Expansive soil and cracks in exterior walls

Would this soil be considered expansive and would the cracks under the windows be anything to be worried about? It is a hard coat stucco and the largest crack is 3/32 but they are around about half the windows and a couple of the doors. No problems with any windows or doors opening or shutting. There is one crack in the block wall in the crawlspace but it is only 1/32 of an inch. I will have one other question about possible mold like substance in the crawlspace. ( it is black, but you can wipe it off and it does spear a bit. I will post a pic. Thanks for your help! The home is located in Newnan Georgia and most of the crawlspace looks like the first 2 photos. There is a vapor barrier down as well.

What is the black dust like substance. I would call it mold-like substance untill I tested it. When you wipe it, it just smears. Any help. (about half of the crawlspace looks like this)

Hi. Phil, we have a lot of good Inspectors with experience on expansive soils on the board, if you went to the control panel and list the area you are in, they might chime in and help.
Unfortuneatly, no expansive soils in my State to be concerned about. :slight_smile:

Only soil testing would confirm that “Guess”

I wouldn’t “Name It” anything, nor would I recommend testing, if the atmosphere is conducive to Mold Growth recommend correction.

“The soils in the crawlspace were dry at the time of the inspection but that does not mean they remain dry all the time. The soil was desiccated, which could indicate a chronic drainage problem. Moisture can adversely affect the house foundation and can facilitate the growth of a variety of molds that can promote unhealthy conditions. Therefore, we recommend that you observe the crawl space during a period of heavy or prolonged rain prior to the close of escrow or within the contingency period.”

You actually expect a client to do that Joe?..even though the words are nice.

Doubt a judge would think much of it either.

If it didn’t rain prior to inspection contingency period ending without rain, well, pretty much worthless.

I understand your point. But dessicated clay (expansive) soil should be pointed out to the buyer in my opinion. If there is nothing else to say (you don’t see water marks on piers, efflorescence, etc.), I put that statement in the report. I have actually had clients go back and observe the crawl space after a rain based on my report recommendation (here it usually rains at least once a month). Moisture issues are high on the list of what gets home inspectors sued. I don’t want to be in that group and am very careful to address any possibility of moisture intrusion in a crawl space (poor landscaping outside the home, etc.). What’s the old saying?..“report what you see.”

That soil does appear to be expansive… I’m not a soils engineer.

The damage caused by expansive soils is well known and is usually compounded by poor drainage around the home or building. I’ve seen foundations and stem walls cracked and displaced from one another. Slabs the were heaved/settled several inches in their centers or from end to end. Sometimes the foundation and stem wall will stay intact and the geometry of displacement becomes apparent through other inspection means. Been in a new home with known expansive soils? Look at the statements usually placed in the home’s garage advising the new owners of what to do and what not to do.

This volumetric expansion and contraction of expansive soils (bentonite / clay) can damage just about anything sitting on top of them… A structural engineer I know indicated to me that the soils will displace just about anything on them, as if the structure is not even there. If you’re in a known area (I think I read almost half the US is) with expansive soils… educate your clients about this. Include a simple diagram of swale/drainage away from the home…

If you see grading and drainage defects in these areas… point them out. If a pattern of geometry indicative of displacement, settling or other defect exists…point it out!

By the way… without seeing anything the entire “picture” of the home… the cracks around the windows are what appear to be stress cracks or just plain typical.

Structural, electrical, plumbing, mechanical systems and the roof are of utmost concern to buyers. These systems are the reason we are hired. Being able to accurately describe their conditions is paramount to performing a service to our clients.


The cracking is one characteristic of expansive clay soil, however a soil test would have to be performed to be absolutely sure. If you want to know more about soil most USDA county offices have county soil maps, which are usually free. Some soil map data is online so start there. The general US soil map is not much help it shows large areas in Missouri where I am not having expansive soil which is incorrect. The county soil data maps I refer to are very detailed in location and in depth. You may find the top few inches of soil as non-expansive followed by several inches of very expansive clay soil. Linear Extensibility is used to determine the shrink-swell potential of soils. The shrink-swell potential is low if the soil has a Linear Extensibility of less than 3%; moderate if the soil has a Linear Extensibility of 3% to 6%; high if the soil has a Linear Extensibility of 6%-9%;and very high if the soil has a Linear extensibility higher than 9%. If the Linear Extensibility is more than 3%, shrinking and swelling can cause damage to buildings and roads. I have attached drawing showing the shrink-swell data and actual photos from a cracked foundation investigation done a few weeks ago. If you compare the diagram to the photos you can see the greatest force is in the second soil layer which corresponds to the horizontal crack in the foundation wall.



Over 70% of foundation and structural cracks are from the exterior of the home; poor guttering/drainage, poor terracing of the soil from the foundation, etc. Small hair-line foundation cracks are usually just drying cracks, and not a structural concern. Cracks wider than 1/4 inch should be referred to a structural engineer. Many cracks shown could be a cause of poor foundation footings, poor foundation construction, poor soil conditions, or all of the above, which are beyond the scope of a normal home inspection. It also depends upon the area of the U.S. where the home is. Randy is pretty much right-on. Many areas of the U.S. have wide temperature swings, which can cause all sorts of foundation and wall cracking/movements.

Molds are always in crawl spaces, probably the dusty substance you noted. Test to be sure, or refer.

Thanks for everbodys help!

Diagonal cracks at the door and window openings are signs of foundation movement. The question is, will it continue and do more damage or is it finished? A soils report would help answer that question. During a transaction, there’s not enough time to monitor cracks with gauges. I would definitely be concerned about cracks that size. A local building department will know if expansive soils are a possibility in that area.

Lots of it here!

The Carolina’s have problems with expansive soils; I know as a contractor I am always concerned with this issue to the extent that I often will bring in a soil engineer to do bearing verification prior to pouring footers. Even with that there is no guarantee that problems wont crop up later. For several years the Carolina’s went through a drought period followed by an unusual rainy season which resulted in an unprecedented number of insurance claims of which virtually all were denied by the insurance companies.

My rule is that any crack over 1/8 th of an inch will get my undivided attention…cracks larger than 3/16th of an inch will most likely result in me recommending a structural and/or geotechnical (soil) engineer be brought into the equation. (Home inspectors should not discount the use of an soil engineer…too many time we think that structural engineers will solve the problem when all you done is caused your client to waste monies by directing them to the wrong specialist)

While it is impractical if not impossible to determine if their is a soil issue under a particular home, it is not difficult to take a few extra minutes to drive or walk around a neighborhood and look for clues from surrounding homes. It is for this reason that I often get to my appointments about 30 minutes early…it gives me not only time to look at quality of materials and workmanship used in that particular neighborhood but also allows me to gather additional information that could be relevant for me as the inspector and that which might be of interest to my client.




Those links you have listed contain the general soils map I referred to as misleading.

In southern Missouri where I live the map shows (brown) or no expansive soil.

This could not be further from the truth. Next to getting a site specific soils test the USDA soil survey I referred to will give you a much better idea of the local soil types. The attached picture shows a section of a soils map from the county I live in and you can see the lines outlining the different soil types in a small area. My county has 55 different soil types listed and each soil type is composed of several layers with each layer having different soil properties. So don’t use that US soils map to make any assumptions about the soil in any specific location.


I forgot the map…


Is this http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx the resource your talking about Randy?


That is a source for the data. I have not use their web site but the data is there. Once you identify your location I would look under the Soil Properties & Qualities tab then on the left click on the Properties and Qualities Rating section, then Soil Physical Properties, Then Linear Extensibility. You will have to just plow your way through this web site. I got the actual maps and book from my USDA office for my area, its much faster than going online.