Can a block foundation wall be displaced, yet still plumb? Yes! This means you should never evaluate a foundation wall merely by checking the condition of interior finishes such as paneling.
The concept seems illogical
When there’s a horizontal shear crack at the first mortar joint near the floor, the base of the block wall is pushed in (Illustration B120). The joint is “sheared” apart. Normally, this results in lower inward displacement measured as outward tipping of the wall.
But if the base shear is combined with inward displacement of the upper wall, the wall and its interior finishes could be plumb.
"Measuring the finishes gives no indication that the wall is failed; you will not notice the bow in the wall from side to side."
Clues may be elusive
Typically, a shear crack at the base of a block foundation wall is hard to see (Photo 1). If you shine a light at the right angle, a shadow near the shear crack may be the only visible clue.
In this case, inward shear movement is visible as a horizontal line parallel to the floor and a crack in the pilaster (Photo 2). This short, perpendicular pilaster reinforces the wall. A crack on the side of the pilaster has been patched and the face of the pilaster has a small hole where the face of the block pulled away.
Paneling complicates the situation
In this case, 2-fee-by-2-feet furring strips were installed to hold wood paneling. With the paneling in place, none of these cracks were visible.
Now, let’s measure the wall with a 6-feet-long level (Photo 3). At the lower end of the level, it’s evident that the wall is displaced about
11/2 inches due to a base shear crack. The paneling was displaced about 3/4 inch because the top of the wall was also tipping inward. In most other areas of this wall, the paneling was not displaced despite significant movement.
Never base your evaluation of a foundation wall merely by observing wall finishes such as paneling. This limited observation may indicate moisture issues, but you’ll have no idea of the foundation wall’s true condition. If paneling or some other finish hides the foundation wall, your report should say that the wall is not visible and has not been not inspected.
Tom Feiza has been a professional home inspector since 1992 and has a degree in engineering. Through HowToOperateYourHome.com, he provides high-quality marketing materials that help professional home inspectors educate their customers. Copyright © 2019 by Tom Feiza, Mr. Fix-It, Inc. Reproduced with permission.
To learn more, attend Tom’s technical presentations at educational sessions for ASHI chapters. If you would like Tom to provide his knowledge for your educational event, contact him at Tom@HTOYH.com.