We recently looked at the brick facade of an interesting building. Two different types of bricks have been used in the facade construction. At the main exterior a darker brick has been used. At the rear of the building a lighter brick has been used in the construction. The lighter brick looks more rustic because it has larger pieces of rock and impurities that are apparent in the clay face of the brick. The mortar work also appears less consistent, for a few different reasons. We’ll look closer at these details and explain some of the reasons and causes behind the differences.
As explained, this building is built with two distinct different types of brick. The street facing side of the building is built with a type of brick known as pressed brick. Common brick, by comparison ,which was used at the rear of the building, is typically less expensive than the pressed brick, and it may contain various irregularities, including larger aggregate particles in the clay.
The pressed brick, on the other hand, is designed to have a more finished and uniform appearance, often with a smooth texture. It’s usually used in areas that are more visible, such as the main exterior or facade of a building, where aesthetics are a primary concern. In this case, the exposed facade only faces the Alley, but a portion of that facade can be seen from the main street, at an angle.
In the picture below, you can see the darker, more uniform brick, at the left, used in the main exterior That street facing brick is a pressed brick, while the lighter, less expensive brick used at the rear of the building is common brick with larger stone particles visible on the clay face.
Often, on our blog, we focus on discussing the principles of proper historic brick restoration and repointing or tuck pointing. We often discuss the differences between the common brick and pressed brick. Pressed brick is a particular type of historic brick which was made from filtered or sifted clay before being consolidated into the form of shape of a brick and then fired at relatively higher temperatures than the common brick. The pressed brick was not only fired higher temperatures than common brick, but it was also fired at more consistent temperatures whereas common bricks are fired in larger quantities and were often subjected to greater disparities in overall temperature during firing leading to several different types of inconsistencies. One of the main types of inconsistencies is that with brick firing at lower temperatures, within the general range of acceptable temperatures, those bricks will fire to a lower degree of vitreousness.
The next two pictures below show the two different types of bricks up close. The first picture shows the common brick, used as a cheaper infill. The next picture shows the pressed brick. This particular brick has a high degree of consistency from one brick unit to the next, but it’s different than the pressed bricks we so often see in the front facades of the more ornate Capitol Hill and Washington DC historic brick rowhomes.
Although the brick below is a very old brick it is not necessarily from an architecturally historic time, it’s not the same as the historic pressed bricks and is actually much newer, by several decades. This building is attached to a historic building but this building is actually an accessory building, similar to a garage. We’re not sure when this brick was built but the original building was probably built very close to or in the year of 1900. Although the bricks used in the construction of this building or this small accessory building are not historic and not the historic pressed brick that we are most familiar with, this is still a type of pressed brick. It is what we would call a dry pressed brick, today. This brick, unlike other bricks made with a typical wet clay plug, is made from clay particles that are slightly larger in size with less hydration.
The difference in the texture of the brick shows this difference. At a glance it almost resembles a wire cut plug mold brick, but there are also other differences in that style of brick. Generally, in a wire cut brick, you will see short lines, in the brick face, where very small particulates were dragged by the wire. This brick does not bear that mark.
By comparison though, when you look at the next brick in the next photo below, this brick is a common brick with significant variation in dimensions and its rectilinear form. For masons, when building with this type of brick it’s relatively difficult to hide the inconsistencies from one brick to the next. A relatively large mortar joint helps significantly, yet you can still see the difference when looking closely.
The wire cut bricks, discussed above, are one of the most common types of modern or contemporary bricks. These types of bricks are cut from a plug extrusion. The plug is a mass of hydrated and mixed clay. The clay is then pressed, in modern production, with a hydraulic machine that extrudes it through a die as the plug is then extruded, the machinery slices each brick from the mass of plug with a wire that cuts through it more smoothly than a wet saw could even cut. The plug is wet and soft and the wire passes through with very little resistance. Yet, a texture, as explained, is left on the face of the brick because very small particles in the plug mold will drag or be displaced in the surrounding clay, just a tiny bit as the wire passes through the clay. This movement, caused by the wire, leaves this distinct texture in the face of the brick.
