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W.R. Meadows SEALMASTIC emulsion-type dampproofing is a breather-type which permits moisture vapor to escape through the film, while remaining resistant to water penetration.


This prevents blistering of applied films. The product can be applied to green concrete (not totally dry).


Product Data Sheet

SEALMASTIC TYPE I (spray-grade) is an asphalt-based, non-fibered, clay emulsion. Under normal use, it resists flow or sag. Its greater resistance to water is ideal where spray application is desired.

SEALMASTIC TYPE II (brush-on/spray-grade) is an asphalt-based, clay emulsion with fibers specifically formulated to offer a tight film that combines both excellent strength and resistance to water.

SEALMASTIC TYPE III (trowel-on grade) is a trowel-applied mineral colloid, asphalt emulsion, fibrated with selected fibers and produced in an ideal, light trowel application consistency. SEALMASTIC TYPE III offers high weather, water, corrosion, and abrasion resistance. It can be used as an adhesive on foam board installations. 

SEALMASTIC emulsion-type dampproofing coatings are ideal for reducing dampness and moisture infiltration through foundation walls, parapets, firewalls, tanks, culverts, cisterns, and bridge abutments. They are also applicable for stone-backing, above-grade cavity wall applications, and below-grade masonry wall dampproofing. The SEALMASTIC product line also helps to minimize internal structural damage from mildew and mold, and is compatible with ICF foam forms. 

Features & Benefits

  • Adheres to damp or “green” surfaces … no waiting for concrete to thoroughly dry.
  • Ready to use … no heating or thinning required; dries rapidly.
  • Fast and economical way to protect concrete and masonry foundation walls from moisture penetration.
  • Easy to apply … available in spray-, brush- or trowel-grades; meets a broad application range.
  • Three application grades available for maximum versatility.
  • VOC compliant. 


  • 5 Gallon Pails
  • 55 Gallon Drums 

Above-grade surfaces: Approximately 70 – 100 ft.2/gal. per coat.

Exterior below-grade dense surfaces, exterior below-grade porous surfaces, exterior above-grade surfaces
Approximately 40 – 50 ft.2/gal. (30 mils wet).

Coverage may vary due to porosity and condition of concrete. 

Shelf Life
When stored indoors in original, unopened containers at temperatures between 40° – 90° F, optimum performance and best use is obtained within one year of date of manufacture. 

ASTM D 1187, Type I
ASTM D 1227, Type III, Class 1

ASTM D 1187, Type I
ASTM D 1227, Type II, Class 1

ASTM D 1187, Type I
ASTM D 1227, Type II, Class 1

All products comply with current federal, state, and local maximum allowable VOC requirements, including U.S. EPA, SCAQMD, and OTC. 

Technical Data
VOC Content: 0 g/L

Surface Preparation … All surfaces to be coated must be thoroughly cleaned of all scale, loose mortar, dust, rust, dirt, oil, grease, and other foreign matter. Use a wire brush, sandblast, or other method in keeping with good construction practices. Before product application, fill voids, cracks, and holes in concrete with cement mortar and allow to dry. If primer is required, use SEALMASTIC SPRAY-MASTIC from W. R. MEADOWS. Do not apply when temperatures below 35° F are anticipated. Do not apply in rain or when rain is threatening.

Mixing … SEALMASTIC TYPE I and SEALMASTIC TYPE II should be thoroughly stirred in their respective containers prior to application. SEALMASTIC TYPE III can be applied directly from the container.

Exterior Below-Grade Dense Surfaces … Apply SEALMASTIC TYPE II by soft bristle brush or suitable spray equipment or SEALMASTIC TYPE III by trowel. Consult spray equipment manufacturer for instructions.

Product should be applied to properly prepared surfaces in a continuous, unbroken film (free of pinholes), filling and spreading around all joints, slots, and grooves and penetrating into all crevices, chases, reveals, soffits, and corners. Carry coating over the exposed footing’s top and outside edge, up to finished grade.

NOTE: Fillers, extenders, and additives in concrete mixes can produce a higher than normal porosity and, as a result, additional coverage coats may be required.

Exterior Below-Grade Porous Surfaces (Three Options):
Membrane System … For severe conditions or for added protection, apply one coat of SEALMASTIC TYPE II or SEALMASTIC TYPE III. Within four hours, apply REINFORCING FABRIC HCR from W. R. MEADOWS over all coating surfaces. Overlap all edges 3″ minimum. Press firmly into place without wrinkles. Application of second coat of SEALMASTIC TYPE II or SEALMASTIC TYPE III should be within 24 hours.

Two-Coat System … If a prime-coat is needed, dilute MEL-ROL LM from W. R. MEADOWS four parts water to one part MEL-ROL LM or apply a diluted coat of SEALMASTIC emulsion product one to one. Allow coat to dry tacky to touch and then apply SEALMASTIC TYPE III in one coat, as described above.

Parge-Coat System … Before application of SEALMASTIC, a parge-coat of cement mortar should be applied to the block wall. This coat should cover the bottom of the footings to grade level, forming a cove at the junction of the wall and footing. Once the parge-coat cures, apply one trowel-coat of SEALMASTIC TYPE III or two spray- or brush-coats of SEALMASTIC TYPE II as described above.

Backfilling … Backfilling should be done within 24 – 48 hours after application. No longer than seven days maximum should elapse. Be careful not to damage or rupture the film or displace coating or membranes. To assure maximum protection, PROTECTION COURSE and MEL-DRAIN from W. R. MEADOWS should be used. Prolonged exposure to ultraviolet light should be minimized.

Interior Above-Grade Surfaces – Vapor Retarder … SEALMASTIC TYPE I, SEALMASTIC TYPE II, and SEALMASTIC TYPE III can be used individually or in combination for dampproofing the exterior face of interior walls in cavity wall construction.

Cleanup … While still wet, material may be removed with soap and water. Once dried, the material can be removed with kerosene or petroleum naptha. Solvent manufacturer precautions should be adhered to when using a solvent for cleanup.

Keep from freezing in the original container. Not intended as a waterproofing membrane. (Refer to MEL-ROL or MEL-ROL LM from W. R. MEADOWS.) Read and follow application information and precautions. Refer to Safety Data Sheet for complete health and safety information.

LEED Information
May help contribute to LEED credits:

  • IEQ Credit 3.1: Construction Indoor Air Quality Management Plan – During Construction
  • IEQ Credit 4.2: Low-Emitting Materials – Paints and Coatings
  • MR Credit 2: Construction Waste Management
  • MR Credit 5: Regional Materials

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