OSB verses Plywood

[armalites]

I'm just doing the costings to line the roof of my workshop to help stop condensation. I'm going to need 20 plus sheets plus extra purlins in the right places.

I can get 12mm shuttering ply at £16 +vat a sheet but 11mm OSB is just less than £10 so it would save £150.

I'm not concerned about the way it looks although ply is nicer but my feeling is ply will be more durable also

 

[richie00boy]

Shuttering ply is rubbish and will delaminate. Osb is better but you must use osb 3 as the 2 grade is not moisture rated so will degrade and blow.

 

[cumbriasteve]

I think OSB comes in various grades re waterproofing, many wooden buildings use it for the flooring and roofing under felt, would not be keen on the floor myself.

One of my sheds was partially lined with normal cheap OSB about ten years ago, it's a bit of a 'dump it in there' shed and not leaking but also not the driest, haven't noticed any issues to date.

I should think it will be fine unless actually getting wet, you could staple a sheet of polythene up first if you think it would help.

 

[armalites]

It shouldn't be getting wet as it will be a 4" gap from the steel roof and will be insulated.

The issues seems to be that the more stuff I get in there the thermal increases and the drips are getting worse, we all know sods law says you leave some that will damaged if it gets wet under somewhere that drips.

 

[cumbriasteve]

In my garage I have an 8" insulated (rockwool) gap under my steel sheets, there is then a ceiling of foil backed plasterboard, the foil facing the steel, there are air vents into this void area, still not decided if that's good or bad.

That has been up for a few years now and there are no damp patches or sign of the plasterboard blowing, I still suspect on the very cold but sunny days the underside of the sheet will condensate although perhaps not enough to cause a problem.