Roofing Question

Looking for guidance regarding 'stains' on the underside (inside) of a new flat metal roof

Hi, I've recently put a new metal roof on my garage. It has been put on top of 18mm ply that was then covered with a waterproof membrane, and then with 50mm of kingspan which is directly under the metal roof. The screws for attaching the roof are are in the 'gully' of the profile and going into the ply and they have 'waterproof' washers. I seem to be getting staining at certain parts of the underside of the ply boards and am wondering what might be causing this ? We have had a huge amount or rain up my way and although it isn't dripping through I am concerned that the wood might start to rot. The roof is about 25 sq metres and is on a 3 degree slope. I can provide pictures if required. Any help appreciated. Stevie

Hi Kevin and JB Building Services, many thanks for coming back to me on this, it's much appreciated. The sheets are definitely meant to be fixed via the gully and not the ridge; and while I can never be certain I'm pretty much sure that the fixings have been put in straight - however I am of a mind that the seal might be the problem area.Thanks again.

2 Answers

Best Answer

the fixings are supposed to be on the high parts of the profile not the low part as the water flows down the low part. Possibly turn the sheets over and refix.

Answered 31st Dec 2012

kevin cassidy building contractors

Member since 16 Dec 2010

the problem may be that the screw is not driven in straight so the rubber washer is not seated properly giving a bad seal which is why it is only happening in isolated areas

Answered 1st Jan 2013

JB Building Services

Member since 31 Dec 2012

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