2.64 gallon pails

Sika® Primer MB

Primer and Moisture Barrier for use with SikaBond Adhesives, SikaLevel
underlayments and other flooring systems on critical substrates


Sika Primer MB is a 2-component, solvent-free, super low-viscosity, epoxy primer for use with under ALL flooring products, wood, carpet, vinyl, LVT, self-leveling underlayments, floating floors, and other flooring systems that require protection from sub-floor moisture.

Where to Use

  • Moisture barrier to help control osmotic moisture propagation in cementitious substrates with a moisture content up to 6% Tramex Method (approx. 4% CM method)
  • Substrate consolidator on concrete, cement, gypsum screeds and old substrates
  • Adhesion promoter for old adhesive residues


  • Regulate moisture
  • Solvent-free (100% solids)
  • Easy roller applied application
  • Shorter construction periods
  • Excellent penetration and stabilization of the substrate
  • Reduction of adhesive consumption
  • Suitable on old substrates when prepared appropriately
  • Suitable for use on floors with radiant heating
  • Low viscosity
  • Compatible with SikaBond wood flooring adhesives
  • Compatible with SikaLevel MB Excel and other underlaymnet System
  • Can be used below floating floors


Coverage is approximately 250-300 square feet per pail, depending on substrate porosity. No dry spots should exist after application is complete - and a shiny film should exist throughout the entire floor area to ensure sufficient moisture barrier properties. Only one coat is necessary for moisture regulation if a proper shiny surface is obtained. Two coats of primer are required if the primer is used as a surface consolidator as well as a moisture barrier. When applying 2 coats estimate 300 square feet per pail - realizing the first coat will give less coverage due to surface porosity and the second coat higher coverage. For small projects that require a 2 coat application it will be necessary to use two pails because material will cure prior to application of second coat. When used as an adhesive promoter or surface consolidator alone coverage will be approximately 400-450 square feet per pail depending on substrate porosity -  again, no dry spots should exist after application.

How to Use

Surface Preparation

Substrate Quality: Substrate must be clean, level, free from dust, grease, minimum oil. Laitance and sections that are no structurally sound must be mechanically removed. Minimum compressive strength > 1160 psi. Tensile Bond strength > 116 psi. The application instructions of wood floor- and subfloor manufacturers must be complied with. Substrate Preparation: All concrete surfaces must have an open textured surface to allow Primer MB to penetrate the surface and function properly as a moisture barrier or surface consolidator. Substrates must be structurally sound and solid, surface dry, and thoroughly clean and free of laitance, oil, wax, grease, paint, latex compounds, curing and sealing compounds, and any contaminant that could act as a bond breaker. Concrete, cement based, gypsum based sub-floors can be mechanically prepared to achieve an open textured surface - blast cleaning or grinding with a diamond cup wheel is appropriate. Acid etching is not acceptable. Thoroughly clean the floor with an industrial vacuum prior to installation of the Sika Primer MB. Consult level/patch system manufacturer regarding priming prior to the placement of materials. If surface contains asphalt (cutback adhesive follow the Resilient Floor Covering Institute "Recommended Work Practices" for removal. When the asphalt (cutback) adhesive is sufficiently removed use the Sika Primer MB to help promote adhesion to the subfloor-or use an industry approved levelling compound over the cutback residue. Due to differences in asphalt based adhesive types and performance capabilities; applicator must verify that preparation of the surface is sufficient prior to using Primer MB or patch/level compound. For unknown substrates please contact Sika Technical Services for best practices at 800-933-SIKA. Floors with other adhesive residue: Must have a minimum of 50% of the old adhesive removed  "regularly distributed" this can be done by grinding or other mechanical methods. All remaining adhesive residue must be structurally sound and securely bonded to sub-flooring. On fibre reinforced concrete, plastic fibres should be flamed off the surface, prior to application of Sika Primer MB as moisture barrier. Please contact our Technical Service for project specific advice. Conditions/Limits: Substrate temperature during laying and until Sika® Primer MB has fully cured: substrate temperature should be above 50°F (10‚°C) and in case of radiant floor heating below 86°F (30°C). Application temperature of substrate must be minimum 5°F (3°C) above the measured dew point temperature! Air Temperature: Room temperature should be above 50°F (10°C) and below 86°F (30°C). Substrate Humidity: Subfloor moisture content should not exceed 6% when measured with a Tramex moisture meter or 4% when measured using the CM method.


