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frequently asked

QUESTIONS

Although the material here is available elsewhere on the site, we’ve assembled key informational points in a scannable question and answer format. These FAQs provide a quick introduction to PHL lime plasters, Limestrong Build products, and the lime plaster use/application process.

about

THE PRODUCT

Why choose lime plaster?

The reasons to choose lime plaster include workability, aesthetic finished beauty, and functional cured performance—especially in the case of breathability. A lime render is the only functional plaster finish option for breathable (vapor permeable) building systems designed to allow infiltrating moisture to escape, thus avoiding structural and interior air-quality issues brought about by mildew, mold, and rot. Breathable systems include old-school materials like adobe brick and wood lath, alternative building materials like strawbale and hempcrete, and ingenious green-building systems based on creative use of building material waste—like wood-fiber insulation (new to America, well-established in Europe), or insulated concrete form (ICF) building blocks made from mineralized wood chips like those offered by ShelterWorks’ Faswall®.

How are PHL plasters different from NHL plasters?

A Pozzolanic Hydraulic Lime (PHL) plaster (like Limestrong Build™) is made from high-purity lime, highly-reactive pozzolan, and aggregate. A PHL plaster is a real-deal lime plaster, not a cement-lime product, as no Portland cement is used. The Romans are widely credited with developing PHL plasters, mortars, and cements. Natural Hydraulic Lime (NHL) products are extracted from very specific lime deposits (typically European) that inherently/naturally contain the necessary hydraulic mineral properties needed to fuel the reactive cure, and so require no pozzolan.

Are Limestrong Build™ plasters made in America?

Yes. American made (blended and packaged), supported, and raw-material sourced (lime, pumice pozzolan, and aggregates).

What substrates (building materials) can Limestrong Build be applied to?

Direct application materials (with the proper surface preparation), include strawbale, earthen cob (adobe brick, rammed earth), hempcrete, masonry units, and wood lath. Other direct-application building materials include the Faswall® ICF system. Most other building materials will accept Limestrong plasters with some additional preparation—for example, poured concrete and pre-cast concrete need to be prepped with a gritted primer coat. Interior drywall, smooth-finished and grit-primed, can accept Limestrong Build Interior Finish. EPS foam needs to be covered with a stucco-type metal lath, as do wood and fiberglass sheathings. See our Substrate-Specific Application Guide publications for complete preparation details.

Why is Limestrong Build Binder not a complete, just-add-water product?

LSB Binder is packaged and shipped without the sand/aggregate component for economical reasons. LSB Binder is used to make both the scratch and leveling (brown) coats of a typical three-coat lime plaster render. Because these two coats use the majority of the material needed for the render, there is a SIGNIFICANT freight-cost savings (in both weight and volume) to have the end user source the needed plaster sand locally.

Why are Limestrong Build Finish Plasters complete and ready-to-mix out of the bag?

Limestrong Build finish plasters are texture-formulated by type (using finely graded lightweight pumice aggregate) and applied as a thin coat. The combination of fine, lightweight aggregates and need for less finish product per job holds down the freight costs. More importantly, factory blended-and-packaged, ready-to-mix finish coat products provide tight, consistent control batch to batch—especially when adding color pigments—to the end user/applicator.

Why does the freight shipping have to be custom-quoted?

Automated shopping-cart type shipping calculators work fine for the widely used process of package/parcel shipping. For LTL freight shipping, not so much. To provide customers buying job-sized quantities of Limestrong Build plaster products (shipped on pallets) with the best possible freight costs, we’ve got to build a custom freight quote. For a detailed look at the process and the cost factors that drive the cost of freight shipping, see the information under the subhead: Understanding Freight Cost on the Shipping Information page.

process

AND APPLICATION

I appreciate the extensive knowledge base, but what if I have specific questions for my specific circumstances?

Limestrong provides a paid consultation service—buy a phone consultation with a lime plaster professional. Depending on your support needs, you can schedule and buy time in 15, 30, and 60-minutes. You will find the consultation to be most productive if you’ve read the base instruction provided in our instructional guides—that will provide you with a foundation of lime-plaster savvy upon which we can build during the consultation.

What if I don’t need 15 minutes? I just have a quick question.

If you’ve read the instructional guides and/or have experience with lime plaster, you will most likely have the background savvy to functionally understand a quick answer to a quick question. In such a case, we’re more than happy to take (or return) a quick call and provide you the answer(s) without needing to schedule a consultation.

Is applying lime plaster like applying stucco (cement-based plasters)?

Many of the application techniques are similar, but the substrate/surface prep, on-wall character, use time-window, and curing times can differ significantly. One who has stucco-application experience has a great start on successfully applying lime plaster—the key is to read through the preparation, mixing, application and troubleshooting guides to fully understand the differences and best practices for working with lime plaster.

Why does lime plaster take longer to cure?

Lime plaster doesn’t cure like paint—by drying out. Rather, it cures (consumes moisture) via a molecular-level chemical reaction, and that reaction needs time and adequate internal moisture to work properly—to build strength and achieve the other functional properties lime plasters are famous for.

The keys to a proper cure are time and moisture—the surface of the curing plaster must be keep misted and moist. The point of the misting isn’t to add water to the lime plaster, but to provide surface water for evaporation, which keeps the internal water inside and available for the curative chemical reaction processes. Curing times tend to be faster in warm weather (as long as moisture is present in the plaster) and slower in cold weather. Proper curing at each coat-stage is crucial to the functional performance and long-lived durability of the plaster rendering.

