Skimflow HPI ImageSKIMFLOW® HPI is a gypsum engineered cement self-leveling underlayment for use over interior surfaces. It can be pumped or poured and delivers high strength, good water resistance and outstanding adhesion.

Applications from as thin as 1/8” and as thick as 3” depth can be achieved in a single pour. SKIMFLOW® HPI remains flowable for 20 minutes, yet will withstand foot traffic at any depth in 2-3 hours. This product offers high density, yet less finished weight and more flexibility than Portland cement self-levelers.

Features and Benefits

  •  Outstanding flexural strength
  •  Suitable for plywood subfloors
  •  Great for use over lightweight and gypsum subfloors
  •  Durable high strength specialty cement
  •  Outstanding heal
  •  Non-alkaline – adhesive friendly
  •  Can pour up to 3” in a single pour
  •  Withstands construction/renovation traffic
  •  As little as 1/8” coverage over other surfaces (example: radiant heat tubing)
  •  Eliminates dusting/adhesion problems


    • 50 lb. (22.7 kg) double wall bag


    • 5 gallon pail (19 L) with pour spout
    • 1 gallon bottle (3.8 L) with pour spout



To maintain warranty, subfloor must be properly primed. Use DEPENDABLE PRIMER SL on all surfaces. All supporting surfaces shall be structurally sound, solid, free of movement and well bonded. They shall be free of dust, oil, grease, tar or other contaminants that may act as a bond breaker. Do not apply over single stripwood floors or over wood subfloors prone to excessive swelling (not exterior glue or “underlayment” grade). Porous substrates will need to be sealed prior to applying primer and may require more than one coat. Make sure that the substrate is properly primed/sealed before continuing.

Concrete Floors

Remove all foreign matter by mechanical means. Floor must be free of efflorescence and excess moisture. To check moisture, test with a calcium chloride test (ASTM F1869), or relative humidity (insitu probe) test (ASTM F2170). To correct moisture problems see DEPENDABLE’s moisture protection products.

Subsurface must be watertight as SKIMFLOW HPI is extremely flowable. Make sure any holes, cracks, etc. that would permit material through to a lower level are patched or filled with DEPENDABLE WHITE SKIMCOAT prior to priming.

Application over textured surfaces generally gives best bond. Extremely smooth, glazed tile must be abraded. Steel trowelled concrete can be scarified or bead blasted to give a suitable surface. A test patch for adhesion should be performed if the installer is in doubt. Before starting installation, establish the level around the area to be filled with a transit, level or laser device. Mark a “do not exceed” level around room or area perimeter by snapping a line or marking a minimum level by setting coated nails or screws just below the level to be achieved.

Wood Floors

Clean and sweep the floor free from dust and contaminants prior to installation. Pre-wet the floor prior to priming; for particularly porous floors mix PRIMER SL 1-to-1 with water as an initial seal. Once the floor is prepared for primer, prime the floor with PRIMER SL full strength, and wait until dry or tacky.

In most cases SKIMFLOW HPI can be poured directly over wood subfloors. For particularly unstable wood floors, mechanical reinforcement may be required. Staple a lath onto the floor after priming to prepare the floor for SKIMFLOW HPI.

Gypsum Floors

Clean and sweep the floor free from dust and contaminants prior to installation. Gypsum concrete must be sealed prior to installing SKIMFLOW HPI. Dependable’s GSL® ACRYLIC SEALER or ACRYLIC EMBOSSING ADDITIVE may be used to seal the floor. After cleaning, mix your sealer 1-to-4 with water and apply a first sealer coat onto the gypsum concrete. After first coat of sealer is dry (minimum 1-4 hours), apply second coat of sealer and allow to dry. Once sealer is completely dry, prime the floor with either ACRYLIC EMBOSSING ADDITIVE or PRIMER SL full strength.

