New shed insulation and treatment

[brittonc]

Hi all,

My new shed arrived today and want to make sure I get things right from the start. I've read other posts about insulation and watched numerous YouTube videos and there seems to be a lot of conflicting advice.

I've got some Barratine Log Cabin treatment for the outside but should I treat the inside too?

I've got breathable membrane to cover the inside and roof. The framework is 75mm deep which I intend to fill with Rockwool as I want to soundproof as much as possible. I read lots about leaving an air gap but the framework is enclosed so is this needed? I'll be using OSB or ply to cover the Rockwool. I will be leaving a 25mm air gap in the roof.

The floor will be covered in DPM, then membrane and 18mm OSB on top. Does it also need some form of insulation and if so, what is the best to use? It's not on a concrete base so limited cold coming directly through.

Any advice appreciated.

 

[Jameshow]

I wouldn't bother with the breathable membrane if your going to clad the inside with OSB / ply as that will be a membrane in and if itself. Bit if you already have it it won't harm it.

Same with the floor of put some 25mm polystyrene and then plywood again no membrane as the plywood / OSB will stop the vapour.

Cheers James

 

[brittonc]

Thanks James. I'm assuming polystyrene won't compress much with any weight spread over the OSB? I don't know what machinery I'll have yet but have some seen items weighing 200kgs or more.

 

[Jameshow]

Depends on the load distribution. If concerned put some 6x2 under the feet?
If on castors then some 6" square Ply pads??

Cheers James

 

[mikej460]

Membrane lets water vapour that collects between the cladding and insulation out to the air gap but also prevents water ingress from the small gaps in the external cladding. You normally staple it to the outer edge of the vertical studs but in this case you could put it inside each gap between the stud stapled to 25mm battens to give you a gap for air to circulate then lay insulation then staple the whole inside with vapour barrier or OSB3 or MRMDF (the latter two are moisture resistant so will act as a suitable vapour barrier). If you do this you will correctly insulate the walls and roof and protect your shed from eventual internal rot.

The floor is another issue due to the potential loading challenges. Normally you would insulate and build a floating floor with OSB3 floor panels. Have you read MikeG's Build a Shed Mike's Way - this will give you the pointers you may need.

hope this helps

 

[brittonc]

Thanks Mike. It an air gap necessary in the walls? I did take a look at Mike G's build a shed but it was a bit beyond me and his construction is brick built so not sure how much relates to pre-made wooden sheds. I was hoping to 'wrap' the inside with membrane, add the Rockwool into the cavities and box in with OSB but want to avoid future issues with rot/mould. With limited space inside I don't want to start adding batons so need to work with the space in the walls, which is about 75mm.