Add one full can of Component A to one full can of Component B then mix with an electric drill and mixing (Jiffy Mixer type) paddle at a low speed to reduce air entrainment (300-400 rpm). Using a paint stick or similar is not sufficient to mix the primer. A minimum mixing time of 3 minutes shall be observed; mixing shall continue until a homogeneous mix has been achieved. Scrape sides of pail with paint stick or paddle to ensure all contents are thoroughly mixed together. Unmixed material applied to the floor will not cure properly. 


After mixing part A and B completely to a homogeneous mixture pour contents of pail onto the floor for best working time. Attempting to work from the pail will reduce working time - see below pot life chart. Apply Sika Primer MB uniformly (crosswise) to the substrate using a medium nap roller, ensuring that a continuous coat is achieved over the entire surface (a mirror finish should be achieved). If Sika Primer MB is used as a moisture barrier as well as substrate consolidation, 2 coats are necessary. A waiting time of minimum 8 hours and maximum 36 hours should be observed between applications of Sika Primer MB. If primer has cured for 8 hours (depending on room and slab temperature) and only a tacky surface remains - then second primer step of a 2-coat system can be applied. Note: If primer is still very soft, then let more time elapse until only a tacky surface exists - then apply second coat. If used as a moisture barrier below floating floors, the second coat of SikaPrimer MB must be fully cured and must NOT be tacky any more before installing the floating system. Primer for SikaLevel-125 & SikaLevel-315: When used as a primer for helping moisture mitigation in cement substrates prior to applying SikaLevel-125 & SikaLevel-315, follow these steps:

1. Prepare the substrate mechanically as in accordance with the guidelines stated in subtitle "Substrate Preparation".

2. Apply the first coat at 75-115 sq. ft. gal.

3. Apply the second coat at 150-225 sq. ft. gal. after a minimum of 8 hours and a maximum of 36 hours after the first coat is applied.

4. Broadcast to refusal oven dried silica sand (20/30)on the second coat immediately.

5. Sweep sand once the epoxy is cured. 6. Apply SikaLevel-125 / 315 on cured epoxy.

Pot Life (Max. open time), If primer is left in pail after mixing:
at 50°F (10°C) ~ 60 minutes
at +68°F (20°C) ~ 30 minutes
at +86°F (30°C) ~ 15 minutes


  • Sika Primer MB can only be over-coated after it has cured thoroughly.
  • Proper coverage must be used to achieve moisture barrier properties.
  • Sika Primer MB will not act as a moisture barrier for gypsum screeds.
  • Sika Primer MB only protects from moisture coming from below the concrete.
  • Sika Primer MB does not prevent moisture occurring between the Primer MB and the floating floor due to secondary sources of moisture or acclimation, e.g. water condensation.
  • Sika Primer MB is not suitable for use with bonded systems due to possible curing and adhesion
  • Gypsum based sub-floors are very susceptible to excess moisture and will be degraded if exposed to excess moisture from below or above.
  • Sika Primer MB will not prevent damage to gypsum based sub-floors that are exposed to excess moisture levels.
  • Sika recommends the use of Portland Cement underlayments for best results. Consult level/patch system manufacturer regarding priming and other application/limitation guidelines prior to the placement of materials.
  • Sika Primer MB will not prevent hydrostatic head.
  • Wood flooring manufacturer's room humidity levels and wood acclimation requirements should be strictly followed.
  • Sika only recommends the use of Primer MB with SikaBond adhesive systems.
  • Sika does not make any standing recommendations as to the structural integrity of old adhesive residues or sub-flooring materials that are not manufactured by Sika.
  • Sika Primer MB must not be applied to a visibly wet substrate.
  • Subfloor must be a minimum 5°F (3°C) above the dew point temperature prior to application.
  • Sika Primer MB is meant for indoor use only.
  • When Sika Primer MB is left on the substrate for more than the maximum allowable open time of 36 hours, prior to placing the adhesive, the surface must be thoroughly cleaned and mechanically prepared (i.e. screened sand) and solvent wiped. Failure to do this, may result in adhesion problems. Wood floor installation in uninsulated areas, basements and ground without basement, only with moisture barrier system Sika Primer MB per requirements of the appropriate SikaBond technical data sheet. For detailed instructions consult the Product Data Sheets or contact our Technical Service. When used in conjunction with SikaBond Wood Floor Adhesives and floating floors, Sika Primer MB does not need to be broadcasted with sand.