Corrugated PVC ontop of OSB3?

[shockfire]

Hi all,

I need to replace the roof on my garage (7m x 3m). It used to be corrugated asbestos cement, however it needed removing because it was in deteriorating condition.

I have access to OSB3 board and plan on boarding it.

However, i'm a bit stuck when it comes to the actual roof covering. Corrugated PVC is within my price range, and looks mega easy to install.

Just wondering if anyone has any experience or comments on applying corrugated PVC directly ontop of OSB3 board? My thoughts are that it should be quite strong with the OSB3 underneath, and then the corrugated PVC will protect from the elements.

The only thing is, after Googling using corrugated PVC ontop of OSB3, I couldn't find any results of if anyone has actually tried this and whether they had any problems (or success).

Any advice would be very much appreciated

Thanks very much,
Shockfire.

 

[oldbutnotdead]

If you're getting the OSB for free then hurrah, if not then it's a bit overkill and you might end up with damp/rot problems if you get any condensation inside the PVC (I've got a corrugated PVC leanto, wads of ventilation cos one end is open but still get condensation on cold mornings. Which drips off so is a nuisance rather than a problem)

What pitch is your roof? If it is quite shallow you could fibreglass it (you can probably fibreglass it if it isn't shallow pitch but it can get difficult stopping the resin ponding at the lower end, plus wandering about on a 40 degree pitch with no battens isn't fun)

Don't forget you'll need rafters and/or purlins with the OSB as well. Is it 8 x 4 sheets or the T & G stuff?

 

[shockfire]

Thanks for your reply

The OSB is not quite free, but is at cut-price, good condition leftovers from a project. All the timber (including new joists) i'm gonna have to buy at full price from a timber yard.

It's a good point about the condensation problems that this could cause, I thought about this and was thinking that painting the OSB could help? Probably not really a solution though, would probably just delay any problems such as rot rather than totally stop the problem from happening. I was also thinking that with the OSB being in direct sunlight, could cause it to warp.

The problem is that I need quite a cheap covering if possible. I'm starting to think that there's no suitable coverings in my current price range, and maybe the solution would be to save up some money

The fibreglass stuff seems quite cool and easy to use, although it's really in the same price range as EPDM, for the size of my garage it's currently approx £300 - £350

Time to get saving up I think

Thanks,
Shockfire.

 

[oldbutnotdead]

Ah.

If you've got to buy new timber you'll almost certainly be better off with a wrinkly tin roof. There's brand new on Ebay going at about £5/sq metre, your garage size is less than 30 sq m so building regs don't come into it (unless its got wooden walls and is less than a metre from the boundary) so no worries about U values and stuff like that.

GRP isn't a particularly cheap solution- comes in at about £15/square metre just for the fibreglass and resin bit. Add £7/sq m for OSB and it starts to sting, then add about £90-worth of trims round the edges and an expansion joint. You could slate it in Eternit for the same sort of money!

You may have someone local selling the stuff- they may also be able to do you the steel Z purlins as well (which might be cheaper than timber and might not- for your 3m span 6" x 2" at 450mm centres are within regs down to 11 degree pitch. Not that you have to worry about regs )

And to reduce condensation irritation (which you'll always get with tin sheet), chuck a roll of breathable roofing felt on the job as well.

Have fun