Flex-Koat 204

High Build, High Solids Elastomeric coating for a variety of Masonry substrates. Vertical Only.

SKU: 204 Categories: ,
This product comes in a selection of colors. Should you wish to order a special color, please call customer service at 800-275-5628 during our business hours and we’ll be happy to assist you.

If you need to order quantities of 50 gallons or more, please call us at 800-275-5628 for the best price and to save on shipping.


Flex-Koat 204 Masonry Coating and Sealant is a high-build, high solids, water-based, elastomeric coating and sealant made from premium 100% acrylic resin. This extremely durable sealant is specifically designed for use on a variety of masonry surfaces. Premium Acrylic Resins are tough and flexible; millions of thin, plate-like mica particles are added to resist cracking and improve film strength. Flex-Koat 204 is manufactured with mildew-resistant agents and is highly resistant to the sun’s ultraviolet rays. Flex-Koat 204 is a permanently flexible, breathable membrane, allowing moisture from the substrate or building interior to escape while remaining impervious to water penetration from the exterior.


Flex-Koat 204 Masonry Coating and Sealant is engineered and developed to perform under severe industrial, commercial, institutional, residential and agricultural applications. Use on any cured masonry such as concrete block, cinder block, EIFS, brick, pre-cast concrete and stucco.

Product Data

Vehicle: Acrylic Resin
Solvent: Water
Flash Point: None
Drying Time: 1 hour to touch (77F & 50% relative humidity) 4 hours to re-coat
Percent Volatile by Volume: 58-60%
Weight per Gallon: 11.39 lbs
Solids-Weight: 56-58%
Solids-Volume: 40-42%
Colors: Standard White and Custom Colors
V.O.C.: 0.72 lbs/gal 86 g/L
Environmentally Friendly
Keep Out of Reach of Children


Surface must be dry, clean and free of dirt, grease and mildew. Avoid using cleaners with built-in wax or silicone additives as this may affect coating bond. Remove any trace of mildew by washing with a solution that kills mildew spores. Remove old coating and/or residue that is loose or peeling by scraping, sanding, wire brushing or pressure washing. Make any necessary repairs or replacements to damaged materials. If substrate indicates chalk, a thorough rinse is necessary. If chalking remains, apply Mastic Primer 101 as a base coat. Cracks must be repaired prior to coating. Treatment of cracks is required to obtain the water-resistant protection of the building and to help prevent further cracking and deterioration. Methods of treatment depend upon the size of the cracks.

Stucco should be cured a minimum of 30 days before application of Flex-Koat 204. Flex-Koat 204 can normally be applied, without thinning, directly over quality, fully-cured stucco. Flex-Koat 204 can be applied in 7 days to new stucco or masonry if you first apply a base coat of Mastic Primer 101.

Note: Before applying Flex-Koat 204, be sure that the stucco is in sound condition and adhering to the substrate. DO NOT APPLY Flex-Koat 204 to badly cracked, chipped or flaking stucco. Repair before coating.


This product is designed as a high-build exterior finish. Maximum adhesion and durability is achieved only when the surface is clean, dry and properly prepared. For optimum water-resistance and crack-bridging, two coats are recommended at 100 to 130 sq. ft. per gallon (wet film per coat should be 12 to 16 mils). Apply first coat with a roller (1 1/4″ – 1 1/2″ Nap) or spray equipment (Airless Sprayer – flow output 1/2 gpm, minimum pressure 2000 psi, tip size 0.023 to 0.027; backrolling with a wet roller will minimize pin holing. Apply second coat. If applying by roller, maintain a continuous wet edge, with final pass completed in a downward direction. A continuous wet edge, with final pass completed in a downward direction. A continuous film should be applied, making sure all surfaces are uniformly coated and free from voids, pinholes and blisters to insure uniform appearance and texture. Material requirements will increase with coarse or highly weathered surfaces. Drying time is retarded by very high humidity. Do not apply at temperatures below 50F. Coating should have ample time to surface dry before evening dew sets or material is rained upon.

Note: All bare and unpainted finishes require a primer coat, see Mastic Primer 101



Clean brushes, rollers, spray and other equipment immediately after use with hot soapy water.