liquid membrane alternatives

[gravelrash]

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?

[Olf]

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.

[Onoff]

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.

[saveasteading]

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.

[gravelrash]

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.

[gravelrash]

anymore input

[JohnMo]

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.

[Olf]

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.

[gravelrash]

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.

[PeterW]

Sand and cement parge coat then..? Could also use bonding as well. Or do you want something semi flexible ..?? 

[Chanmenie]

what about this stuff

 

A liquid airtight membrane no less 

 

https://www.intelligentmembranes.co.uk/product-category/control-range/

[gravelrash]

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.

[Iceverge]

The real deal won't break the bank if it's only a small area. 

[tonyshouse]

Wet plaster for me every time, insulation in the cavity - on mine was 300mm

[saveasteading]

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?

[Olf]

@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

[Onoff]

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? ?

[PeterW]

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..??

[gravelrash]

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. 

[Onoff]

A picture says a thousand words etc.

[Pocster]

You need walk on glazing for sure 

[gravelrash]

23 hours ago, pocster said:

You need walk on glazing for sure 

You still got the glass units....?