How to Prime and Pour Self-Leveling Underlayment

A 55 lb bag of ARDEX K 15 takes 7 quarts of water, while a 55 lb bag of LATICRETE NXT Level Plus takes 5.0 to 5.5. That gap is why pouring self-leveling concrete has no single water, mixing or primer rule. This guide gives the order of work and names the product behind every number.

What Is the Order of Work on Pour Day?

The order is clean, seal gaps, prime, mix, pour and protect. Each maker prints its own numbers for the middle steps, so this guide names the product every time it quotes one.

It reads four current sheets: ARDEX K 15 (a buildsite.com copy marked updated 2025-01-23), Custom Building Products LevelQuik RS (TDS-108, dated 1/18/2024), LATICRETE NXT Level Plus (DS-505-1026) and MAPEI Ultraplan 1 Plus (edition date October 11, 2024). A 2008 QUIKRETE sheet appears only with a dated label.

For how many bags to buy, use the self-leveling concrete calculator. This article covers the work, not the quantity.

How Do You Prepare the Floor and Seal Gaps?

The floor must be sound, clean and dry, and open spaces must be blocked so fluid leveler cannot leak out. That is the common thread in the ARDEX, Custom Building Products and MAPEI sheets.

ARDEX says to clean mechanically, by shot blasting if necessary, and to vacuum. It lists acid etching, adhesive removers, solvents and sweeping compounds as things not to use. CBP names grease, oil, dust, curing compounds, waxes and sealers as contaminants. It also says the concrete must be fully cured and able to absorb water. MAPEI asks for concrete at least 28 days old.

On gaps, CBP says to block open spaces so leveler does not spill into adjoining areas. MAPEI says to fill holes and cracks with a MAPEI patching compound or screed, and to fill plywood joints with acrylic caulk. The 2008 QUIKRETE sheet says to seal all perimeter openings. No sheet read gives a drain-sealing method.

Moisture is a separate check. ARDEX, LATICRETE and MAPEI each state that their product is not a vapor barrier, and ARDEX points to testing concrete humidity to ASTM F2170. Wood subfloors need their own preparation and are not covered here.

Which Primer Do You Use, and How Long Must It Dry?

Use the primer your leveler’s maker names, and pour only after it has dried. MAPEI’s sheet says not to install over unprimed surfaces, and the other sheets read also call for primer.

In ARDEX’s water-drop check, clear water on the surface means the primer is dry, and milky water means it is not. LATICRETE says Primer Plus turns from milky white to clear when dry to the touch.

Suction changes the ratio. For Primer Plus, high-suction concrete takes 1:5 for the first coat and 1:3 for the second. No sheet read covers one brand’s primer under another brand’s leveler.

Primer example from the LATICRETE sheet (DS-65437). At 1:3, the sheet gives about 100 sq ft per gallon of diluted primer. One part primer plus three parts water makes four parts, so 1 gal of primer plus 3 gal of water makes 4 gal. At 100 sq ft per gallon, 4 gal covers about 400 sq ft. That is the sheet’s figure for normal suction, not a rule for other primers.

How Much Water Goes In, and How Long Do You Mix?

Each maker prints its own water amount per bag, and the sheets that give one warn against adding more. ARDEX puts it as “Do not overwater!” and lists yellowish foam during mixing, or settling sand, as signs of overwatering.

Mixing methods agree more than water does. ARDEX, CBP and LATICRETE all call for a heavy-duty 1/2 in drill at 650 rpm or more with a paddle. ARDEX and LATICRETE say 2 to 3 minutes, and CBP says 2 minutes and warns not to overmix. ARDEX puts water in the container first, then powder.

The MAPEI sheet disagrees with itself: its table says 1 to 2 minutes, while its procedure says 2 to 3. The bag-side sheet shows 2 to 3 minutes. MAPEI warns that overmixing traps air.

Two-bag example. ARDEX instructs mixing two bags at a time. Doubling each sheet’s water per bag gives:

• ARDEX K 15: 7 qt x 2 = 14 qt, which is 3.5 gal.
• CBP LevelQuik RS: 5.25 to 5.75 qt x 2 = 10.5 to 11.5 qt.
• LATICRETE NXT Level Plus: 5.0 to 5.5 qt x 2 = 10 to 11 qt.

These are examples from each sheet. Only the ARDEX sheet says to mix two bags.

How Do You Pour Self-Leveling Concrete and Keep a Wet Edge?

Pour in ribbons, spread to depth with a gauge rake, smooth right after, and keep a wet edge between batches. MAPEI describes the ribbons and says to work as a team. CBP and MAPEI both name a gauge rake, a smoother and a wet edge.

The 2008 QUIKRETE sheet describes continuous strips about 1 ft wide, with the next batch poured onto the edge of the previous one. ARDEX names a spreader, then a smoother or a spiked roller used immediately, and asks for cleated shoes with non-metallic spikes. ARDEX is the only sheet read that names a spiked roller. LATICRETE says to smooth the surface and the pour lines right after placement.

The measures differ. ARDEX gives a flow time of 10 minutes at 70 F. MAPEI gives up to 15 minutes. CBP gives a pot life in the bucket of more than 15 minutes at 70 F and 50 percent humidity. LATICRETE gives an initial set of 20 to 30 minutes, which is a set time, not a flow time. The 2008 QUIKRETE sheet says its product stays fluid about 20 minutes.

How Do You Protect the Floor, and When Can You Walk or Tile?

Keep the room inside the temperature range on the bag, then wait for the walk-on and flooring times your sheet prints. MAPEI also says to close doors and windows, turn off HVAC to avoid drafts and shade the floor from sun.

ARDEX also says to turn in-floor heat off 48 hours before, during and 48 hours after. MAPEI’s limitation text separately gives 50 to 90 F for 48 hours, so confirm which line applies on your bag. The 2008 QUIKRETE sheet lists 1 to 2 days to walk on its standard product and 1 to 2 weeks to flooring.

What Do the Sheets Say Not to Do?

The sheets share a short list of warnings. None of them states a rule for adding water or remixing after the leveler thickens.

• Do not overwater or overmix. ARDEX, CBP, LATICRETE and MAPEI warn against it, and LATICRETE says extra water weakens the product.
• Do not use damp curing, curing compounds or sealers. LATICRETE and MAPEI say so.
• Do not mix in other products. MAPEI says not to mix with other self-leveling underlayments. ARDEX and LATICRETE say never to add cement or admixtures outside written recommendations.
• Do not use it as a wear surface. ARDEX, CBP, LATICRETE and MAPEI each say so.
• Do not roll heavy loads early. LATICRETE says no rolling dynamic loads for at least 72 hours at 70 F. MAPEI says no forklift or scissor lift for at least 3 days.

More pour-and-finish tools are listed under slabs and flatwork calculators.

FAQs About Pouring Self-Leveler

Sources and Further Reading

Self-leveler products differ, so use the data sheet printed for the bag in your hands. Reviewed for accuracy by Prof. Dr. Khalil Mudassar, PhD. Last updated 2026-10-19.