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

Wednesday, October 24, 2018

This question seems like a no-brainer. Concrete block houses have a stucco finish, wood frame houses are faced with siding, and brick houses are (duh!) brick. But you could be wrong if you use this common-sense approach, because concrete block houses can be faced with brick or siding, wood frame houses can be finished with stucco, and what looks like a brick house may be a wood frame house with brick facing.

     Here are a few guidelines for determining the type of house structure hiding under the surface:

  1. Stucco or EIFS (Exterior Insulated Finishing System - also called synthetic stucco) over a wood frame wall will sound slightly hollow when you pound on it with your fist. Stucco over concrete block will feel like solid rock.
  2. Windows in wood frame walls are set close to the outside face of the wall, typically within 1-inch or less, but windows in a concrete block wall are recessed about 3-inches.
  3. Some houses are a combination of two different types of wall structures. It was popular in our area during the 1960s and early 70s to build a house that had three concrete block walls and a front wall framed with wood studs. This allowed to builder choose from multiple different materials for the surface of the front wall, making the front elevation of the home more interesting. Also, sometimes we see a concrete block house with a later addition built with wood stud frame and finished in stucco to match the original house. So don’t assume that all the walls are the same construction type.
  4. To tell the difference between a structural brick house (where the bricks are what actually supports the roof) and wood frame house faced with brick, we suggest looking in the garage. A structural brick house will have the back of the bricks exposed there, and you will see a tie beam at the top of the wall, like in the photo below. A wood frame house with brick facing will have drywall in the garage. Also, the bricks in a structural brick house are noticeably bigger than bricks used for facing.
  5. A concrete block wall will be about 10-inches thick, which is wider than any of the other types.
  6. The one absolutely certain way to determine the wall structure type is to look at the top of the wall in the attic, which your home inspector will do as part of the inspection.

    Because concrete block is considered by most homebuyers in Florida to be the sturdiest type of construction, many of them assume that a stucco finish on the wall means concrete block, and it can be a disappointment on the occasions when we have to tell a homebuyer that it is not what they are getting. But, as the 2018 Hurricane Michael proved, even concrete block is not hurricane-proof unless the entire structure is built to the highest windstorm-resistant standards.

    The building code requirements for constructing a wood stud frame wall, with reinforcement at corners and engineered metal connectors at top and bottom, make it both strong and hurricane-resistant. Still, it is no match for concrete construction in coastal exposures. A wood frame wall does have the advantage of more room inside for insulation. Each wall construction type has its own advantages and disadvantages.

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To learn more about exterior walls and structures, see these other blog posts:

What is the average lifespan of a house foundation?

What causes vertical cracks in fiber cement siding planks?

What causes raised white lines of residue on a block wall that are crusty and crumbling? 

What is the difference between soil subsidence, heave, creep, and settlement? 

How much ventilation is required for the under-floor crawl space of a home? 

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

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

How can I tell if a diagonal crack in drywall at the corner of a window or door indicates a structural problem?

What causes the surface of old bricks to erode away into sandy powder? 

What are the pros and cons of concrete block versus wood frame construction?

Should I buy a house with a crawl space? 

Why is my stucco cracking?

There's cracks running along the home's concrete tie beam. What's wrong? 

What would cause long horizontal lines of brick mortar to fall out?

How do I recognize serious structural problems in a house?

What is engineered wood siding?

Should I buy a house that has had foundation repair? 

What is a "continuous load path”?

Should I buy a house with asbestos siding?   

How can I tell if cracks in the garage floor are a problem or not? 

What do you look for when inspecting vinyl siding?

Why is housewrap installed on exterior walls under the siding? 

Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael? 

How can I tell if the concrete block walls of my house have vertical steel and concrete reinforcement?

Should I buy a house with structural problems? 

What are those powdery white areas on my brick walls?

What causes cracks in the walls and floors of a house?

What are the common problems of different types of house foundations? 

• What are the warning signs of a dangerous deck?

How can I tell whether my house foundation problems are caused by a sinkhole or expansive clay soil?

        Visit our EXTERIOR WALLS AND STRUCTURE 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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