Portland cement-based stuccos/plasters also cure via a chemical reaction, but it’s a super-charged one, leaving a narrow window to work with the mixed mud and get it on the wall before the fast-setting chemical bonds form. The cost of that high-early strength and fast cure? Poorer workability, brittle inflexibility, and high impermeability.

What is a Limewash?

A limewash is a mineral-based (lime) paint that creates a subtle matte finish with a soft and porous feel that becomes integral to the plaster surface. A color-tinted limewash is applied in at least two coats, using a large, natural-bristle brush and scrubbing it into the texture of the plaster using a consistent pattern. See the LSB publication: Mixing and Applying a Limewash for complete instructions.

Limestrong Build lime plasters contain no gray Portland cement, but rather bright-white lime and near-white pozzolan, making an ideal base for limewashes, providing resonant, enduring color—color that is integral to the finish, color that mellows to a beautiful, distinctive patina as it ages. Medium-to-light colors are most effective as limewashes.

Can mixed lime plaster mud be stored and reused?

Once mixed, Limestrong Build plasters can remain usable for 3 to 5 days IF stored tightly covered and kept cool (but not allowed to freeze). A pozzolanic hydraulic lime (PHL) plaster—being slightly hydraulic—is strongly affected by temperature. If stored in warm-to-hot conditions, the mixed plaster mud will set faster than if stored in cool, above-freezing temperatures. Within the 3-to-5 day window, retempering (remixing to soften; adding a bit of water if needed) may be necessary to return the mud to an ideal working consistency.

Is the final color influenced visually by the finish texture?

Absolutely. Color is perceived as light reflected from the plaster surface to the eye, with the colorizing pigments working to reflect some color wavelengths and absorb others in the visible light spectrum. The perceived intensity and/or richness of the reflected-back color is affected by the finished texture and varied grain direction of the troweled plaster surface. A textured surface defuses and scatters the reflected light, creating a soft, matte look. A tight, smooth-finished surface returns a more intense, gleaming appearance. The true beauty of a lime plaster surface is the mottled, multidirectional interplay of color, shade-shifts, and depth that results from the finish technique. Plaster delivers a fascinatingly unique visual aesthetic that’s simply not possible with single-note paint colors.

Can I get an actual sample swatch of a plaster color in the Standard Palette?

Yes. Order 3 x 3 inch swatches of standard palette colors from the Limestrong Color System page.

The Limestrong Standard Color Palette doesn’t have the color/shade I want. Now what?

Some options:

1) Limestrong offers a custom color service—we call it the Limestrong Color Lab. Based on a paint swatch reference of your choosing, we can recreate most colors using our eight core color pigments. We then provide the color/shade recipe you’ll need to use in your finish batches. Visit the Custom Color Service page for details on the process and the service levels available.

2) Develop the color yourself by leveraging the instructions in our Color Development Guide. The guide walks you through the process of finding/formulating the right recipe color using our eight core color pigments. Order single color pigment packs and sample quantities (or single bags) of our Finish Plasters and start experimenting. Use the color/shade combination recipes of the standard palette as a starting point. The guide provides a formula for recording the recipe you develop so you can repeat that color batch to batch on the job.

3) Develop the color yourself using liquid pigments sourced from local paint stores. Most paint stores will sell you the base pigments they use to build the paint colors they mix. Take in your own container (one that will seal tightly). You’ll need to work out how much you’ll need per batch to get the color/shade you want, then multiply that by bags/batches to complete the job. Instructions for mixing in liquid pigments are included in the Mixing Limestrong Build Plaster guide.

Can Limestrong Build Finish Plasters be applied over interior drywall?

We sell a finish plaster specifically formulated for use over drywall: Limestrong Build Interior Finish. It is a fine-grained plaster designed to be applied in two thin sixteenth-of-an-inch coats (total 1/8 thickness). It can be applied over new or painted drywall by prepping the surface with a gritted primer. See the substrate-specific application guide (Application Over Drywall) for complete instructions.

Do I have to use a (third) finish coat?

No. The biggest advantage is applying the final thin finish coat is consistent color control across the wall. If the natural off-white of our cured lime plaster is what is wanted, or the plan is to add final color using the limewash process, the first two coats (scratch and leveling) can be applied slightly thicker and the leveling coat finished with the desired final texture.

The leveling coat can be colored, of course, but because the volume of plaster-to-color is significantly more than with a thin finish coat, more pigment will be required. The deeper the color, the more pigment is needed. In mixer-quantity batches, deeper colors are harder to hold consistently batch to batch. On the other hand, if the final color is a very light shade, the requirement for pigment goes down and the possibility of noticeable color shifts (cured on the wall) between batches goes down.

Can LSB Binder be used for the third and final finish coat?

Yes. The key is to use a finer gradation of sand/aggregate if a smooth-to-lightly textured, tool-finished surface is desired. Because the finish coat is applied thin, the top-end/larger sizes of sand grains in the sand stockpile will have to be screened out—or a finer-grained plaster sand blend has to be sourced. Note that damp sand is difficult to screen…it will need to be spread and sun-dried first.

As a rule of thumb, the largest sand grain size should be no more than half the height of the finish coat, allowing the applicator to push the large grains to the back and bring finer grains to the surface. If a grain-gouged finish texture is wanted (wherein the large grains are at the same thickness as the coat and roll around under the trowel, cutting paths through the finish), then the finer gradation of sand is not needed. In either case, work it out the look you want on practice panels first.