I suspect rain is blowing under the rather narrow steel ridge capping fitted to one of my barns.
Second hand box section rolled steel sheeting was laid on top of an existing but leaky felted roof. I am now finding that water is making its a way under the steel roofing and through the felt.
There are several possibilities... the sheets are secured with heavy duty roofing nails with a trapped plastic seal. The laps are screwed at
18" intervals but there is no mastic seal. The ridge cap is narrow so rainwater could splash and blow under.I have in mind to fabricate a template/former in 12mm ply to fit tightly to the roof sheet, pierced with holes to allow conventional canned expanding foam to be fed into the ridge and form a tidy seal. Freehand attempts leave an unsightly bulge and reveals large gas pockets when trimmed.
How do I stop the foam sticking to the plywood? And, how long does it take before full expansion is reached?
Any other constructive thoughts?
regards