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Attaching Old Concrete to New with Radiant Heating

2K views 5 replies 2 participants last post by  kevin327 
#1 ·
Hi guys,
I am remodeling my downstairs bathroom, it is 4' below grade in Chicago Suburbs. I am tearing up the floor for a recessed shower, and am planning on tearing up all but about 2" from each wall for screed guides and then install pour a new floor with electic radiant heat under entire bathroom. I am wondering what is the best way to connect the new pour to the old concrete slab. I don't know the width of the floor yet, but I am guess 3". I am planning on insulating below the slab to help keep the radiant heating pointed up, tie in the new pour with 4-6" of rebar pins spaced 8-12" apart, extending 6" into new pour, I will have a wire mesh in pour for strength, but also to attach the radiant cables to. I am also planning on keying the concrete as well. Is this overkill. I am just concerened about tiling everything and then seeing the floor joint crack in 5 years. It is below the frost line which is 36-42" here. I will be using Kerdi to waterproof the shower.

So what do you guys think about my strategy for the concrete joining?

Thanks,
Kevin
 
#2 ·
There are a lot of people on here with more expertise on this, but it sounds a bit overkill to me. If the existing floor isn't cracked and doesn't heave, why not clean it thoroughly and use a liquid bonding agent with one of the many concrete topping mixes?
 
#4 ·
I am leaning towards the expansion joint. I have thought about just a contraction joint, because that is the only way I know for sure the slab is going to go. (shrinking) But I feel like the expansion joint will cover both the expansion and contraction.
 
#6 ·
That is the other option I am considering. The problem with that is that I have cutback adhesive that I have been warned about adhesion problems with. I think this would be magnified because of the constant heating and cooling of the radiant on top. Also, I am removing the floor for the recessed pan section anyways. Plus I do not want to have to work around raising the floor atleast a 1/2" to 1" around the doorways and transition to other rooms.
 
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