dpmiller Posted March 18, 2020 Share Posted March 18, 2020 I see confusion here... Are we talking about studs or joists just now? Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 (edited) 3 minutes ago, dpmiller said: I see confusion here... Are we talking about studs or joists just now? Hi dpmiller.. the pozi-joists/ ceiling shown in pic top of page 2. Edited March 18, 2020 by zoothorn Link to comment Share on other sites More sharing options...
andyscotland Posted March 18, 2020 Share Posted March 18, 2020 25 minutes ago, zoothorn said: The joist width is indeed 100mm. So if 300mm gaps between, & 400mm centres. Just measured to check. (The joist height.. I think n/a just for now.. is 200mm). Ah ok. In that case you could try the pre-cut 380mm but it may be a bit too wide and need to be trimmed. My hunch is it will probably compress/bow in ok. Ultimately you're only going to get 3 widths out of a 1200mm roll either way (as you will need at least a bit wider than 300mm). So it's the same amount of materials and the same number of cuts to get a 1200mm and cut it down with an offcut, or a 3*380 and trim each one. Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 56 minutes ago, andyscotland said: What thickness are your joists? If the gap is 300mm then for the centres to be 400mm means the joists are 100mm thick which seems high? Hi Andy.. thickness, do you mean their Height, or Width? If my gaps are 300mm wide, I just need to establish what width of stuff to buy. If 300mm.. it'll fall out. If 500mm.. it'll perhaps likely no be able to go in. If its very dense.. then 400mm might still not be able to squash in. I don't know. I may have asked this a few weeks ago, but I just can't find where. Link to comment Share on other sites More sharing options...
andyscotland Posted March 18, 2020 Share Posted March 18, 2020 Thickness I meant width, which you've answered above. You won't get 500mm into a 300mm gap. I'd be tempted to try with the pre-cut 3 x 380mm, you might have to trim it a bit but my hunch is not. And even if you do you'll have the same wastage as you would if you bought an uncut roll and cut it to say 3 x 320mm with an offcut, so it's not going to make a difference cost-wise. Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 4 minutes ago, andyscotland said: Thickness I meant width, which you've answered above. You won't get 500mm into a 300mm gap. I'd be tempted to try with the pre-cut 3 x 380mm, you might have to trim it a bit but my hunch is not. And even if you do you'll have the same wastage as you would if you bought an uncut roll and cut it to say 3 x 320mm with an offcut, so it's not going to make a difference cost-wise. Pre-cut 3x 380mm. So you mean I can buy 380mm stuff.. or is your suggestion me to cut it from a 1200mm roll? Its I think due to the fact that I have unusually small gaps, is why the problem here. Why this is built like so.. I have no idea. Seems too many joists to me. Link to comment Share on other sites More sharing options...
andyscotland Posted March 18, 2020 Share Posted March 18, 2020 6 minutes ago, zoothorn said: Pre-cut 3x 380mm. So you mean I can buy 380mm stuff.. or is your suggestion me to cut it from a 1200mm roll? Its I think due to the fact that I have unusually small gaps, is why the problem here. Why this is built like so.. I have no idea. Seems too many joists to me. It does seem a lot of joists, but there's almost certainly a reason. Possibly to do with the weight loading / span. Unlikely the builder used extra materials for the sake of it. If you look at the link I posted above earlier this morning, you can get the FrameTherm 35 (and most other insulation) in a variety of formats. It generally all starts off as a 1200mm roll, and you can buy it like that, or with the roll pre-cut at the factory into different widths. There's also some products that are scored, rather than cut, so you get score lines for both 3 x 380 and 2 x 570 on the same roll and then you cut/tear along the scores for the widths you want. Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 @andyscotland terrific thanks for that. I was concerned pre-cut meant me doing it.. I've only a handsaw/ could only see a zoot fluff nightmare ! Right good. So I'll buy (140mm) 380mm x 3. Two of. And fill the remaining 1.5m (two of won't quite be enough) with PIR offcuts. Plan sorted. Really helpful Andy- thanks. Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 But trouble is I have 3x builders merchants here, none sell the stuff.. I can't buy it online (without £45 delivery) so it rules this stuff out. Ok back to square 1. I have 300mm wide gaps between joists. What else can I put in here? Link to comment Share on other sites More sharing options...
andyscotland Posted March 18, 2020 Share Posted March 18, 2020 1 minute ago, zoothorn said: But trouble is I have 3x builders merchants here, none sell the stuff.. I can't buy it online (without £45 delivery) so it rules this stuff out. Ok back to square 1. I have 300mm wide gaps between joists. What else can I put in here? They will surely supply some form of mineral / rock wool insulation? It's a pretty standard product. Ask them what they have that's equivalent/closest. Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 Just now, andyscotland said: They will surely supply some form of mineral / rock wool insulation? It's a pretty standard product. Ask them what they have that's equivalent/closest. Its the rockwool stuff, but its 400mm wide so I don't know whether it'll go in, bend in.. and its godawful stuff too. If I break 50mm off each bit the job will be an unpleasant nightmare. 100mm excess width.. is alot extra/ & its pretty solid slabby stuff. Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 Had to make a choice.. went for only thing available (without a wait.. need to get cracking now) & that's 600mm wide rockwool. So Ive got to cut the damn stuff in half, then got bamboo canes to support it all. Not happy, esp Jewson wherby I cannot see the damn price online > go in, & have to take their word for it that the price is what they say it is (which seems dearer than I was quoted before). But I have no way of knowing or checking the price. So I think Ive made a wrong decision, if its gonna slump down between the canes fk it.. but its bought now. Is there any extra way I can keep this wretched stuff up? What is this ridiculous system wherby prices are 'hidden' from me the customer?? fkn absurd & drives me fkn mad. Link to comment Share on other sites More sharing options...
