Types of Home Foundations and Common Problems
Without a stable foundation, a home can experience a variety of serious issues, including cracks in drywall, sticking and poorly operating doors and windows, sloping floors, sinking foundations, water intrusion, cracks in the foundation, and moisture damage. Foundation problems can be some of the most difficult and costly problems to repair.
The primary purpose of all foundations is to transfer the load of the home, all of the belongings, and occupants, to the soil under the foundation. Foundations with walls like basements and crawlspaces must resist the lateral loads of soil against the foundation walls. Foundations must be able to also resist environmental factors like snow, wind, and earthquakes to name a few. Foundations must be able to perform these tasks without moving, cracking, deteriorating, and admitting water over the entire life of the house.
Soil Can Help or Hurt a Foundation
When building a home from the ground up, the ground should be analyzed first. A commonly overlooked part of building a home is the soil that surrounds it. The soil under the home is the device that supports and keeps the home in place. Good soil will prevent the home from sinking and or sliding down the street. Some soil types, such as sand and gravel, can be good for supporting a house. Loose fill can't support heavy leads, for example. Where clay-rich soil can expand and contract with changes in moisture levels, which can cause the foundation to settle or walls to crack due to pressure. Bad soil can be found just about anywhere, but it's the most common in the midwest and western parts of the United States.
Ideally, the soil under a foundation is undisturbed and permeable to encourage good drainage, with the stability and strength to provide proper support. Now with major developments being created, it is becoming common that soil is being trucked in to create a level area for the foundation, or to replace the bad soil. If fill soil is required, the fill should be properly compacted so that it acts like undisturbed soil.
The most common types of foundations are:
- Concrete Slab
Slab foundations can be found just about everywhere, and are the predominant foundation in some markets. These foundations are ideal for level ground or ground with a minimal slope. The primary advantage of concrete slab foundations is that they are usually the least expensive to build. Disadvantages include difficult access to plumbing and electrical components that are installed in or under the concrete. This can make remodeling and repair disruptive and expensive. Another disadvantage is the lack of additional storage space that a basement foundation affords. Living in the northeast we won't experience many houses like this but they are still worth mentioning.
Houses built in the Northeast are very likely to have basement foundations. Basements are not suitable for areas where the water table is high, and they're expensive to build where bedrock must be removed by blasting or excavation.
Basement foundations are more expensive to build than concrete slabs and crawlspace foundations, and they can be prone to water intrusion. (we would recommend installing a perimeter drainage system to counteract this) But the basement foundation comes with some significant advantages. The basement provides a large amount of bonus space--to store personal belonging and locate large items like the furnace and water heater. If you want to expand your living space, finishing part of the basement will be less expensive than building an addition to the home. And if you want to remodel the main level of the home, a basement offers easy access to plumbing, wiring, and ductwork for remodeling-related alterations.
These foundations can be found just about everywhere, and are the predominant foundation in some markets. A crawl space can be the main foundation for the entire house. It can also be easily added to an existing basement foundation --a popular option when adding on to a house with a basement.
Like a basement foundation, a crawl space provides access to structural, plumbing, electrical, and HVAC components for easier remodeling and repair. The primary disadvantage of crawlspace foundations is that they are prone to water intrusion and condensation, and mold and wood rot that results from excess moisture. (To prevent this we could encapsulate the crawlspace and add a perimeter drainage system and a dehumidifier)
Common Foundation Problems
Water causes more damage to foundations and houses than any other issue. Keeping water, including liquid water and moisture in the air, out of the house is the best thing you can do to avoid foundation problems and problems elsewhere in the house.
Keeping water away from other components can cure up to ninety percent of foundation water problems. As a general rule, the soil should shape away from the foundation of the foundation at least six inches vertically within the first ten feet horizontally. Hard surfaces, such as driveways, should slope away from the foundation at least 1/4 inch per foot. Roof runoff should be channeled away from the foundation by a system of gutters and downspouts. As a general rule, downspouts should discharge at least five feet from the foundation.
Cracks in Foundation
Cracks in your foundation should be treated as serious business. Hairline cracks are cracks that are less than 1/4 inch in width. Hairline cracks aren't severe but do require you to monitor them. If you do have a crack(s) in your basement that are larger than 1/4 inch there is a lot to learn from how the crack looks and where it is located that could reveal the cause of it.
Consider calling us when a crack becomes larger than a 1/4 inch or when it:
- Presents out-of-plane displacement (one part of the crack sticks out beyond the adjacent part of the crack)
- Is allow water into the basement/crawlspace
- The crack looks like stairs (masonry block foundation)
- Horizontal crack that continues to get larger