Green Construction in Today’s Built Environment – FAQ by Randy Ruth

by Randy Ruth

When people talk about “green” construction, I often wonder what the environmental benefit of the construction is. Is it new construction? If so what is the environmental impact? I would hope that a perfectly good existing building wasn’t torn down to make way for supposed progress.

It is my belief that the greenest building is the one that is already standing and most likely played a role in a community’s development. It could be an old department store, manufacturing warehouse or barn. Sometimes plans call for only the façade of a building to be saved which helps keep the architectural integrity of a community intact. This can be a positive compromise because the more useful modernized building can be built and yet some historic fabric is retained to tell the story and retain the flavor of what the building was in its local context.

In the end, as long as something is retained for adaptive reuse, whether it is for aesthetics or the entire structure, there is a measure of success in reducing a “green” construction project’s carbon footprint.

In most instances, a building that has been saved from the wrecking ball is old. What does old really mean? Well that’s pretty subjective but I would like to think of old in the context of US building history as being pre 1930, or roughly 80 years and older. When an old building is going to be adaptively reused one way or another then appropriate materials should be used to fix what is broken with compatible repair materials. Using in-kind repairs will further promote the legacy and overall usefulness of a building for years to come while lowering its impact on the environment.

Old buildings are usually very strong and often made of brick and stone that has proven to stand the test of time. However it’s the mortar that binds those materials together and meant to be sacrificial. Mortar should fail first not irreplaceable historic masonry units. The embodied energy to replace a masonry unit is much greater than the mortar. Therefore, it is imperative that a suitable replacement mortar be used to mend what is failing and the mortar be weaker and slightly more permeable than the surrounding masonry units.

In the case of masonry mortar, lime is typically the binder in these old buildings and should be regarded as key to the dynamic that has allowed the building to be in service so long. Often the original mortar is still in place, proving its superiority and therefore should be replaced in-kind. The use of modern day Portland cement based mortars, which are stronger and denser when placed over the top of lime based mortars, are less sympathetic to the historic masonry and can trap moisture causing further damage to the historic fabric. The historic masonry units and adjacent historic elements can best be kept in conservation with the use of the right lime mortar. The correct Natural Hydraulic Lime (NHL) mortars when used where they are appropriate can become a compatible repair materials that is sympathetic  to the working dynamics of an historic masonry building. Secondly, NHL mortars remain reversible without damage to the building unlike the alternative which is the too over-used hard, brittle and dense Portland cement based mortars which are known to cause irreversible damage in conjunction with historic masonry fabric.

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How Lime Mortar Traditionally Got it’s Color and How We Can Replicate this Today – FAQ by Randy Ruth

by Randy Ruth



Seven factors that can affect the color of lime mortar in no particular order of significance, Lime, aggregate, pigment, water content, rate of absorption, original surface texture and erosion. By its self, the color spectrum of lime can vary from bright white, light grey, slight pink or ochre colors. This color is dependent on a few factors such as the original stones chemical makeup and burning temperature. When an appropriate limestone is thoroughly burned (calcined) at a particular temperature to produce hydraulic or non-hydraulic quicklime and then hydrated to produce either a lime putty or dry lime hydrate, the result will be a white or off-white color. The first factor affecting the whiteness index of the lime will vary depending on the raw mineral impurities in the limestone. A limestone with a higher calcium content with all other factors aside will produce a whiter hydrated lime. If that same limestone is burned at a slightly higher temperature, the result will be a slightly grayer hydrated lime. Although, lime plays a role in the final color of a mortar, its significance today, when replicating a mortar joint is minimal, often due to the lack of availability or technical characteristics like Hydraulicity. Aggregate has a huge effect on the color of lime mortar. Historically aggregate for masonry mortar would be sourced from either local sand beds, found near creeks or rivers, or from the trimmings of stone on site and possibly brick pieces or dust as a pozzolanic additive.

The larger screenings of the aggregate play a role in the overall tone of the final mortar color but it is the fines that do most of the work. The smallest particles in the aggregate AKA fines will give the biggest impact on the final color. Brick dust, limekiln dust and clay impurities are pozzolanic fines that can be found accidentally and at times intentionally accompanying the aggregate. Today these impurities are almost never allowed into a replicate mortar mix, as the resulting technical data from such a mix design is often cost/time prohibitive for a project even if historically appropriate. As a result powdered pigments are often used today to achieve a particular mortar color. Just because pigments are predominantly used today in mortar mix designs, doesn’t mean that they weren’t used over 100 years ago. Colored mortar is an important design element in any building of today and yesteryear.

