Dallas has a rather unique mix of homes with slab (also called "slab on grade") and pier and beam foundations. The majority of pier and beam foundations in the Dallas area can be found on older homes built up to the 50's and early 60's.
Pier and beam foundations are still built today, but usually only by a few custom builders and contractors. Most large production builders use only slab on grade, but most of them incorporate this with post-tension cables, which helps to increase strength and durability on Texas soil.
The soil in the Dallas area tends to be very expansive because it contains a good deal of clay, which expands and contracts depending on the amount of moisture. Hot, dry conditions in the summer can lead to foundation problems on both pier and beam and slab foundations, but are generally more common with slab.
Here are some advantages and disadvantages to both that may be worth considering. Every house is built different, so these are not the only factors to consider. As always, consult with a licensed structural engineer if you have specific questions about foundations.
PIER AND BEAM FOUNDATIONS
- Allow for easy access to service or relocate plumbing, electrical and other mechanical items provided there is adequate crawl space under the house.
- In many cases, foundation issues with pier and beam can be both less common and also less expensive to repair than slab foundations as long as it was initially designed and built properly. I have seen a few instances where an inexperienced contractor attempted to build a pier and beam foundation that failed, and the result wasn't pretty. If you plan on building a home with a pier and beam foundation, make sure the builder and their contractors have experience with pier and beam foundations and can provide references.
- Some othe remodeling projects may be easier to construct on a pier and beam. It depends on what you're doing.
- It may be easier to prevent and detect termites in pier and beam homes since they must tunnel along the concrete piers and/or wall in the crawlspace of a pier and beam foundation before reaching wood (assuming no wood is touching the ground). Check to make sure the piers have termite guards that can make it extremely difficult for termites to build tunnels up the concrete piers. And since the tunnels are normally visible along the exterior concrete walls as well, it can make them easier to detect overall. Termites can tunnel through cracks as small as 1/32 of an inch, which can make it harder to detect in slab foundations, especially if the termites tunnel through a crack directly into a part of the house that is not accessible or viewable.
- Pier and beam foundations must be vented properly to avoid excessive moisture. The moisture can sometimes lead to mold, rotting wood or a musty smell if not vented properly.
- Broken vent screens can allow bugs and rodents to get under the house, which can be a real pain (especially if a rodent happens to DIE under the house). The screens can be repaired, but rodents and bugs can easily chew through the older screens.
- Proper ventilation of pier and beam foundations can lead to colder floors in the winter, especially if there is no insulation under the floor.
- The floors can creak and move in some cases. Large items of furniture, especially items like China cabinets that contain movable, breakable pieces can rattle when someone walks or runs by. If you have young children (especially if they're HYPERACTIVE) or even large pets, it's a good idea to test the stability of the floor.
- Pier and beam foundations are still prone to movement and foundation problems. Pier and beam homes can sometimes flex vertically, which may cause areas of the floor to appear higher or lower than surrounding areas, which can cause problems with flooring, etc. Tile floors can break and become loose when pier and beam foundations flex.
- Risk of pipes bursting in hard freezes, especially if vent covers are missing. Home owners should make sure all vents are covered during sub-freezing weather.
- They are generally LESS EXPENSIVE to build than pier and beam foundations.
- The floor generally feels more SOLID than pier and beam in many cases. No shaking/vibrating of the floor means no rattling furniture when you walk by. Thus, they may also be quieter than pier and beam foundations.
- Recent improvements in technology and engineering of post tension slab foundations have led to some significant improvements in quality, design and durability, especially on Texas soil, which very expansive because of both the high clay content and the hot, dry climate. The earliest that most builders began using post tension cables in foundations was around 1999. Foundations built with post-tension cables are usually easy to spot by looking for the patch holes at the base of the foundation. Once the concrete in the foundation dries, the cables are tightened and a small amount of concrete is applied to cover the hole.
- Foundation repairs on slab foundations can be more expensive than pier and beam in many cases.
- Plumbing repairs under the house can be extremely expensive and difficult repairs because they are hard to detect and can require parts of the foundation to be jackhammered and rebuilt in order to access the damaged plumbing in some cases.
- Can have a higher tendency to crack since they only touch the top level of the soil, whereas pier and beam foundations can go deep into the soil and can even anchor on bedrock in some cases. Some engineers design slab foundations with deep grooves in the ground to help guard against movement.
- Relocating electrical and plumbing can be more expensive and difficult with a slab than with a pier and beam foundation.
- Some remodeling projects may be harder to accomplish on slab foundations.
- Termite treatment can require holes to be drilled through the floor and foundation, which may have to be repaired and could possibly damage the look of the floor, depending on the material.
There are many things to consider when deciding what foundation best fits your needs and wants. As always, consult a licensed structural engineer if you have specific questions or suspect a problem with your foundation.
Proper care of a foundation, regardless of type, is essential to avoiding expensive repairs. The Foundation Repair Association performed a study in 2000 and found that the most common reason for foundation problems was lack of maintenance. And since Texas has very expansive soil and also a hot climate, it's important to keep the area around the foundation properly irrigated. People new to the Dallas area often don't realize this and fail to maintain their foundation properly.
Most foundation experts I've spoken with recommend watering the foundation with soaker hoses for 15-30 min per day at least 3-4 times per week during the hot, dry season. It's important to keep the hoses around 18-24 inches away from the house to avoid water pooling under the foundation and causing additional problems Soaker hoses used in conjunction with electronic hose timers can be a good way to ensure your foundation receives a steady dose of evenly distributed moisture around the perimeter.
And here's a great link to an article about foundation maintenance from foundationrepair.org that covers many details about proper maintenance and care of foundations.