Vapor Barrier placed under EPS – Need to fix?
Jay M| Posted inGeneral Questionson
Hi GBA Community,
Prepping for a basement concrete radiant slab install and the vapor barrier was placed under the layer of EPS.
12″ Gravel – 15 Mil VB – EPS – 10 Gauge Wire Mesh – Pex
Is this a major cause for concern? I’m reading that this may cause the slab to take longer to dry. Is this the only bad thing about the VB under the EPS? Should I worry about anything else? I obviously would need to weigh this against re-working the assembly.
Thanks,
Jason
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Replies
In some cases the foam could float, but if you keep the water ratio relatively low it should be fine.
JMrtns,
If the rebar or mesh isn't down yet, you could alway lay another layer of 6 mil poly over the foam.
Ads Michael said - what you have isn't ideal, but it isn't the end of the world either.
Thanks Malcom and Michael for getting back to me. I forgot to mention two things that may help:
- All the insulation seams were taped to hopefully avoid the float (although a 6 mil poly probably would have been easier/cheaper)
- We don't plan on finishing the basement for at a least a couple of years. This should allow enough time to dry, right?
It may not be the right way to do it but it's very common and doesn't seem to lead to any big problems. Given your circumstances I wouldn't worry about it.
I do know of one example where the foam floated but they weren't expecting it and it caught them by surprise. With taped seams and a dry mix you should be fine; just keep an eye on it. If you want to sleep better you could add another layer of 6 mil poly. I probably wouldn't.
We did it that way 11 years ago with no problems.
Chris