Certified Home Inspections by a Home Builder

Common Foundation Problems, the Causes and Cures

Of all the problems "Home Inspectors" encounter during a home inspection, foundation problems can be one of the most perplexing. An ideal foundation should be crack free, strong, solid, completely settled and have positive drainage all the way around the home, plus a minimum of 5 inches of clearance, between grade level and any siding.

Expansion and Contraction
Compaction
Improper Grading
Early Backfill
Concrete Mixes and Placement
Incorrect Curing
Shrinkage Cracks
The Bottom Line

Expansion and Contraction

Expansion is usually caused by frost heaving or sometimes water absorption into clay type soils that lift the home's footers and or walls, often unevenly and cause cracking. The frost lifts the home during the winter and drops it during the spring. This is seen most often in older homes with "Rock and Mortar" type foundations that were not built below frost levels. Occasionally additions are built illegally on monolithic or patio slabs and this portion of the home will raise with frost while other parts of the home will not, due to the that portion of the house's foundation being placed below frost level.

Farris Contracting crew installing Foundation

The Consequences- Often the old "Rock and Mortar" foundations will simply ride up and down on the frost level yearly, without consequence for many years. As the home gets older the masonry breaks down and the lifting and lowering will start to break the foundation down. Often as the foundation breaks down, and starts to crumble, the wood structural framing above starts to settle. Some homes I have inspected have settled as much as 4 to 5 inches from one side of the home to the other. This results in cracked drywall, pinched doors and door frames, and uneven or sloping floors. Uncorrected, the problem can escalate to complete failure.

Compaction

Footers which are the base of foundation walls should be placed on undisturbed or completely compacted soil. As is the case with all human endeavors this is not always done satisfactorily.

The Consequences- Usually within the first year of construction any footer with inadequate soil compaction will settle on its own. The result is that as the footer drops or settles the concrete wall above must also settle, which results in a crack. Small amounts of settling usually result in small superficial cracking. However cracks may allow water into basement areas often damaging structural elements such as drywall, insulation and or causing wood-rot to "furred" out interior basement walls.

Improper Grading

Farris Contracting crew installing Foundation

Excessive water buildup around the foundation or part of the foundation can result in heavy lateral pressures against the wall often causing cracking. Additionally improper grading may cause the soil under part of the foundation to turn to mud allowing, settling and cracking.

The Consequences- In addition to the above problems, water ponding against the foundation increases the chances of water infiltration through any minor cracks. Improper grading on homes built on hillsides sometimes may allow the soil under the footers to wash away, on the low side or allow the soil below the footers on the low side to settle slowly causing larger and larger cracking in the foundation and structure. Possible complete failure may result over a long period of time, it the settling is not restricted by deep retaining walls and or possible mud-jacking, or hydraulic lifting of the settling foundation.

Early Backfill

Frequently seen when freshly poured concrete walls are subjected to soil pressures of back-filled dirt before the walls have developed enough strength to sustain the weight and pressures.

The Consequences- This type of cracking may be harmless if there is adequate rebar in the foundation walls and also adequate grading. Often mistaken for shrinkage cracking. Will normally stabilize.

Concrete Mixes and Placement

When filling wall forms, often 2 or 3 trucks are often needed. If one truck's load is significantly dryer than another truck's load, a line will develop between the two loads, and the accompanying stresses caused by the drying concrete will cause a crack where the two loads came together.

The Consequences- This type of cracking is often harmless; it is similar to a shrinkage crack. With a good foundation coating, and good exterior grading, this type of cracking is often harmless.

Incorrect Curing

Concrete should be allowed to dry slowly. That is part of the purpose of concrete coatings and sealants to allow the curing of concrete to proceed at a slow rate. This increases the strength significantly. Often in the rush of construction, the concrete forms are pulled off after a day or two. It is much better to allow the forms to be in place from 5 to 7 days or more to allow slower curing. If the forms are pulled off early the walls that are in direct sunlight will start to cure quickly. The walls that are in the shade will be slightly behind in the curing process, this will frequently cause shrinkage stresses that crack the concrete at the lines between the dryer and wetter concrete.

The Consequences- This could be considered a type o f shrinkage cracking. However it is one that is easily avoidable. Usually this type of cracking is hairline, or small enough that the thin edge of a dime could not be inserted into the crack. Again with proper exterior grading and good foundation coatings the risk of water intrusion through the crack is minimal, which makes this problem usually harmless. With adequate rebar in the foundation it is also structurally harmless.

Shrinkage Cracks

When walls forms are filled with fresh concrete, the more water that is added to the concrete, the wetter the concrete is, and the easier it flows. This minimizes voids and pockets around windows, vents, doors, or beam pockets but it also makes the finished concrete weaker. The dryer the concrete when pouring, the stronger it is after curing. Frequently excess water is added for the flow properties, this excess water results in greater shrinkage. So by adding extra water, the net result is extra shrinkage in a weaker concrete mix. The result is shrinkage cracking.

The Consequences- With adequate rebar and also proper grading and foundation coating the resulting shrinkage cracking, is usually harmless. However it does increase the possibility of water intrusion, if the other variables are not in order.

The Bottom Line

Of all the structural components in a home the foundation, is extremely important. Almost any other part of the home can be repaired fairly easily and relatively inexpensively. Foundation problems however often run the gamut from, harmless to potential complete failure. Have your home inspected by a professional who can recognize the difference between harmless and extremely harmful.

This free report was written, and all rights reserved by it's author Randy Farris of Farris Inspection Service.

Farris Inspection Service provides "buyer's " Pre-Purchase Inspections in addition to a '"seller's " Pre-Inspection program that provides services to buyers and sellers at very competitive rates. Call (509)- 599-0400 to schedule your inspection today.

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