Ask a Tradesman
Leaky flat roof - osb board
I have just had a very leaky wet roof replaced where the OSB board had got soaked through to such an extent that the ceiling underneath has now to be replaced. I asked for new OSB boards to be fitted but the roofer has not done this insisting that the existing boards will be fine once dried out. As the ceiling is down I can see the boards from underneath and they look solid but are very dark from where they have been wet. I am worried that the new roof wont last for the 10 to 15 years as expected. Should I insist he takes new roof off and replaces the OSB board?
Roofer has agreed to redo roof at his expense so thanks very much for the advice!
It looks like the contractor has tried to cut corners here and got caught out! Unfortunately for you and for him, he has cut corners on the most fundamental part of the project undertaken, the sub-structure!!
With the exception of new Marine grade boards, New boards should always be used if the existing boards have become sodden wet, even if they do dry out they would of expanded and become very weak and brittle.
The new boards should also be screwed (not nailed) into place using galvanised or stainless screw fixings.
Are you 100% sure the contractor has quoted you for new boards, prior to the roof removals? As a contractor usually makes a provisional allowance for re-decking based on what is found after roof covering removal! It is very hard to quote on something you cannot see.
There is no mention of insulation in your email? If the roof has been removed for more than 25% of its surface area, current building regulations will require the roof to be removed and the surface to be insulated prior to re-instatement of the roof coverings.
Answered 10th Mar 2013
A leaky flat roof usually means that the felt is not sealed correctly which in time will rot away at your boards. 9 out of 10 times if a flat roof is leaking then your boards will be sodden so for the sake of risking it and saving a couple of hundred £££ s I always advise for them to be replaced. I would get your builder to go a give it a good check to make sure all joints are sealed and stuck down correctly.
Answered 6th Mar 2013