Some historic bricks in Washington DC have black spots. These spots indicate that the brick used is an ironspot brick and / or tapestry brick. These types of bricks are very common in what we think of as a third wave of historic masonry construction in DC. The first wave of masonry construction was built around the years 1790-1850 and was built by/for the early federal government and wealthy landowners.
The second wave occurred from approximately 1850-1910 and saw a rapid expansion of residential and commercial buildings as the city grew. Most of the buildings in the historic districts of Washington DC were built during this time.
The third wave was from about 1910 to the 1940s and included construction after about the mid-1910s, characterized by the widespread use of ironspot and tapestry bricks in rowhouses and apartment buildings. Neighborhoods like new Hill East River terrace, Trinidad and neighborhoods outside of the downtown adjacent regions of the city were built during this time period.
At the particular brick shown in the photo below, you can see the black pronounced iron spot locations but some iron spot bricks have a much higher degree of iron spots over the surface of the face of a brick. This happens to be a brick similar to an early wire cut brick but is actually a bit older than most of the modern or mid 20th century wire cut bricks. In this particular case, you can see where a pink colored mortar has been applied as part of a pointing process but even at the time of that repointing, the masonry voids in the adjacent bricks were left unaddressed as this was only a spot repair.
Unlike common brick deterioration though, part of the recessed joints in this particular brickwork are actually intended. This brick was initially built with a raked mortar joint. Raked mortar joints have a relatively uniform recess applied to each mortar joint above, below, and at each perpend joint on the sides of each brick where they meet together.
Raked mortar joints in brickwork create a distinctive visual effect. Raked mortar joints are created by removing a portion of the mortar from the face of the joint, typically to a depth of about 1/4 to 3/8 inch. Mortar is actually applied similar to typical mortar application, when bricks are pressed down into place and set at level with each other, mortar oozes out from the joints between the bricks. The raking of those joints and the creation of the recess happens after the bricks are actually set in place and even after the mortar binding them has hardened a little bit.
This raking process is done while the mortar is still somewhat plastic but has begun to set. The result is a recessed joint that creates a shadow line between the bricks.
The visual effect of raked joints is most pronounced when light strikes the wall at an angle, which is common for most of the day as the sun moves across the sky. This angled light creates shadows within the recessed joints, emphasizing the horizontal and vertical lines of the brickwork. The effect is a pattern of light and shadow that adds depth and texture to the wall surface.
From an aesthetic perspective, raked joints are often preferred, by some people in certain architectural contexts, for several reasons:
- Emphasis on Brick Units: By creating shadow lines between the bricks, raked joints highlight the individual brick units. This can draw attention to the color, texture, and pattern of the bricks themselves, making them a more prominent feature of the facade.
- Texture and Depth: The shadows created by raked joints add visual texture to what might otherwise be a flat surface. This depth can make large brick walls more visually interesting and less monotonous.
- Traditional Appearance: Raked joints are often associated with traditional or historic brickwork, lending a sense of craftsmanship and age to a building. This is technically a bit of a misnomer though.
- Scale and Proportion: The shadow lines can help to visually break up large expanses of brickwork, potentially making a building appear more in scale with its surroundings.
- Architectural Style: Certain architectural styles, particularly those that emphasize the materiality and texture of building materials, often favor raked joints for their ability to enhance these qualities.
However, it’s important to note that while raked joints offer aesthetic benefits, they can also have some practical drawbacks. The recessed area can collect water, dust, and debris more easily than flush joints, potentially leading to increased maintenance needs or weathering issues in certain climates.
The choice of joint style, including raked joints, is often a balance between aesthetic preferences, architectural style, practical considerations, and the specific characteristics of the bricks being used. In some cases, architects or designers might choose to use raked joints selectively, perhaps on more prominent facades or in combination with other joint styles to create specific visual effects.
In the image below, you can see the applied pointing mortar which is already cracked because it was probably applied and mixed incorrectly, years ago, but not long enough to justify the premature deterioration. It’s clear though, where the Rick joint has been fattened almost near to the edge of the brick, it loses that visual aesthetic and visual interest of the raked joint.
For the sake of comparison, here you can see the original rate joint in the next picture below.
Iron spots in bricks, particularly those found in Washington DC’s third wave of historic masonry construction, are a fascinating aspect of architectural history and materials science. These spots, which give ironspot and tapestry bricks their distinctive appearance, are the result of specific manufacturing processes and raw materials used in brick production during the early 20th century.
The origin of iron spots in bricks can be traced back to the composition of the clay used in their manufacture. Clay deposits naturally contain various minerals, including iron compounds. When these iron-rich clays are used to make bricks, the iron content can manifest as visible spots or speckles on the surface of the finished product.
We can Help
Our company focuses on historic restoration more than modern building upkeep, maintenance, and construction, but our company understands both types of construction very well and a full picture well-rounded approach is needed in any niche in the construction industry. Although we focus on historic restoration, repointing, tuckpointing and historic brick repair, our company also has technical knowledge and competencies in the areas of modern and contemporary construction as well as we become one of the leaders in that area of the market today. Understanding both historic and modern or contemporary construction is useful because both aspects help understand the challenges and potential solutions for challenges in building science and construction.
We can help with a variety of historic masonry restoration needs and upkeep, from modest tuckpointing and or repointing to complicated and extensive historic masonry restoration. Infinity Design Solutions is a historic restoration specialist contractor specializing in both historic masonry restoration such as tuckpointing our repointing, and brick repair. If you have questions about the architectural details or facade of your historic building in Washington DC, reach out and say hello and if we can help we’ll be glad to assist you. You can email us or call us on the telephone at the following link: contact us here.
