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Mapei Primer T TDS


Primer T is a low-VOC, water-based acrylic primer that enhances the performance and adhesion of self-leveling underlayments (SLUs) on nonabsorbent surfaces such as ceramic tile, vinyl composition tile (VCT) and adhesive residue, as well as profiled, absorbent surfaces. Suitable for a wide variety of substrates, Primer T combines excellent versatility with an easy, low-odor application.


  • Use over properly prepared ceramic tile, VCT, natural stone or exterior-grade plywood substrate before applying SLUs or cementitious adhesives.
  • Use over substrates that have residue of well-bonded old cutback adhesive, floor-covering adhesive or polyurethane adhesive.
  • Use before application of self-leveling underlayments over properly prepared sound and stable concrete substrates, whether smooth and nonabsorbent or profiled and absorbent.


  • One-component, versatile primer for a wide variety of substrate conditions
  • Low-odor and VOC compliance for safe use in interior, occupied environments
  • Single-coat application for faster turnaround and lower installation costs
  • Easy handling and application
  • Ideal primer for use with the SLUs Ultraplan® Easy and Novoplan® Easy


  • LEED (Version 3.0) Points ContributionLEED Points
  • MR Credit 5, Regional Materials*.....................Up to 2 points
  • IEQ Credit 4.2, Low-Emitting
  • Materials - Paints & Coatings .........................1 point
*Using this MAPEI product helps contribute to LEED certification of projects in the categories shown above. Points are awarded based on contributions of all project materials.


  • Do not install over any substrates containing asbestos.
  • Substrate and ambient temperatures must be between 50°F and 95°F (10°C and 35°C).
  • Protect from freezing.
  • Test concrete substrate using a calcium chloride test (ASTM F1869) to ensure moisture vapor emissions rate is below 5 lbs. per 1,000 sq. ft. (2,27 kg per 92,9 m2) per 24 hours.
  • Verify substrate is free of bond-inhibiting or bond-breaking materials such as curing compounds and dust.
  • For use only in dry, interior environments. Do not apply on wet substrates.
  • Use undiluted over moisture-stable, exterior-grade plywood.
  • Use undiluted over dense, nonabsorbent surfaces, such as floor-covering adhesive residue, and properly prepared ceramic tile and VCT.
  • Dilute product for application over absorbent, porous substrates 1:1 to 2:1 (water:primer).


  • Properly prepared ceramic tile, VCT and natural stone
  • Substrates with traces of well-adhered, water-resistant glue (cutback adhesive, floor-covering adhesive or polyurethane adhesive)
  • Dimensionally stable and moisture-stable wood
  • Properly prepared sound and stable concrete substrates, whether smooth and non-absorbent or profiled and absorbent
  • Use over dust-free gypsum-based SLUs before application of cementitious or gypsum-based SLUs
Consult MAPEI Technical Services Department for installation recommendations regarding any substrates and conditions not listed.


  • All substrates must be interior, structurally sound, dry, solid and stable.
  • Mechanically prepare existing ceramic, quarry and porcelain tile, as well as cement terrazzo.
  • Thoroughly clean all surfaces of any substance that could interfere with the bond of the installation material, including dirt, paint, tar, asphalt, wax, oil, grease, latex compounds, sealers, curing compounds, form release agents, laitance, loose toppings, foreign substances, and poorly bonded or incompatible adhesive.
  • Repair cracks in substrate before proceeding.
  • Expansion and movement joints must be honored through the finished flooring system.
  • Do not acid-etch surfaces before applying Primer T.
  • When applying MAPEI underlayments to plywood flooring or oriented strand board (OSB), the installation specifics (finished flooring, load, use and/or deflection) may require the use of MAPEI's Mapelath? or diamond mesh (meeting the requirements of ASTM C847) on top of the primed surface before application of the underlayment. In all cases, one can anticipate better performance when utilizing lath, particularly over OSB. Refer to the current Mapelath TDS for installation instructions. Differential or excessive movement within a plywood substrate may lead to hairline cracks at plywood joints.


