guide:

Application over Drywall

Limestrong Build Interior Finish is a fine-grained lime plaster product formulated to be used over specially prepared and primed drywall[1] surfaces. It is NOT to be used as an exterior finish coat[2].

lime plaster interior finished walls

Interior finish lime plaster over drywall makes for fascinating and deeply beautiful ceilings and walls—something paint can never attain.

Coverage

Coverage per bag-batch is 80-100 square feet using TWO coats at 1/8 inch total thickness max. LSB Interior Finish is packaged in 32 lb. bags—enough to mix with two (2) gallons (8 liters) of water in a common 5 gallon bucket to make one batch. Bucket-sized batches also work seamlessly with the formula color/shade calculations used in the Limestrong Color System[3].

Preparation

NEW DRYWALL. Before applying LSB Interior Finish, drywall should be finished and sanded to a Level 3 industry standard, with all joints coated flat. Screw holes should be filled and outside corners beaded and filled. Hollow joints, screw heads, and corner bead may show up in the final plaster finish if not properly finished.

PAINTED DRYWALL. In most cases, LSB Interior Finish can be applied directly to previously painted drywall. Repair dents, nail pops, holes, etc. before application.

PRIMING DRYWALL. New drywall surfaces MUST be primed prior to application of LSB Interior Finish. Prime the drywall surface with a high quality latex based or PVA primer gaged with Limestrong Build Grit™, a fine pumice aggregate. LSB Grit provides mechanical key for the plaster to adhere to the drywall and allows the lime plaster to spread evenly over the primed surface without sliding. Apply the gritted primer with a roller. Primer coat should dry for 12 hours before applying first coat of finish plaster.

Mixing

WATER. Add 2 gallons of water (8 liters) to a clean 5-gallon bucket. (If using a liquid tint to color the plaster, remove one quart of water from the bucket and set aside for later use.)

POWDERED COLORANT. Add weighed/measured pigment powder to pre-measured mix water while agitating water slowly to avoid settling. Tap to knock free any pigment clinging to sides of container. Mix at high speed with drill-attached paddle (30 seconds to one minute), making sure colorant is completely dissolved in the water. Add dry plaster immediately.

LIQUID COLORANT. Do not shake tint container. Pour entire contents of the liquid pigment container into the mix water. Rinse the container twice with the saved water and use a small paint brush to clean all of the tint pigment from the sides and bottom of the container to ensure all the tint is used. With all the tint in the water, mix with the drill to bring up any tint that may have settled to the bottom.

MIXING IN PLASTER. After colorant has been dissolved into the mix water: 1—Pour one-third to half the bag of plaster into the pre-measured water. Mix well with the drill for 2 minutes. Scrape any unmixed plaster that sticks to the side of the bucket into the wet mix. 2—Repeat Step 1 until all remaining plaster powder has been added to bucket. Mix thoroughly and scrape sides of bucket often.

Application

FIRST COAT. With a standard hawk and trowel, apply first coat with a thickness of 1/16 (or slightly more) so the plaster covers the biggest particles (grain height). Apply as evenly as possible while avoiding trowel lines and ridges. Allow the plaster to dry/cure about half way, then trowel over it again with a clean trowel to knock down ridges, high points and even-up imperfections. Avoid polishing the surface, as it needs a bit of tooth for the second coat to bond to. If the plaster pulls or stretches, spray the trowel or plaster directly with a very small amount of water to lightly lubricate the plaster surface.

SECOND COAT. The application of the second coat is applied after the first coat is completely dry. Apply this coat to grain height and then double back over the surface with more plaster, working in random directions. This coat is where you can create a troweled texture, if desired.

STORAGE. Store mixed, unused LSB Interior Finish plaster in an airtight container and keep from freezing or extreme heat. Limestrong plaster can be kept for 3 to 5 days. Retemper as necessary to return it to working consistency.

SOAP FINISH. Made from a blend of premium olive and coconut oil, Limestrong Soap Finish concentrate is formulated to seal and protect Limestrong finishes and imparts a silky feel. See Applying a Soap Finish for complete details on the process.

Finish Textures

Finish textures should first be worked out and technique rehearsed on practice panels.

TROWELED SMOOTH. When the surface has dried slightly, you can come back with a clean trowel and, optionally, a small amount of water to further smooth the surface. (Optional final protective finish: apply Limestrong Artisan Soap Finish[XR1]).

SPONGE FLOAT. With a stucco sponge float or a tile sponge, you can create a sandy, matte finish that typically is more mottled in color. To create this finish, wait until the finish coat is about 50% dry, then, using a slightly damp sponge, move the plaster around in a swirling pattern.

WOOD FLOAT. A wood float finish is similar to a sponge float, but smoother. The subtle texture is created from the biggest sand grains dragging under the float. Wait until the finish coat is 50% dry and, using a damp wood float, swirl and scour the surface to the desired finish texture.

DRAGGED. A dragged texture is created when some kind of texturing tool is dragged across the wet plaster. This is a timing-critical process and has to be done evenly in a single pass to achieve a good result. Typically the dragged pattern is set in the wet plaster, allowed to dry slightly, then smoothed just a bit with a trowel to soften the effect of the texture.

Safe Use Precautions

Limestrong Build plasters contain hydrated (slaked) lime, which (because of a high pH) is somewhat caustic. Breathing the dust can cause respiratory irritation. BE SMART. Protect yourself. In all situations, if irritation develops, seek medical attention[XR2].