Self-Leveling Underlayment for Hydronic Radiant Floors
Hello GBA community – I’m a homeowner in Western MA working with contractors to get a hydronic radiant floor installed in our kitchen that is being renovated. We have new 3/4” AdvanTech subflooring but only realized how uneven the floor is after putting in the cabinets – we wanted the cabinets in before the finished floor and with no hydronic under them for overall height reasons. Across our longest run of cabinets (about 12’) there is a 2.5” difference in the floor (which is mostly flat, but definitely not level!). Our flooring plan is engineered hardwood over Viega Climate Panels (1/2” tubes with 7” spacing). After finding out about the level difference, I have been trying to figure out what our options are, and at this point, I’m resigned to either (1) let it go and deal with a very slant floor and wildly different toekick heights or (2) pour self-leveling underlayment. With the SLU, I wouldn’t be expecting to get fully level, as we cannot afford the 2.5 inches because of a full-height cabinet – we can max out at about 1 inch additional on the floor at the lowest point. Also, 2.5” of SLU would be a much bigger job requiring a mesh, if I understand correctly.
At this point, our plumber who is installing the hydronic system told us that we can’t do the SLU under the Climate Panels because he cannot float the Climate Panels and the SLU does not accept nails (which is true), so the other option is SLU over the Climate Panels, which would force the wood floor (either over that section or entirely?) to be floated or glued. The SLU product I have been looking at is Mapei Ultraplan Easy, which supposedly works well over wood if the correct primer is used and can feather down to 1/16” thick, and I estimate 12 50# bags would be needed to cover the ~110 s.f. that I estimate as low at a 3/4” depth.
I’m far out of my expertise here. Questions for you all:
– Is SLU my best option here or what else could I use? Is it not worth the hassle to partially level the floor?
– If we do go forward with the SLU, is using it over part of our floor (110 s.f. out of 450 s.f. in the room total) going to make the floor heat feel uneven? I imagine the concrete will hold the heat better than the wood.
Gotta love old houses. Thanks for any suggestions.
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