JackofAll Posted June 9, 2023 Share Posted June 9, 2023 Was thinking about fixing a plastic 50x50x6mm angle bracket to the inner side of the outer leaf to support the window boxes. I know @Iceverge cantileverd his osb "box" but 300mm is a lot(in our case). Anyone with a 300mm cavity done this or suggest something better. Link to comment Share on other sites More sharing options...
Iceverge Posted June 9, 2023 Share Posted June 9, 2023 Our windows rested on the external concrete cill and were bolted to the outer leaf. Our 18mm OSB boxes didn't actually take any weight of the window but are quite strong so long as the window isn't too wide. I'd be slightly weary of having a cold metal bracket on the external leaf connecting to plywood. It'd be inviting condensation on the ply in my mind. Link to comment Share on other sites More sharing options...
SteamyTea Posted June 10, 2023 Share Posted June 10, 2023 Make a T bream out of OSB. A decent adhesive, two battens either side of the T's "leg" should make it very sturdy. Link to comment Share on other sites More sharing options...
JackofAll Posted June 10, 2023 Author Share Posted June 10, 2023 16 hours ago, Iceverge said: Our windows rested on the external concrete cill and were bolted to the outer leaf. Our 18mm OSB boxes didn't actually take any weight of the window but are quite strong so long as the window isn't too wide. I'd be slightly weary of having a cold metal bracket on the external leaf connecting to plywood. It'd be inviting condensation on the ply in my mind. Re. metal bracket, that's why I was suggesting a plastic one, nylon could also do but would the condensation still be an issue? Link to comment Share on other sites More sharing options...
JackofAll Posted June 10, 2023 Author Share Posted June 10, 2023 4 hours ago, SteamyTea said: Make a T bream out of OSB. A decent adhesive, two battens either side of the T's "leg" should make it very sturdy. Sorry for crude drawing, but is this correct Link to comment Share on other sites More sharing options...
Oz07 Posted June 10, 2023 Share Posted June 10, 2023 where's the window? Link to comment Share on other sites More sharing options...
SteamyTea Posted June 10, 2023 Share Posted June 10, 2023 If it is between the leaves, then no. Loose one bit and rotate 90⁰. Link to comment Share on other sites More sharing options...
JackofAll Posted June 10, 2023 Author Share Posted June 10, 2023 3 hours ago, Oz07 said: where's the window? Good Question, didn't feel the need to draw, just drawing what I thought steamy meant. Link to comment Share on other sites More sharing options...
JackofAll Posted June 10, 2023 Author Share Posted June 10, 2023 @SteamyTea is this what you mean? Link to comment Share on other sites More sharing options...
JackofAll Posted June 10, 2023 Author Share Posted June 10, 2023 I am thinking of fixing the windows to the boxes with the outer face slightly proud of the box butting up to the inner face of the outer leaf,(a strip of compriband foam between the two) hence the need for a bracket of some description to take the weight. Or is this a bad idea? Link to comment Share on other sites More sharing options...
Iceverge Posted June 10, 2023 Share Posted June 10, 2023 8 hours ago, JackofAll said: Re. metal bracket, that's why I was suggesting a plastic one, nylon could also do but would the condensation still be an issue? Should work fine if the nylon is strong enough. Green building store used compacfoam. https://www.greenbuildingstore.co.uk/kirkburton-passivhaus-strategy-for-windows-overheating/ What kind of windows are you using? The worst heat loss in our house is through the window frames. I would have liked to have overinsulated the frames if I could have easily done so. Link to comment Share on other sites More sharing options...
JackofAll Posted June 11, 2023 Author Share Posted June 11, 2023 12 hours ago, JackofAll said: @SteamyTea is this what you mean? Link to comment Share on other sites More sharing options...
JackofAll Posted June 11, 2023 Author Share Posted June 11, 2023 7 hours ago, Iceverge said: Should work fine if the nylon is strong enough. Green building store used compacfoam. https://www.greenbuildingstore.co.uk/kirkburton-passivhaus-strategy-for-windows-overheating/ What kind of windows are you using? The worst heat loss in our house is through the window frames. I would have liked to have overinsulated the frames if I could have easily done so. Thanks @ Iceverge obviously never thought of compacfoam. Will check out price difference between nylon/compacfoam.Using internorm KF410 upvc aluclad. Link to comment Share on other sites More sharing options...
JackofAll Posted June 12, 2023 Author Share Posted June 12, 2023 On 11/06/2023 at 00:56, Iceverge said: Should work fine if the nylon is strong enough. Green building store used compacfoam. https://www.greenbuildingstore.co.uk/kirkburton-passivhaus-strategy-for-windows-overheating/ What kind of windows are you using? The worst heat loss in our house is through the window frames. I would have liked to have overinsulated the frames if I could have easily done so. @Iceverge just noticed the ply box header does not span the full distance of the cavity,cavider why? Also am I correct in saying that there's a gap between the stone bed connector and the face of the window? Unsure why the didn't use joint sealing tape in same gap. Link to comment Share on other sites More sharing options...
Iceverge Posted June 12, 2023 Share Posted June 12, 2023 48 minutes ago, JackofAll said: just noticed the ply box header does not span the full distance of the cavity,cavider why? Defo not. The outside leaf will be cold and possibly wet for much of the year. Any ply here wouldn't last the battle. I'm not sure about the gap there. 1 Link to comment Share on other sites More sharing options...
fclauson Posted June 19, 2023 Share Posted June 19, 2023 On 09/06/2023 at 23:03, JackofAll said: Was thinking about fixing a plastic 50x50x6mm angle bracket to the inner side of the outer leaf to support the window boxes. I know @Iceverge cantileverd his osb "box" but 300mm is a lot(in our case). Anyone with a 300mm cavity done this or suggest something better. We built a 250mm cavity 11 years ago you will need to think about moisture update in the outter leave - it sits at ambient temp and acts as thought its single skin wall sitting in a field - we are currently investigation cracking which we think is due to freezthaw of a moisure rich external wall Link to comment Share on other sites More sharing options...
JackofAll Posted June 20, 2023 Author Share Posted June 20, 2023 (edited) On 19/06/2023 at 06:09, fclauson said: We built a 250mm cavity 11 years ago you will need to think about moisture update in the outter leave - it sits at ambient temp and acts as thought its single skin wall sitting in a field - we are currently investigation cracking which we think is due to freezthaw of a moisure rich external wall Surely the same could be said for any twin leaf wall, be it 100mm or 300mm cavity as the outer leaf will always be exposed ambient temp from the inside. Is the crack through the block or in the plaster? Edited June 20, 2023 by JackofAll Link to comment Share on other sites More sharing options...
fclauson Posted June 20, 2023 Share Posted June 20, 2023 True - but (and I am still researching) passive /low energy homes might be more prone than those where there is some heat coming from the inside will come back when and if I find more detail on this Link to comment Share on other sites More sharing options...
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