Learn more about the history of brickmaking and how bricks are manufactured here
Brick making in historic times was extremely tedious and difficult, it required an incredible amount of toil and labor. Bricks are heavy and dirty because they basically come from clay which is very similar to mud. In historic times, much of the heavy work was done by hand. Without the use of modern steam, electric, or fuel burning equipment. The process of drying bricks prior to firing was also very slow. There are several steps in the process of making historic bricks, modern methods that, by comparison, are similar and follow the same sequence of steps but historic methodologies are completely different. The differences between the processes have had significant impacts in the differences of materials and compatibility used today for restoration and tuckpointing of historic brick masonry, even in modern times. These differences still make an impact today because historic buildings are still plentiful in the urban areas of Washington DC and other early cities along the East Coast of the United States.
The picture below shows an example of a building built over a 100 years ago with historic bricks. The building maintains a pressed brick at the front of the front facade and a common brick at the side alley facade. Stained glass units remain at the window headers but the lower units have been replaced with modern windows. Marble front steps and a marble plinth at the round turret from the original construction remain in place.
Aside from a few specific details, this building is very typical of the masonry buildings built in Washington DC around the late 1800s early 1900s. The structural load path of these buildings is a double wythe brick wall above grade and often a stone or triple wythe brick foundation below grade. The historic masonry used for this construction is a common brick at the side and rear walls. A historic common brick is a low temperature fired brick, generally with a structural capacity of less than 2000 PSI. These traditional bricks buildings, although built with Historic technology that goes back millennia, are still standing in most cases and if maintained properly can remain standing and in functional use for for hundreds of years more.
Some of the principal key steps in the brickmaking process follow below. As technology and modern heavy equipment have been developed, the process has changed at almost every stage.
Historic methods of brickmaking were simply tough work and this process remained nearly exactly the same for thousands of years. The industrial revolution brought us technology which would change the methods of making bricks, but those changes came way after the inception of the industrial revolution. It took decades before that technology made it’s way throughout the industry.
| Historic Methods | Modern Methods | |
| 1 | Hand and work animal excavation of silts from river beds | Mining of clay with heavy modern earth moving equipment. |
| 2 | Very little sifting was completed because Of the lack of steam or hydraulic power equipment. | Sifting by mechanical belt and lifting equipment. |
| 3 | Bricks were handformed by mold. In some cases with wooden frames and steel baseplates.
The mold was wetted to allow the brick to slip out and the internal baseplate was covered with a thin dusting of sand to facilitate the later release of the clay in the brick shape. |
Plug running and wire cutting, Modern brick clay is extruded, in its moldable plastic state, through hydraulic equipment and cut into individual bricks, often by an automated wire.
The plug is pushed through the machine as an extrusion that passes through a dye. The dye shapes the plug into the dimensions of a brick four sides. The other sides are cut by wire. |
| 4 | Bricks were laid in a yard and dried by the sun. This process required time and tending, as bricks dried they all had to be individually turned and flipped to allow all sides to dry. | Brick drying on on conveyor, heated by modern power and fuel sources. Is the heat and timing, essential variables in the process can be easily controlled with sophisticated automated systems. |
| 5 | Firing was done in inefficient and inconsistent wood fired kilns | Firing and cooling on conveyor with high heat applications. |
| 6 | Bricks were stacked by hand, moved by cart and animal | Detaching with lifting machinery and shipped by industrial truck. |
In the image below, you can see the great amount of inconsistency between pressed press brick and the historic common brick. The picture below shows an example of common brick installed at the side alley facade (on the left side) and press brick installed at the front facade (in the right side in the image below).
Essentially, as detailed in the steps of production, listed above, the process differences between historic and modern methodologies are significant. The technical advances in these processes, not only allow modern bricks to be created at a much lower comparative cost, adjusted for inflation, but it also allows for a greater consistency, durability, and aversion to permeability in the fabric of modern bricks. Historic bricks, although deficient in several ways, are still able to perform at a structural capacity for hundreds of years. With these great differences in mind though, it is very important that historic bricks are maintained by very specific methods of restoration and care.
Historic bricks must be tuckpointed, as the sacrificial mortar joints deteriorate over the many decades since the original construction. Those mortar joints are intended to be sacrificial, meaning that the mortar joints are intentionally made to deteriorate faster and be softer and more vulnerable to the elements then the brick units themselves. These considerations are extremely important when tuckpointing a building facade. Untrained mason’s use of modern mortar, incompatible with historic bricks is detrimentally destructive to historic buildings. The importance of using trained specialists in the field of historic masobry repointing cannot be overstated.
The picture below shows an example where a historic brick wall has been patched with a modern mortar. The mortar used was similar to concrete, a void in the wall was filled to seal the wall from the outside. In this case, the modern cement is excessively hard and incompatible with the remaining adjacent mortar and historic bricks. This incompatibility means that the modern materials will move and react differently to environmental conditions and as the building experiences natural small micro movement, the new mortar will become a pressure point which can damage these surrounding brick masonry wall. Natural micro movements happen in buildings all the time, almost every day of the year. These small micro movements can be as small as just a millimeter of actual movement. When a extremely heavy building, over hundreds of tons moves just a millimeter, incompatible materials, moving at different rates can be crushed and damaged at the pinch points.
Modern mortar is typically a gray color due to the dark color of Portland cement.
By comparison, as shown in the photo below historic mortar is generally a lighter tan color. The picture below shows an example of a common brick installed at a rear ell. The brick has several pieces of stones, of varying shapes and size inside of the brick itself. The substrate materials of modern bricks, by comparison are filtered before being fired and do not contain comparatively large stones of this type.
As you look at the table above, which showcases and highlights the main steps in the brick manufacturing processes, with comparison between modern and historic methodologies, you can see a clear distinction. Historic methodologies rely completely on animals and human labor. The process was tedious and very limited. Materials could not be listed and filtered and moved without extreme exertion. Every step in the process was difficult and costly. The ability to filter, compact, dry, and fire the substrate materials was very limited. As a result, historic bricks are limited in structural capacity, and have low tolerances to compatibility with modern mortars. Understanding all of the historic methodology is essential to understand the reasoning behind why it’s of such significant importance to restore and maintain historic brickwork using proper compatible techniques and proper mortar or correct compatibility.
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.
In this article we talked about the terminology and concepts of historic masonry restoration, follow the links below for more related information from the IDS website:
- Binders in mortars and concrete
- Brick burns
- Butter joint
- Capillary action
- Cementitious siding
- Cheek wall, masonry — Draft
- Chemical testing
- Code, building — Draft
- Cold joint
- Cold weather masonry work — Draft
- Damp proof course
- Downspout
- Electrical distribution panel — Draft
- Fenestration
- Ferrous metals
- Great Chicago Fire
- Green bricks
- Gutter, roof
- Lintel
- Oxidation
- Parapet coping
- Plug, clay
- Pressed bricks
- Raking, of mortar joints
- Raggle, aka reglet
- Rectilinear
- Roman bricks
- Roman arches
- Roof eave
- Roof termination
- Row buildings and row homes
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- Rubbed bricks
- Rubble stone masonry
- Sand, Builder’s
- Sedimentary rock
- Scratch coat
- Sprung arch
- Strike, or striking of mortar
- Tapestry bricks
- Tooth-in, interlocking masonry connections
- Vitreous
- Water diversion systems
- Zipper-joint
These concepts are part of the fundamentals of historic masonry restoration, tuckpointing, and brick repair.
The links in the list above will take you to other articles with more information on defects, failures, preservation and repair of historic masonry. 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, fill out the webform below and drop us a line. We will be in touch if we can help.
