I'd like to install radiant floor heating in my 10 x 20 sun room. my plan is to lay it all out and cover it with 2 inches of concrete. My major concern in doing so is I'll be laying this new slab over an existing formed slab that is 4 feet off the ground resting on a block foundation. It is 6 inch reinforced concrete. my new slab will weight 3600 pounds (24 cf x 150#) spread over 200 square feet. Can 6 inches of concrete handle that weight? There are currently no supports underneath.
Thanks

 

Thats only 18lbs per square foot....it should be fine. An average person will put more stress on it that what you propose. I think they also can provide a lightweight mix that would be even easier.

Its the foundation that you need to make sure of.

 

Running the arithmetic for the dimensions you listed, the actual weight of concrete will be 5000 lb. (10' x 20' x 0.1667' x 150 lb./c.f.). Not sure how you came up with 24 c.f. or 3600 lb., as that's the weight if you'd only put down a 1-1/2" overlay. But whatever--without knowing the size, number and condition of the reinforcement bars in the existing slab, as well as the condition of the actual slab itself, it's not possible to accurately determine whether or not it can safely support the additional loading. That being said, you might give some thought to hiring a local engineer or testing lab to do a field review and evaluation. An experienced person with a sounding hammer and a Pachometer will be able to give you a practical slab evaluation and a good approximation of the steel reinforcement therein.

Gut feeling is that it should support the intended load, but I won't stake my engineering licenses on it without having more information.

 

I tend to agree with BridgeMan45. Even though the load is evenly spread out and the loading per square foot is relatively low you can't get around the fact that it is a lot of weight and it will be cutting into the safety margin for your floor. It would be sort of like having 30+ adults in room all the time. Then if you ever tile the floor, add furniture and maybe have a house full of friends over for a party it could push the floor to it's limit.

 

That's what I was afraid of Engineers, bore samples and lab tests to really be sure. $$$$
Think I'm gonna chicken out and abandon the radiant floor heating and just add a light weight wood floor with some foam insulation under it and a rug on top.
Thanks for your replies