In an article last week, we looked at the issues of insidious damage in historic brick walls. This week we are looking at how proper restoration, such as repointing, can prevent detrimental failure. The outline of todayâs article follows:
How deterioration and destruction can be mitigated by repointing and historic masonry preservationDeterioration and destruction of historic brick masonry can be effectively mitigated through repointing and historic masonry preservation. Historic brick masonry repointing can be a tedious and laborious process, but it pays off. The benefits of repointing can be the difference between a building that last for decades more, even indefinitely, with few incidences of water ingress through the masonry walls and walls that are drought with problems and eventually collapse. The picture below shows an example of a deteriorated area of historic brick mortar. You will notice that the existing brick is actually in ok condition, in this case, over 114 years after the original construction of this Capitol Hill rowhome in DC. Understanding the repointing processHistoric brick repointing involves several steps to ensure the longevity and aesthetics of the structure. Last week we looked at areas of significant deterioration which led to drastic failure of brick masonry structural walls. First, an assessment of the brickworkâs condition is conducted. Different walls of a building may be built with different types of mortar, even when those walls were built at the same time. This examination helps identify areas with damaged or deteriorated mortar joints and bricks, and disambiguate between pressed brick and common brick and butter joints of mortar and low lime binder mortars.. Once identified, the next step is to carefully remove the deteriorated mortar. This process is referred to as joint ârakingâ and it must be done carefully to minimize damage to the surrounding bricks. The reporting process, in itself leaves the bricks as they are, in their current state and just removes and replaces the mortar at the outer edge of the wall, generally to a depth no greater than 1.25 inches. In some cases selective bricks may also need to be removed and replaced, where they are damaged or failed. this is relatively rare in most cases and is technically separate from the reporting process itself but it may be advantageous to do these types of work at the same time. After removal, the new mortar mixture is prepared to be similar to the historic mortarâs composition with highest focus on compressive strength, followed by permeability. People often misunderstand the process and believe that color and texture matching are central to ensuring the repointing work blends seamlessly with the existing masonry. In reality though, those elements are second to strength and permeability. The repointing process then involves the tedious process of filling the grooves left by the removed mortar with the new mortar mixture. The exposed mortar joint is tooled to give it a contour or tooled shape. Often common walls of historic masonry had a flush strike. Finally, after the repointed mortar has mostly cured, the area of repair is cleaned to remove any excess mortar and to reveal the restored brick masonry. It is important to NOT use the same acidic cleaners used on new modern âhardâ mortars. Overall, historic brick masonry repointing requires a careful approach, attention to detail, and a commitment to preserving the historical integrity of the building. This process not only indirectly bolsters or ameliorates the structural concerns but also ensures the continued longevity of historic brick structures. The picture below shows a different and unique circumstance, an aberration from a typical pointing process. This particular wall was built next to an adjacent finished wall. Often in rows of rowhomes, buildings will be built together at the same time and share the internal side walls of the buildings. In this particular case though this wall was built with the other one in place in a âblindâ type of process. The builders of the currently remaining wall shown in this picture could not access the outer side of the wall, currently viewable in the picture below. At that time, the other older building, now collapsed and gone, was built right up to the property line and this new building, the wall shown here, was built tight against that building. there was a small interstitial space, but that space could not be accessed by the builders. Critical areas of RestorationOften we find that particular areas of the building need a higher level of attention than the remainder or larger portion of the buildingâs historic brickwork. The picture below shows a thickened triple wythe base of an exterior wall at the ground level, next to a concrete walkway. You can see the few small remnants of a scam pointing done years ago by an untrained contractor. There are deep voids remaining in the older mortar behind the areas of scam pointing. scam pointing is a process of smearing newer mortar on top of an existing joint without providing the essential step of raking the old mortar away from the brick mortar joint. Above, we explained that the raking step is an important part of the brick repointing and restoration process. That process involves removing deteriorated mortar to a depth of up to 1.25 in into the wall area. That is relatively deep compared to the amount of raking done in the section of the wall shown in the photo below by prior contractors, years ago. you can see that there is a stark visual difference in the color and texture of the newer mortar and the original mortar from over 100 years ago. the small few pieces that are left that are basically flush with the surface of the brick are the areas of newer mortar. the areas of mortar behind that of a lighter, whiter, color are areas of original mortar and those areas of original mortar are only removed to a depth of approximately 3/8 of an inch, except for a few critical areas where erosion of that remaining existing mortar has dug out the joint to a depth of over 2 inches deep. those areas are critically damaged from deterioration. The next photo below shows a closer view of the same area of the wall. With this clearer detail, you can see the extreme amount of deterioration at the lowest areas of the wall. At the brick at the corner, next to the stone threshold to the entry door of the building, the mortar is recessed all the way through to the depth of the brick, over 3.5 inches deep. This level of deterioration, if more extensive than the area