Note: Choose all appropriate safety equipment before use. Refer to MSDS for more information.
1a. Over nonabsorbent surfaces: Apply Primer T undiluted. (Add no water; no mixing is required.)
1b. Over porous, absorbent surfaces (typically absorbent, proiled concrete substrates): Dilute Primer T with water from 1:1 to 2:1 (water:primer). Mix with water in a separate clean container with a low-speed mixer (at about 300 rpm) and paddle to a homogenous consistency. Do not mix at high speeds, which may cause product foaming.
1c. Over gypsum substrates: Dilute 2:1 (water:primer). Mix as indicated in Step 1b and apply two coats if required. Ensure that gypsum substrate is sound and dust-free.


1. Read all installation instructions thoroughly before installation.
2. Apply product with a 3/8" (10 mm) nap roller. Ensure surface receives a complete, thin film of product.
3a. Nonabsorbent substrates and wood require only one coat of undiluted Primer T.
3b. Absorbent substrates may require more than one coat of diluted Primer T to seal off the substrate and prevent substrate outgassing.
4. Underlayment can typically be applied with 2 to 5 hours. Drying times will vary depending on porosity of surface, temperature and humidity. Maximum wait time from initial application is 24 hours.
5. If Primer T sits for more than 24 hours, re-apply a second, undiluted coat and install underlayment within correct application window. If application window is missed again, remove primer mechanically and start the installation on clean substrate.


Clean equipment immediately with water. Mineral spirits may be used to remove primer that has dried on tools.

Product Performance Properties

Laboratory Tests Results
Polymer type Acrylic
Percent solids 43% to 45%
VOCs 92 g/L
pH 7.0 to 8.0
Viscosity (RV2 @ 20 rpm) 1,400 cps
Density 64.2 lbs. per cu. ft. (1.03 g per cm3)
Consistency Pourable liquid
Color White
Application temperature range 50°F to 95°F (10°C to 35°C)

Shelf Life and Application Properties

Shelf life 2 years in original container. Protect from freezing during transport and storage.
Window for application of SLU at 73°F (23°C) 2 to 3 hours of drying time up to 24 hours from application over porous substrate (concrete and wood); 4 to 5 hours of drying time up to 24 hours from application over nonporous substrate (ceramic, VCT)
Flash point (Seta) >212°F (100°C)

CSI Division Classifications

Cast Underlayment 03 54 00


Product Code Size
36691 1 U.S. qt. (946 mL)
36657 2 U.S. gals. (7,57 L)

Approximate Product Coverage

Typical Application Tool Coverage*
3/8" (10 mm) nap roller 2 U.S. gals. (7,57 L): 400 to 800 sq. ft. (37,2 to 74,3 m2)
Per 1 U.S. qt. (946 mL): 50 to 100 sq. ft. (4,65 to 9,29 m2)
*Coverage depends on the substrate profile and porosity. Typically, one can anticipate 300 sq. ft. per U.S. gal. (7,35 m2 per L) on a smooth substrate without dilution. Dilute product 2:1 (water:primer) for porous, absorbent substrates.

Refer to MAPEI's Material Safety Data Sheet (MSDS) for specific data related to VOCs, health and safety, and handling of product.


Before using, user shall determine the suitability of the product for its intended use and user alone assumes all risks and liability whatsoever in connection therewith. ANY CLAIM SHALL BE DEEMED WAIVED UNLESS MADE IN WRITING TO US WITHIN FIFTEEN (15) DAYS FROM DATE IT WAS, OR REASONABLY SHOULD HAVE BEEN, DISCOVERED.
MAPEI Headquarters of the Americas
1144 East Newport Center Drive
Deerield Beach, Florida
Phone: 1-888-US-MAPEI
Technical Services
1-800-992-6273 (U.S. and Puerto Rico)
1-800-361-9309 (Canada)
Customer Service 1-800-42-MAPEI (1-800-426-2734)
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Edition Date: December 10, 2009 PR5778 PRTD_L09Evp® 2009 MAPEI Corporation. All Rights Reserved. Printed in the USA.