Inspecting Residential Foundations
Ian Webster
There are some initial questions to ask about the foundation of the house your thinking of purchasing: 1. How old is the house? Older homes tend to have more damage to their foundations due to poor quality materials. 2. Was the house built by a licensed contractor or the homeowner? 3. Did the builder follow the applicable building codes at the time of construction?
For at least the past 40 years or so most single story homes were built with proper foundations. But there are areas of the country that have what are called "expansive", or, soft soils. These type of soils can present a settling problem as they tend to move under the weight of the house above. Especially when there is any water present. A foundation wall that has not been properly reinforced will tend to crack as it spans the soft soil area. The amount the footing moves depends on many factors, the extent of the soft soils, the load imposed on the footing from the house above and the depth of the stem wall. Whatever the cause, large cracks are easily seen from both the outside and inside.
It is always a good idea to inspect a foundation wall if there are visible cracks. If the crack is large enough to insert a small object, like the tip of a pencil, you may have a water infiltration problem. This water can cause further damage to a basement or crawl space and the crack will need to be sealed and made watertight. Even if the crack appears small you should check the walls above to see if any damage has occurred to rest of the house. Look carefully at the openings inside the house above where the foundation wall has moved. If there are cracks in the finish around the openings that means the wall framing has moved as well. This type of damage can be old and there may not have been any more since that time. If there is recent paint and the crack has reappeared, then the wall is still moving.
If the damage to the footing is severe enough to need repair, where do you start? It is both risky and cost prohibitive to remove the soil beneath the footing and try to replace it with adequate support of any type. The only practical way is to bridge the settled area with some structural support. This can involve jacking up the floor under the settled floor framing and providing a cross support to keep the framing above in place. This is an area where a local engineer can help solve the problem. It does not take long and the cost is usually quite low to have a proper structural solution to the problem that will actually work and keep the settlement from reoccurring. Just patching and painting over the sheetrock or plaster cracks will only hide the problem temporarily, and the cracks will soon reappear.
If you are in area where soft soils are common you will want to do a thorough inspection of the foundation walls. Small cracks are due to the normal amount of shrinkage that takes place in most concrete. Large cracks are a different matter and can be indicative of a structural failure of the concrete. When concrete fails it is the reinforcing steel that is holding the wall in place. If the house was poorly built in the first place or built over soft soils, look closely at any and all cracks. If the house is two story, the greater loads imposed on the footings justify a closer look. If you have the combination of soft soils and a high water table and there are significant cracks in the concrete, you may want to reconsider buying that particular house as the cost of repairs can be high.
Finally, I would recommend that if you are uncertain about whether there is costly damage to a house you are contemplating buying, get another opinion. Ask an engineer if they would mind stopping by and taking a look at the foundation. Quite often they will do so for no charge. The peace of mind alone is worth the time and effort.
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