TANK Posted February 4, 2023 Share Posted February 4, 2023 I'm about to put in a rough concrete floor down in my 6x3m outbuilding. I want to put some insulation in first, and have a selection of leftover boards which are varying in thickness between 40mm-60mm. Is it a big no-no to use slightly different sizes? Or can i still use them, as the finished level of concrete will still be the same? I'm not overly bothered with the finish, it's just an outbuilding for storage mainly, but just thought would be prudent to stick some insulation down whilst I have the chance... Link to comment Share on other sites More sharing options...
Conor Posted February 4, 2023 Share Posted February 4, 2023 No harm at all, just make sure they are all flat and don't rock about. 1 Link to comment Share on other sites More sharing options...
TANK Posted May 4, 2023 Author Share Posted May 4, 2023 just another quick question linked to this. A couple of the boards are non foil backed. does this matter? cheers. Link to comment Share on other sites More sharing options...
JohnMo Posted May 4, 2023 Share Posted May 4, 2023 Put some polythene over the top, as concrete reacts with the aluminium 1 Link to comment Share on other sites More sharing options...
TANK Posted May 21, 2023 Author Share Posted May 21, 2023 (edited) ok, finally going to move ahead with this now the weather is nice. one final question if you please: I think I saw somewhere that you shouldn't pour the concrete right up against the walls, in order to allow the building to 'breathe'. I now can't seem to find any reference to this, and although it still seems logical, am starting to wonder if I made it up in my head! if it isn't supposed to directly against the walls, then what forms the perimeter - wooden form work/shuttering? If so, does that remain in place or is it somehow removed? Many thanks again good peeople. Edited May 21, 2023 by TANK Link to comment Share on other sites More sharing options...
Dave Jones Posted May 21, 2023 Share Posted May 21, 2023 use a dpm under the lot. Link to comment Share on other sites More sharing options...
Redbeard Posted May 21, 2023 Share Posted May 21, 2023 Are you planning some internal insulation in the walls? If so, have an insulation upstand from the under-floor insulation to just above finished floor level, so that your internal insulation can connect tightly to it. I think I'd do an upstand in any case. Link to comment Share on other sites More sharing options...
Iceverge Posted May 21, 2023 Share Posted May 21, 2023 2 hours ago, TANK said: ok, finally going to move ahead with this now the weather is nice. one final question if you please: I think I saw somewhere that you shouldn't pour the concrete right up against the walls, in order to allow the building to 'breathe'. A perimeter upstand of say 25mm PIR will reduce the conductive heat loss from the slab -> walls -> ground. I'd you're not bothered about this you can just pour to the walls. 1 Link to comment Share on other sites More sharing options...
TANK Posted May 21, 2023 Author Share Posted May 21, 2023 Ah right. Yes that will work. Thank you. Link to comment Share on other sites More sharing options...
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