Total Repointing, FAQ Friday

Q: What is the correct method for total repointing?

A: Correct total repointing requires removing the joint to a depth of approximately 2-1/2 times its width and then using a compatible mortar in relation to the final p.s.i. and both the liquid and vapor transmission rate as that of the remaining joint and brick. High lime content pointing mortar is compatible with
the soft and absorptive nature of historic brick which rely on their “fired skin” to protect themselves and the building from rain intrusion. If high concentrations of Portland cement were in the repointing mortar instead of lime, when moisture in the brick were to expand and contract during freeze/thaw cycles, often the unyielding mortar forces the softer face of the brick to exfoliate thus leaving a vulnerable unburned “salmon” center of the brick exposed to the elements.

Green Construction in Today’s Built Environment- FAQ Friday with 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.

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

Stucco Over Historic Stone Buildings, FAQ Friday

Q: Why are beautiful stone farmhouses and other historic stone buildings covered with stucco? Is it for insulation? If the stucco over stone is an original and historically accurate detail, is it then OK to remove it to expose the stone and leave it that way? Will this enhance or deflate the value of the building in its authenticity?

A: Traditionally the only exposed stone is one with a gauged mortar joint. “Free stonework” are irregular pieces of stone shaped to fit with large, squared corner stones with alternating lengths used as borders. Ashlar work is varying sizes of cut blocks of stone that are laid in uniform coursing. You will sometimes see semi-coursed stonework on the front of a building and haphazard stone joinery on the sides and the back of the building. If the stone was shaped with tools used by masons it most likely was meant to be seen. You will often see remnants of the original external plaster or whitewash in the pours of the stone of the building which has already had the stucco removed to tip you off that the building was originally covered or coated and not exposed.

Fieldstones are stones picked up off the field when settling a property and preparing the ground for farming. They are laid up in “rubble work.” Some masons pronounce it “roobil” work. I think they are just repeating the accent of the old-timers. Rubble is junk. Fieldstone is just junk stone It is not dressed up in any way.

But the question remains, “Why did they cover the stone with exterior plaster?” Well, when you don’t gauge the joints and keep them tight the surface exposure to the elements is increased and accelerated the erosion of the pointing mortar. This may quickly deteriorated the bedding mortar and the integrity of the wall. It will at least aid in the transmission of water into the building. So, the same soft, punky mortar that was used for bedding was also used for exterior plaster, (stucco), and finished off with a shelter coat of whitewash. Whitewash is pure calcium carbonate lime and water. It was used as a waterproofer and protecting coat for both beauty and function. Whitewash could be thought of as a coating like an eggshell. It is soft, breathable and will protect the otherwise frail stucco render. Today the appearance of rubblework exposed is thought of as a thing of beauty. Historically fine stonework was squared and formal with straight, true and gauged joinery as the sign of high-end work. Really, it still is throughout the world, but “beauty is in the eye of the beholder.” If historic stone buildings where not plastered, (receiving an external stucco render), but instead received the inverted “v” joint to deflect the downward and angled drive of the rain, they usually were whitewashed right over top of the stone and joint in rubble work. When you don’t see the whitewash over the stone anymore it is because the acidity of a constant rainwater bath has loosened it and it has come off and was not renewed. More often than not it remains under the porch of houses and forebay areas of barns where it has been protected. Look closely in the pours of the stonework on the sides of the building and under the eaves or behind pent roof to see it remnants of the stucco or whitewash has remained. Another tell-tale sign that the building was originally stuccoed over the stone is that the widow trim remains proud to the stonework. If the trim comes out past the stonework at a thickness of 1-1’1/2″ past the stone, then that is indicative that the stone was covered with stucco the meet the outer edge of the wood trim.

The only insulation gained by exterior plaster is that of slowing a driving wind. Overall masonry is a poor insulator. 1940 and newer stucco may have had perlite incorporated into the mix to add an insulatve element.

To correctly restore something would mean to put it back to its original design. For correct architectural restoration of a stucco over stone building means that the plaster should remain and be finished as it was originally. However, many people with unsound exterior plaster, which has lost its bond to the substrate or has cracks throughout it or has paint that is flaking, consider the removal of the offending stucco and coatings without replacing it but rather exposing, cleaning and repointing the stone. It is an option that will help mitigate the water infiltration problem. It is an option for overcoming the eyesore of flaking paint. It even increases the value of the building in many cases more than what the cost was to expose and repoint the stone. But my advise is to “just say no” when you have a formal exterior such as a building with a mansard roof. An exposed stone building which has been repointed and does not have the stucco or whitewash renewed should be reserved for a simple country farmhouse, outbuilding or barn in my opinion. It may effect the value of the property in a negative way by removing historic details. A local historic appropriateness review board may not allow these modifications and a historical society may frown upon changing the unique and appropriate details originally found at the historic structure.

