Do I need a breathable membrane on outside of workshop?

jgoodman05

Hello,

I'm building a workshop at the moment , and wall sandwich is planned as follows -inside out -

ply / vapour barrier / 2x4, insulation / breathable membrane / cladding.


Questions:

Do I need a breathable layer on outside - only ones I can find are expensive and come in rolls twice what I need?

If I do need it , can anyone recommend a not too expensive brand?

Anyone recommend where I can get reasonably priced featheredge / shiplap?


Cheers

mp22

Check out the cheaper brands of roofing felt the membrain type might do for a shed

jack of all

Breather membrane is essential to keep your insulation from being wetted by driving rain whilst allowing trapped water vapour to escape. Homevalue do their own brand breather membrane which can't be too expensive. Unless you know a builder or someone doing a build you could try adverts.ie, someone may have some left over from a project.

CJhaughey

I would prefer to make the wall as follows:
Ply/Vap barrier/Stud/OSB/Breathable membrane/Batten/Cladding.

jgoodman05

Cheers Jack Of All, is that homevalue hardware?

Double Barrel

I do not like vapour barriers used in wood construction. It is just about impossible to install VB's under field conditions and not puncture the barrier.

If it was mine I would put OSB (taped and jointed) on the inside of the framing to make it airtight. So, working outward, OSB taped and jointed, 2x frame, properly installed cellulose insulation (by the book), exterior sheeting of OSB or if a higher R value is required, exterior grade wood fibreboard and lastly a breathable external render.

This allows the frames to breathe to the outside.
You could put building (mineral) felt and battens between the OSB and the render depending on the render.

jack of all

jgoodman05 wrote: »

Cheers Jack Of All, is that homevalue hardware?

Yep.

teepee

if you are going to use a breathable menbrane to your self a favor and use tyvek supor plus its the best you cant go wrong . its costly all right but you cant relplace it six months down the road :eek: .