Breather Membrane

A_Novice · 29 May 2019

Hi,

Just a quickie. If you are studding out a single skin garage and you have block, breather membrane, studs from out to in. Which way should the printed side of the breather membrane be?

I would think facing outward to stop any water that gets through the block from penetrating the timber but would allow moisture out if any got into the timber side.

Does it matter which way round it goes?

Sound correct?

Thanks

John D v2.0 · 30 May 2019

It won't matter but why a breather membrane, what purpose does it have? Normally you would have them in an insulated buildup behind some cladding or rain screen.

A_Novice · 30 May 2019

Thanks John.

It seems there are some that use them and some that don't. In my case building control require it and as far as I can gather it stops water or vapour getting through the single brick skin and into the timber frame. Also let's vapour out of the timber frame into the cavity if some did happen to penetrate the vcl.

The manufacturer confirmed it is one way permuable so the printed side faces out.

In reality I imagine it is not needed especially as the single skin of brick won't be facing the elements very much.

John D v2.0 · 30 May 2019

Are you planning an insulated buildup or just studding it out? Might as well put some rockwool in at least, then the membrane would make more sense on the cold side. But even then if you are expecting water on the membrane it might be worth deciding where the water will go after that.Normally the cavity on the cold side would be drained to outside in case of condensation or water penetration.
Some people are in favour of just filling every void with insulation and hoping for the best, but if building control are involved sounds like they will know what they're doing.

A_Novice · 30 May 2019

The plan is to insulate the studs with celotex, add then I think 12.5mm of insulated plasterboard with the foil in for the vcl.

The builders are then going above for the first floor which is all timber.

Good point about where it goes from the cavity. The single skin hasn't got any weep vents so is odd BC want the breather membrane but no vents or cavity trays installed.

I'm learning as I go so trying to understand it all.

^woody^ · 31 May 2019

Any breather membrane has a side which repels moisture (with the advertising writing on!) and a side which attracts moisture, so needs to go the correct way around.

With garage conversions, the additional work of forming drained cavities is not required as the amount of penetrating or condensing moisture is typically too low to worry about. But if this is a new build extension or at first fllor, then it should have a properly designed drained and vented cavity.

John D v2.0 · 31 May 2019

^woody^ said:
Any breather membrane has a side which repels moisture (with the advertising writing on!) and a side which attracts moisture, so needs to go the correct way around

Is that a bit like one way glass, have to install it the right way round?

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Breather Membrane

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