Air tight membrane

[Russell griffiths]

Never had to buy this before, can anybody recommend a good product that won’t cost the Earth 

everything I buy that isn’t an of the shelf item at the builders merchants comes with a massive price hike for being SPECIAL. 

[dpmiller]

air tight, but what vapour permeability?

 

[Russell griffiths]

Sorry should have added more detail

 

internal membrane for a ceiling, fitted to timber joists with counter batten to provide service void

happy to be vapour closed but I have looked at some of the clever ones that open and close to allow vapour to escape back into the room

 

silly money, I don’t know who makes up the prices. 

[dpmiller]

We are using Protect VC Foil Ultra. While it was supplied with the TF kit it's a brand that's common in the merchants and isn't the most expensive product out there?

[Carrerahill]

5 hours ago, Russell griffiths said:

Sorry should have added more detail

 

internal membrane for a ceiling, fitted to timber joists with counter batten to provide service void

happy to be vapour closed but I have looked at some of the clever ones that open and close to allow vapour to escape back into the room

 

silly money, I don’t know who makes up the prices. 

Can you not use foil backed plasterboard?

[Russell griffiths]

17 minutes ago, Carrerahill said:

Can you not use foil backed plasterboard?

Not having plasterboard, timber ceiling. 

[A_L]

If being a vapour check is O.K.

 

https://novia.co.uk/uploads/components/variation/NoviaVC2Mar19-5c865c7509c30.pdf

[ProDave]

Protect Bariair was the cheapest I could find. I got it to order from Jewsons.

[Oz07]

Do you just tape all joins or trap with batten @ProDave? Is that tape you linked the other day the cheapest?

 

I've sourced the smart ply airtight osb at about 30 quid a sheet thinking that might be easier to fix and less susceptible to damage. Still have to take though 3.6 l/metre per board plus ceiling perimeter. 

@joe90 you went for battens over your board joints rather than tape?

[ProDave]

1 minute ago, Oz07 said:

Do you just tape all joins or trap with batten @ProDave? Is that tape you linked the other day the cheapest?

 

The Protect Bariar has an inbuilt tape at the edges but I didn't trust it, so I made sure each joint was pinched, either behind a batten, or if nothing convenient, I screwed a strip of plasterboard or OSB offcut over the joint to keep it squashed together.

 

For all other joints I used the Tescon Vana that I bought from the German seller on ebay.

[Oz07]

Do you staple to joists/trusses?

[CC45]

staple & then bit of tape.

[joe90]

On 01/08/2019 at 20:57, Oz07 said:

@joe90 you went for battens over your board joints rather than tape?

 

Sorry been away on hols, sort of, used ordinary osb, no membrane, internally below insulation. All joints both vertical and horizontally were covered in 3” osb strips bubble glued and screwed on, didn’t bother trying to land joints on rafters as too much waste and a faf. At the rafters I cut osb to give a 10mm gap around rafters and foamed it too death. I believe this is airtight enough with no droughts and my air test proved this. If you want it more airtight then paint it with a non breathable paint . I am not a fan of tapes and membranes ?.

[Oz07]

Sounds good @joe90 no sweat on the delayed reply. What thickness did you go for 12mm? How about wall plate junction surely you used tape or membrane there?

[joe90]

51 minutes ago, Oz07 said:

Sounds good @joe90 no sweat on the delayed reply. What thickness did you go for 12mm? How about wall plate junction surely you used tape or membrane there?

Yes, 12mm, at the wall plate see above about rafters. Between wall plate and bock this was wet plastered over with metal mesh, top of wall plate - rafters, OSB, = foam.