Sarking Repair - would OSB be suitable (and which type if so)?

[Oxbow16]

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

[Tosh]

I would think OSB3 would be fine as long as there's no risk of it getting wet i.e. its not certified for exposue to weather, though it can cope with humid condidtions. Its regularly specified for metal roof substrates with a membrane between metal and OSB. We've got around 150sqm of it on our roof so it better be ok 😬

[Alan Ambrose]

This is a personal thing, but I hate OSB and any other boards made with wood dust, wood chips etc. Ply I somehow put in the 'proper wood' category. The price difference on 1 sheet of good quality exterior grade ply vs. 1 sheet of OSB3 won't be much in the great scheme of things. The 1mm won't be an issue - you'll be lucky if the roof doesn't have +-10mm dips and humps in it - maybe more depending on the age of the building.