I had to pour self-leveling concrete in my kitchen (and will need to do it in my living room, but that'll have to wait a month or two.) I learned a few things in the process, and I'm documenting them here for posterity.
Materials:
- I used Custom's LevelQuick RS (rapid setting) compound with Custom's primer. You MUST use the same brand primer and compound. You MUST use the primer! (see below)
- When buying the compound at a big box store, check the dates on the package. You want a recent date and you want all the dates to be the same. I had one bag that was a newer date by three months, and it turned out way better. (Or save yourself the trouble and aggravation, and order from a distributor that has a high turnover.)
- Tools: Variable speed drill with a speed setting, two bladed "egg beater" bladed mixer (not the spiral one that they sell as a "premium"
, buckets, measuring tool for water, latex caulk and foam weather stripping, floor squeegee
Preparation:
- I washed the floor with Trisodium Phosphate at the maximum strength mixture (2 cups per gallon water, I think?), using a foam mop and scrub brush (mostly scrub brush) which removed old vinyl glue, mold, mildew, gunk, cabinet finish left over from when the cabinets were finished in place on the slab in 1980. I then washed the floor twice with water to remove all of the TSP. The TSP provided a slight etching effect. The TSP did not remove old vinyl backing. I was cautioned NOT to use an oil based stripper to remove the vinyl backing, but I ignored the advice -- I just made really sure to wash the areas that got the stripper two or three times with TSP and then a few more times with plain water.
- Before you apply the primer, put a bead of latex caulk around edges the room and (indoors) at 15 to 20 foot intervals -- or over any expansion joints in your concrete -- (outdoors) over any expansion joints or at 8 to 12 foot intervals. Cover it with foam rubber weatherstripping that's the same depth as you expect to pour. Basically, glue the weatherstripping to the floor with latex caulk. Since the self-leveling concrete will have a different expansion ratio than the concrete it's set on, it may otherwise crack and buckle.
- Also before priming, use some wood and latex caulk to "dam" any doorways that you don't want to pass. You can remove the wood and latex while the concrete is curing.
- I used 2 coats of primer applied with a roller, per the instructions of some professionals that I read online. I used it undiluted. 2 bottles covered about 100 sq feet with two coats. The primer does 2 things. It seals the concrete so that the concrete does not suck all of the moisture out of the compound you pour onto it, and it provides a 'wicking' action so that the self leveling concrete will 'flow' across it with minimal prompting. In areas where I didn't have 2 coats or where I'd missed a little near the edges, it did not flow at all. If you're installing self-leveling concrete and it isn't flowing, you probably didn't prime well enough.
- Mixing for a small area takes 2 people, pouring takes one. (one to pour the mix, one to hold the mixer, one to pour.) That means you need three people. Mixing for a large area will take seven people if you are using 5 gallon buckets -- One to pour, one to run buckets, one to clean buckets and bring them back to mixers, and two mixing teams.
- Add the water first, and use the coldest water that you can. (I pre-measured the water and let it sit inside in the A/C for a while.)
- This is not a summer project in an un-airconditioned house. The ideal temp for pouring this stuff is 70 degrees F.
- I was using 5 gallon buckets to mix in; when it comes time to do a larger area I will probably use 35 gallon trash cans.
- Use the exact amount of water stated on the package. For Custom LevelQuick RS, it was 6.5 quarts.
Pouring:
- You MUST pour it all at once while it's still wet. The Custom RS claims that it's working time is ten minutes. You MUST plan your pour so that you maintain a "wet edge" -- and one bucket of mix can about cover 20 square feet, depending on depth. Think about that before you pour. See above on staffing recommendations...
- When you pour, start SLOWLY close to a corner and make an even arc. If it doesn't flow into the corners, persuade it with a little more pour ... and if it really doesn't, use your rubber squeegee to "agitate" it. Not much more should be required.
- The mixing should be constant. (It takes 2 minutes to mix -- one to get the concrete into the bucket, one minute at 650 rpm.) Again, ONE pour. Have your helpers keep the buckets coming to you.
Finishing:
- Don't have an open window or fan blowing dry air onto it. You'll form a 'skin' over it, and things will dry at different speeds. (Ask me how I know...)
- Once it's cured completely (4-24 hours depending on material, how well you measured water...), tap on it with a hammer to make sure it's adhered properly to the subfloor. If it hasn't, you'll hear a hollow noise. (You'll be going "tap tap tap tap tap THUNK" If you find such an area, chip that area up with a chisel, re-prime, and re-lay the SLC.
- If there are lumps, scrape them off with a flat, straight blade (painter's tool, putty knife, trowel edge, etc.) after it cures enough to walk on.
Home Depot carries LevelKwik RS. Lowe's carries Mapei brands, which I normally like better, but their stock was VERY old and I didn't trust it to cure completely.
I was scared sheetless over pouring this stuff in my house, because I've had to chip up some old stuff and it is NOT FUN LET ME TELL YOU. It turned out to be really simple. If you're planning to lay a tile that is larger than 16x16 in any dimension, and your floor has any ridges, lumps, or dips in it, I would plan to do a layer of self-leveling concrete first.
