Green Building Forum - Breathable floor with VCL

Green Building Forum - Breathable floor with VCL - any point Tue, 19 May 2026 16:44:20 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306125#Comment_306125 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306125#Comment_306125 Sun, 30 Jun 2024 15:16:02 +0100 Peter_in_Hungary
As bought it has concrete floors.

An 'eco friendly' architect is recommending removing the concrete floors and replacing them with something vapour open. There are no problems with the walls or plastering despite concrete floors for about 50 years.

Their plan is to replace the floors as recommended and then they want to put down engineered wood or click fit flooring (budget dependant) However all the instructions for the various flooring require a VCL under the flooring otherwise the guarantee is void.

Question - is it worth digging out the floors for something breathable only to put a VCL under the engineered wood or click fit flooring?]]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306126#Comment_306126 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306126#Comment_306126 Sun, 30 Jun 2024 15:54:34 +0100 djh
I could understand if the ground is wet and the concrete was damp as a result, but that doesn't sound like the case. Although then I'd think a capillary break would be more important than breathability.

I'd think the first thing would be to question the architect as to the basis of his recommendation.]]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306127#Comment_306127 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306127#Comment_306127 Sun, 30 Jun 2024 17:35:38 +0100 Peter_in_Hungary Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306128#Comment_306128 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306128#Comment_306128 Sun, 30 Jun 2024 17:53:01 +0100 owlman Schluter decoupling matting usually requires sticking down but I once used a similar German product that was a floating mat, which was screeded on top. The advantage being it allowed movement between the substrate and the finished flooring. I'll try and dig out details. I tiled on top but I see no reason why you couldn't float or even glue down wood flooring.]]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306129#Comment_306129 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306129#Comment_306129 Sun, 30 Jun 2024 18:43:39 +0100 djh Posted By: Peter_in_HungaryThe architect said that the concrete floors would push moisture into the walls so should be removed and replaced with something that allowed moisture to escape other than in to the wallsI think his thought process is flawed/confused and should be challenged.]]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306130#Comment_306130 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306130#Comment_306130 Sun, 30 Jun 2024 18:50:28 +0100 Peter_in_Hungary
Apart from the architect not liking concrete floors in stone/rubble buildings there is nothing wrong (unserviceable) about the floors.

Do I recall people here removing concrete floors to replace with limecrete for permeability reasons? Hence would it make any sense to put a DPC on top?]]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306131#Comment_306131 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306131#Comment_306131 Sun, 30 Jun 2024 20:12:17 +0100 Dominic Cooney If the existing floor is concrete with no damp issues in the floor or walls, then removing the concrete only to replace it with a DPC would be a waste of time and funds. Unless they want more insulation in the floor, but that is a different story with a load of other considerations.]]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306132#Comment_306132 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306132#Comment_306132 Sun, 30 Jun 2024 20:18:24 +0100 djh
Limecrete floors are permeable, just as concrete floors are. Limecrete is typically laid on something like leca balls or foamed glass pieces for insulation, and they also have the feature of providing a capillary break. But unless the ground underneath is dry, there can still be vapour flow. Hence the likes of rush mat flooring to keep things vapour open.

Incidentally, it occurs to me that a concrete floor is not normally flat enough to put hard (rigid) flooring directly on it. It would probably need levelling first.]]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306133#Comment_306133 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306133#Comment_306133 Sun, 30 Jun 2024 23:29:12 +0100 Peter_in_Hungary
With the floor there for 50 years with no problems in the walls my option would be 'if it aint broke - don't fix it']]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306134#Comment_306134 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306134#Comment_306134 Mon, 01 Jul 2024 09:50:18 +0100 fostertom Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306135#Comment_306135 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306135#Comment_306135 Mon, 01 Jul 2024 13:24:50 +0100 djh Posted By: fostertomIt always puzzles me that the usual thinking, rules and objectives for walls, roofs etc aren't applied to floors. Why don't we install internal VCL in floors (other than for a sort-of different reason under wood flooring, as above) and vapour permeable materials outboard of (i.e. below) that?Because a floor is different to a wall, because the ground is wet. The air is not (in the same way).

I have straw bales in my walls and am happy with that. I would be happy with them in my roof as well, but there's no way I would use them as floor insulation. There are too many cases where people have tried and then the bales rot.]]> Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306138#Comment_306138 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306138#Comment_306138 Mon, 01 Jul 2024 15:21:21 +0100 fostertom Breathable floor with VCL - any point https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306139#Comment_306139 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18151&Focus=306139#Comment_306139 Mon, 01 Jul 2024 16:41:09 +0100 djh

Posted By: fostertomNot necessarily - you could be on top of a mound of gravel.

In the very special case of having a natural capillary break under your house, I'm sure that floors could be treated specially - viz the same as walls :bigsmile:

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