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Identifying Problems with Your Historic Brick Building

Identifying Problems with Your Historic Brick Building | Wisconsin Historical Society

If your historic house or building is constructed with brick, your maintenance routine should include an annual inspection to evaluate the condition of your bricks. By making this annual effort to review your building’s masonry exterior, you can identify potential issues that could turn into significant problems if not addressed. The most common problems you may encounter with your brick masonry are described below.

Mortar Deterioration

If your house or building has existed for 100 years or more, you will probably find mortar missing or deteriorating between your bricks. Mortar deterioration is caused primarily by moisture penetration. Other factors can include wind erosion, or bricks that have been coated with paint or sealants that do not allow moisture vapor to escape.

If your mortar has deteriorated significantly or is missing altogether, you will need to replace the mortar by repointing. Repointing is the act of carefully removing the failed mortar and replacing it with mortar that matches the look, texture, color, composition and hardness of your original mortar. (The original act of installing the finish layer to a mortar joint is referred to as “pointing.”)  You should hire an experienced preservation mason to repoint your mortar.

Brick Deterioration

EnlargeBrick chimney

Dane County. The brick on this chimney has experienced severe deterioration - the brick has shifted, cracked and spalled. Source: WHS - Historic Preservation - Public History.

During your annual masonry inspection, you might find that some of your bricks are cracking or spalling. These problems occur under the following conditions:

  • Excessive moisture enters the bricks and freezes in the winter. Bricks naturally take in and let out moisture, but excessive moisture can enter through failed mortar joints, exposure to cascading water due to a lack of effective gutters or sealants that do not allow normal water vapor to escape.
  • Repointing work is done with mortar that is harder than the bricks. As a brick contracts and expands by taking in and letting out moisture, it puts pressure on the adjacent mortar. If the mortar is harder than the brick, this pressure will crack and spall the faces of the bricks. Even if the mortar is softer than the brick, the same results are possible if the mortar is harder than the original mortar. Make sure your repointing mortar is equal to or softer than the historic mortar behind it.
  • EnlargeCracking brick

    Madison, Wisconsin. Even though this is brick building has been painted, the joint cracking is evident. Source: Photographer Mark Fay.

    Foundation settling puts downward pressure on the bricks. Downward pressure from foundation settling can cause your bricks to crack.

If you must replace your original bricks, try to find salvaged bricks that match the size, texture, color and age of your original bricks. Many communities in Wisconsin have architectural salvage or just salvage yards that reclaim these bricks from demolished buildings. A few companies also make reproduction bricks. You can find these companies by doing a web search for "reproduction historic bricks."

In rare instances, you might be able to remove a brick that is damaged on its face, turn it around and reinstall it in the same location so its undamaged backside becomes the visible face of the brick.

Brick Erosion

Your annual masonry inspection could reveal brick erosion or excessive wear. Some early houses and buildings were built with bricks that were very soft. Bricks are fired in a kiln, and early kilns were not able to control the firing process as well as they are today. Brick erosion and wear can also be caused by bricks that were formed from clay that is not dense enough to hold up over time.

Brick erosion can also occur if your house or building was treated with an abrasive cleaning technique such as sand blasting or high-pressure washing. Even soft bricks have a harder exterior, so sandblasting and high-pressure washing can remove the harder crust on the outside of the bricks. These cleaning techniques are so damaging to bricks and mortar that both practices are banned in all preservation best practices guidelines. If your house or building is listed on the National Register of Historic Places, it is against the law in Wisconsin (WI Statute 101.1215) to use an abrasive blasting technique on the exterior of your historic building.

Structural Failures in Your Brick Walls

Your annual masonry inspection could reveal that sections of your brick walls are bowing inward, outward or even collapsing. These problems are considered catastrophic structural failures. These problems will typically be caused by excessive foundation settling or heaving, or massive amounts of water entering your brick walls. This water problem most commonly occurs from a roof leaking over a long period of time.

You will have to address the underlying problem or problems to remedy a collapsing brick wall area. When you have solved the underlying problem, you will have to hire a preservation mason under the guidance of a preservation-oriented structural engineer to carefully take down and rebuild your brick wall.

Stair-Step Mortar Cracks

You might find cracks in the mortar between your bricks that look like stair steps. These mortar cracks are primarily caused by foundation settling or upward heaving. Often when stair-step cracks happen, they never get any worse. Old houses and buildings can settle a bit over many years, and if no other moisture or structural problems exist, you can repair cracked mortar joints by repointing them. If a crack does get worse, you will have to address the structural foundation problems with a preservation mason under the guidance of a preservation-oriented structural engineer.

Bricks Covered with a White Powdery Substance

EnlargeEfflorescence on brick

Madison, Wisconsin. Efflorescence can be found on all types of masonry walls - here the efflorescence is evident on the brick surface below the window. Source: Photographer Mark Fay.

During your annual inspection, you might spot efflorescence, a white powdery substance on your bricks. Efflorescence happens when salts in the mortar or brick are dissolved by excess moisture and migrate to the surface of the bricks. When the moisture evaporates, the remaining salts leave behind a white powdery film. Efflorescence rarely happens to brick houses and buildings built before 1920, because the lime and sand mortar used up to this time did not contain Portland cement. Lime-based mortars have few, if any, salts in them.

Efflorescence indicates there is too much moisture in your brick walls, so you should hire a masonry expert to help you fix the moisture problem first. When you have solved the moisture problem, clean the efflorescence off your bricks with this two-step procedure:

  1. Scrub off the white powder with a stiff scrub brush and water.
  2. Clean the brick surface with a biodegradable detergent.

 

Bricks Containing Surface Debris: Dirt, Moss and Mold

You might find bricks that are dirty or have moss or mold growing on them. Dirty bricks are usually the result of exposure to airborne pollution and particulates in the air that attach to the bricks and mortar. Often this natural patina is not damaging to your bricks and can be considered protective, so cleaning may not be necessary. If you find moss or mold, or discoloration that is beyond what seems “normal,” then you should try to clean the surface using the gentlest means possible. Use the same cleaning procedure described above for efflorescence.

EnlargeSandblasted brick

The top half of this brick was sandblasted. Note the sandblasting not only removed the hard outer layer (still evident on the lower half), it also damaged the inner, softer brick. Pock mocks are evidence of sandblasting. Source: WHS - State Historic Preservation Office.

CAUTION: Never remove dirt, moss or mold with high-pressure washing or any kind of high-pressure blasting, such as sand blasting. If you wash your bricks, never allow the water pressure to exceed 1000 pounds per square inch (PSI). Place the spray wand tip no closer than 12 inches from the surface of the brick. The use of higher-pressure power washing will erode the harder surface of your bricks and cause permanent damage.