apply lime plaster over wood lath old lime kilns

Top: Applying the scratch coat over wooden lath for a barrel-vaulted ceiling. Above: Old lime kilns at the base of Millcreek Canyon, Utah. Limestone was quarried locally and burned in these huge furnaces to convert it to the functional form needed to make mortar and plaster.

about

LIME PLASTERS

Modern Portland-type cements have been widely used in concrete, mortar, and plaster renderings since the 1850s, but the move away from “old world” cementitious formulations to quick-setting Portland-cement based products has not been without penalty, as detailed below. Nor are cement-based plasters and stuccos compatible with breathable wall systems like strawbale, hempcrete, adobe brick, and other earthen materials. Some commercial insulated concrete form (ICF) wall systems, like Faswall®, dictate a lime plaster render to preserve the featured breathablity of the structure.

ABOUT LIMESTRONG. Limestrong Build™ is a pozzolanic hydraulic lime (PHL) plaster made from high-purity lime, highly-reactive white pumice pozzolan, and aggregate. It is not a cement-lime product. The workability and durability characteristics inherent in lime plasters are so desirable that hydrated (slaked) lime is commonly added to standard cement-and-sand plaster formulations to amplify ease-of-use and increase performance. Unlike tweaked-up cement-lime products, Limestrong Build plasters eschew the use of brittle-setting Portland cement altogether. What is gained in quick set and early strength at the front end with cement-lime plasters is offset by performance losses going forward—losses in terms of flexibility, breathability, durability (functional life-span), aesthetic beauty, and ease of application.

The reactive quality of the sustainable ingredients, the wisdom and Old World pedigree behind the mix design, and the consistency in production make Limestrong Build a predictable, workable, high-performance PHL plaster.

The lime plaster marketplace also features Natural Hydraulic Lime (NHL) products that are extracted from very specific lime deposits (typically European) that inherently/naturally contain the necessary hydraulic properties/minerals, although the high costs of importing NHL products put them out of reach for many.

box holding various plaster trowels

old-world

PEDIGREE

Before society developed the means and the know-how to produce and sustain the intense temperatures necessary to produce Portland cement clinker, incredibly effective cements were made with less energy-intensive methods, then craft-finished and cured to an impressive permanence. Roman PHL cements and plasters are proof of that kind of durability. Our Limestrong Build plaster products are a fusion of those old-world materials and methods and an enlightened interest in sustainable practices and responsible living.

Why choose Limestrong Build?

choose

FOR PERFORMANCE

Pozzolan-lime plaster owes its long history of use and functional longevity to several factors:

Breathability. By breathing—taking moisture in, then releasing it—a Limestrong Build render doesn’t trap water behind it. When used in conjuntion with vapor permeable building systems, internally-generated moisture from bathing or cooking is able to pass through the plaster and escape, effectively averting mold, rot, and decay in the wall. As a matter of fact, a lime render is the only functional plaster finish option for breathable building systems like strawbale, earthern cob/adobe, hempcrete, and specific insulated concrete form (ICF) types. Lime plasters are also funtionally-compatible finishes for rigid board wood-fiber insulation panels.

Flexibility. Instead of cracking like brittle-hard, inelastic cement-based stuccos, a Limestrong Build render moves with the subtle shrinking and expansion of building.

Autogenous Healing. The long-lived reaction of lime and pumice pozzolan and water to each other and the surrounding atmosphere means Limestrong can repair itself on a microscopic level as it cures, sealing cracks and filling voids, growing in strength and integrity as newly-assembled building materials move and flex and settle. Synthetic stuccos and Portland-cement based plasters and mortars can’t do that—they quickly set up: hard, brittle, and inflexible.

Strength. Pozzolan-lime plaster gains its strength and durability from two curing reactions. The first is a pozzolanic reaction between the pumice powder and the hydrated lime, which creates a flexible cementitious binder that provides both bonding and compressive strength. This amplifies the inherent strength derived from the second curing carbonation reaction—the atmospheric carbon dioxide transforming the reshaped, hydrated lime back into limestone.

