Sun, 19 Apr 2026 03:32:13 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267675#Comment_267675 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267675#Comment_267675 Fri, 20 Apr 2018 13:19:26 +0100 djh
http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9731

This is an update about the render beads. I used the Wemico ones that were discussed (I see their website now actively blocks me from looking at it because I don't have Javascript enabled, so I'm not going to post a link). They were very good at build time, working well to finish the render neatly and simultaneously protect the window. For the most part they still look good and are working well.

However, there's one window (actually a sliding patio door) that faces south and gets a lot of sun where the render bead has pulled away from the window and opened a gap of a few mm. So I'm going to need to fill the gap with some mastic or silicone etc. I'm just letting the area dry out in the sun.

I think what's happened is that the render has moved a bit, presumably because the straw behind it has moved a bit. So I don't think any amount of stickiness would have kept it in place, or another way to put it something had to give and I'm glad it was the adhesive.

And I'm very glad my sills did have upstands on the end! (not that there's one under the door)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267685#Comment_267685 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267685#Comment_267685 Fri, 20 Apr 2018 19:37:57 +0100 fostertom
I see the tape as something to hold the render bead in place for a few weeks max until it can be embedded in the render. Then the real watertight seal is applied, into the ideal 3mm gap that the foam tape creates, between hopefully scrupulously cleaned surfaces - a gunned bead of quality silicone mastic of recommended depth:thickness ratio.

This is not what the likes of Wemico recommend - they really do think their DS tape is good enough alone.

The only problem with the above, is that the DS tape is sometimes not recessed back into the joint depth but comes flush with the render face. Worth checking on your chosen make/model.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267689#Comment_267689 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267689#Comment_267689 Fri, 20 Apr 2018 19:54:42 +0100 djh Posted By: fostertomThen the real watertight seal is applied, into the ideal 3mm gap that the foam tape creates, between hopefully scrupulously cleaned surfaces - a gunned bead of quality silicone mastic of recommended depth:thickness ratio.
Actually, I doubt that would have stayed sealed either in my case. In general the foam tape that is part of the bead does seem to have held up for a few years now at any rate.

Given that silicone is notorious for pulling away from the substrate after a while, are there any other suggested ways of sealing the gap?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267699#Comment_267699 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267699#Comment_267699 Sat, 21 Apr 2018 12:26:23 +0100 fostertom Posted By: djhsilicone is notorious for pulling away from the substrate after a whileIs it, if ideally dimensioned, prepared and applied? We see some heavy-duty uses of such sealants that look very good longterm. Like edge-to-edge glass half way up a skyscraper.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267769#Comment_267769 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15683&Focus=267769#Comment_267769 Mon, 23 Apr 2018 19:26:28 +0100 gravelld
Surely silicone doesn't have the flexibility of a foam tape. I'm not sure what does cause silicone to pull away after a while, I assumed it was the failure of adhesion given movement.

Of course, it's probably also useless talking about "silicone", there's such a vast difference in performance between different products.]]>