In the past we’ve discussed a variety of different types of repairs to masonry construction. Some of the main restoration types include repointing and tuckpointing of historic brick masonry. Today we are taking a close look at a very specific type of repair within stone masonry units. By comparison, repointing or brick pointing is a type of masonry restoration that addresses the mortar joints surrounding the individual masonry units within a wall or construction assembly. This type of restoration can apply to both brick and stone, but it specifically applies to repairing the historic mortar where it has deteriorated in the joints that surround each individual masonry unit. With large masonry units, such as stone treads, in the example that we are going to look at today, the size or area of the damage may be relatively small in comparison to the overall size of the masonry unit. In such cases where the damage is limited or small in overall scale, sometimes it makes sense to repair the area within the unit instead of replacing the unit. Dutchman patches are commonly used in the conservation of historic stone buildings, monuments, and sculptures. They can be applied to a wide range of stone types, from limestone to marble and sandstone. The picture below shows a historic marble staircase. The treads and risers are monolithic, together, one piece of cut stone. These individual pieces are cut from much larger stones but exrraxted entirely whole. At a glance, you can see that there are signs of dirt and stains on the face of the treads and risers, but it almost looks as if there is no significant damage. When you look closer though you can see there are spots in the middle of the treads and parts of the nosing and risers as well where patches have been installed. In the past, there was a handrail installed in the middle of this stairway. Sometime ago that handrail was removed but the locations where the handrail post mounted to the stair treads left an omission. That omission was filled with a Dutchman patch. A Dutchman patch is a type of patch, different than filling a void with mortar, in this case the area of the stone was cut out larger than the original void or core cut-out After the larger area was cut, a new piece of closely resembling or matching stone was cut to the same shape and then installed within that void to create a near seamless patch. When you look closely though you can see the evidence of the patchwork. In the picture above, you can see several areas where the patching was installed. The patching was intended to blend in with the adjacent stone, however there are several places where the rusting iron oxide, from the ferrous metal handrail and post left iron oxide, rust stains, on the face of the stone treads. Iron oxide stains on the face of stonework can be challenging to remove because they result from the oxidation of iron particles which have entered into the stone, which can penetrate deep into the material. The process to remove these stains depends on the severity of the staining and the type of stone involved. Iron oxide stains often penetrate deep into the stone’s pores, making surface cleaning insufficient. The method for removing stains depends on the type of stone. Some stones are more sensitive to cleaning agents, and aggressive approaches can cause further damage. Aggressive chemical treatments can alter the stone’s appearance, weaken its surface, or cause discoloration. Striking the right balance can be difficult and complicated. A chemical poultice can be used, in some cases, for light to moderate staining. It involves applying a thick paste made from a chemical cleaner and an absorbent material to the stained area. The poultice draws out the iron oxide stains over time. Common chemicals include rust removers or diluted acids like citric acid. Some stains can be treated with biological agents like poultices made from specific types of fungi or bacteria. These organisms can break down the iron oxide over time. For more severe stains, acids like oxalic acid are used. However, using acids requires caution as they can harm the stone surface. In some cases, high-pressure steam cleaning can effectively remove iron oxide stains without the use of chemicals, but special equipment is required and efficacy can be limited. This method can be less invasive and more environmentally friendly. For extremely stubborn stains on harder stones, sandblasting or abrasive cleaning may be employed. However, these methods are aggressive and most often damage the stone or masonry surface. The choice of method should be determined by the type of stone, and the severity of staining. It’s important to assess the specific situation and follow the most appropriate and least invasive method to remove iron oxide stains without causing further harm to the stonework. Part of the challenge of Dutchman patches is the creation of an aged or weathered appearance on the new patch. This helps the patch to blend seamlessly with the older, weathered stone around it. The patch below is not completely visually effective because of the difference in the color of the two stone sources. The same challenge applies with brickwork, when replacing bricks selectively within a wall, for example, it may not be possible to procure bricks that convincingly match or visually resemble the original adjacent brickwork. In historic buildings, in DC neighborhoods such as Capitol Hill, for example, most of the original historic construction is from over one hundred years ago and bricks of the exact same source may not be available today, at all. In other cases though, even when procurement of a brick from the original source is possible, that brick, to be used for installation within an existing building assembly, may not have had the same exposure and aging or weathering required, over the past 100 years, for example. These varied characteristics can make a noticeable visual difference. The picture below shows an area of repair from a closer distance. At this location or within close proximity, there are two different patches that have been applied. One patch is within the field of the tread itself, in the middle of the flight of stair treads. The other smaller patch is at the nosing. These patches were likely needed for different reasons, and just coincidentally happened to be in proximity to one another. The patch at the middle of the tread was at the location where a post was formerly installed. The smaller patch at the nosing of the tread is likely a repair that happened after damage at the tread. Often, the noses of stair treads and risers are the most vulnerable parts of the structure of a stairway. Often the nosings will take the full brunt of equipment like hand trucks, often used to carry heavy materials or furniture and heavy equipment in and out of buildings. When a hand truck frame hits the edge of a stair nosing it not only is a strike with a hard force, but it’s also a concentrated area so it essentially multiplies the overall force of the impact. This outside corner of the nosing is at the most vulnerable spot because a 90° or near 90° corner has the least amount of support from adjacent materials at the sides of the outside corner. Here in the picture below you can see debris on the edge of the stair riser. It’s also interesting that the Dutchman patch in the stair nosing, both into the field of the tread and into the field of the riser has had an additional area of damage, after the original patch. A piece of the broken patch area was then used to fill in and plug an additional patch within the original Dutchman patch. It is a patch within a patch. The next picture below shows a different angle, from a closer distance at the same area of repair. You can see the outline of the patch I’m within the Dutchman patch more clearly. Although this particular type of repair is not always perfect, in some cases it can be executed in a way that is almost good enough, and sufficiently difficult to notice. Essentially, the overall visual integrity of the masonry area can remain aesthetically near indiscernible. The alternative of removing and / or replacing and rebuilding the stairway altogether may be exorbitantly expensive and may also not achieve the desired historic or classical architectural aesthetic. Preserving historic masonry and repairing damaged elements without fully replacing them is central to maintaining the authenticity and historical integrity of architecturally unique historic buildings. There are several techniques, in addition to dutchman patching, used in historic masonry restoration to achieve proper repair and preservation:
These techniques, often carried out by experienced conservators and restoration experts, play a critical role in preserving historic masonry and architectural elements. The emphasis is on retaining as much of the original material as possible, thus maintaining the historical authenticity and aesthetic of the structure. 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, it’s not just the loss of value to the property owner, there’s 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 Dutchman repairs in stone stair treads first appeared on Infinity Design Solutions.</p> Via https://www.ids-dmv.com/masonry/dutchman-repairs-in-stone-stair-treads/
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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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