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Pouring concrete on a residential garage floor with radiant heat

raj99 Member Posts: 1

I'm planning to pour concrete on my garage floor (it's a new home) and am looking on advice/best practices to avoid significant cracks especially given the weight of the vehicles which will be resting on this floor. Currently I have the foundation slab poured, the garage graded, and the vapor barrier, insulation and PEX tubing laid out. The home is based in the Seattle area.

What is the minimum recommended thickness of the concrete pour as measured from the insulation? Is 6-sack concrete with fiber the right mix for this application? Should the garage slab be tied to the foundation slab, e.g. with 2' stub steel or will it flex a bit due to the insulation and may crack over time with that movement, or should I separate it with a barrier to avoid this issue?

Any advice/pointers from those who have successfully done this before would be highly appreciated!


  • Gordy
    Gordy Member Posts: 9,546

     The first step to minimize cracking is a good sub base. Compaction, and soil stability is a must. So being you already have your vapor barrior, insulation, tubing in place I hope you took the time to insure a good sub base.

    What is your foundation configuration?  If it is frost walls with  slab poured in the middle do not install tie bars in the perimeter into the walls.  Most slabs in a garage are designed to float with freezing, I know it will be heated but what if. If the slab is tied to the walls, and settling should occur this will promote cracking in the middle of the slab.

    Well placed control joints are the next key factor to control where you want the concrete to crack. You did not state the size of slab, or the size vehicles it will support

    Thickness depends on load. 4 to 6 inches will be sufficient for an average vehicle load..

    Dont forget the perimeter insulation detail!!!

    6 bag mix design should be fine with fibre mesh. Keep in mind all concrete cracks unless prestressed or post tensioned. So dont be disappointed. I can find cracks in any sizeable slab of concrete.

    Finally cure is very important for the first 7 days. Continuous wet burlap with visquine over it.

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