Workshop wall

[motownmartin]

I wasn't sure which forum to post this.

The question is:

Is this the correct make up of a workshop wall, if not what is?

Lost piccy

Where it says breathable membrane its an air gap with the breathable membrane being the thin blue line.

Is it really necessary to have an airgap, is so, how big, its 25mm in the diagram.

 

[MikeG.]

Martin,

that is a very-nearly..........

........the problem with it is the OSB, which is virtually vapour-impermeable due to the high levels of glue. Your breathable membrane won't be doing anything much at all, because no moisture will get past the OSB.

In a workshop, I would replace the plasterboard with the OSB, solving 2 problems in one go. The OSB is a good surface for a workshop, being more robust than plasterboard (and you can fasten stuff directly to it), and it obviously does the sheathing (racking resistance) job wherever it is in the the wall structure. Being on the inside of the wall its vapour-resistant properties are exploited exactly where they should be. My only caution with OSB is to be sure to maintain gaps around the edge of all sheets, because it really does bow if not given room to move.

Having moved the OSB to the inner face, your breathable membrane is doing its job properly, and is also holding the insulation up.

The airgap behind the cladding is exactly right. Just a tip if you haven't done it before (excuse sucking eggs lesson if you have!) .......use 2 inch counterbattens so that you can get a decent amount of each board onto a batten if you need to butt-join two boards. Stagger vertical joints for a really first rate job......and stain your boards before you nail them in place, as they will shrink and expose bare wood otherwise. One nail per board per batten........30mm up from the bottom if you have 25mm overlap.

Look how much money I've saved you.......all that plasterboard!!

I look forward to the pictures!

Mike

 

[motownmartin]

Is this what you mean

I'll have more questions at a later date about the make up of the roof

Thanks again Mike

 

[MikeG.]

Not quite, Martin. You can (should) omit the outer skin of OSB.

Mike

 

[motownmartin]

Next attempt

 

[pobo]

this is the way (diagram 3) i built my workshop about 16months ago works very well, keeps the warms in and the cold out. I think at some point i may open a small section to see its still working.

i used plasterboard on the inside as its easy to put fittings on the inside, will show problems with leaks quick, helps with lighting (light colour) and most important its cheap.

so basically
clad
25mm gap
breathable layer
insulation
water proof membrane
inner skin

pete

 

[motownmartin]

Thanks Pete

 

[hpl]

Martin

I understand Mike as saying that you don't need the outside sheet of OSB at all, just the sheet on the inside. If this wasn't the case it wouldn't be saving you money. I think I would be right in saying that OSB costs more than plasterboard.

Johnny B

 

[MikeG.]

Martin,

except for the remnant text "OSB" in the airgap, that drawing is spot on.

Given what I said earlier about the relative vapour impermeability of OSB, you could even omit the polythene layer between the studs and the OSB.

The OSB benefits from a coat or two of white emulsion inside.........it helps hold the layers together, and it throws the light around the room much better.

Mike

 

[Niall]

Well if Mike's right then that might be an oops from me - built mine with OSB on inside and outside, like Martin's first drawing. Reasoning was to create more mass to help with sound insulation. Been OK for 6 months so far though, with quite a mix of heat and cold / wet weather. Hopefully on the plus side, I made my walls such that the sapce inside the wall is continuous with a well ventilated roof space, and there's also a continuous though narrow gap to a ventilated sub-floor. The only thing to impede rapid air movement is the rockwool insulation inside the wall. If that makes sense.

Mike - it's not too difficult for me to get at the inside surface of the outer sheath of OSB. I could cut some holes in that, to allow better air movement to / from the gap behind the outer cladding. Do you think it's necessary / worthwhile?