Green Building Forum - Best flat roof water proofing membrane with penetrations Sun, 24 May 2026 17:10:51 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180885#Comment_180885 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180885#Comment_180885 Tue, 30 Jul 2013 11:58:54 +0100 Shevek
What's easiest to install? What has the best environmental credentials? What has the longest guarantee?

I've had self-adhesive PDT recommended (i.e. Resitrex SK W).

And what about GRP (fibreglass) or cold liquid-applied, fleece reinforced resin (e.g. Kemperol http://www.kemper-system.com/UK/eng/liquid-waterproofing/kemperol-2k-pur-solvent-free/ )?

Edit:
One reason for us as self-builders not to use Kemperol:
http://www.kemper-system.com/UK/eng/approved-contractors/
To maintain the quality of installation, Kemperol V210 and solvent-free 2K-PUR waterproofing and related surfacing systems are only installed by approved and certified contractors

We need something we can install ourselves.]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180916#Comment_180916 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180916#Comment_180916 Tue, 30 Jul 2013 18:48:46 +0100 jamesingram Am I right in thinking this bit of roof is on top of a loft conversion, so looks not so important ?
messy to work with though.
Flat roof waterproof membrane, fibre glass
http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=9988&page=1#Item_18]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180917#Comment_180917 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180917#Comment_180917 Tue, 30 Jul 2013 19:14:05 +0100 Shevek Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180930#Comment_180930 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180930#Comment_180930 Wed, 31 Jul 2013 00:13:03 +0100 SteamyTea Posted By: jamesingramGRP easy to DIYNot if you want it to last, especially if it is part of a green roof substrate.
We had a thread on it a while back. You know it had to be dry before you can apply it :wink:]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180935#Comment_180935 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180935#Comment_180935 Wed, 31 Jul 2013 07:59:10 +0100 joe90

P.S. ST is right it has to be dry but thats not hard to achieve.]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180941#Comment_180941 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180941#Comment_180941 Wed, 31 Jul 2013 08:55:28 +0100 SteamyTea Oddly enough one thing that polyester resins does not like is constant immersion in fresh water (why the 'osmosis' problem is greater for river boats than sea boats).
I agree that anyone with some half decent practical skills can do it with a bit of advice/training, it is more about what you do when it is going wrong.
Main point is that for it to last 40 or 50 years without problems then care needs to be taken.

I think that GRP should be used a lot more in the building trade (I liked the stone pillars I made for the Excelsior hotel at Heathrow, almost looked real).]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180943#Comment_180943 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180943#Comment_180943 Wed, 31 Jul 2013 09:12:10 +0100 Shevek Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180945#Comment_180945 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180945#Comment_180945 Wed, 31 Jul 2013 09:26:55 +0100 SteamyTea Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180959#Comment_180959 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180959#Comment_180959 Wed, 31 Jul 2013 13:00:51 +0100 djh Posted By: ShevekPresumably GRP will be fine laid over Magnesium Oxide board?
Posted By: SteamyTeaNot sure, it does not work with plaster, is unreliable with newish concrete. Best way would be to try a sample and see.

Could you just use a polythene slip sheet between if there is a problem? i.e. DPM or similar]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180977#Comment_180977 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180977#Comment_180977 Wed, 31 Jul 2013 16:23:52 +0100 SteamyTea Posted By: djhCould you just use a polythene slip sheet between if there is a problem?Yes, but then you may as well lay up some flat sheets in the warm and dry, cut to shape and just lay up over the joints. What we did for most jobs as it was quicker, easier, cheaper, tidier and just better if done right.]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180994#Comment_180994 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=180994#Comment_180994 Wed, 31 Jul 2013 18:59:22 +0100 jamesingram Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=181010#Comment_181010 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=181010#Comment_181010 Wed, 31 Jul 2013 23:50:45 +0100 djh Posted By: SteamyTea
Posted By: djhCould you just use a polythene slip sheet between if there is a problem?
Yes, but then you may as well lay up some flat sheets in the warm and dry, cut to shape and just lay up over the joints. What we did for most jobs as it was quicker, easier, cheaper, tidier and just better if done right.
Indeed, if you can do it on a table indoors, it will be much easier.]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=181017#Comment_181017 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=181017#Comment_181017 Thu, 01 Aug 2013 08:09:32 +0100 SteamyTea Posted By: djhif you can do it on a table indoorsWhen I was a kid I made a couple of kayaks in my parents garage. The food from the freezer tasted a bit odd :bigsmile:]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=182066#Comment_182066 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=182066#Comment_182066 Fri, 16 Aug 2013 12:17:28 +0100 Rex Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=182067#Comment_182067 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=182067#Comment_182067 Fri, 16 Aug 2013 12:23:04 +0100 Shevek Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=182072#Comment_182072 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=182072#Comment_182072 Fri, 16 Aug 2013 13:15:46 +0100 ferdinand2000
One of the key things is to avoid structural stress on the GRP.

We stripped back the tiles and installed plywood 3ft up the line of the roof to allow for snow and GRP'd over that, before replacing the tiles. I can't remember the precise detail.

The places with what problems there were were where people could walk on joints by mistake.

It is also nice and repairable.

We also installed translucent roof panels in the middle of slate roofs in a listed building, made from GRP "slates", which were undetectable, but that's another story.

I'd say that if your penetrations don't move you should be OK.

Ferdinand]]> Best flat roof water proofing membrane with penetrations https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=182161#Comment_182161 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=10947&Focus=182161#Comment_182161 Fri, 16 Aug 2013 23:23:05 +0100 SteamyTea Posted By: ferdinand2000We also installed translucent roof panels in the middle of slate roofs in a listed building, made from GRP "slates", which were undetectable, but that's another story.Would like to hear about that.]]>