Looking for suggestions on installing concrete below tile on elevated floor

lwl353

Originally, we were planning on pouring an approximately 2" thick concrete slab on the main floor of our house to run our in-floor heat through as well as gain some passive solar heat. We were going to finish the floor by polishing it to a nice shine. The quotes have came back and it's becoming very pricy to have the polishing completed.

Having said that, we're still looking at putting down about 1-3/4" of a concrete type product as a sub-floor, then installing tiles on top for the finished product.

Does anyone have any suggestions of what type of concrete I could pour that will not cause the tiles to pop, be relatively easy to work with (moderately self-levelling) and isn't over priced. My initial thoughts are to just order regular portland cement concrete with 3/8" aggregate, but request a higher slump.

Thank you

Ron6519

You need a light, weight gypsum based mix. It's self leveling. You need to find out the particulars of the subtrate needed.
What were you putting this concrete over?

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Bud Cline

What type of in-floor heat are you planning to use?

oh'mike

Just a few more details needed---

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lwl353

I am utilizing a solar thermal system with electric backup with flexible pipe embedded (I am not the in-floor heat provider). I am likely going to install it over 3/4" t&g plywood, but this is not set in stone.

As for the light-weight gypsum mix, how well does that store heat from passive solar gains? It would seem to me that the gypsum mix wouldn't store and release heat as well as a standard weight concrete.

oh'mike

Sounds like you need mass----I think concrete is the best solution---However--

Concretemasonry--or itsreallyconcrete--(members) have a great depth of knowledge on that --so I'll see if either one check in before I put in my two cents---Mike---

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Bud Cline

Tile over lightweight (Gypcrete) has its issues. The lightweight must be addressed before tile can be applied to it.

Ron6519

It might be helpful if the OP mentioned the structural supportthis was going on.
The "elevated" aspect has piqued my interest.

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lwl353

Ron6519 - I'll be designing my floor joist system to support the additional weight of the concrete, I don't have a concern there.

I'm looking for some suggestions on a product that I can pour pretty much level the first time, will allow a good bond to tile and will provide sufficient mass for passive solar heating purposes.

Does anyone have an opinion on how a small aggregate concrete mix with a slightly higher slump would work in this application?

Bud Cline

You could use Self Levelling Compound (SLC) and add some pea gravel to it for bulk.

The SLC would serve as your thermo-mass and your tile-backer at the same time.

jimmy21

im not an expert on the matter, more curious than anything. but isnt 1 3/4 a little thin for concrete? Especially with flexible pipes running in the middle?

stuart45

Maybe something like this.
www.youtube.com/watch?v=5WOAPU2PiQc

itsreallyconc

normally thermal mass depends on mass,,, suspect passive solar would benefit from 1 1/2" just as well as 4" BUT no date to confirm,,, you are correct in getting small coarse aggregate for thin floors especially when encasing infloor heat,,, depending on your location ( e b/f or not )/amt of work/avail power, polished conc should compare quite well against tile but its not my house - self levelers are a pita unless 1 has some experience placing them

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jomama45

We usually do this at least once a year, oftentimes in zero-entry accessible homes. It allows for curbless showers.

We've never had a problem getting the standard pea stone (3/8") mix to work out for loading the floor joists, as it's only about 22#'s per sq. foot for standard weight concrete. Lightweight agg. would only get you down to about 18#'s per sq. ft. with the agg. we have available here. Not worth it for the extra money in most cases. Obviously, the additional weight of the concrete has to be figured into the equation when the floor system is engineered.

As for the mix, we typically use a 5.5 bag (same as 3500 pis mix, but with straight cement) with a double dose of fibers, as well as a mid-range water reducer to bring the slump up to about 6" to ease installation.

Just be forewarned though. This is far from self-leveling and requires quite a bit of labor and experience to get down flat enough for tile. If you try to bite off more than you can chew, you'll likely burn out or the concrete will set faster than you can finish it. You can always use a self-leveling compound over it if it get's away, but it's a waste IMO when putting a good finish on the concrete right away is far easier & cheaper. That being said, I'd likely hire it out to a pro if you don't think you have the experience.

nobel

now the thing is this that if you want to install new tiles in the floor and want to make is concrete then you should to use the varnish inside the tile this is my personal experience.