Hi

Following on from my lead replacement thread... In the same area of roof, we have a hole in the sarking board and felt from where a flue was removed. While the slates are off to redo the leadwork, we'll be looking to put this right as well.

I've just been up to measure and it is 11mm thick.

The existing is ply. Can I use OSB for the repair or would it be best to stick with the same and use ply? I note ply tends to be 12mm whereas 11mm OSB is readily available (not sure how much 1mm difference would matter though?). If OSB is suitable, what type/grade would I need? I'm don't really know anything about OSB to be honest...

Many thanks

Thanks tony. I've taken the ladder away now, but i'd guess the hole is around 12" - roughly the size of an LP.

I had thought to mend it from below (in fact, I posted last year about it but then the plan changed). But now that the slates have to come off in that area to put in the new lead work, I thought it made sense to strip off a few more just below the ridge so that the hole and surrounding area can be accessed. I'll mark out in a photo below what I thought would be best to cut out (from above) and replace.

The other thing is that we will be introducing an air gap for ventilation as there wasn't one before, plus putting in new better insulation. Fixing from below would impede the air gap between those two rafters.

But I'm all ears if you or anyone else things an alternative fix is a better solution.

Many thanks

Pic to follow

Posted By: greenfingerIf OSB is suitable, what type/grade would I need?

I think I have OSB on the garage in preference to ply because the roofers said it wasn't as prone to mould? Whichever you choose you'll need a waterproof grade (OSB 3 or 4)