Slab on slab remodel

myhomemn_123

I am looking to add pex for radiant heat in my basement living area. There is already a good 5" slab.  What is the minimum slab overpour I would need for the pex? Do I need to put insulation board down under the pex?

hot_rod

At least 1" of foamboard, 2" ideally.
1-1/2 is about a thin as you can pour concrete mixes.
Do you have a good ceiling height? Stairs will need to be re-worked if you lift much over 1/2- 3/4".

Radiant ceilings are nice in basements less $$ and you can build it into the sheetrock, with some furring strips along the joist. So no loss of height.

Ceilings respond quickly also, very little mass to rev up.

Radiant walls, the same thing.

myhomemn_123

I just like underfloor heat. No issue with Ceiling height or other rework issues. So a 2" slab on top of insulation board is sufficient? 

myhomemn_123

I plan on putting tile over it

hot_rod

You will want a cleavage membrane over concrete if you tile. All concrete cracks and the crack will telegraph to the tile set. That adds a bit more height to the build up. And cost.

Personally I like the Roth Panels over basement slabs. A bit of insulation value, 6” on center tube spacing and an aluminum cover sheet. A low mass system. Cement board would need to be adhered and fastened over it, however.

myhomemn_123

Yeah I looked into the panels but $2000-$2500 for quote for panels from those companies for 320 square feet isn't great lol. 

hot_rod

Do you have small batch redi-mix plants near you for a short load? Around here it is 3 yard minimum.

We do have those 2 yard buggy’s that you pull behind a pickup for real small pours, at 3 different locations, very handy. It looks like a mini concrete truck with a Honda engine spinning it.

A small grout pump can handle a 3/8 pea gravel mix, which is what you want for a thin pour. Beef up the fiber mix amount also. Add a plasticizer and it will flow like a gyp pour, almost a self leveling mix.

realliveplumber

Look into Schluters Ditra heat. Ditra XL could be used over the existing slab and add r value without foam board.

. Its electric floor warming, and can be as thin as 5/8" - 3/4"
including the tile. Much thinner than hydronic radiant. .

you could incorporate it with hydronic radiant walls/ceilings to match the heat loss.

(Although my wife keeps her Ditra heat bathroom floor at about 87 degrees, and it is more than enough to keep the air temperature at 78. )

They are a first class company that stands behind their products.

myhomemn_123

Thanks everyone for the help.