In the picture below, we can see common brick that was made in individual molds without the wire cut texture on the face of the brick.
The pressed brick stands out in comparison to the common brick. This particular brick also has a very uniform aesthetic, even with a larger brick joint than is commonly found in the butter joint profile used with historic pressed bricks. At the top of this wall there is a staggered corbeling that has a dentil type aesthetic. Dentil reliefs and shavings are common in historic architecture., even in wood elements.
By comparison, dentil molding, commonly seen in historic architecture in both wood and pladter, features small, rectangular blocks resembling teeth. This dentil design is a repeating motif often used in cornices and moldings along the tops of exterior facades, like the one shown here. This architectural detail draws inspiration from ancient Greek and Roman architecture. Each dentil is evenly spaced, creating a visual pattern that adds a layer of detail to the structure.
In cornices, dentil set masonry contributes to the building facades’s overall appeal, providing an additional detail. This detail might be somewhat subtle in brick masonry, but the building stands apart from other buildings with just a plain vertical face. At certain degrees of sunlight, for example, the shadows created by the alternating brick relief becomes accented and the building has a more dramatic and ornate feel overall.
In the photo above, you may also notice there’s a difference with the mortar used at the face brick and the common brick. The mortar at the common brick is set flush to the face of the brick yet the mortar at the pressed brick is recessed, only about 3/8 of an inch but that 3/8 of an inch recess makes quite a different aesthetic appearance. Essentially, the bricks stand proud of the mortar and this difference creates a drastic shadow that highlights the three dimensional surface.
The corner of the brick wall has been damaged. The brick, in the up close view, is the pressed face brick. Where the corner is broken off, you can see that the material inside of the face of the brick looks slightly different, yet the actual texture is similar. The outer face of the brick has been stained with decades of exposure to dirt in the air, and that outer face of the brick is a little bit darker, overall.
Buildings on the alleys are often damaged by large trucks making deliveries and or trash trucks that constantly come through the alleys on routine trash pickups. These trucks are large and often just barely make the turns of the tight alleyways without damaging the brick walls. Often bollards, heavy and strong steel tubes used to prevent vehicles from the walls, are installed to protect the building corners, but they’re usually just marginally effective and in this case no bollard is installed at this corner.
The next picture shows an even closer view of the cracked and broken surface of the brick. Although you can see a difference in the color at the face of the brick, there is relatively high consistency of the materials beyond the face of the brick. Both the mortar joint and the brick itself were damaged by the impact and abrasion. There are ways to repair damaged bricks, using special types of mortar for patching and/or epoxies, but it’s difficult and expensive, on a unit basis.
In most cases it’s relatively easy and often even more cost-effective to just replace the damaged bricks with other bricks. However, in this particular case it’s very difficult to procure a brick similar to the ones used at the exterior facings of this particular building’s walls.
Here in the next picture below, you can see there are large pieces of aggregate or stone inside of the brick. This brick was fired with those portions of stone inside of the plug which is the main constituent material of the brick. Mostly, bricks are made from a mixture of clay and other hydrated materials that come from the earth.
The mortar used at this somewhat concealed area of the building is very similar to the mortar used at the remainder of the building, it is a lime mortar, but unlike typical historic lime mortar. However, the mortar used in this construction has been sifted and mixed a bit more thoroughly.
Although this building has not yet been repointed, overall the mortar is in somewhat decent condition. There are exceptions at specific locations, but it’s not yet time for repointing or wholesale restoration. Each historic building is unique, to a degree, and the analysis of which steps to take in restoration should be determined in a case by case basis. In some cases, buildings need to be repointed to preserve and safeguard the building from water damage that emanates from water entering through the exterior facade. In some cases the rate of deterioration is increasing and can lead to worse damage
Historic masonry upkeep and preservation
To 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.