shown, can indicate the building is in imminent danger of collapse. There though this most extensive amount of deterioration is limited to just affecting a few bricks at the edge of the wall. There is extensive damage to the other areas, but those areas of deterioration are not nearly as extensive. When a wall gets this bad though, especially in a larger area, repointing or tuckpointing may not be enough, the wall and its extensive deterioration may be too far gone at that point. Although we use the standard of 1.25 inches as the maximum amount of raking for repointing of joints in brickwork, there are cases when specific or acute areas of mortar must be repaired to an even deeper depth. If the amount of deterioration though is not limited to just spots and few spots at that, then repointing without needle shoring or an additional method of temporary stabilization of the wall may not be safe. Temporary needle shoring is a method of masonry stabilization, primarily used during construction, renovation, or restoration projects to provide immediate support to unstable masonry structures. The process involves strategically inserting temporary metal rods or âneedlesâ through the masonry to prevent further movement or collapse while necessary work is performed. First, a thorough assessment of the masonryâs condition is conducted to identify areas of weakness, structural damage, or instability. Here in our article from last week we show several examples of this type of critical instability. Once these areas are identified, holes are carefully drilled through the masonry at specific locations to accommodate the needles. The holes are typically larger in diameter than the needles to allow for adjustments. Metal needles, often made of steel or a similarly strong material, are then inserted through the drilled holes. These needles span the thickness of the masonry and protrude from both sides. On the exterior side, nuts and washers are often used to secured the needles to a temporary supporting structure and hold them firmly in place. The needles function as temporary reinforcements, redistributing the structural load and preventing any further deterioration or movement of the masonry during construction or repair work. Once the necessary work is completed, and the masonry is stabilized, the temporary needle shoring can be removed and the temporary holes used to allow for the needles can be removed. Temporary needle shoring plays a vital role in preserving the safety of workers executing the repairs (in cases of unsecured overhead loads) and the integrity of historic or damaged masonry structures during construction or restoration projects. The next three photos below show more examples of scam pointing. This particular photo in the next picture below is from a direct facing view of a portion of a brick wall. The contractor ostensibly doing the supposed repairs just smeared a white mortar paste onto the surface of the underlying substrate mortar. The underlying original mortar was already significantly aged and deteriorated and the new mortar smeared on top never really made cohesion or an effective bond to the substrate mortar. One of the problems with pointing without a raking process is that the new mortar needs to bond to a relatively stable substrate and the outer deteriorated edges of remaining mortars, where a wall is aged and deteriorated, are not strong. They are mostly sand and have lost the majority of the original binding components in the mortar mixture. The next picture below is actually a collage of two different photographs, looking at different angles of the same wall. This is the same wall as shown in the photo above. This historic brickwork still shows both the newer fake or scam mortar and the remaining original mortar, just below the surface. The original mortar is clearly from the time of the original construction of the building. you can see chunks of unslaked lime left and remaining in that original mortar. Historic masonry upkeep and preservationTo properly maintain, repair, and care for these historic buildings, a knowledge, interest and understanding of historic building principles is required. Here in Washington DC, historic masonry buildings are extremely expensive and the amount of financial loss caused by improper repointing and low quality construction is staggering. However, in addition to the direct financial value of the property, there is also a cultural loss when historic buildings are damaged. By comparison, consider neighboring poor cities, when historic buildings are damaged, itâs not just the loss of value to the property owner, thereâs also a loss to all inhabitants and visitors of a city, present and future, who care about architecture, history, and culture. We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the historic built environment of Washington DC and neighborhoods such as Capitol Hill, Dupont Circle, and Georgetown and become educated on on the difference between proper historic preservation versus improper work which leads to significant damage to the historic fabric of a building. From a conservation and preservation perspective, several approaches can be taken to improve conditions related to deteriorated historic brick masonry. Primarily, lime mortar brick joints and low temperature fired soft red clay bricks should be inspected and checked on a routine maintenance schedule, either seasonally or at least annually. If brick masonry is kept in good condition, the life of embedded wood elements can be significantly extended. Hire a professional contractor which specializes, understands and appreciates historic construction elements and buildings. You can learn a lot more on our blog. Feel free to check it out. If you have questions about the historic masonry of your building in Washington DC, contact us or fill out the webform below and drop us a line. We will be in touch if we can help. <p>The post How Brick Repointing Can Prevent Detrimental Failure first appeared on Infinity Design Solutions.</p> Via https://www.ids-dmv.com/masonry/how-brick-repointing-can-prevent-detrimental-failure/
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About UsInfinity Design Solutions LLC (IDS) is a full service general contracting company in the heart of the Dupont Circle neighborhood of Washington, DC. We focus on repair and renovation of buildings and facilities in both historic designated neighborhoods and the commercial-zoned central business district of the city. Follow Us
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