Stucco Cracking on Concrete Block Walls

Why does my stucco have cracks? There are many reasons for stucco to crack. I am going to discuss the 2 causes that have by far the greatest effect on a home. When the temperature changes from 30 degrees to 80 degrees, the exterior walls on your home become longer at about 1/16’’ to 1/8" for every 16 feet of wall length. So a wall that is 64 feet long will become about ¼ to 1/2 inch longer with a 50 degree change in temperature. This expansion and contraction of the block wall cracks these brittle materials. The structural design of your home takes this brittleness into account. Cracks by themselves do not indicate a structural problem with a home. One should have a professional inspect the home, if they have concerns.

Many of the stucco cracks on block wall reflect the cracks or weaknesses in the block wall. The block expands and contracts as discussed above. As the concrete block is installed the mortar joints can shrink causing cracking along the mortar joints. Windows and doors in a wall are weak places in the wall. There are often stucco cracks below the windows.

Your home is reinforced with steel reinforced columns every so many feet (4 feet to 8 feet is common). These columns are constructed with a 5/8’’ reinforcing bar in a concrete filled block cell. These “filled cells” are usually on each side of the windows and doors in a home. When there is a strong reinforced component next to a weaker window or regular block area, cracks in the block can occur due to changes in temperature.

Wet and dry cycles also cause cracking or can cause existing cracks to get wider. Gutters help along with timely repainting of your home. You will find that the paint will age more quickly on walls of your home that receive the greatest amount of sunlight.

Why does my neighbor across the street have less cracking than my home? Probably, because you cannot see the cracks from across the street. Just kidding, but I have walked across the street with many home owners to show them the cracks. There are an almost unlimited number of conditions that cause stucco cracking. Therefore the amount of visible cracks can vary widely from wall to wall or home to home.

Can stucco cracks leak water into a home? Yes, most of my calls during the rainy season are for water damage to homes from water entering through normal stucco cracks. I tell everyone to maintain the cracks in the spring as they occur during the cold winter season. I suggest repainting a new home after 5 years. If you wait too long, the cost of the re-painting job becomes more expensive.

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