Durability. When properly mixed, applied and moist-cured, a Limestrong Build finish will last for the life of the building. Depending on the surface finish type, Limestrong holds up well to impacts, as it flexes and sheds crushed material rather than shattering like brittle cementitious plasters. As a rule of thumb, the rougher the exterior finish, the more durability is inherent in the finish. Rough textures are not only quicker and easier to apply, they soften the look of the structure, as reflected light is dissipated and defused.

Like any exterior finish, Limestrong must be protected from direct and relentless contact with water. A roof with deep gable ends and generous eaves is ideal. Exterior plaster renders must not come in contact with the ground

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FOR EASE OF APPLICATION

Working with Limestrong Build is joy—without the ticking-clock of a hot chemical reaction (as with Portland cement products), mixing and applying LSB plaster is straight-forward, relaxed and forgiving. The performance characteristics are predictable and sustainable across the entire scope of the job.

Once mixed, Limestrong Build can be kept and retempered for use for 3 to 5 days if kept cool and protected from air—a lid on a bucket; a plastic cover sheet over a wheelbarrow—which provides the applicator with a generous working window.

Limestrong Build can be applied with a hawk and trowel or sprayed on using a conventional compressed-air stucco applicator. LSB can be used in a wide range of temperatures and climates. It must be protected from freezing as it cures, with curing times greatly influenced by the humidity and temperature of the surrounding air. It can be months before a Limestrong render fully cures, (hence its ability to flex, breathe and autogenously heal), although a functional cure is typical within three to five days, and in some cases, up to ten.

REFER TO OUR KNOWLEDGE BASE FOR FULL DETAILS ON CORRECTLY MIXING, APPLYING, AND CURING Limestrong Build (LSB).

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FOR BEAUTY

There is nothing common or industrial-looking about a Limestrong Build plaster rendering. In the hands of a skilled applicator, the finish can be glass smooth or one of any number of troweled-in textures. The beauty of a Limestrong-finished wall is limited only by the creativity and skill of the hand that applies it.

The interplay between texture, light, and color is especially dynamic in lime plaster renderings. Color can be introduced to a LSB finish coat in a couple of ways.

Blended In. Colored pigments can be mixed into the finish coat. Our ready-to-mix Limestrong Build Finish plasters come packaged in single-batch-sized bags and combines beautifully and consistently with our dry Limestrong Color System pigments. Based on these core pigments, the perfect color can be chosen from a standard palette of popular colors or custom-developed using the services of the Limestrong Color Lab.

Washed On. The use of limewashes—translucent, pigmented lime paints—creates character and a deep vibrance that makes for a one-of-a-kind finish that is integral to the plaster itself. Such imbued color richness, even for the lightest of colors, is possible because both the white lime and the white pumice in the cured, open, naturally-light surface readily absorb and hold the colored pigments.

A skilled applicator will work in both color and texture, applying thin washes to build rich, fascinating color and texture interplays that are not possible with conventional plaster finishes and certainly not typical painted surfaces. The limewash process is a true fresco technique that penetrates the plaster and becomes part of it while preserving the plaster’s ability to breathe. The washed-in layers of color will mellow and soften with time, resulting in a beautiful patina that only amplifies the visual appeal.

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FOR SUPPORT

We understand that the enduring beauty and function of a lime plaster rendering goes beyond what we put in the bag—it must be properly mixed, applied, and cured. To that end, we have assembled a training and support structure around Limestrong Build plasters that is unmatched in the lime plaster arena.

Learning. First, we built an extensive knowledge base around the process of preparing for (tools, equipment, substrate preparation), mixing (proper sequencing, mud tests, holding and retempering), applying (methods by coat type, surface finishing), curing (timing, protection, moisture), and troubleshooting a lime plaster render. This lime plaster know-how is available as intralinked webpages and as downloadable/printable PDF files. Backing the knowledge base are lime plaster pros available via phone or text to answer quick questions and a consultation service for those who want more extensive and project-specific help.

Color. Limestrong finish plasters cure naturally to a soft off-white. That intrinsic whiteness also means the plasters readily accept colorants. The Limestrong Color System includes a 21-color standard palette as well as a custom color lab service to help those looking to match a specific color.

