All About Lime Paint, FAQ Friday

Although they date back thousands of years, some of the best examples today of lime paint are those pictured in scenic postcards of gleaming white and pastel colored villages, so abundant throughout the Mediterranean. Many architects and designers currently seek a return to these methods and products of the past. Lime paint changes and evolves as it slowly ages, giving buildings an appealing, provincial look. Additional coats can be added as time goes on, enhancing the depth of colors. Modern paints often seal in humidity, which later leads to peeling and other exterior damage to a building’s surface. More like a stain than paint, lime paint is absorbed into the wall, penetrating the background. Once cured, the lime paint allows the surface to breathe, becoming a peel-free surface as it allows humidity to escape.

Examples:
Lime Paint base (Natural), has no color added. It can be used to whitewash an old masonry building with only two coats and turn a dingy structure into a “museum-like” historic landmark. This is the Gambrel Roof House in Historic Fallsington, PA.

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A home in Lambertville, NJ originally had a shelter coat of lime wash put on the soft under-fired brick. #345 St. Astier Lime Paint was used to refresh the building, protect the brick and maintain good breathability for the coating so as not to trap moisture in the wall.

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A home in Stirling, Scotland which has had the facade restored using colored limewash over a lime/sand render. The home is located along the way up to Stirling Castle.

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The Coastal Heritage Society Preservation Team members of Savannah Georgia whitewashed the retaining wall at the Roundhouse Railroad Museum using St. Astier lime paint.

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A home in Massachusetts originally had a harled finish coat of lime stucco. The St. Astier Lime Paint #429 was used to refresh the building’s exterior look while protecting the soft lime stucco with a “like to like” compatible coating that will wear down over time rather than flake and peel off. The work was accomplished by Florentine Masonry Restoration.

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Lime Mortar and Hardscaping, FAQ Friday with Randy Ruth

When it comes to hardscaping with masonry, I am all for mortarless construction. The beauty of a well built dry stacked stonewall or paver application creates a natural aesthetic on any property. Often times however, there is a need or desire for a more permanent structure requiring mortar. Traditional brick garden walls in a Flemish bond pattern are a particular favorite of mine. The truth is hardscaping options are endless with so many creative ideas for an architect or master mason. Variations in brick bond patterns can come up abruptly with changes in architectural style creating such visually stimulating surround that once immersed, one may find themselves in a peaceful wholesome setting. I find myself not feeling this way in locations recently constructed but in older, aged locations, where there is a bit more character. This character comes from the details in construction.

With mortar taking up about 20% of the surface area on a wall, it is no surprise that mortar detail has a subtle yet powerful effect on the visual appearance of a masonry wall. In the construction of modern brick walls, Portland cement sticks tenaciously between the bricks, with characterless mortar joints. The two most prevalent types of mortar joints I see are concave and grapevine. While the concave mortar joint is meant to keep a watertight seal between the brick, it looks out of place. Rather it would be happier on the façade of a modern home, office building or utilitarian structure. The grapevine mortar joint style might be a romanticized take on old historic brick jointing that is often abused in modern construction but is not as aesthetically displeasing.

Despite my opinions on joint profiles, it’s the overall appearance that a modern Portland cement causes a hardscape wall to have. Unsightly control joints and modern joint profiles are a direct result of mortar used on a hardscaping project. The use of lime-based mortar can counteract such unsightly details and can be truer to the envious historic gardens of yesteryear in aesthetic quality.

Construction of hardscaped brick walls do not need to have control joints when lime is employed as the primary binder in lieu of Portland cement due to lime’s natural flexibility and free lime content which permits autogenous healing of micro-cracks. The use of lime in new construction is also “green”. The carbon footprint of using lime as a primary binder reduces co2 emissions by as much as 80% when compared to Portland cement. This reduction in emissions represents a greater step forward toward sustainability in our built environment. The breathability of lime mortar also promotes the idea of free flowing and natural earthen feelings associated with hardscaped locations. When our spaces work with moisture and process water rather than trying to trap it, a harmony is produced. This can help bring into sync the man built environment with the natural growing environment of an outdoor space.

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Reconstruction of Historic Lime Mortar and Renders FAQ Friday

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Q: I want to restore my old stone house and have heard there are ways to reuse the mortar already in my building during the repointing process. Can you explain how to do that and what are the positive and negative impacts?

A: Reusing old historic mortar is possible in more ways than one. The first methodology would be to leave sound mortar alone and keep using it for as long as possible, only doing “patch” pointing in areas that need to be fixed. In cases where a building owner desires to repoint the whole building you can follow the backyard guidelines below.

Of course if one were to follow these guidelines then there must be a conservation mindset in the back of their head. Knowing this, a mortar analysis would be highly recommended to help conclude an appropriate mortar mix design.

Reconstitution of historic lime mortar and renders

The purpose of this procedure is to separate the lime from the historic aggregates to reproduce a mortar joint or render while retaining as much of a buildings historic fabric as possible without the use of acids.

Beginning with the removal of any loose, cracked or friable render or mortar in the gentlest means possible, put debris aside.

Using a concrete barrel mixer place all saved debris in the mixer with large heavy stones or steel balls, about the size of a bowling ball. Make sure that the chosen crushing medium is harder than the debris to minimize contamination of the crushed aggregate by foreign matter. The mixer should be filled only to the point where the crushing medium will effectively fall from the apex of the mixing rotation and crush the debris to what would be the consistency of a pre-blended dry bagged mortar. This process should take anywhere from 20 – 60 minutes depending the quantity of the material loaded in the mixer (less is faster) and the desired fineness of the aggregates. Be sure not to over mix. Over mixing will result in the deformation of the aggregate.

Once the debris has been crushed to the desired particle size, place in 5-gallon pails or wheelbarrow for the separation process.

Place the end of a hose running water beneath the crushed aggregate. While the container is filling with water be sure to slowly agitate the wet aggregate mix with a hoe or trowel. Be sure to allow the fine lime particles to spill over the sides of container to be discarded. Make sure that the larger aggregate stays settled to bottom of the container for reclamation. This process should take approximately 20-60 minutes depending on amount of crushed debris and its binder to aggregate ratio. The process is completed when the water runs fairly clear and the remaining fines in the mixture can be easily made into a ball that resembles saturated beach sand.

Upon completion of filtering the lime from the aggregate allow to dry in the open air and strong sun by spreading it out on as thinly as possible over a tarp.

Once the aggregates are dry, the large particles of broken stone, any other foreign matter and large unbroken debris can be dry screened out using the desired sieve size. Typically anything retained on a #4 sieve can be discarded.

Now that the aggregate is dried and sieved, new mortar formulations can commence. Depending on the amount of work to be done with the reclaimed aggregate and the amount that was actually reclaimed, determination of how much other similar aggregate is to be gauged in to the new repointing or rendering mix.

Click for information on our Ecologic™ Mortar

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