Adhesive Residue

SKIMFLOW HPI can be poured directly over old adhesive residue. Dependable recommends the installer mechanically remove as much of the old adhesive as possible. Once the residue is removed prime the floor with ACRYLIC EMBOSSING ADDITIVE full strength, and the floor is ready for the pour. If the old adhesive residue is Cutback adhesive, Dependable recommends the installer encapsulates the floor with two coats Dependable’s CUTDOWN II. Consult Dependable for technical data sheet for details.


Use a long handled roller, soft bristle broom or paint brush to apply DEPENDABLE PRIMER SL at full strength. Do not dilute. Do not cover until very tacky or dry (about 1 hour). See PRIMER SL data sheet for details.


Mix 1 bag SKIMFLOW HPI into 5 quarts (4.7 liters) cool clean water. (10 lbs. to 1 qt. water or 5kg. to 1 liter water). SKIMFLOW HPI can be mixed in large quantity in mortar mixers or special pumps or in smaller quantities (up to 3 bags) in a 20-40 gallon container. Use only a very clean mixing container that does not contaminate SKIMFLOW HPI with other material. Pre-dampen container to provide proper first mix. Pour in proper amount of water and then add powder while mixing. Do not over-water. If a problem is encountered while mixing and you are not getting a lump and powder free mix, try starting with 2/3 of proper water, adding powder until just wetted, then adding remainder of water and thoroughly mix at 850-1200 RPM. Mix for at least 2 minutes, but no longer than 3 minutes to a homogenous lump-free mixture. Do not shake.



Pump or pour contents onto floor. Because SKIMFLOW HPI is very flowable, allow it to build in one area until it reaches at least desired depth and maintains that depth even as material flows away. Begin at a corner of room or at a deep part of fill. Plan the pour before starting. Either work back and forth along a line of the room or from the center of the fill outwards in all directions to keep pouring against the freshest material possible. Lightly work the transition points between pours and material over or under desired depth with a screed, spreader,  lightweight float or straightedge to the desired depth. Material should remain highly flowable for 20 minutes and can be walked in for over 45 minutes at normal temperatures. Any imperfection can be smoothed by surface trowelling or drawing a straightedge or smoother over the surface. As material gets stiffer and begins to gel, it may be smoothed or trowelled to a featheredge. Once material begins to gel, stay off the area for about 1.5-2 hours, after which floor should bear foot traffic.In very hot or windy conditions, protect from wind and mist fog floor. Direct sunlight, heat and wind can cause rapid drying of the product which may reduce working time. To avoid rapid drying, provide protection against these elements. Let material continue to dry before covering until evaporative moisture lessens. Moisture level may be checked by a surface moisture meter, a plastic film taped to the floor, or a plastic bucket left on the floor and the area carefully observed for residual surface moisture upon removal. In thin 1/4” applications, SKIMFLOW HPI may be covered in 4-24 hours depending on drying conditions (temperature, humidity, thickness) and requirements of adhesive and floor covering. For impervious coverings (vinyl, laminate, etc.) be sure SKIMFLOW HPI is thoroughly dry (at least 16-24 hours). Pours deeper than 3/8” require longer time or forced drying.

Multiple lifts: SKIMFLOW HPI may be placed in multiple lifts or layers. Allow the previous layer to harden and dry until there is no discernible evaporation. Once dry, prime again with Primer SL and apply the next SKIMFLOW HPI layer. Remember thicker areas of product take longer to dry.

NOTE: Temperature and humidity levels affect the drying characteristics of SKIMFLOW HPI. However, unlike Portland cement materials, SKIMFLOW HPI may be force dried with the use of heat or fans once set.



For Interior use only.
Do not use…

• Where hydrostatic pressure (water) is present or moisture emissions exceeds level permitted for installed floor covering.
• Where surface or ambient temperature falls to or below 45°F 72 hours before or after installation.
• Over presswood, particle board, masonite, chipboard, single stripwood floors, luaun or similar dimensionally unstable materials susceptible to moving or swelling.
• As a trowelled patch or at less than natural minimum flow thickness.
• Exterior, exposed applications or as a wear surface.