Sandblasting Historic Buildings FAQ Friday

Q: Someone wants to sandblast my house. Should I let him sandblast ?

A: Invasive cleaning methods such as sandblasting or high-pressure washing should be a questionable intervention upon historic fabric of any kind and should be considered carefully. Quartzite sand should never be the medium used on historic brick whose frail “fired skin” will be destroyed and thus expose a porous “salmon” center. Never sandblast sand upon any stone with intricate carvings or upon a terra cotta unit whose glazing would be irreversibly removed.

Other media is available such as ground up walnut shells, baking soda, diatomaceous clays, glass beads. Which media to be used is to be judged on their effectiveness using the most non-invasively method first. The non-invasive method is the one that works upon the historic substrate to lift only the undesirable contaminant. One could employ quartzite sand, (in varying gradation and at various p.s.i. pressure), when there is a sacrificial element allowance and need for aggressive cutting is desired such as in the case of removing tenaciously adhered Portland cement staining from a poor repointing job or from a cementicious whitewash when the substrate is common fieldstone that has no intricate carving. 

Modern brick will lack the porous “salmon” center known to be the remaining condition of an historic brick fired in a down-draft kiln. Modern bricks are thoroughly fired in a tunnel kiln which results in more uniform densification throughout. But even modern brick will become “pitted” by the sharp sand action of a sandblaster. If any case where all the drawbacks and limitations are realized and anticipated beforehand still warrant the use of sand as the medium, this method is at your disposal if a test sample proves it is effective. However, be sure of this fact.

The surface area of masonry which is exposed to the elements is increased once sandblasted and micro-cracks may be introduced by any violently aggressive sandblasting especially by inexperienced operators. A final draw back in the use of this already unpopular method is that silica dust will be produced. At least a water mist used as a knockdown to dust must be engineered into the application. Water greatly reduces the dust when the sand comes out of the orifice and is pulverized into dust upon impact. A vacuum sandblaster is used when one must collect all of the contaminant such as paint along with the sand. Some municipalities do not allow sandblasting of any kind because of the negligence and misuse of the tool and because of the irreversible damage caused to historic structures. Not allowing sandblasting is generally a good idea since more damage is done than good over all. Should you let him sandblast? Most probably not.

Deteriorating Brownstones- FAQ Friday with Randy Ruth

Fall is officially here. The leaves are beginning to change and its perfect weather for a bonfire and pumpkin pie! Randy has another frequent asked question to share, this one is about deteriorating brownstones.

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.

http://www.international.icomos.org/publications/monuments_and_sites/15/pdf/Monuments_and_Sites_15_ISCS_Glossary_Stone.pdf

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. 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.

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

Techniques for Plastering a Wall, FAQ Friday with Randy Ruth

Q: I have painted drywall in my home and would like a lime plaster finish. How can I achieve this?

A: There are many ways to achieve a lime plaster finish over painted drywall. The first issue to address is who is going to do the work? If you hire a good plasterer then they should know how to approach this issue.  Even still, you could enlighten them with new products that they may not know about, that you have discovered in your research.  If you are a more do it yourself kind of person with some trowel experience than you might be surprised what kinds of finishes you can achieve with a little bit of practice on some 12” x 12” sample boards.

How you ultimately approach, this task is dependent on three major factors… budget, authenticity and texture. Depending on the budget allocated toward a lime plaster finish, a person can achieve a wide range of finishes. The polished mirror finishes often-associated Venetian plaster can but not always be associated with higher costs. This is due typically to higher materials cost and higher wage costs because of the skills required to achieve that level of finish. Speaking of wage costs it should be noted that ceiling applications are much more labor intensive, rightfully so and should probably left to a professional plasterer. A rougher coarser finish can hide slight imperfections in artisanship, thus it typically costs less than other finishes. Since we have now linked the relationship between budget and texture to how you can achieve a lime plaster finish over drywall, it is time to move on to authenticity.