The types of pigments used in mortars have not changed all that much in past few hundred years. Iron oxide, carbon black, and natural ochre’s hold a solid footing in the industry today, each presenting their own limitations. It has been proven that carbon blacks can fade dramatically over a 30 year period in masonry mortar. Even though their tinting strength is very good, if not controlled carefully shades of grey can be very difficult to achieve. Natural ochre’s can produce wonderful colors and be very accurate when making accurate replicate mortars. The problem is in their tinting strength, and consistency in production on a large-scale. It may take above a 10% dosage of natural pigment to achieve the same color in a mortar using iron oxide pigments conforming to ASTM C979. Because of their durability, tinting strength and quality in production, iron oxides have been deemed the best pigment for coloring mortar on a large-scale. Even when using appropriate pigments at the correct concentration, water content in a mortar plays a big role in determining final color. Using the same exact mix in two batches and varying the water content by 10% will produce a significant change in color. From experience, I have noted that this problem is most evident when trying to achieve a red colored mortar. Light grey’s can also be problematic but are less evident and are usually deemed acceptable. That is why it important to measure all ingredients in a mix carefully to ensure consistency from batch to batch. The practice of mixing mortars consistently should carry over to pre-dampening of masonry units. By pre-dampening consistently as possible, the rate of absorption is controlled. This is a good practice just so mortar will not reach a flash set, and to control curing of the mortar which plays a role in the final color.


There is some debate on how a replicated mortar should look when not replacing all the mortar. Should it look new, with a smooth surface that stands out because of the way light reflects off two different surface textures? Alternatively, should it blend in with adjacent mortar joints? Personality, I believe in the latter. If a new mortar is inherently the same color at its core as the old historic mortar, than even though a slicked smooth replacement mortar will eventually blend in it can still distract the eye. A good repair for just about anything should be as seamless as possible. Besides, won’t a different texture erode differently, resulting in the continuation of a miss match over time? This brings me to erosion in mortar. As a mortar erodes, the color of the aggregate begins to come through. This color can sometimes throw off the human eyes perception of what is the color to be achieved when color matching. Someone explained this to me so well once that I must share. He had asked a room full of people what the color of foam on the head of a beer is. All replied white in color. We all got it wrong. The answer is amber like the color of the beer. This is because of the way light is reflected back to the human eye off a larger Surface area. Now that is in extreme case of a dark color turning lighter but the principle is still applicable to mortar. However, in most cases the rougher the color the darker a mortar is, and depending on who well the color of the sand is matched, you may just get a replacement mortar that will be seamless for generations. Ecologic™ Mortar

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Burning Lime, The Traditional Way

This is an incredible video that really shows the difficulties of burning limestone the old way. Stacking wood, limestone and coal in an old kiln these men go through the process using traditional methods to turn regular limestone into caustic burnt lime.

Uploaded on Nov 27, 2010

This is from the Edwardian Farm series – how to make 10 tons of lime mortar in a massive kiln using layers of limestone and coal burnt for days!

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“Deteriorating Brownstones – FAQ by Randy Ruth”

by Randy Ruth

Q: I have an old brownstone house and some of the stone have been falling off, what can I do to prevent further damage and fix the damage that has already occurred?

A:  When you have brownstone deterioration or any form of stone deterioration and want it to stop, you have to first identify the root cause. Sometimes it’s as simple as replacing downspouts or replacing roof flashing, to prevent further damage to the stone. Other times it can be a long complicated series of tests and empirical analysis. Depending on the cause of the deterioration of the brownstone, a number of solutions can be applied.

If the stone is only sugaring or sanding with light deterioration, then perhaps doing nothing for a maybe a year and watching the stone for further deterioration is sufficient. However, if the stone is in much worse shape with possibly a ¼ inch or more of stone loss, then some could be some very serious problems with the integrity of the stone.

Brownstone as with many different types of sandstone has bedding planes. These bedding planes in the stone tend to detach from one and other depending on how the stone was laid in the wall. Imagine a layered cake as the stone, with each layer on top of one and other. If the stone cake is put on its side there is a greater chance that moisture can get between the layers and cause delimitation and or exfoliation. This being a common problem associated with sandstone, a more detailed resource for classifying the type of stone loss you may have can be found here.

It is always recommended that when fixing damage to stone that a qualified professional be brought out to see what the damage is and come up with an appropriate course of action. There are many different ways to approach fixing a stone like whether consolidation is appropriate is an appropriate first step or not. In my eyes, it is always best to honor the original detail of the stone and artisan who created it by only fixing what is broken. When patching stonework an important approach is to make sure that appropriate sympathetic patching materials are used. (Lithomex) The use of impermeable materials can cause further deterioration of the stone by trapping moisture. This will result in a faulty patch that can accelerate deterioration to the adjacent stone.

Brownstone with Water damage

Brownstone Before

 Brownstone Repaired with Lithomex

Brownstone After

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A Message from Ian Cramb, a younger man…

We got an email back in 2011 with some amazing photos of Ian Cramb. These photos are from 1958 in Iona, Scotland. Ian was working on the cloisters of Iona Abbey at the time. Iona is a small island off  the west coast of Scotland near Oban. These photos came from another Ian, Ian Taylor who spent a month living in Iona as a student in 1958 where he captured these photos during his stay on the island.

Also, in the recording below Ian talks about the apron he is wearing in the photo. He only wore that apron during his time in Iona and every morning it was blessed before he began the day’s work at the Abbey.

ian-cramb001 ian-cramb-iona

Get Ian Cramb’s book here: The Stonemason’s Gospel

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