Ceramic tile question

I have a 14 foot by 18 foot room that is going to have in floor heat. Can I use the self leveling mud or should I pour some lite weight concrete and top it off with self leveling mud? I will need about 2 and 1/2 inches of mud on top of the pex tubing. Or am I way off and should do something else? This floor is on two by tens that has been doubled up to withstand the weight.

I have seen them use lightweight concrete for this job and it self leveled. If you go with electric in floor heat you will only need to build up the floor 1/8" or so. Unless you already have the boiler and everything in place already.

They make a system that is pex and reflective and fastens to the underside of the floor . No need for overlays .

I already have hot water heat in the rest of the house. I just need to do the plumbing. The floor is already dropped two and a half inches. so 100% wet lite weight.

I am not a fan of that method. The heat can't get through the floor as well as an in floor system can radiate heat

Understood. I have been in several houses with the radiant heat like yours and really like it. Given a choice it is what I would go with, but I don't realy have a choice right now

U.S.G makes a product called "gypcrete" that goes in very liquid, but sets up like concrete. It has a gypsum base, and is self-leveling. I don't think you would need 2 1/2" though. You can rent the pump.

I have already dropped the floor roughly two and a half inches so I have enough cover over the tubing, and the floor level matches from the adjoining room. I had heard of gypcrete but thought concrete would be better. Is gypcrete lighter than lite weight concrete?

It sounds like what you are doing is "in-filling" and encapsulating the pipe ? Correct. I would think you need a certain thickness over the top, depending on the material being used.

I think when it comes to the materials you propose to use, you really need to pay strict attention to specifications of such materials.

The Gypcrete I attached a link to below shows a compressive strength of up to 3200 psi, but at 3/4" thick-7.2lbs/sq.ft.

The problem I see with this material is 2 things, one being I firmly believe you will not achieve the same compressive strength at 2-1/2". The material is designed as an underlayment, if you form it per your job as described, place same, I do not believe it will achieve any strength by virtue of design. The other is being gypsum based, in many instances gypsum based materials are not as strong, another example where its true is spray applied fireproofing, for structural steel.

Maxxon and I have used their underlayment products on a large scale, does appear to offer a material that will achieve a satisfactory compressive strength, and that is thick enough to embed or encapsulate pex, and is designed for the purpose,(link attached). But it can only infill 1-1/4", so maybe that and an underlayment layer to make height?

Maxxon has a bunch of products elsewhere on their website, you have to look at dry density for weight calculating, compressive strength/thickness, and point load,to insure you have the strength you need at the thickness's required, as well as dry density weight for loading, it tells you per square foot what it weighs and thicker/stronger is definitely heavier.

You could use a 1000 psi light weight small aggregate concrete, or maybe 2000 psi if they offer it, them use and underlayment if your not the best finisher, leave enough room for the self leveling underlayment, it will leave a nice level-flat surface.
Gyp crete2000/3.2K

Therma floor

Hi JOB,

The weight of a 2.5" thick slab of regular (not lightweight) unreinforced concrete covering a 14' X 18' area would be in the neighborhood of 7,600 lbs. Whatever material you eventually decide to use, be sure to determine that your framing is adequate to carry it. It takes relatively little time to make sure it's right, compared to the time you would spend correcting it if it was wrong.

Stan

Thanks for the links, that was very helpful

Seems the therma floor link was a dud, but its on the site, just pay attention to the specifications, and of course your framing should checked to make sure the load is acceptable etc. You don't want to exceed that, say for example its a 100 lb per square foot rating and by placing 150lb/sq.ft. material, the floor needs to be built stronger etc.

Light weight concrete, may be an option, the aggregate is likely to have expanded or shale processed by using heat to kind of make it like popcorn, one of the suppliers of this aggregate is nearby, its one that is ASTM specified and or called for by specifications of many jobs I have been involved with.