Ok maybe this is blasphemy speaking about concrete in the TF forums but I'm curious. I've been planning on using radiant floors in my house design when I came accross this -> Insul-Deck . Hmmm, since I have to pour concrete on my (first) floor anyways, why not go all the way and have concrete joists while I'm at it. No squeaks, no bounce. Anybody here have experience with this type of flooring ? Any comments would be appreciated.

P.S. Rough pricing of $4-$5 /sq. ft. for the forms is what the rep mentioned to me. I haven't priced manufactured wood joists so I can't compare.

I poured a concrete deck for my house. Like you, I'm using RFH and wanted the no-bounce no-squeak advantage of concrete.

For me, the foam-form products were too expensive. Also, they require a lot of work in terms of bracing and rebar placement.

I used a product called Speedfloor. You might check it out.

www.speedfloorusa.com

Jon

I've never used either of those products, but simply wanted to suggest that by adding a joist or two every now and again, ie: 16 inch or 12 inch centres, using 3/4 " t & g plywood, gluing the ply and the joist hanger seats, with a 2" light-weight concrete topping works well for in-slab heating. (and sound-proofing)

I could see using that first product where the underside of the slab is exposed to an unheated space, but other than that, looks like a waste of money to me. IMHO.

Might want to look at pre-stressed concrete joist if you insist on using concrete for joists. Might be an option if there is a supplier available Locally.

Thanks for the replies. I agree that insulation on an un-exposed slab is a waste of money, however it does double duty of acting as the form for the joists, thereby replacing (wood) joists altogether.

A quick calculation using $180 /cu. yd. of regular concrete works out to $2.14 /sq. foot for a 3" thick floor slab with built in joists(plus $4-$5 /sq. ft for the forms). I haven't priced light-weight concrete, but my research seems to indicate that it's quite pricey ($6-$9 sq. ft.) for a 2" slab + the price of wood joists.

My concrete contractor is going to love me (and my wallet).