5 gallon pail of Ecologic Sand Mastic Platinum.
Traditional sash window set in limestone opening and sealed with Sand Mastic.
Smoothing Sand Mastic between a window frame and stone sill with a stainless steel trowel.

Ecologic Sand Mastic Platinum

Regular price $70.90

Due to the nature of the material, sales of all building lime products are final.

Ecologic Sand Mastic Platinum is a traditional, flexible type of mortar, specifically for sealing gaps and joints between wooden substrates, such as window and door frames, and the surrounding masonry. The finished product is a waterproof mastic that retains some flexibility to absorb the difference in natural movement between the two substrates, preventing cracks and reducing water ingress.

Made from a dry, powdered blend of hydraulic lime and well-graded sands, Sand Mastic is designed to harden slowly but remain flexible, reducing the risk of cracking when forming joints.


Mix Ecologic Sand Mastic Platinum as needed with a combination of Purified Raw Linseed Oil and Purified Boiled Linseed OilA 50/50 mix of raw and boiled linseed oil is prepared first, just before mixing with the Sand Mastic powder. The final consistency should be stiff enough to place and tool within a joint and remain standing up, in place, on its own.

Approximate Mixing Ratios
Sand Mastic
Linseed Oil
Linseed Oil
1 gal ~ 34 cup ~ 34 cup
5 gal ~ 1 quart ~ 1 quart

Ensure all surfaces are clean and dry and free of any water, debris, and other oils. Any damage to the adjacent masonry should be repaired first with a mortar or masonry filler. A hawk and pointing iron can be used to apply the Sand Mastic. Use a smooth stainless steel trowel to achieve the desired finished profile.

Backing material, such as Traditional Oakum Caulking, should be packed into the gap or joint at least 34 inch deep but not deeper than 2 inches. Priming raw wood jambs and the backing material can be accomplished by using the 50/50 Linseed oil blend just prior to installing the Sand Mastic.

The Mastic doesn’t require painting, but if you do want to paint it, Linseed Oil Paint is recommended.