coroline roofing / purlins

[sammoseley]

Hi
I'm fitting coroline/onduline corrugated bitumen sheets to my garage roof, pitch is about 7 degrees, fixing instructions say if the pitch is less than 10degrees, you need to close board it or deck it instead of just putting purlins across the rafters, but I can't see why I can't still use purlins ie. tiling lath say 6 inch centres, surely this wouldn't be much worse than covering the whole thing in ply/decking.
I'm tempted to go with that to keep the costs down, but would appreciate advice if its a really bad idea (if the pitch is above 10 degrees you can use purlins at 450mm centres so by that logic I can't see it being a major issue)
Cheers
Sam

 

[noseall]

Mebbe it is summat to do with the fact that a shallow pitch allows people the ability to walk on it, hence the need for reinforcement.

Probably.

 

[sammoseley]

cheers noseall, hadnt thought of that, fair point! still might take my chances on it tho!
if i did 'close board / deck' it any idea what the cheapest way is? OSB?

 

[noseall]

if i did 'close board / deck' it any idea what the cheapest way is? OSB?

Sounds like a plan. Use (min) 18mm.

 

[sammoseley]

thanks