Koster Repair Mortar - Fillet, Repair and Water-Repellent Finishing Mortar - W 530 025

Pre-Order By Phone 800-515-1002
Available in 3-5 Days
Free Local Delivery Available (NYC & Greater Area)*
Pick Up Available in Westchester & NYC
Need Product Help? Speak With A Pro 914-920-3232

KOSTER Repair Mortar is a watertight repair mortar and plaster with excellent adhesion even to old building material substrates. With the addition of KOSTER SB Bonding Emulsion, it may be used as a polymer-modified cement mortar. 

Unit Size 55 lb bag (W 530 025)

Fields of Application KOSTER Repair Mortar can be used for waterproof repairs and touch up, creation of water-repellent plasters, concrete repair, or smoothing rough surfaces or joints prior to the application of bitumen thick film sealants, even under pressurized water. It can be used for fillets or cants in wall/floor junctions which are stressed by pressurized water prior to application of bitumen thick film sealants and cement based coatings.

Substrate The surface must be sound and solid, free of oil and grease. The material may be applied to all cementitious substrates. Before installing a fillet on an external basement wall, prime with KOSTER NB 1 Grey (coverage approx. 0.8 lb/ft2 ). If larger surfaces are to be plastered, a plaster key made of repair mortar and water/KOSTER SB Bonding Emulsion (25% admixture to the mixing water) should be applied before application.


KOSTER American Corporation is a subsidiary of KOSTER Bauchemie AG of Germany.

Founded in 1982 KÖSTER BAUCHEMIE AG specializes in the development and production of high-quality waterproofing products and systems. Today, KÖSTER forms a group of more than 20 companies with worldwide activities in more than 50 countries. Its headquarters are located in Aurich, Germany.


Our R&D facility, production and technical department are all located on the same campus in Virginia Beach, VA. This allows each department to work closely together to ensure each product conforms to the highest standards of quality. 


KOSTER operates two production facilities in Virginia Beach. The liquid facility produces all of our epoxy coatings while the powder facility produces our self-leveling underlayments as well as other cementitious waterproofing products. 
We place tremendous value on producing our products ourselves in order to ensure the highest level of quality control from development to application. We strongly believe in providing our customers with an excellent and safe experience with our products.