Radiant Floor and Slab Ledge

[Crazy68Dart]

With a radiant floor setup a slab ledge does not work very well, or does it? If anything it is going to complicate the insulation around the interior perimeter.

I know my contractor talked about turned a few blocks to create a ledge. (unrelated to me talking to him about radiant, I've not brought this up yet as I am still undecided).

What is the general consensus?

Thanks.

 

[Crazy68Dart]

Ttt

 

[Chris705]

I used a ledge created by a 6" wide top block and 12" block below that. I scored 3" used foam board off of CL and had enough to do all the inside of the 12" block and under the slab. I cut 8" strips of 2" to run at slab edge and chamfered the top edge with a 45. Then used the 3" board to lock the vertical 2" in place. I have a 5" slab. To be honest I was going to go 6" thick but my subgrade was so rock hard I had to use a pickax to break it up to install my plumbing, I had graded to be flush with top of the 12" block and expected it to settle at least the one inch but it never did. Not sure the ledge helps unless you find it helpful to grade to it.

 

[Crazy68Dart]

The ledge helps with, in my case anyway, giving support to the perimeter of the slab where the backfill goes in. That stuff will settle over time. The slab will crack.

I found some sketches online and I know what I need to do now. Thanks for the help!

 

[thomasj1]

Great advice, Chris!