Limestrong Fortifier

LIMESTRONG PLASTER FORTIFIER is a dry, polymer-based additive that provides increased bonding to difficult substrates when blended into the lime plaster scratch coat mud[1]. It can also be added in exterior finish coats to amplify hardness and weather reistance[2].

Hard-to-bond surfaces include those that are hard and non-pourous, non-absorbent, non-breathable and/or smooth. Specifically, difficult-category substrates include modern hard-fired brick, manufactured stone and board-form products, concrete/cinder block, cementitious backer boards and underlayment panels, and smooth poured concrete. These substrates present a bonding challenge for lime plasters that the addition of Limestrong Fortifier can mitigate.

Limestrong Fortifier should NOT be used when applying and Limestrong Build scratch or finish coats when plastering breathable substrates, like strawbale, hempcrete, Faswall®, or earthen materials.

Increased bonding over hard, dense surfaces. When applying a lime-plaster scratch coat over cast concrete or masonry block, having enough “tooth” or roughness to the surface for the plaster to get good mechanical purchase is always a concern. Adding Limestrong Fortifier to the scratch coat mix increase bonding strength of the plaster to such substrates.

Increased bonding over smooth, closed surfaces. Formed concrete and precast concrete panels are the most common substrates in this category. Even with the addition of Limestrong Fortifer to the plaster mud, a bonding agent should first be roll-applied to the smooth concrete to provide a more compatible mechanical and chemical bonding surface.

Weather-resistant slurry of mineral paint. A thinned, brush-applied lime-plaster slurry enhanced with Limestrong Fortifier can be applied to improve the look of a concrete or cinder block wall, weathered concrete, slump block, stucco, even dated-looking cultured stone veneers.


RATIO: Limestrong Build Binder. When mixing the scratch coat, use two (2) packs of Fortifer for each 50 lb. bag of Binder—that works out to about 4% by weight of the Binder product.

RATIO: Limestrong Slurry. When mixing a slurry finish, use a single 1 lb. pack of Fortifier per each 32 lb. bag of Limestrong Build Fine Finish (Steps 1 – 4) to increase bond and weather resistance.

RATIO: Limewash. Use a single 1 lb. pack of Fortifier per five mixed gallons (made from a 10 lb. bag) of Limewash to provide enhanced weather resistance overall.

STEP 1. Start with all of the required mix water and color pigment.

STEP 2. Add enough dry plaster to achieve a milkshake-like consistency.

STEP 3. Add ALL of the fortifier pack contents.

STEP 4. Mix thoroughly at high speed for one full minute.

STEP 5. Mix the remainder of the plaster (if mixing a scratch coat). Add water if needed to bring to a workable consistency.

STEP 6. Mix plaster for an additional three (3) full minutes.