Building shed from scratch - membrane considerations driving me insane!

11 May 2016
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United Kingdom
Hi all, firstly apologies for the lengthy post, and if I’m not explaining the situation well – this is my first build and although I’ve read a lot on both this forum and others, a lot of this is still fairly new to me!

I'm currently in the middle of building a shed, that essentially will be a compromise of trying to fit all of my bulky tools and other items that we currently have in the house, and a gap of c. 2.7mx2m between fence panels on 2 sides and a tree on another.

As such, I've settled on a 2.44x1.84m framed shed, with a planned 10cm overhang on the eaves.

The frames for the floor and the walls have been constructed. For the sides that are nearest the fence panels, I plan to clad in 15mm structural ply, whilst the visible faces will be clad in shiplap.

I’m aware that it's rather late to be making changes in the build stage, but I’ve just been considering whether the stuff we’re storing might end up being subject to some rust in the shed’s current form.

Big-all has been extremely helpful already in suggesting that I put a breathable membrane in along with some battens, which is a plan I’m currently considering (whilst being mindful that any further expansion of the shed footprint is going to be tight!).

So, current shed plan:


Proposed shed plan:


A couple of questions:

Corners: I’d always anticipated putting in 15mm finishing strips to each side, to protect the ends of the shiplap and ply. Given that the shed length will be 2.44m which fits my sheet ply exactly, do I continue with this length, even once I add battens? Then, when the walls come further out of the frame, I would just add thicker wood as a finishing strip?

Door frame: at present, I had expected to double up on the 3x2 stud nearest where I plan to put the door. If the cladding starts to move further away from the studs, I expect that I’ll also need to move the second stud nearer to the exterior, so that I have something solid to screw into?

Bottom of shed: at the moment, the walls sit flush with the shed base. When I put vertical battens in to provide the air gap between the membrane and the cladding, what happens to the base (i.e. I’d have a 19mm gap where I can see the ground now?)

Many thanks in advance, if there are any questions, please shout and I’ll do my best to clarify!!
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Rust requires water and oxygen , you can’t do much about the latter but good ventilation will help keep everything as dry as possible.
i would go for 2x1" treated on the corners to help make up for the fact that your planks will be say 4.5 or 4.8m so will need to be padded out at half to take it from 2398mm[half plus saw blade] to 2440mm otherwise your cutting lots off sheets to fit

12mm ply will be more than enough internal and 9mm or 11mm osb under the outside cladding will be more than enough
Thanks chaps.

To confirm, are we recommending that we should have a ply outer as well as cladding (with the cladding attached directly to the ply)?
Does this not accelerate the possibility of rot as well (i.e. on the same theory that if I didn't use battens for a breathable membrane, the shiplap would be directly butted up?)
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Day 10 in the shed build saga...
I now have 2 sides framed, membraned, battened, clad, and now up and fixed securely to the base of the shed. I also have all fingers, wife and dog intact, so I'd say things are going pretty well so far...

I'll try to post some pictures later in case anyone is interested. As it's going relatively smoothly, my thoughts are now shifting to how I deal with the roof part...

When all 4 walls are up, I'll essentially have a shiplapped cube. My intention once this is done is to start constructing roof trusses, and sitting them on the top of said cube.

At this point, I have a couple of questions...

1. I assume it's easiest for me to batten and clad the triangular ends of the shed in situ?
2. If I am going to put membrane on the roof and then batten, would I shiplap to the height of the rafters, or to the rafters+battens? I assume the latter, but just wanted to check...!
3. With regards to any ridge beam that I put in, should I continue the beam past the ends to provide a solid end for any overlap, or should I cut these flush with the ends of the cube, and then just screw in a separate overhang to the completed (and clad) ends of the shed? I realise that this question might be a bit confusing and I'm likely using incorrect terms, so will do my best to clarify if required!!
4. Ventilation... Obviously I've gone to the trouble of wrapping the whole thing in Tyvek - should I be thinking about putting any vents in, or will the small gaps that are inevitably going to be present (i.e. between floorboards, door frames etc) and the fact that the membrane is breathable sufficient?

Many thanks guys - really appreciate the input throughout!!

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