Raine Posted March 18 Share Posted March 18 I once read that external brick & block wall cavities need to be 10mm wider than the insulation. I.e. 150mm Dritherm 32 would need a 160mm cavity. I can't find where I read that now. Is that correct, or should I ignore / forget it and go for 150mm cavity? Link to comment Share on other sites More sharing options...
nod Posted March 18 Share Posted March 18 You need 50 mil wider than your cavity bat Unless you full fill Link to comment Share on other sites More sharing options...
joe90 Posted March 18 Share Posted March 18 I full filled my 200mm cavity with Dritherm, two layers of 100mm batts. 1 Link to comment Share on other sites More sharing options...
HughF Posted March 18 Share Posted March 18 You can get away with 10mm gap if you use interlocking PIR with taped joints, but that's such a faff to do properly, just got full-fill rockwool. 1 Link to comment Share on other sites More sharing options...
Canski Posted March 18 Share Posted March 18 We always add 10 mm to full fill cavity widths as the dritherm tends to expand (especially when wet) and push against the block walls a bit. 2 Link to comment Share on other sites More sharing options...
Iceverge Posted March 18 Share Posted March 18 Or use EPS beads. 1 1 Link to comment Share on other sites More sharing options...
mjc55 Posted March 18 Share Posted March 18 1 hour ago, joe90 said: I full filled my 200mm cavity with Dritherm, two layers of 100mm batts. I seem to remember you saying that you built using masonry walls (please ignore if wrong) in which case what did you use for wall ties? Link to comment Share on other sites More sharing options...
nod Posted March 18 Share Posted March 18 1 hour ago, HughF said: You can get away with 10mm gap if you use interlocking PIR with taped joints, but that's such a faff to do properly, just got full-fill See if you can find a bricklayer that can work to a 5 mil tolerance Link to comment Share on other sites More sharing options...
Moonshine Posted March 18 Share Posted March 18 1 hour ago, mjc55 said: I seem to remember you saying that you built using masonry walls (please ignore if wrong) in which case what did you use for wall ties? stainless steel wall ties i did 150mm cavity with wall ties. You can used Ancon ST1 ties for 200mm cavity but they are expensive. I found vartry very helpful http://www.vartryengineering.com/products/extra-long-wall-tie-large-cavities.html Link to comment Share on other sites More sharing options...
Temp Posted March 18 Share Posted March 18 Pricing error on Jewson site? Says... Ancon ST1 Type 1 Heavy Duty Wall Tie 200mm Pack of 250 £3.08 inc VAT https://www.jewson.co.uk/p/ancon-staifix-standard-heavy-duty-wall-tie-200mm-l-CIWT0275 They obviously mean per tie but it does say "box of 250" in several places. The page for the longer version doesn't. 1 Link to comment Share on other sites More sharing options...
Moonshine Posted March 18 Share Posted March 18 (edited) 8 minutes ago, Temp said: Pricing error on Jewson site? Says... Ancon ST1 Type 1 Heavy Duty Wall Tie 200mm Pack of 250 £3.08 inc VAT https://www.jewson.co.uk/p/ancon-staifix-standard-heavy-duty-wall-tie-200mm-l-CIWT0275 They obviously mean per tie but it does say "box of 250" in several places. The page for the longer version doesn't. Let's find out, just ordered 5 boxes for £13 🤣 Edited March 18 by Moonshine 2 Link to comment Share on other sites More sharing options...
joe90 Posted March 18 Share Posted March 18 5 hours ago, mjc55 said: I seem to remember you saying that you built using masonry walls (please ignore if wrong) in which case what did you use for wall ties? My builder supplied longer stainless wall ties. Link to comment Share on other sites More sharing options...
joe90 Posted March 18 Share Posted March 18 (edited) for 150mm cavity…. https://www.wickes.co.uk/Stainless-Steel-Housing-Type-4-Cavity-Wall-Tie-250mm-101-125mm---Pack-of-50/p/263631?gad_source=1&gclid=CjwKCAjwzN-vBhAkEiwAYiO7oDKQ4uQf84JBkQLArRQUChf3VZT2FmNyO91GhmH9wFRYv6DutBiTVBoCe20QAvD_BwE&gclsrc=aw.ds Edited March 18 by joe90 Link to comment Share on other sites More sharing options...
