waterproofing new osb board roof on pent shed

Ant555

Im replacing a pent shed roof and have bought 2 x OSB3 board sheets + roof felt

Existing roof has bowed due to lack of support (am addressing this) and also got quite damp when the felt failed so its being ripped off and replaced.

There will be shed roof felt on top of my new boards but im wondering if i should go belt and braces and waterproof the new osb 3 boards as it may give me a bit of extra time on the roof should the felt deteriorate at some point in the future.

Any thoughts or suggestions as to what waterproofing product might be useful if any.

shed very similar to this one below


Many Thanks

Section62

Ant555 said:

There will be shed roof felt on top of my new boards but im wondering if i should go belt and braces and waterproof the new osb 3 boards as it may give me a bit of extra time on the roof should the felt deteriorate at some point in the future.

Any thoughts or suggestions as to what waterproofing product might be useful if any.

I would lay a sheet of reasonably thick polythene under the felt. It will stop most of the water leaking through deteriorating felt from reaching the OSB.  If you are fixing the felt with clouts then they will breach any waterproofing layer - so focus spare cash on applying a suitable sealant around and over them, as well as making sure any felt overlaps are well sealed and sufficient to prevent capillary action.

Ant555

Section62 said:

Ant555 said:

There will be shed roof felt on top of my new boards but im wondering if i should go belt and braces and waterproof the new osb 3 boards as it may give me a bit of extra time on the roof should the felt deteriorate at some point in the future.

Any thoughts or suggestions as to what waterproofing product might be useful if any.

I would lay a sheet of reasonably thick polythene under the felt. It will stop most of the water leaking through deteriorating felt from reaching the OSB.  If you are fixing the felt with clouts then they will breach any waterproofing layer - so focus spare cash on applying a suitable sealant around and over them, as well as making sure any felt overlaps are well sealed and sufficient to prevent capillary action.

Yes, ill be using clout nails and layering the roofing felt sheets accordingly but Ive also bought a tin of this to seal the felt overlaps.

https://www.wickes.co.uk/IKOpro-High-Performance-Roofing-Felt-Adhesive-2-5L/p/151401

Just wondered if I should waterproof the osb sheets this week with some product ahead of the actual job this weekend.

Bendy_House

You could coat it in a roofing compound such as Cromapol. This is designed to seal and protect pretty much any type of roof finish. A couple of coats would probably even be enough on the OSB on its own! (But I'm not suggesting that...)