Authenticity refers to the quality of the product. Is it lime, acrylic, or a blend? Sometimes authenticity does not matter however; with the ever-increasing customer demand for low or no VOC products, it may play a role in your decision-making. There are flexible “lime” plasters that have chemical additions as well as many acrylic based bonding agents available on the market. If you want a more real lime plaster system on your painted drywall, than LimeWorks.us has a solution for you.

You should begin with a clean sound surface, free of any soaps or detergents and of course with no pealing or flaking paint. A quality finish is only as good as the quality of what is beneath it. Then simply trowel apply Takcoat^TM evenly over the entire wall 1/16^th to 1/8^th inch thick. This will act as a transition coat from paint to plaster. Takcoat^TM uses hydraulic lime and natural additives to achieve a bond that can stick to glass, ensuring a good bond to the painted wall. Once the transition coat of Takcoat^TM has cured for a about 3 days, a second coat of lime can be applied to achieve the finish. Depending on the what the kind of finish is desired another coat of lime can be applied, or even three, four or five. It all depends on what you or the client wants.

If a rough finish or soft-sanded finish is desired than Ecologic® Mortar in either coarse or fine sand can be applied. If a fine polished, finish is desired than NHL 2 can be applied paper-thin in multiple coats to create depth to the finish, which is polished with black soap diluted with water.  all of the products mentioned  can be blended together to make the right finish for you or the client. Custom colors can be matched for you, or you can add your own iron oxide or natural lime proof pigments.

Because of all the case specific challenges, answers to this FAQ are just a basic overview. If you plan to tackle this issue head on, give a call or shoot an email to randy@LimeWorks.us. We can help you with choosing the proper products and application techniques.

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

FAQ Friday with Randy Ruth

Hooray, Today is Friday! Another rainy weekend will be upon us here in Pennsylvania, but now it’s time for another FAQ Friday with Randy Ruth. Today’s question is another very common question on the use of lime mortars vs. cement. After you finish reading please visit our new facebook page and “Like” us…

• Q: Could I perhaps use cement and sand?  What is the advantage of using lime on old stone structures
• A: You should not use only cement and sand for a variety of reasons, the first being that in today’s mortars, lime adds workability and plasticity to the Portland cement mortars. Without lime in the mix or proprietary additives, the cement and sand mortar will have extremely poor workability. Secondly, modern-day cement is much different than early cement or lime, it is very hard, dense, vapor impermeable, and brittle. Cement can trap moisture inside the wall and erode the mortar behind the repair mortar, this can cause further unseen deterioration and masonry unit (stone, brick, terracotta) deterioration, thus resulting in a delayed and much larger/costly masonry repair.

The advantage of using an appropriate lime mortar on old stone structures deals with compatibility. There is a rule of thumb when approaching a restoration project and that is to repair in kind with like materials. By following this approach an individual can avoid unforeseen problems associated with trying something “new and improved” when there is such a well over 2,000 years of lime building history. There have been a number of studies done around the world on historic structures that conclude that even a small amount of Portland cement added to a lime mortar mix, can cause detrimental damage to the adjacent masonry and historic bedding mortar.

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

FAQ Friday, with Randy Ruth

This is the first in a series of blog entries that will feature mason, Randy Ruth. Randy is the lab technician at LimeWorks and receives lots of questions on masonry and the use of our materials. We will feature some of these questions each Friday in our FAQ Friday blog entry. First question…

• Q: I have an old stone basement foundation (house was built in 1900) and need to “re-point” or fill in holes in the basement walls.  Would your Ecologic mortar work? I am not sure that lime based mortar was used originally; would this still be OK or how can I tell if lime was used?
• A: “cement” was not produced in the united states until 1870 in Coplay, PA, only up until around 1910 was Portland cement starting to find its place in society as a masonry binder. Prior to 1910, most mortars used were based on either lime putty, Natural hydraulic quicklime or natural cement. Regardless of what the exact mix design was used to build your basement foundation, Ecologic® Mortar would most likely be suitable for repointing your old stone basement foundation walls as it would be sympathetic to the adjacent mortar mix by maintaining good vapor permeability. An easy way to determine if you have a lime based mortar, especially in stone construction, is to break a piece from the wall in visually inspect for any white nodules or specks. The white nodules are an indicator of what is called a “hot lime” mix and commonly found in stonework . Any presence of those nodules or specks suggests a high lime content mortar, and should thus be repaired with a comparable material.