Large format tile needs a flat floor. Most Kansas City slabs and subfloors aren't flat enough out of the box, especially in older homes, basements and remodels where flooring has come up. So before we set 24×48 or larger porcelain, we fix the floor. We grind the high spots, fill the low ones, and when the floor needs it, pour a self-leveling underlayment such as ARDEX K 15 to give the tile a true, flat base.
Floor leveling is part of the tile job. We level floors that we're tiling, so you get one crew, one schedule and one proposal from bare floor to finished tile.
Typical cost: professional self-leveling usually runs $3–$9 per sq ft installed, depending on depth and prep. On a 300 sq ft floor that's roughly $900–$2,700, on top of the tile. See the cost guide or add leveling in the instant estimator.
Why large tile needs a flat floor
The bigger the tile, the less it forgives. A 12×12 tile can follow a gentle dip in a slab. A 24×48 tile bridges right over it. One end rocks, the edges sit higher than the tile next to them, and you get lippage: uneven edges you can see in raking light and feel underfoot. Worse, the tile ends up with hollow spots under it, and hollow tile cracks.
That's why the industry tightens the flatness requirement for large tile. For tile with any edge 15 inches or longer, the substrate should vary no more than 1/8 inch in 10 feet and no more than 1/16 inch in 24 inches, measured from the high points (LATICRETE's large-format installation guidance explains the limits). Many slabs miss that by a wide margin.
Flat and level aren't the same thing. A floor can slope evenly toward a drain and still be flat. Another can be level overall and still have a ridge in the middle that a long tile will teeter on. For tile, flat is what matters. We'll only make a floor level as well when the room calls for it, for example where the new tile meets a hardwood floor or a doorway. Our installation guide goes deeper.
How we check the floor
Before we price the job, we measure the floor the way the tile will see it:
- Straightedge checks across the room in both directions, looking for humps, dips and ridges over 10 feet and 24 inches
- Transitions to doorways, stairs, cabinets, appliances and adjoining floors, since every bit of height we add has to finish cleanly there
- Cracks and joints in a concrete slab, including control joints that have to carry up through the tile
- The subfloor and framing over wood, because a bouncy floor needs structural attention before it needs leveling
- Moisture and old residue such as adhesive, paint or patching compound that a new underlayment can't bond to
Then we tell you which fix the floor needs, and what it costs, before any tile is ordered.
Three ways to flatten a floor for tile
| Fix | When we use it | What it involves |
|---|---|---|
| Grind the high spots | A few humps or ridges, or a slab that's high in places | Diamond grinding takes the high areas down so the tile doesn't rock |
| Patch the low spots | Isolated dips, old floor-drain areas, chipped or uneven sections | A trowel-applied patching compound fills the low areas flush |
| Pour self-leveling underlayment | Widespread dips, wavy slabs, or a large area that's out of tolerance | The slab is cleaned and primed, then a pourable cement underlayment is spread so it flows out flat |
Most floors need a combination: grind what's high, then patch or pour what's low. The setting mortar under the tile is not a leveling layer. Building up extra thinset to fix a bad floor leads to voids, and tile leveling clips only even out the tile edges, not the floor beneath them.
Self-leveling underlayment before tile
Self-leveling underlayment is a pourable cement-based product. It's mixed to a liquid, poured over a primed floor, and spread so it flows out into a smooth, flat surface. For tile, it's the most reliable way to fix a floor that's out of flat across a whole room.
We work with ARDEX self-leveling systems. ARDEX K 15 Premium Self-Leveling Underlayment is a common choice before tile over concrete. According to ARDEX's K 15 product data, it:
- installs up to 1½ inches thick neat, and up to 5 inches with aggregate in most applications
- is walkable in 2 to 3 hours
- accepts porcelain, ceramic and quarry tile after about 6 hours
- reaches 5,500 psi compressive strength at 28 days
- is for interior, dry areas, over properly prepared and primed concrete
What that means for your schedule: in most rooms we prep and pour one day and can start setting tile the next. The underlayment doesn't add a week to the job.
