Adding Onduline to felted shed Roof (ed.)

4 Feb 2021
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United Kingdom
Hi there

New to the forum .

I recently got help to built a new shed which is approx 5m x 3m and has a pent roof which i believe has a 15° slope. I had covered the roof with felt with an overhang all the way round but had a leak coming in . I bought a tin of blackjack all weather roof coating and painted it all over the roof but still had a leak coming in from somewhere . I currently have a tarp covering the roof but was unsure whether to buy another tin and try one more coat or i have been looking at onduline corrugated sheets.
The roof is made with 11mm OSB board and my question is would i be able to put the corrugated sheets directly on top of the felt ? and if so would i need to put battons down first incase the screws - nails go through too far .

Any advice appreciated

Thanks John


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Looks like the leak is coming down from the top of the slope.
Take another look up there
I had a look and i also think its coming in at the top somewhere and running down the top of the OSB board . Really frustrating as i cant see anything
Leaks are normally at laps and edges of felt. No need to cover the whole lot in sealant.

Damp looks concentrated at the joists. Is there a problem with the nailing through the felt?
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A while ago but did you sort this? I have similar and suspected it was leaking through where the felt tacks were. I've coated with bitumen paint but primed first in the hope that the bitumen would cover the tacks.

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