How do you raise a concrete slab floor

2 years ago

last modified: 2 years ago

I need to raise my concrete slab floor in two rooms about an inch to match the floor in the other rooms. After it's raised I'm going to 24x48 tile layed on it. How would you all suggest raising it? Any idea of an approximate cost?

The contractor, who I like, is suggesting self-leveling concrete but wants 2400 just for labor plus whatever the self leveling concrete costs. I'm debating if it's worth it for 4k+. The rooms total 352 sq ft and the concrete is in fine condition just has a little residual carpet glue that didn't scrape off.

Thanks!

Featured Answer

millworkman

2 years ago

Only you can decide if it is worth the $ for the 1". It will likely still require some SLC as carpet typically will cover a multitude of sins and for that large of tile the concrete slab must be dead flat.

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Comments (11)

ShadyWillowFarm
2 years ago
You can just angle the transition strip and save $4k. Take a nice Caribbean vacation.
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Thanks, franztini, for taking time to share your thoughts. I agree with you- Warmboard is great for new construction, it would be quick solution. In your situation, you probably already have some insulation in the slab from your previous radiant heat. My slab has no insulation at all. It is desired that insulation over slab has R=19. This would require 4" thick insulation. I can't raise floor that much and would be ok with R=10 (maybe even lower). Roth panel seems as a great option for slab since it is made of insulation. Also, aluminum on top may heat floor faster. Though, for some reason, I have tough time to find contractors in NJ that have experience with Roth panels. Also, comments related to Roth panels I saw on web seem to be older. I was wondering if there were any issues with RP. The drawbacks - it may be time consuming to install (especially for hardwood flooring) and R value is only 4.5 and no additional insulation can be added underneath. Though, I would still consider if people have good experience with it. Also, there could be some additional tricks to improve insulation such as insulation on perimeter (don't know much about it). I looked at HeatPly. Because it is made of plywood, I would need additional insulation. Also, you may note it doesn't have the benefit of having aluminum on top to heat floor faster. Though it is great that it is provided with boiler and tubing. If you don't need insulation, it may work well for you. I found out that in order to insulate under Warmboard, I would need to use sleepers (rigid insulation will not work). While this will be the right way to provide insulation, this will require raising the floor level. I am taking time to make the right decision but have really hard time with it and the cold weather is around the corner.
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Thanks EATREALFOOD. Dh didn't say much when I told him. oldbat2be, your floor looks perfect. Mine is concrete slab which seems to make a difference. Christine, I've been doing internet searches and find pretty much the same answer everywhere, even eHow, that you can't lay a tile across that joint, there has to be a grout line over it filled with a special caulk, not grout. Called a soft joint. The other part we are puzzling over right now is using a flexible membrane under it. I was going to use Ditra, but was told that it wasn't made for this. There are some paint on membranes, and there are some mesh membranes. And people who use the paint on type seem to do the whole room with it. I also just saw a youtube video that says the industry standard requires a soft joint every 10 feet in a large room, or even a shower wall to prevent cracking when the house shifts. I didn't know that. Maybe that's why we had some cracks in our first tile floor. Also, our floor isn't completely flat and the pros seem to be divided on how much is acceptable. We either have a huge low spot that is 1/8" lower than either side, or we have two high spots that are 1/8" higher. And is a 1/4" high spot enough that we have to go get another super grinder, or can you adjust it with thinset? That's the big issue we're trying to solve right now.
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Your photo looks like a surface stain rather than an integral color. Depends on the look you want. We did have some pigment added to ours, just so it would be less "sidewalk" colored. We are really happy with how it turned out. We do have hydronic heat, which is wonderful. That alone requires serious insulation since you don't want to be heating up the earth. Our contractor was extremely fussy with the subs regarding protection of the slab during construction. The whole thing was always covered with a layer of Ramboard and a layer of a felt-like geotextile. (Think of all the things that go on during construction with your finish floor already in place.) I think it was after the interior construction that the concrete guy came back and did the polishing and sealing steps. (We looked at tiling the slab instead, but it was going to be another 10K)
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Craftsman Creations
2 years ago
last modified: 2 years ago
Dead flat is required for large format tiles. Prep to get the subfloor flat is the most important part of the job. With your description of the large height difference in the floors, I‘d advise against choosing such a large tile. I’m surprised your prep quote was as little as it was. Pick something smaller, and face up to transitions in doorways. Even so, you will still need flattening prep, and it would still be $$$. This is not work suited to a novice. This is a $30 a square foot and up job from a certified pro.
ci_lantro
2 years ago
^^^Yes, with large format tile, Craftsman stated exactly my concerns. Almost for sure, you are looking at considerable expense on floor prep to make the floor suitable for large format tile, excluding the raising the floor bit. And paying top dollar for qualified/ experienced in large format tile setting labor.
Timothy Winzell
2 years ago
Talk to the tile installer. They may have more expertise in the issue and be able to coordinate the leveling with their installation process.
Nev H1
Original Author
2 years ago
Thanks everyone!
everdebz
2 years ago
If you're done, may I ask, see if anyone wants to post about carpet glue - if there's an 'easy' remedy... ?
SJ McCarthy
2 years ago
@Nev H1 Remember: large format tiles will automatically raise your floors by 3/4" - 1.5" All by themselves.

You mention the 1" difference. Is that the CURRENT difference or is that the difference that will be LEFT OVER AFTER the tile is laid???

^^^^This is a REALLY important question! Like STUPID important. As in, if you raise it NOW and then lay tile you could end up with the OPPOSITE problem...the tile could sit WAY TOO HIGH! Oops.

A basic idea for TOTAL COSTS to prepare/level/flatten a concrete subfloor = $2 - $5/sf. Now ask yourself how much that is worth.

The cost of INSTALLATION for the TILE = $8 - $15 per square foot (that's JUST LABOUR).

If you've been quoted $4,000+ for the ENTIRE JOB...then someone is sniffing something! A LARGE FORMAT tile is SUPER SPECIAL to install. And SUPER SPECIAL = MORE EXPENSIVE to install. The range for install = $12 - $18/sf for labour (in my area = hyper expensive market).

Your 'contractor' is too low...but that could be a local phenomena. Where are you?
Nev H1
Original Author
2 years ago
That floor right now is 2 1/8 in higher. The tile is 5/16 Ditra heat duo adds another 5/16. Then the layers of thinset
Nev H1
Original Author
2 years ago
@sjmccarthy

Can't edit last comment on phone

Is my thinking correct. Thanks for the help.

That's just for the self leveling concrete. I'm.nrwcing myself for the cost to lay the tile. Haha.
btydrvn
2 years ago
Just curious..what two rooms only total 354 sq.ft. …what shape are the rooms?…And is a tile that big really appropriate for rooms that size?..there are so many options for easy to install floor coverings..why choose this one?

How do you raise a concrete slab floor

millworkman

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