gravelrash Posted December 9, 2021 Share Posted December 9, 2021 I have an area of blockwork behind web joists that can only be sealed by spraying for airtightness, has any one got cheap alternatives for liquid membrane. I looked at permaseal which is vapor barrier but is used as a radon and CO barrier and a guy has suggested bitumen paint...has anyone used these? Link to comment Share on other sites More sharing options...
Olf Posted December 9, 2021 Share Posted December 9, 2021 2 hours ago, gravelrash said: cheap alternatives for liquid membrane None I'm afraid. Liquid (and fabrics) airtight membranes provide level of vapour permeability ('intelligence' in marketing blurb), but that comes at a premium. Otherwise timber frame buildings would be stapled with polyethylene DPM all round - and then rot... Depending on the size of the area and potential for condensation/evaporation on the other side you may as well get away with bitumen or similar stuff - it will just block all the moisture migration, either direction, with all the consequences. Link to comment Share on other sites More sharing options...
Onoff Posted December 9, 2021 Share Posted December 9, 2021 4 minutes ago, Olf said: None I'm afraid. Liquid (and fabrics) airtight membranes provide level of vapour permeability ('intelligence' in marketing blurb), but that comes at a premium. Otherwise timber frame buildings would be stapled with polyethylene DPM all round - and then rot... Depending on the size of the area and potential for condensation/evaporation on the other side you may as well get away with bitumen or similar stuff - it will just block all the moisture migration, either direction, with all the consequences. Is English your first language out of interest? The OP WANTS airtightness. Link to comment Share on other sites More sharing options...
saveasteading Posted December 9, 2021 Share Posted December 9, 2021 3 hours ago, gravelrash said: area of blockwork behind web joists That sounds like a small area of internal wall. The internal wall could be (wiIl be) covered in plastic, so an area of bitumen spray sounds ok to me, and much better than nothing. It will depend on what else you are doing to the wall, and where your general barrier will be going, but you can probably work out a lapping detail to keep the joists 'inside'. I have always found that bitumen on block requires at least 2 coats as the first doesn't enter all the dimples. if you can get a brush in all the better, but still at least 2 coats. Link to comment Share on other sites More sharing options...
gravelrash Posted December 9, 2021 Author Share Posted December 9, 2021 the section is along side of roof web joists 225mm deep (warm Roof above), ceiling boards under joists, rest of wall block walls to be wet plastered. Link to comment Share on other sites More sharing options...
gravelrash Posted December 10, 2021 Author Share Posted December 10, 2021 anymore input Link to comment Share on other sites More sharing options...
JohnMo Posted December 10, 2021 Share Posted December 10, 2021 Could you fill the gaps, with a hybrid mastic? But you can get Soudatight LQ for £45 a tub and then go around the perimeter of the house at dpc level and get that airtight also. Link to comment Share on other sites More sharing options...
Olf Posted December 10, 2021 Share Posted December 10, 2021 17 hours ago, Onoff said: The OP WANTS airtightness And I'm stressing out that airtightness for buildings is not equivalent to vapour barrier. Similarly to 'flat roof' having a slope, which surprisingly surprises some people. Link to comment Share on other sites More sharing options...
gravelrash Posted December 10, 2021 Author Share Posted December 10, 2021 I need to make the blocks airtight in a position that I can not plaster, there are no holes... just sealing the blockwork with something. Link to comment Share on other sites More sharing options...
PeterW Posted December 10, 2021 Share Posted December 10, 2021 Sand and cement parge coat then..? Could also use bonding as well. Or do you want something semi flexible ..?? Link to comment Share on other sites More sharing options...
Chanmenie Posted December 10, 2021 Share Posted December 10, 2021 what about this stuff A liquid airtight membrane no less https://www.intelligentmembranes.co.uk/product-category/control-range/ Link to comment Share on other sites More sharing options...
gravelrash Posted December 10, 2021 Author Share Posted December 10, 2021 1 hour ago, PeterW said: Sand and cement parge coat then..? Could also use bonding as well. Or do you want something semi flexible ..?? has anyone read my thread -its inaccessible for parge or plaster...its behind the webjoist. the thread started with an alternative lower cost product than purple, blowerproof etc. Link to comment Share on other sites More sharing options...
Iceverge Posted December 10, 2021 Share Posted December 10, 2021 The real deal won't break the bank if it's only a small area. Link to comment Share on other sites More sharing options...
tonyshouse Posted December 10, 2021 Share Posted December 10, 2021 Wet plaster for me every time, insulation in the cavity - on mine was 300mm Link to comment Share on other sites More sharing options...
saveasteading Posted December 10, 2021 Share Posted December 10, 2021 3 hours ago, Olf said: And I'm stressing out that airtightness for buildings is not equivalent to vapour barrier. Similarly to 'flat roof' having a slope, which surprisingly surprises some people. You are getting sensible suggestions based on the limited information provided. Airtightness/vapour barrier purposes are rather fundamental, so please explain what you don't understand. Likewise sloping roof. What is your concern? Link to comment Share on other sites More sharing options...
Olf Posted December 10, 2021 Share Posted December 10, 2021 @saveasteading I'm not the OP, just being called by @Onoff trying to gently respond that Eton education does not guarantee fluency in buildingese. Imho @Iceverge provided a solution, so for me EOT Link to comment Share on other sites More sharing options...
Onoff Posted December 10, 2021 Share Posted December 10, 2021 9 minutes ago, Olf said: @saveasteading I'm not the OP, just being called by @Onoff trying to gently respond that Eton education does not guarantee fluency in buildingese. Imho @Iceverge provided a solution, so for me EOT Oh Zoot wherefore art thou? ? Link to comment Share on other sites More sharing options...
PeterW Posted December 10, 2021 Share Posted December 10, 2021 11 hours ago, gravelrash said: has anyone read my thread -its inaccessible for parge or plaster...its behind the webjoist. the thread started with an alternative lower cost product than purple, blowerproof etc. sorry read that as in the gaps between.! Got a photo..?? Link to comment Share on other sites More sharing options...
gravelrash Posted December 11, 2021 Author Share Posted December 11, 2021 simples.. A block wall resides 75mm behind and parallel to the Web Joist, the roof deck sits directly on top of the joists. While 75mm is sufficient for a babbys hand to get in behind the joist my fat hands can not...so not possible to parge, plaster and would probably slice my sausages in to bacon on the steel webs trying to brush paint. So looking for a low cost liquid to create airtight barrier that can be sprayed. Link to comment Share on other sites More sharing options...
Onoff Posted December 11, 2021 Share Posted December 11, 2021 A picture says a thousand words etc. Link to comment Share on other sites More sharing options...
Pocster Posted December 11, 2021 Share Posted December 11, 2021 You need walk on glazing for sure Link to comment Share on other sites More sharing options...
gravelrash Posted December 12, 2021 Author Share Posted December 12, 2021 23 hours ago, pocster said: You need walk on glazing for sure You still got the glass units....? 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