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What are the common problems with concrete block homes?

Friday, December 31, 2021

Concrete block has plenty of advantages as a material for house walls. It’s not susceptible to rot, termites don’t eat it, it’s dimensionally stable, tolerates minor moisture intrusion, is hurricane resistant, and considered by many homebuyers as a superior construction type. But there are a few common problems:

Spalling - A concrete block home is not 100% concrete block. The walls are strengthened by a poured concrete tie beam running around the top of the walls, and also concrete columns or poured block cells from tie beam down to the foundation slab. The concrete is reinforced with steel bars that will rust if moisture reaches them. The rust causes the steel bars to expand, which opens long cracks in the surface, like in the photo above. Eventually chunks of the wall will start to fall out if not repaired, as in the photo at right. The key to avoiding this problem, and a very expensive repair, is to keep the walls well sealed and repair any minor cracking as soon as it appears. See our article There's cracks running along the home's concrete tie beam. What's wrong? for more on this.

Termites - Florida homeowners often assume that concrete block homes don’t get termites. But they do, and the way that many older block homes are constructed actually makes them more likely to a have a termite infestation that’s invisible until major damage has been done. For details, go to How do termites get into a concrete block house? 

Efflorescence - These powdery raised lines or areas in a block wall are caused by moisture accumulation in the wall that leaves behind a mineral deposit as it evaporates on the surface. Like spalling, it’s an indicatation that water is getting into the wall. Although primarily just a cosmetic problem, the water in the wall can lead to problems at the interior surface over time. Find out more at What causes raised white lines of residue on a block wall that are crusty and crumbling?

 Cracking Due To Minor Settlement - A wood frame home with vinyl, wood, or cementitious siding can absorb minor movement of the structure without cracking. But a block wall with stucco finish develops hairline cracks with only minor settlement, and they need to be repaired as they happen to avoid further problems.

Lack Of Load Path Reinforcement - Concrete block homes are often touted as the best choice for hurricane resistance. But the collapse of many older CBS homes in Mexico Beach, Florida,  the Catergory 5 hurricane Michael in 2018 led to an understanding of the importance of a strong connection between the top and bottom of the walls, called a “continuous load path.” This is required in newer block homes, but missing in older ones. See Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael? and How can I tell if the concrete block walls of my house have vertical steel and concrete reinforcement? for more on this.

    We personally prefer concrete block over wood-frame home construction. But both have unique advantages that are covered in our article What are the pros and cons of concrete block versus wood frame construction? 

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Field Guide for Home Inspectors, a quick reference for finding the age of 154 brands of HVAC systems, water heaters, and electrical panels, plus 210 code standards for site-built and manufactured homes, and the life expectancy rating of 195 home components. Available at for $19.95.
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Here’s links to some of our other blog posts about CONCRETE BLOCK:

How can I tell if the exterior walls of a house are concrete block (CBS) or wood or brick?

Do stucco walls mean a house is concrete block?

 What causes stair-step cracks in a block or brick wall?

Why is the concrete window sill cracking?

What causes a horizontal crack in a block or brick wall? 

What does CBS mean in house construction?

What is "Ocala" block?

Should I be suspicious about a concrete block house covered with siding?  

• What causes a vertical crack in an exterior concrete block or brick wall? 

• How can I tell if cracks in the wall or floor are getting worse or staying the same?

Why do concrete blocks have holes in them? 

How does concrete spalling cause structural failure if not repaired?

    Visit our CONCRETE AND CONCRETE BLOCK page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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