Ordering. It matters to us that the experience of ordering and taking delivery of Limestrong Build plasters is a good one. As job-sized order arrive via freight carriers (an unfamiliar process for many), we have prepared a shipping and delivery document to detail the process and staff our fulfillment center with logistical experts who understand the industry and will secure the best freight rates.

think

INSIDE THE BOX

The bland visual appeal and non-breathing nature of synthetic and plastic stuccos means they are rarely used inside a living space. Those longing for the timeless beauty found inside historic structures with those grand, plaster-finished interiors, try to fake it with drywall-mud textures and faux painting techniques.

Not necessary. Limestrong Build Finish plasters (Coarse Finish or Fine Finish) are ideal for the interiors of buildings made from unconventional alternatives like strawbale, hempcrete, and adobe or earthen cob materials or wood-framed structures using a wood lath substrate. They also work wonderfully with breathable ICF building systems like ShelterWorks’ Faswall®. Limestrong Build also offers LSB Interior Finish, a thin-coat interior lime plaster finish product designed to be applied directly to (properly prepared, primed) drywall. Lime plaster wraps a room with a gentle, intricate beauty and does away with the need to paint and repaint. Those living or working in the building also avoid the VOC concerns that plague paints. The acoustic quality tends to be better too.

For builders and architects trying to recreate interior themes that mimic outside finishes and natural rock textures—casinos, lodges, restaurants and bars, movie-sets—Limestrong Build can be sculpted and finished to fit the need.

technical

DATA (SIMPLIFIED)

Chemically, hydrated (slaked) lime and fine-ground pumice perform almost magically. The impressive durability of cured Limestrong plaster happens on two levels.

FIRST: Hydrated lime, when mixed with water and exposed to air, will return to its limestone (CaCO3) origin as it cures, acquiring carbon dioxide from the atmosphere that “carbonates” and hardens, or sets, the hydrated lime.

SECOND: Lime has no hydraulic cementitious properties on its own, but in the presence of water and pozzolan, a pozzolanic reaction occurs and Calcium Silicate Hydrate (CSH) is formed. CSH is the chemical binder that makes concrete what it is. This binding glue further strengthens the hardening plaster as the hydrated-lime-to-limestone curing process takes place, resulting in a plaster that effectively melds the compressive and bond strength of hydraulic cement and the breathing, self-healing, enduring flexibility inherent in lime plasters.

RESULT: Combined with an application-easing plant-based binder, our pure lime + pumice pozzolan + water formulation is an impressive performer! It works today like it has worked for millennia, as historical evidence readily attests. Why? Because 100% of the lime is converted to the cementitious binder (CSH). This simple pozzolan hydraulic lime (PHL) combination triggers none of the deleterious by-products that make modern plaster, mortar and concrete—made using Portland cement—so problematic and short-lived. PHL formulations produce densified, flexible, self-healing mortars and plasters that are not nearly as susceptible to brittleness, chemical attacks, and other problems that plague modern cement products.

sustainable

AND GREEN

A Limestrong Build render not only performs beautifully, it stands as an environmentally sound alternative to synthetic stucco and other Portland cement-based products. Unlike the energy-intensive process to produce Portland cement clinker, hydrated lime is obtained by lower-temperature firing. As for the pozzolan component, our pozzolan is made by mining and crushing an abundant, clean, white pumice (a safe amorphous silica) created by volcanic events and purified by centuries of relentless wave action in an ancient inland sea that once covered parts of Utah, Nevada and Idaho.

made

IN THE USA

Limestrong Build plaster products are made from US-sourced materials and blended and packaged in Idaho. The formulations were developed by a passionate, seasoned lime plaster expert and are supported by savvy lime plaster professionals.

Two primary LSB products are available. Limestrong Build Binder is bagged and sold as a binder-only product, greatly reducing shipping and packaging costs for job-sized quantities, as the heavy sand component is sourced locally. Limestrong Build Finish plasters are an all-in-one, ready-to-mix, thin-coat finish product that can combined with color pigments (like those of our Limestrong Color System) or soft-colored with a limewash.