Breathable membrane

[Astrokev]

Hi All

I'm getting close to wanting to cover the walls of my obsy build.

I don't know whether to invest in putting up breathable membrane (Tyvek or equivalent) to help protect the wall frames, before I put T&G boarding on the outside, or just put the T&G boards directly on top of the frame studding.

What do folks think?

If I should put membrane up, please can anyone suggest the make I should go for?  Tyvek seems a leading brand (and probably a top price) but are there others that would suffice at a cheaper cost?

Many thanks for any help

Kev

 

[Skipper Billy]

I used Tyvek on mine but most houses up here are timber framed so most builders have loads of ends of rolls and I got enough to do my obsy for a bottle of Whisky !

Your local builders merchants should be able to suggest alternatives??

[Astrokev]

9 minutes ago, Skipper Billy said:

I used Tyvek on mine but most houses up here are timber framed so most builders have loads of ends of rolls and I got enough to do my obsy for a bottle of Whisky !

Your local builders merchants should be able to suggest alternatives??

Thanks for that suggestion.

Just browsing the B&Q website, they sell vapour barrier which is much cheaper than Tyvek, but t his isn't breathable. Would this be inviting problems if it's not breathable?

Thanks

[JAO]

Used Protect A-1 Roofing underlay, which is available from Screwfix (https://www.screwfix.com/p/protect-protect-a1-roofing-underlay-1-x-45m/31795). Ten years on its has lasted very well.  Observatory is very dry and damp hasn't been an issue. Indeed it has faired better than some of the Shiplap, which I have had to replace.

[Skipper Billy]

52 minutes ago, Astrokev said:

Just browsing the B&Q website, they sell vapour barrier which is much cheaper than Tyvek, but t his isn't breathable

I think a non breathable membrane might be asking for trouble - a proper membrane allows moisture out but not in. 

[wetwalker]

Hi I've been using cromar  vent 3 from Screwfix for wall and roof linings in wooden stables and shed/workshop construction for a number of years now its breathable ,hard wearing and cheap about £46 for 1x50m.

Ian

[spillage]

As mentioned breathable roof membrane. I would start at the bottom and use a staple gun with a small overlap.

[Astrokev]

Thanks everyone, a great help as always.

kev

[r3i]

On 4/30/2018 at 23:52, Skipper Billy said:

I think a non breathable membrane might be asking for trouble - a proper membrane allows moisture out but not in. 

I used the cheap ScrewFix non breathable membrane on my observatory - 5 years on, no trouble here (touch wood)  There's plenty of ventilation around the rolling roof mechanism and there's also a solar powered fan to keep the air moving, so I've not had any problems with moisture build up.

Having said that, if I was to do it all again, I would be tempted to splash out on a breathable membrane - in the time honoured spirit of over engineering 

[Astrokev]

The membrane will be mainly for the walls, behind shiplap. For the roof, I will be using EPDM rubber so don't think I need use the membrane here.

I think I've seen some folks put membrane underneath the floorboards (ply), on top of the floor joists. Is there any benefit in doing this? The floor will not be subject to rain and, since the membrane will be breathable it will presumably let moisture vapour from the ground through, so I can't see the point of using it here.

Please can folks advise?

Thanks

[RayD]

I used Tyvek.  Easy to install and made for the job.  You can get 100M for about £100, use what you need and easily sell the rest. 

Membrane on the floor isn't essential but it does stop damp air causing issues on the floor which is not normally treated on the underside.  I put Celotex insulation in the floor which has effective built in damp proofing, but probably would have added a barrier had I not used it.  If you use one, the outside faces down so works the same way as it would on walls.  With this said, the way yours is installed with plenty of air space, I wouldn't think it necessary.

Best tip I had during my build was from @carastro which was to put some chicken wire around the outside to prevent the wildlife taking refuge under.  Was £5 or so from Wilko and gives me confidence that that's one thing I don't need to worry about.

Really enjoying your build Kev.

[Astrokev]

3 minutes ago, RayD said:

Really enjoying your build Kev.

Thanks Ray, that's very kind.

Thanks for your thoughts on vapour barrier - very helpful. I'd also already noted your use of chicken wire as suggested by @carastro. This is on my list of things to do!

[carastro]

Glad it helped Ray and you are passing on the tip.  Unfortunately I didn't know about that beforehand and its now too late to do it.  Have now blocked the edge with paving slabs on my lawn side as they were digging holes to get under the decking.  But I think wildlife is getting in from the side that is up against the fence as next door mentioned animals digging under the fence.

Carole 

[Astrokev]

1 hour ago, carastro said:

Glad it helped Ray and you are passing on the tip.  Unfortunately I didn't know about that beforehand and its now too late to do it.  Have now blocked the edge with paving slabs on my lawn side as they were digging holes to get under the decking.  But I think wildlife is getting in from the side that is up against the fence as next door mentioned animals digging under the fence.

Carole 

Crikey, they seem very determined to get under your obsy Carole!

Thanks for your tip which will hopefully do the trick. We've had badgers in the garden last year digging holes, but doubt they'd fit under my obsy! ;-)