# Internal Walls - 9mm or 12mm



## Fitzroy (31 Aug 2020)

I’m finally getting to the end of my todo list of projects. Desk, shelves, gate, .... so I’m back to thinking about progressing the interior of the workshop. Frames will be insulated with rock wool with a gap behind. But what to use internally, I was thinking 9mm ply, but do I really need to go 12mm?







Just wish it was still this empty but it now has shelves and lots of other paraphernalia in it. 

fitz.


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## MikeG. (31 Aug 2020)

You've got an external sheathing of OSB. That's not a good idea at all.


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## clogs (31 Aug 2020)

I like the floor a lot....
go for the heavier wall board, u've spent a bit and a little more will pay dividends when u want to fix heavy stuff....

I'm putting up plaster board right now....12mm thick and where I need cupboards and shelves it gets 3/4 ply glued n screwed to the back....


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## Fitzroy (1 Sep 2020)

MikeG. said:


> You've got an external sheathing of OSB. That's not a good idea at all.



I know, I know, or I know now having followed many build threads but it is what it is. I don’t see a practical modification I can do at this stage. History will judge me. Along with the vermin who should live under my shed in the glass wool insulation I put there .

So will 9mm do, or is that my next mistake?

F


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## MikeG. (1 Sep 2020)

If you are completely confident in your insect mesh arrangements outside the sheathing board meaning the void behind the cladding is well protected, then you could take a hole cutter to that external ply from the inside, and pepper it with holes....in each "compartment" created by the studs.

9mm is perfectly fine. It's what I have in mine, and most of the shed builds use. If you need to fasten heavy stuff to the walls then either fix it into the studs, or screw a batten across some studs to support it. Leave a small gap (2/ 2.5mm) between each sheet.


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## Cabinetman (2 Sep 2020)

Hi, I used 12 mil plasterboard on 16 in spaced studs, I wish I had given a little more thought to where my timber storage brackets were to be fixed, I would have put more timber inside the wall where it was needed, 
I think I would put plastic sheeting between the OSB board and the insulation, depends what sort you’re going to use, bats that go between layers of brickwork on houses don’t absorb moisture so you might get away with without the plastic. Good luck and I love the floor! Ian S


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## MikeG. (2 Sep 2020)

Plastic isn't necessary with OSB. It has so much glue that it is virtually vapour impermeable, so it acts a a vapour barrier itself. It's a different story with your plasterboard, of course, where a vapour control layer is necessary. And it doesn't depend on the type of insulation, which has little bearing on whether or not a vapour barrier is required.


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