Foundation Inspections
Total Care Home Inspectors has spoken to numerous homeowners that have told stories about instances that happened in the during the night. The stories are all similar according to their discriptions. They are awakened by a crack or pop. Part of their house cracked like a dry piece of kindling wood. However, often the part that cracked is the foundation.
They also speak about door and windows that work perfectly one day and stick the next day. Sometimes the sticking is seasonal. That is, the doors and windows work fine for three to four months and then trouble begins. Magically, the doors and windows work fine four to six months later.
In all these cases, the common denominator is some form of major structural movement. The movement can be within the house or it can involve the entire house.
All too often, however, the term settlement is used to describe any movement. This can be misleading, as settlement is really just one form of movement which can affect the way the inside and outside of your house looks. Cracks can develop in your house from other forces such as landslides, heaving frost or soil swell, soil shrinkage, erosion of soil from beneath your foundation, earthquakes, construction blasting, soil creep, etc. You see, lots of things can be happening! Sometimes, two or more at once.
Common Causes
It is not uncommon for a house to be built on fill dirt or on a hillside. Have you seen huge earthmoving machines working on a new subdivision? They scrape dirt from the high spots and deposit it on the low areas. The dirt that is used for fill is supposed to be compacted. However, it may not always be. Gravity and water entering the soil over time compacts the loose fill. If the compaction is not the same under the entire foundation, your foundation may fracture.
Hillside construction is a simple matter of high school physics. Gravity is constantly pulling the soil down the hill. I learned this in my first geology class. This soil creep, as it is called, takes place at a faster rate the closer one is to the surface of the ground. So, houses dug into a hillside basically have their backsides exposed! The part of the foundation that is shallow and is near the surface is subject to movement, while the remainder of the foundation is quite stable where it is dug deeply into the hillside. Perhaps you have seen foundation failures like this.
Hillsides also pose another problem. The soil creeping down the hillside can exert huge forces on the uphill part of the foundation. These walls can crack or tilt inward from the force of this pressure.
Water, or the movement of water in soils, can cause foundations or slabs to crack as well. For instance, imagine if a sewer line or water linethat runs beneath your house develops a leak. It erodes soil from beneath your house and floor. Eventually the foundation footer, wall, and/or floor cracks in response to the absence of the support. Remember, your foundation was designed to work with adequate support beneath it.
Certain parts of the nation have clay soils. Some of these clay soils shrink and swell in response to the amount of water they contain. This movement can be dramatic. As the soil beneath your foundation dries out, your foundation drops. In wet weather the clay swells and lifts your foundation. This is no problem if the movement is the same at every point along your foundation. In more cases than not the movement is not equal. Stress builds and your foundation cracks.
Solutions
If your foundation develops a crack or a fracture, it usually can be stabilized. If the crack is vertical or diagonal, it may require a support from beneath that cradles the footer or foundation. If your foundation develops a horizontal crack, it can be stabilized in several ways as well.
In all instances, it would be wise to consult with a licensed structural engineer who specializes in residential problems. If you try to solve the problem yourself, or merely trust the workmen, you may have a problem occur at a later time. Some of the solutions can actually transmit the stress of the problem to another portion of your foundation. These cracks may happen months later. The contractor will generally say that those are not his fault, when, in fact, they may be! Have a structural engineer develop the solution. Then hire a contractor to perform the work.
Some inspectors may be inclined to believe that small cracks, which are typically the result of shrinkage, are not worth noting. However, consider the following case involving a house with slab on-grade foundation in a neighborhood with no apparent geological issues, no cracks in the streets, no broken curbs, nothing. The house had been completely renovated, and appeared to be in perfect condition. It was tastefully furnished, and had a new roof, new windows, new doors, and new carpeted and tiled floors, to name the major improvements. The only visible blemishes were cracks in an old patio slab that could have resulted years earlier, due to the absence of expansion joints, the installation of which was not in common practice when the house was built.
Vertical cracks in foundation walls are relatively common, and typically result from shrinkage. However, those in the above pictures that were taken from inside a garage are probably seismically related, but not everyone agrees on the significance of such cracks. And when money is involved, opinions can range from rational to ridiculous. A veteran foundation contractor that I once knew paid little attention to such cracks unless there was a significant degree of rotation, but that was in a less litigious era. He would explain how they occur and sometimes pacify his nervous clients by explaining that he had to crawl through an eighteen inch crack in the stem wall, meaning the screened foundation access hatch, to enter the crawlspace. However, there are issues besides cracks that inspectors need to be concerned about. For instance, if the soils around a foundation extend above the footing and do not slope away for a distance of at least six feet, structural problems could result, as you can see from the picture of a foundation wall that was taken from inside a crawlspace. Soils were piled high on the outside of the stem wall that allowed moisture to pond, penetrate, and eventually deteriorate the concrete to a point that exposed the rebar, as you can see from the picture.
Shrinkage cracks are common in slab foundations, and are usually quite small. However, it is not unusual to find larger ones where the slab meets the footing. These are referred to as cold-joint separations, and are usually not discovered until carpeting and padding are being replaced. Because of their size, they can seem structurally alarming but they’re really not and are easily repaired with non-shrink grout. However, people have been reported to become hysterical, believing that their house is about to fall down, or that the seller had deliberately concealed defects that the inspector should have magically known existed. It’s a recurrent nightmare for those inspectors who have tried to convince a disgruntled client that such cracks have little significance. The truth is that all cracks are structural but not all of them are structurally alarming, and people really do need to be educated and cautioned about them, no matter how small, in which case their response is likely to be rational instead of hysterical.
We should not leave the subject of foundations without talking about sloping floors. Some floors are built out of level, and some are caused by differential settling, which is a result of weight bearing down on footings situated in soils that are either inherently unstable, inadequately compacted, or have become destabilized by moisture. Significantly, most builders pay little attention to weight, and could only guess at the weight of a house, whereas a shipwright could tell you down to the last pound what a ship weighs. Consequently, houses do have a tendency to settle, usually listing to one side, or settling more or less equally on opposing sides, which leaves floors crowned in the center. Similarly, many structural engineers agree that one inch of slope in twenty feet is tolerable, and report that differences in elevation are typically not noticed until it exceeds this.