wozza Posted March 18, 2020 Share Posted March 18, 2020 (edited) I am currently paying £11.55 (+ vat) for 100mm Rockwool RWA45 (600mm wide) from local Travis Perkins (job lot ordered and not collected) Edited March 18, 2020 by wozza Link to comment Share on other sites More sharing options...
andyscotland Posted March 18, 2020 Share Posted March 18, 2020 49 minutes ago, zoothorn said: Had to make a choice.. went for only thing available (without a wait.. need to get cracking now) & that's 600mm wide rockwool. So Ive got to cut the damn stuff in half, then got bamboo canes to support it all. Not happy, esp Jewson wherby I cannot see the damn price online > go in, & have to take their word for it that the price is what they say it is (which seems dearer than I was quoted before). But I have no way of knowing or checking the price. So I think Ive made a wrong decision, if its gonna slump down between the canes fk it.. but its bought now. Is there any extra way I can keep this wretched stuff up? What is this ridiculous system wherby prices are 'hidden' from me the customer?? fkn absurd & drives me fkn mad. You could get some cheap garden netting and staple it onto the joists as you put the insulation up. Doesn't need to be anything special or particularly strong. Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 3 minutes ago, andyscotland said: You could get some cheap garden netting and staple it onto the joists as you put the insulation up. Doesn't need to be anything special or particularly strong. Hi Andy.. but I need to try & keep it as high as possible (in my case up to the cables, that run under the top 'tier' wood top of the joist).. in order for there not to be a big void immediately below the floor, surely? If I staple netting over the whole thing I can only do this logistically on the underside of the lower wood 'tier' of the pozi-joist.. meaning a 60mm void. Surely this void = cold just below the floor. I just don't get the idea of this insulation job, especially having to negotiate around all the cables & not touch them. I mean how on earth ProDave did his, I have no idea. I can see the results, but how he did it.. & where the cables are is a mystery. Link to comment Share on other sites More sharing options...
andyscotland Posted March 18, 2020 Share Posted March 18, 2020 Is this in your intermediate floor? Why would a void there be cold? It will be the same temp as the room above, it's still above the insulation. Link to comment Share on other sites More sharing options...
dpmiller Posted March 18, 2020 Share Posted March 18, 2020 staples and string. it's what SWMBO has done with ours... Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 1 hour ago, andyscotland said: Is this in your intermediate floor? Why would a void there be cold? It will be the same temp as the room above, it's still above the insulation. Yes my intermediate floor. I don't know why, I just assumed like the PIR behind the pB it needs to be close to it, rather than pushed back with a void behind the pB. Or, wouldn't cold get in the void from the sides.. where there's only a bit of timber between here & the wall cavity-? I still have a hunch the top room will be cold, because of the huge no. of timber studs used, the relatively average-at-best ceiling insulation (builder put in minimum required & ceiling not sealed), the big stone wall forming one of the 4 walls, the big glass areas on two walls (french doors, big window).. & the floor not being a nice warm 200mm celotex + screed, but instead 22mm of chipboard > 60mm void > & some fancy bum fluff. Link to comment Share on other sites More sharing options...
zoothorn Posted March 18, 2020 Author Share Posted March 18, 2020 49 minutes ago, dpmiller said: staples and string. it's what SWMBO has done with ours... didn't think of that- dammit. Link to comment Share on other sites More sharing options...
zoothorn Posted April 6, 2020 Author Share Posted April 6, 2020 Ok thanks for the help- done the job (600mm W rockwool @ 140mm thick.. breadknife cut in half to 300mm W). So whether or not it has -any- noise containing properties after all that.. who knows.. IE the innitial idea of putting something 'sound containing' in was ultimately totally n/a it seems, as I was constrained fully in terms of what stuff I had to use, by the 300mm W of my joists it seems to me. And whether or not I've done it right- who knows. The many cables at the sides Ive done my best to avoid touching.. but these areas are voids/ I've especially no idea if this is correct here, above door area pic 3. Link to comment Share on other sites More sharing options...
PeterW Posted April 6, 2020 Share Posted April 6, 2020 That’s a very tidy job ..!! Getting something up those holes at the edges would be my preference to stop any flanking noise. Link to comment Share on other sites More sharing options...
Mr Punter Posted April 6, 2020 Share Posted April 6, 2020 Nice. I hate doing ceilings with Rockwool as I always get a bit down my back, a bit in my eyes and then inhale the rest. Link to comment Share on other sites More sharing options...
Big Jimbo Posted April 6, 2020 Share Posted April 6, 2020 Zoot the Hoot. Walls, and ceiling look the biz fella. Well done. Link to comment Share on other sites More sharing options...
zoothorn Posted April 14, 2020 Author Share Posted April 14, 2020 On 06/04/2020 at 15:40, PeterW said: That’s a very tidy job ..!! Getting something up those holes at the edges would be my preference to stop any flanking noise. Hi Peter.. missed this reply, thanks.. the thing is these holes/ gaps I've left due to being where majority of cables congregate > exit thru wall LHS of the door (in old wall). I'm not sure about the proximity of cables/ fluff you see, so reticent/ waiting for advice. Got fluff left.. but should I just stuff these areas & cover the cables then? Link to comment Share on other sites More sharing options...
PeterW Posted April 14, 2020 Share Posted April 14, 2020 Stuff it in - you’re de-rating the cables for 8” at most which is fine. Link to comment Share on other sites More sharing options...
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