Over a wood subfloor? K 15 is a concrete product. Wood floors need a self-leveler made for wood, such as ARDEX Liquid BackerBoard, plus the right lath or primer. The framing also has to be stiff enough for tile. We check the joists and subfloor first and tell you if the floor needs more than leveling.
Basements, slabs and older homes
- Basement slabs are often poured with a slope toward a floor drain, and they collect dips and ridges over the years. A pour can flatten the area you're tiling and feather back to meet the existing slope.
- Older Kansas City homes often have patched slabs, old tile or vinyl residue, and floors that move between rooms. We remove what the underlayment can't bond to before we prime and pour.
- Kitchens and open plans have long runs of tile, where a dip that's invisible with 12×12 tile becomes obvious with 24×48. Flattening the whole run keeps the grout lines straight across rooms.
- Cracks and joints get treated, not buried. Control joints in the slab carry up through the tile as movement joints. Active or structural cracks need a different fix.
What floor leveling costs
Professional self-leveling usually runs about $3–$9 per sq ft including materials and labor (FloorChem Depot's self-leveling cost guide, September 2025). Many contractors also have a minimum charge, often $500–$700 (Flooring Clarity, June 2025). Premium underlayments like ARDEX K 15 run about $60–$80 per 50-lb bag, which covers about 50 sq ft at 1/8 inch.
| Floor | Typical leveling cost |
|---|---|
| 100 sq ft bathroom | $500–$900 (usually minimum-charge territory) |
| 300 sq ft kitchen or living area | $900–$2,700 |
| 600 sq ft open plan or basement | $1,800–$5,400 |
The biggest swing is depth. A skim of 1/8 inch over a fairly flat slab is at the low end. Filling a 1/2-inch dip across a basement takes several times more material. Grinding, heavy adhesive removal and wood-subfloor prep add to it. We measure first and give you the leveling as its own line in the tile proposal, so you can see exactly what it costs.
What we don't do
We level floors for the tile we install. We're the wrong call for:
- Sinking or settling slabs, foundation problems, or mudjacking and polyjacking. You need a concrete-lifting or foundation contractor.
- Leveling only, for LVP, hardwood or carpet that someone else is installing
- Epoxy, garage coatings or polished concrete
- Exterior slabs, patios and driveways
Where we work
We level and tile floors throughout the Kansas City metro. In Kansas that includes Overland Park, Leawood, Olathe, Lenexa, Shawnee, Prairie Village, Mission Hills and the rest of Johnson County. In Missouri it includes Kansas City, Lee's Summit, Liberty, Parkville, Blue Springs, Independence and the Northland.
Questions about floor leveling for tile
Do I need to level my floor for 12×24 tile? You need it flat to the large-format tolerance, since 12×24 has a 24-inch edge. Plenty of floors are close enough with a little grinding and patching. We measure and tell you.
Can you just use more thinset to make up the difference? No. Mortar is made to bond tile at a set thickness, not to flatten a floor. Building it up creates voids, slow curing and hollow tiles. The floor gets fixed first.
How long before you can tile over self-leveler? With ARDEX K 15, porcelain and ceramic tile can go down after about 6 hours, so usually the next day. Other products and thick pours can take longer.
Is this the same as concrete leveling or mudjacking? No. Mudjacking and polyjacking lift sunken slabs from underneath. Self-leveling underlayment is a thin layer poured on top of an interior floor to make it flat for flooring.
Will leveling fix a bouncy floor? No. Bounce comes from framing or subfloor stiffness, and a pour on top won't stiffen it. Tile over a bouncy floor cracks. We'll tell you if the floor needs structural work first.
Will the floor end up higher? Slightly, by the thickness of the pour where it's needed. We plan the height at doorways, stairs, dishwashers and adjoining floors before we pour.
Ready to tile? See large format tile floors, or get a quote with the room size and the tile you're considering.