(My floor was out 7/16's -- almost half an inch -- in some places compared to the highest points, and I'm laying a 12x24 tile.)
Materials:
- I used Custom's LevelQuick RS (rapid setting) compound with Custom's primer. You MUST use the same brand primer and compound. You MUST use the primer! (see below)
- When buying the compound at a big box store, check the dates on the package. You want a recent date and you want all the dates to be the same. I had one bag that was a newer date by three months, and it turned out way better. (Or save yourself the trouble and aggravation, and order from a distributor that has a high turnover.)
- Tools: Variable speed drill with a speed setting, two bladed "egg beater" bladed mixer (not the spiral one that they sell as a "premium"
, buckets, measuring tool for water, latex caulk and foam weather stripping, floor squeegeePreparation:
- I washed the floor with Trisodium Phosphate at the maximum strength mixture (2 cups per gallon water, I think?), using a foam mop and scrub brush (mostly scrub brush) which removed old vinyl glue, mold, mildew, gunk, cabinet finish left over from when the cabinets were finished in place on the slab in 1980. I then washed the floor twice with water to remove all of the TSP. The TSP provided a slight etching effect. The TSP did not remove old vinyl backing. I was cautioned NOT to use an oil based stripper to remove the vinyl backing, but I ignored the advice -- I just made really sure to wash the areas that got the stripper two or three times with TSP and then a few more times with plain water.
- Before you apply the primer, put a bead of latex caulk around edges the room and (indoors) at 15 to 20 foot intervals -- or over any expansion joints in your concrete -- (outdoors) over any expansion joints or at 8 to 12 foot intervals. Cover it with foam rubber weatherstripping that's the same depth as you expect to pour. Basically, glue the weatherstripping to the floor with latex caulk. Since the self-leveling concrete will have a different expansion ratio than the concrete it's set on, it may otherwise crack and buckle.
- Also before priming, use some wood and latex caulk to "dam" any doorways that you don't want to pass. You can remove the wood and latex while the concrete is curing.
- I used 2 coats of primer applied with a roller, per the instructions of some professionals that I read online. I used it undiluted. 2 bottles covered about 100 sq feet with two coats. The primer does 2 things. It seals the concrete so that the concrete does not suck all of the moisture out of the compound you pour onto it, and it provides a 'wicking' action so that the self leveling concrete will 'flow' across it with minimal prompting. In areas where I didn't have 2 coats or where I'd missed a little near the edges, it did not flow at all. If you're installing self-leveling concrete and it isn't flowing, you probably didn't prime well enough.
- Mixing for a small area takes 2 people, pouring takes one. (one to pour the mix, one to hold the mixer, one to pour.) That means you need three people. Mixing for a large area will take seven people if you are using 5 gallon buckets -- One to pour, one to run buckets, one to clean buckets and bring them back to mixers, and two mixing teams.
- Add the water first, and use the coldest water that you can. (I pre-measured the water and let it sit inside in the A/C for a while.)
- This is not a summer project in an un-airconditioned house. The ideal temp for pouring this stuff is 70 degrees F.
- I was using 5 gallon buckets to mix in; when it comes time to do a larger area I will probably use 35 gallon trash cans.
- Use the exact amount of water stated on the package. For Custom LevelQuick RS, it was 6.5 quarts.
Pouring:
- You MUST pour it all at once while it's still wet. The Custom RS claims that it's working time is ten minutes. You MUST plan your pour so that you maintain a "wet edge" -- and one bucket of mix can about cover 20 square feet, depending on depth. Think about that before you pour. See above on staffing recommendations...
- When you pour, start SLOWLY close to a corner and make an even arc. If it doesn't flow into the corners, persuade it with a little more pour ... and if it really doesn't, use your rubber squeegee to "agitate" it. Not much more should be required.
- The mixing should be constant. (It takes 2 minutes to mix -- one to get the concrete into the bucket, one minute at 650 rpm.) Again, ONE pour. Have your helpers keep the buckets coming to you.
Finishing:
- Don't have an open window or fan blowing dry air onto it. You'll form a 'skin' over it, and things will dry at different speeds. (Ask me how I know...)
- Once it's cured completely (4-24 hours depending on material, how well you measured water...), tap on it with a hammer to make sure it's adhered properly to the subfloor. If it hasn't, you'll hear a hollow noise. (You'll be going "tap tap tap tap tap THUNK"
If you find such an area, chip that area up with a chisel, re-prime, and re-lay the SLC. - If there are lumps, scrape them off with a flat, straight blade (painter's tool, putty knife, trowel edge, etc.) after it cures enough to walk on.
Home Depot carries LevelKwik RS. Lowe's carries Mapei brands, which I normally like better, but their stock was VERY old and I didn't trust it to cure completely.
I was scared sheetless over pouring this stuff in my house, because I've had to chip up some old stuff and it is NOT FUN LET ME TELL YOU. It turned out to be really simple. If you're planning to lay a tile that is larger than 16x16 in any dimension, and your floor has any ridges, lumps, or dips in it, I would plan to do a layer of self-leveling concrete first.
(My floor was out 7/16's -- almost half an inch -- in some places compared to the highest points, and I'm laying a 12x24 tile.)
