Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.

If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
Need to contact us? Visit

How would you insulate between old and new slab?

Live in NY, I have a early 1900's carriage barn with about 4-6 inches of concrete with rebar, no vapor barrier (not sure when the floor was poured) No Cracks.
I took off the old barn doors and put on patio doors, raising them up 4 inches, (max I could get for headroom)
I'm going to install radiant and pour new concrete with color as a finished floor, just wondering what some opinions are here.
Insul tarp vs. plastic and foam vs other options for 4 inches of pour room.



  • nibsnibs Member Posts: 462
    Am in the process of pouring my slab, over my pex.
    Many people here much more knowledgeable than I however absent a site inspections, and assuming no vehicular loads, if the existing concrete is in good condition, I would lay a vapor barrier, taped at the joins, then 1.5 inch XPS styrofoam, with taped joins, staple 1/2 " pex to the foam then pour your slab using fiber and a super plasticizer for max strength, order your cement with 1/2" minus aggregate if poss. Do not saw cut the control joints use an insert. If you want to use bigger pex then you may want to use thinner insulation.
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!