Sika 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 underlayment System
  • Can be used below floating floors



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


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.