Raine Posted March 22 Author Share Posted March 22 On 18/03/2024 at 15:07, Moonshine said: Let's find out, just ordered 5 boxes for £13 🤣 What's the news @Moonshine? Did your 5 boxes arrive yet? Link to comment Share on other sites More sharing options...
Moonshine Posted March 22 Share Posted March 22 9 minutes ago, Raine said: What's the news @Moonshine? Did your 5 boxes arrive yet? They have a 4-8 week lead time on them,so i have a bit of time to wait 1 Link to comment Share on other sites More sharing options...
Raine Posted March 22 Author Share Posted March 22 On 18/03/2024 at 10:05, Canski said: We always add 10 mm to full fill cavity widths as the dritherm tends to expand (especially when wet) and push against the block walls a bit. Yes, I think that's the same explanation that I read / heard before. The problem with that though is that cavity closers (which need to be a tight fit to prevent cold bridging) seem to be sized to match the insulation batts. So, for a full fill cavity, if I go with 150mm Dritherm or Rockwool Full Fill Cavity Batts, and allow 10mm for insulation expansion, that would be a 160mm cavity, but I can't find any 160mm cavity closers. Plenty at 150mm though. I guess I'll have to spec the cavity at 150mm then, and hope that it doesn't push the blocks out of plumb. Link to comment Share on other sites More sharing options...
joe90 Posted March 22 Share Posted March 22 1 minute ago, Raine said: guess I'll have to spec the cavity at 150mm then, and hope that it doesn't push the blocks out of plumb. It didn’t with my 200mm cavity. Link to comment Share on other sites More sharing options...
Hughgo12 Posted March 22 Share Posted March 22 (edited) Nearly pulled the trigger on the Ancon's at £3 but realised i'll probably never build anything with a 50-75mm cavity Edited March 22 by Hughgo12 Link to comment Share on other sites More sharing options...
Iceverge Posted March 22 Share Posted March 22 4 minutes ago, Raine said: Yes, I think that's the same explanation that I read / heard before. The problem with that though is that cavity closers (which need to be a tight fit to prevent cold bridging) seem to be sized to match the insulation batts. So, for a full fill cavity, if I go with 150mm Dritherm or Rockwool Full Fill Cavity Batts, and allow 10mm for insulation expansion, that would be a 160mm cavity, but I can't find any 160mm cavity closers. Plenty at 150mm though. I guess I'll have to spec the cavity at 150mm then, and hope that it doesn't push the blocks out of plumb. Don't bother with cavity closers. Fix some airtight membrane to the wall and window followed by a J bead screwed to the window and then some plasterboard. Link to comment Share on other sites More sharing options...
joe90 Posted March 22 Share Posted March 22 1 minute ago, Iceverge said: Don't bother with cavity closers. Fix some airtight membrane to the wall and window followed by a J bead screwed to the window and then some plasterboard. That’s what I did 👍 Link to comment Share on other sites More sharing options...
Iceverge Posted March 22 Share Posted March 22 All the more reason to use EPS beads too. 1 Link to comment Share on other sites More sharing options...
NandM Posted March 24 Share Posted March 24 (edited) On 22/03/2024 at 15:31, Iceverge said: All the more reason to use EPS beads too. Does the window strap or membrane go across the entire cavity to stop blown in cellulose from going everywhere? *Edit* or perhaps I do the fill after the windows are in place? Edited March 24 by NandM Link to comment Share on other sites More sharing options...
Iceverge Posted March 24 Share Posted March 24 3 hours ago, NandM said: Does the window strap or membrane go across the entire cavity to stop blown in cellulose from going everywhere? *Edit* or perhaps I do the fill after the windows are in place? The straps will be intermittent. You could also use angle brackets to bolt them to the outer leaf. The airtight membrane will be continuous around the perimeter of the window. If you have batts then these will be in before the windows. If you use EPS beads then these will be done after the windows and plasterboards. 1 Link to comment Share on other sites More sharing options...
Moonshine Posted March 27 Share Posted March 27 (edited) On 22/03/2024 at 15:11, Raine said: What's the news @Moonshine? Did your 5 boxes arrive yet? Apparently they are now at my local store awaiting collection, lets see what i find when i get there 🤣 I wonder what my legal options are if there are just 5 ties Edited March 27 by Moonshine Link to comment Share on other sites More sharing options...
joe90 Posted March 27 Share Posted March 27 3 hours ago, Moonshine said: wonder what my legal options are if there are just 5 ties Receipt clearly states “pack of 250, quantity 5” 🤷♂️ Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now