Shed wall construction

[gjh]

OK, the start of my winter project. I'm building a playhouse for my 2yo & 4yo, which will be an 2.5mx2.5m shed with a raised platform inside.

I know, starting an outdoor project in winter makes no sense but this has to be completed by March - i hope to get it closed in within a fortnight of starting, then i can take my time on the interior, which i aim to plaster, skirting, fitted cupboards, carpet upstairs, laminate downstairs, etc, etc - i'm a very slow worker!

My first question though is about the wall construction, i've googled loads and got lots of conflicting advice. But here is what I have settled on for now, working outside in....

1. 18mm pressure treated shiplap
2. pressure treated battons (size?)
3. breathable membrane (Tyvek?)
4. 18mm WBP PLY or OSB?
5. Timber frame (2x4) on 400mm centres - gaps packed with rockwool
6. breathable membrane (Tyvek again?)
7. plasterboard

Does this seem right to those in the know? The most conflicting advise i've seen is with regards to the placement of the breathable membrane. With the two arguments being:

1. It has to go behind the plasterboard (6) to stop warm moist air reaching the cold side of the insulation and then condensing there and soaking the insulation.

2. It has to go on top of the OSB (3) to protect the OSB from any water that penetrates the shiplap.

I've not yet decided on OSB or WBP WPLY as i've not priced up either, but I suspect that price might push me towards OSB, in which case i'd feel happier with the membrane on top of it (then again, i've not priced up the difference between OSB+Membrane vs PLY either!).

Would having both layers of membrane cause any issues?

Can anyone else offer any advice? I want this to be a sturdy, weatherproof construction that I can remove the platform from in the future when the kids get bigger and still be used as an outdoor playroom till the kids are in thier teens - at which point it'll become my quiet room where i can go and relax in peace with a good book!

 

[gjh]

I think i might be over engineering this a bit here...it is afterall only a shed!

Reconsidered plan:

1. 12mm pressure treated shiplap
2. pressure treated battons (25mmx25mm)
4. 9mm WBP PLY
5. Timber frame (pressure treated 2x4) on 400mm centres - gaps packed with rockwool
6. plasterboard

So thinner shiplap, thinner PLY sidings and no membranes.

This is still sturdier than a shed from a garden center, one of which is still standing in my garden ten years later (though it is a little worse for wear, hence this project).

I assume the WBP ply will still be thick enough at 9mm to add strength and rigidity to the structure, plus would be able to withstand the occasional bit of water that makes it past the shiplap? And i'm also assuming that once the walls are plastered, then there will be no/little moist air escaping into the frame?

Any help/suggestions would be gratefully recieved!

 

[foxhole]

Plasterboard and laminate will not survive high moisture content of a shed.

 

[gjh]

so your suggestion is?

 

[dhutch]

so your suggestion is?

Dont plaster it or put laminate down?

I would just leave it a the ply and paint that white.

ie
1. 12mm pressure treated shiplap
2. pressure treated battons (25mmx25mm)
4. 9mm WBP PLY
5. White paint

Unless your heating it i see no reason for insulation. If you want to insulate it, it would use some 25mm closed cell foam board between the ply and shiplap with the batterns. KISS.

Daniel