes that does make a lot of sense, thanks. I don't think I have to worry about headers as the windows are almost right up tot he eaves, which have a decent overhang. Link to comment Share on other sites More sharing options...
Alex C Posted July 23, 2016 Share Posted July 23, 2016 Plastic packers. Foam around the window inside and out then trim back neatly. Silicone the outside and tape the inside for airtightness. what you do with the cladding and battens depends on being horizontal or vertical cladding. The detail linked above is a good one. TRADA also have sections knocking around that are helpful. Link to comment Share on other sites More sharing options...
Crofter Posted July 23, 2016 Author Share Posted July 23, 2016 Thanks, that basically tallies with what I've read elsewhere. NorDan suggest only filling about 50mm of the frame depth and then leaving a gap, with a bead of mastic in front of it which should be open to drain at the bottom. This will all then be hidden behind the reveal. I've gone for Torx-head yellow zinc fixings as the stainless ones had some iffy reviews with several mentions of them bending or sheering. Aim to start installing on Monday.. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 23, 2016 Share Posted July 23, 2016 I've just fitted a Pv array on a roof and used A2 stainless fixings. They're rock solid with zero shear, snapping etc and I'd not consider anything else for that particular task. Stainless can be soft as butter but these ones I used were concrete solid. tough at the top Link to comment Share on other sites More sharing options...
Crofter Posted July 23, 2016 Author Share Posted July 23, 2016 What brand were they? I was just going by what Screwfix had. It's not really an exposed location, just an issue of cosmetic appearance really. The Torx heads will look quite neat I think. Link to comment Share on other sites More sharing options...
Declan52 Posted July 23, 2016 Share Posted July 23, 2016 12 minutes ago, Nickfromwales said: I've just fitted a Pv array on a roof and used A2 stainless fixings. They're rock solid with zero shear, snapping etc and I'd not consider anything else for that particular task. Stainless can be soft as butter but these ones I used were concrete solid. tough at the top Sitting down on the job watching them other two guys do the work. Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 23, 2016 Share Posted July 23, 2016 The one on the left is called Grindy, the one on the right is Choppy. ?? Link to comment Share on other sites More sharing options...
Nickfromwales Posted July 23, 2016 Share Posted July 23, 2016 I was called a fat Billy Elliot as if you zoom in, you'll see I broke 4 tiles getting up there Link to comment Share on other sites More sharing options...
Declan52 Posted July 23, 2016 Share Posted July 23, 2016 1 hour ago, Nickfromwales said: I was called a fat Billy Elliot as if you zoom in, you'll see I broke 4 tiles getting up there One too many beer and kebabs will do that. Link to comment Share on other sites More sharing options...
Crofter Posted July 31, 2016 Author Share Posted July 31, 2016 Just to update, first two windows went in today. First one I installed as per the instructions, removing the sash first. It was actually very akward getting the sash back in and I needed to call in some helpers. For the second window, which was much larger, I decided to leave the sash in place and fix angle brackets to it before installation. This worked out much easier, as even though the window was very heavy to handle, there was no need to hold a heavy sash up in the air and carefully fix it back to the mechanism. With that big window installed, I could remove the temporary boards and use them to finish building the floor. I'll update the blog at some point as there's been a reasonable amount of progress now. Link to comment Share on other sites More sharing options...
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