General Home Systems: Foundation Basics

The Basics

The foundation is an essential part of understanding your home. It provides a stable, rigid base in which to support the entire home. The foundation not only supports the structure, but it also protects it from moisture and soil contact. The foundation must rest on firm soil and be protected from water entry or excessive dampness.


Basement and crawl spaces

Foundations vary in different parts of the country. In northern regions, the foundation must extend below the frost line. This is because frost causes the soil to expand, and the foundation must be below the frost line so it will not move with this warmer areas, the foundation may be a crawl space or concrete slab on grade. In coastal areas, it may be on piers or post that raise the house above potential high water.


The majority of homes in the northern climates are built on foundations that form a crawl space or full basement. A basement rests on a footing that supports the entire weight of the structure. Foundation walls can be brick, concrete block (CMU’s), poured stem walls, or similar materials. The basement floor is generally concrete and crawl spaces tend to have a dirt floor.

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Full basements are the most complicated type of foundation because of potential water problems and the pressure of the soil outside the basement walls. Crawl space and slab foundations require protection from moisture as well.


Slab foundations

“slab on grade” means that the foundation is poured directly on the soil. This type requires a footing of thicker concrete around the edges with reinforcing steel set at intervals throughout the entire footing. This provides structural strength and helps resist cracking as well as movement. This type of foundation allows plumbing, heating  and utility lines to be set in the slab. A slab foundation may be reinforced with steel cables stretched around the edge of the slab. Special hydraulic jacks stretch the cables. These post tensioned steel cables compress the concrete and provide rigidity and strength.

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Local conditions should be considered in maintaining a foundation. Slab foundations should be protected from excess moisture, thus preventing heaving and cracking. Excess moisture can make the soil swell and lock of moisture can cause the soil to shrink.


Pier, Post, Caisson Foundations

This type of foundation is used in areas where soil conditions will not support a basement or slab on grade.

Pier, post and caisson  refer to  a vertical post set in the soil down to a firm bearing soil or rock. This is generally a concrete reinforced post that supports a beam that forms the base of the house. This type of construction requires a site evaluation and engineering design.

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Protecting your basement foundation

Under normal circumstances, routine maintenance will prevent damage that requires costly repairs. Most damage to basements occur slowly over many years, don’t ignore a problem until you see a water leak or major crack. Take time to inspect your basement and it should prevent any major problems.

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Grading to Protect the Foundation

Proper grading around the house if the best protection against expensive damage. Check around the house to see if the soil slopes away from the structure. Initial construction, weather, and many other elements could erode away the original slope.  To divert surface water, the soil should pitch away from the house with a 1′ per 1 linear foot for about 6 feet beyond the foundation. This is a 6′ drop in 6 feet.

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The soil should also be 6″ below any wood siding or trim to prevent water and insect damage. If wood comes in contact with the soil, it will wick up moisture and cause rot.

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All hard surfaces  such as walks and driveways should also be pitched away from your foundation. Only a slight grade is required for these, 1/4″ per foot is adequate for hard surfaces.


Check Gutters and Downspouts

Gutter can collect amazing amounts of water and must direct it away from your foundation. Downspouts must be properly installed and working properly to avoid water damage, downspouts must be extended to the point where the natural grade of the soil moves the water away. Keep gutters clean to prevent overflow and clogging.

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Window Wells

Window wells hold soil away from the foundation windows. The window well should fit tight against the foundation wall to prevent leaks. The grade around the well should pitch away from the well so water is not directed into the well. Keep the window well free of all plant material and debris. Routine maintenance should preformed to prevent any unwanted moisture

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 Foundations Summary

Simple maintenance and frequent inspections will prevent many problems in the future. Minor problems discovered will prevent major costly problems in the future. Most moisture problems can be solved with minor observations and scheduled maintenance.