Chris' Corner: Here a crack, there a crack (part 5)

Here a crack, there a crack (part 5)


Russel Ray is a very professional, knowledgeable and experienced home inspector from San Diego CA and fellow Active Rain blogger.  Over the last while, he has written a series of posts on the subject of cracks in a property.  If you have a crack and are unsure of the impact on your property, consult with a professional, such as a structural engineer, however, as a primer, and to gain general knowledge, I have found Russel's information very helpful.  This is Part Five of the series and discusses the possible effect pressure from outside material on below grade foundation walls ...


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Here a crack, there a crack....
(part 5)

DISCLAIMER: This discussion is based on several decades of experience in real estate, including as a home inspector and general contractor. I am not now a concrete professional or licensed structural engineer, so if you are not comfortable with common concrete cracks and our discussion here, hire one of those two professionals to help you. This discussion, however, should help you be a little more knowledgeable about cracks so that you don't just automatically assume the worst. Cracks happen, kind of like ActiveRain blogs.

I'll presume that you have read previous lessons.


Lesson Five

So far, we've discussed

  1. curing and shrinkage cracks in the foundation stem wall in the garage,
  2. cracks in the garage floor, and
  3. cracks in the foundation stem wall of the house proper, the living area.

Let's stick with foundations, specifically raised foundations with crawl spaces. These can be more problematic because the foundation is basically a big hole in the ground with four concrete walls around it:


Illustration 1


The soil on the outside of the walls is exerting pressure on those walls, as indicated by the black arrows in Illustration 1, and will have a tendency to crack and bow inward at the red arrows. When that happens you'll often see a long horizontal crack in the wall, usually at about the midpoint of the wall (those red arrows again). A horizontal crack here usually indicates some serious problems that need to be addressed to keep the foundation wall from collapsing.

Figure 1 and Figure 2 show two actual foundation crawl spaces, one constructed with concrete and one constructed with concrete masonry units (CMU's, also known as cinder blocks). 


Figure 1. Concrete wall


Figure 2. CMU (cinder block) wall


As you can see in Figure 1 and Figure 2, there's no soil in the interior of the crawl space pushing back on the exterior soil, so the tendency is for the concrete wall to bow inwards and possibly even crack, as shown in Figure 3 and Figure 4 (and those red arrows in Illustration 1).

Figure 3. Cracked and bowing wall


Figure 4. Cracked and bowing wall


Figure 5 shows a close-up of the crack shown in Figure 4. You can see how deep the crack is, and it's just a matter of time before this wall collapses, rebar notwithstanding.


Figure 5. Close-up


In an earlier lesson we discussed poor rebar placement in the concrete. Figure 6 shows such a condition. The rebar was placed way to close to the exterior of the concrete, and as the wall bowed inward from the force of that exterior soil, the rebar forced its way out of the concrete and began rusting.

Figure 6. Poor rebar replacement.


This now becomes much more serious because there's virtually nothing supporting the interior floors. At this house, the floor on this side of the room had a serious slope in it.

Figure 7 shows the most beautiful, luxurious crawl space that I've ever been in. The homeowner had this done during renovations. His home inspector, whom you know very well, had recommended that he install a vapor barrier on the ground to help prevent moisture damage to the foundation and subflooring, and insulation under the subflooring to help stabilize interior temperatures.

Figure 7. Luxury


When the owner called that home inspector out a year later to inspect the work of others, that home inspector was floored (pun intended) by what he had done. This crawl space is now basically a conditioned area. The two vents you see on the left wall had been closed but left in place in case a future owner (or home inspector) doesn't believe in a closed crawl space. I am one who does, but as you can see, there is a lot of expense involved.

The renovated foundation for this home should now be able to take just about anything that Mother and Father Nature can throw at it, except for maybe "the big one" or the first or second coming, depending on your religion.

If you have a traditional open crawl space, you'll probably having ongoing maintenance expenses. You can take those ongoing maintenance expenses and put them at the front end of construction to create a closed crawl space and have little if any ongoing maintenance expenses under normal conditions, i.e., no earthquakes, no floods, etc. 

As always, if you are not comfortable discussing foundations and cracks, hire a professional to help you.

Join us soon for Lesson Six.


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Comment balloon 0 commentsChris Smith • April 20 2011 02:35PM