Koster KNULEVEL - Self-Leveling, Interior Cementitious Underlayment - 50 lb Bag - SL 290 022

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Self-Leveling, Interior Cementitious Underlayment


KOSTER KnuLevel is a high quality, self-leveling, fast setting, cementitious underlayment intended for interior use on concrete floors. It is easy to mix, pour, and spread, producing a smooth, level surface ready to receive flooring systems. It is walkable in 3-4 hours. KOSTER KnuLevel is intended to be applied onto a cementitious substrate. KOSTER KnuLevel accepts most major types of floor coverings and is compatible with most adhesives. It is not intended as a wearing surface. Do not use over KOSTER VAP I® 2000 moisture control systems.

Technical Data

 Working Time: approx. 25-30 min at 70°F (ASTM C1708)
Thickness: 1/8 in. to 1 1/4 in. (neat)
Initial Set approx. 30 min (ASTM C191)
Compressive Strength: >5000 psi at 28 days (ASTM C109)
Walkable: approx. 3-4 hours
Install Flooring: approx. 16 hr (depending on temperature and humidity



Substrates to receive KOSTER KnuLevel must be sound, clean, and free of curing compounds, oil, grease, paint, loose particles, or any contaminant that may weaken bond. The tensile pull off strength of the substrate must be at least 200 psi (ASTM C1583). Do not acid etch substrates. Do not clean concrete substrate with chemicals. May be applied over traces of adhesive residue. Do not bridge movement joints with KOSTER KnuLevel. Environmental temperature must be 60 - 90°F.


For use directly on concrete: Consult individual product data sheets for information. For direct application to concrete, the concrete surface must be absorptive. Dense, hard-troweled concrete, or concrete with residual curing compounds must be mechanically abraded to minimum ICRI CSP3 until water is easily absorbed. Clean the surface thoroughly by sweeping and vacuuming to remove dust. Prime the cleaned concrete substrate using KOSTER SL Primer. Apply a thin, even coat of primer at 400 - 800 ft2/gal. Thick application may cause bonding problems. Allow to dry to a translucent green film, usually 30 min to 1 hr at 70°F and 50% RH. High humidity or low temperature will extend drying time. Keep the primed surface clean until the underlayment is installed. Install KOSTER KnuLevel within 48 hours after primer application. Concrete moisture must be less than 90% RH. Test concrete moisture according to ASTM F2170. If concrete moisture exceeds 90% RH, DO NOT INSTALL KOSTER KnuLevel. Instead, install KOSTER VAP I 2000 moisture control coating and use KOSTER LevelStrong Self-Leveling Underlayment.


Mix TWO bags of KOSTER KnuLevel at a time. Pour 9.5-10 quarts (9-9.46 L) of clean potable water into a clean mixing vessel (4.75-5 qts water for each 50-lb bag). Do not over-water! (It is recommended to start at the lower water demand of 4.75 qts/bag.) Add two 50-lb. bags of KOSTER KnuLevel in increments while mixing with an electrical mixer equipped with a suitable helical or egg-beater style mixing paddle at 600 - 700 rpm. After all material has been added into the mixing water, continue mixing for 2 to 3 minutes. The resulting consistency must be smooth, flowable, and lump free.

 Installation: Pour mixed KOSTER KnuLevel onto the floor and spread using a gauge rake. A smoothing tool may be used to blend freshly poured material into adjacent pours. Wear non-metallic cleated shoes. KOSTER KnuLevel will level itself over 20-25 minutes at 70°F with no troweling. Spike Rolling may not be required. Protect poured underlayment from excessive heat, cold, premature drying, or freezing. Setting and drying times will be shortened in hot temperatures and extended in cold temperatures.

Coverage (Dependent on application)

Thickness  ft²  bag
1/8" 50
3/16" 33
1/4" 25
1/2" 12
3/4" 8
1" 6.25


Clean mixing equipment thoroughly with water and stiff scrub brush to avoid getting hardened product into subsequent batches. Keep mixing bucket clean.

Packaging SL 290 022
50 lb bag

Store in a cool, dry place.

Eligible LEED Credits
Recycled Content

May cause skin irritation. May cause serious eye irritation. May cause serious eye damage. May cause respiratory irritation. Keep out of reach of children. Avoid breathing dust. Wear eye protection/face protection

The information contained in this technical data sheet is based on the results of our research and on our practical experience in the field. All given test data are average values which have been obtained under defined conditions. The installer is responsible for the correct application taking into consideration the specific conditions of the construction site and the final results of the construction process. This may require adjustments to the recommendations given here for standard cases. Specifications made by our employees or representatives which deviate from the specifications contained in any Company literature may not be relied upon in the absence of written confirmation from the Company. The installer must comply with all testing, technical requirement, guidelines, and industry customs at all times. The terms, conditions, and limitations contained in the written warranty for the product controls over the specifications contained herein. This guideline has been technically revised; all previous versions are invalid.