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Identifying Problems with Your Historic Brick Foundation

Identifying Problems with Your Historic Brick Foundation | Wisconsin Historical Society
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.

If your historic house or building was built before 1930, it could have a brick foundation. Brick foundations were used during all periods of historic house construction in Wisconsin through the 1920s. You might be able to solve some of the typical problems you will face with your brick foundation on your own, while other problems will require the expertise of a professional mason.

The Nature of Historic Bricks

EnlargeFoundation wall

A brick foundation wall that is bowing inward along its length and height. Source: Bob Yapp

Bricks are smaller than stones and vary in their hardness. Bricks are made from wet clay and then fired in brick kilns to cure them and make them harder. All fired bricks have a harder outside surface than inside. The kiln firing process varied over time as technology changed and improved, and some early bricks were not fired as well as later bricks. By the late 1800s, bricks were much harder than the earlier versions. These harder bricks were structurally stronger, less prone to moisture damage, and could handle harder mortar with Portland cement.

Bricks laid after 1900 are harder and not as easily scratched as bricks laid before 1900. You can determine the hardness of your bricks by using a small screwdriver to scratch the surface of your bricks. Use medium hand pressure to scratch the face of several bricks in an out-of-the-way area: 

  • If your bricks show almost no sign of scratching, you have hard-fired bricks.
  • If your bricks show no more than a surface mark, you have medium-fired bricks.
  • If your bricks show scratches that are 1/16-inch deep, you have soft-fired bricks.

Early brick foundations were laid using soft, lime-based mortars. Starting in the 1890s, the lime mortars used in brick foundations may have had small amounts of Portland cement added to them. The Portland cement allowed faster and harder curing for use with the newer, harder bricks.

Typical Brick Foundation Problems

You may want to hire a preservation masonry professional to identify the cause of any problems you are having with your brick foundation. The most common problems you are likely to encounter with your brick foundation are discussed below. Click the link on each subject to learn how to solve the problem.

Common ProblemLearn More
  • Mortar is missing or crumbling between your bricks.
Repairing Mortar on Your Historic Masonry Building
  • Your bricks always seem wet and are deteriorating from excessive moisture. To solve this problem, you need to get the water to move away from your foundation. Grade the ground around your foundation so it is angled away from your foundation and add ground extenders to your gutter downspouts.
Maintaining the Gutters on Your Historic House
  • Your interior foundation walls are parged or painted and appear to be trapping water because the parging or paint is flaking off.
Remove all the loose cement or paint and allow the rest to flake off over time. Any coating on the inside of a brick wall will prevent the normal migration of moisture. The trapped moisture freezes inside the wall, causing mortar deterioration and spalling of the bricks.
  • One or more sections of your foundation wall are bowing inward or collapsing from exterior forces such as water and tree roots.
  • Your foundation wall has cracks that look like stair steps.
  • Your foundation shows efflorescence, a white powdery substance leaching in between the bricks.
  • Your bricks are cracked or broken.
  • The surface of your bricks is coarse and shedding small brick particles excessively.
  • Your foundation wall has sunk (settled) or heaved upwards.
  • Your bricks are dirty or have moss or mold growing on them.
  • Your bricks are cracking or pieces are flaking off the face of the bricks, known as spalling.
  • The cement coating (parging) on the exterior of your brick foundation wall is deteriorating.  You should hire a professional mason to dig around the exterior of the foundation and coat the exterior surface with a waterproofing material. Have the mason verify the condition of the mortar when the foundation is exposed, because excessive moisture for an extended period of time can leave mineral deposits that break down the mortar. If this is the case, the foundation may need to be repointed while the foundation is exposed. The mason should also install tiling around the foundation to channel water away from your foundation.
  • The mortar between your bricks is showing excessive deterioration, and water is entering your basement. This problem occurs because no exterior waterproofing was ever installed below ground. You should hire a professional mason to dig around the exterior of your foundation and coat the exterior surface with a waterproofing material. Have the mason verify the condition of the mortar while your foundation is exposed, because excessive moisture for an extended period of time can leave mineral deposits that break down the mortar. If this is the case, your foundation may need to be repointed while it is still exposed. The mason should also install tiling around the foundation to channel water away from your foundation.
Identifying Problems with Your Historic Brick Building
  • Your bricks show deterioration and excessive wear. This happens because the bricks used on your house are the earlier, softer bricks. 
There is no solution to this problem.