Building your dream home starts with choosing the right foundation. Many people don’t realize how many different types of foundations there are. Choosing the right one is critical to the longevity of your custom home.
Choosing the Right Foundation
There are several factors that come into play when choosing the right foundation for your home. Lot elevation, the soil composition, and the neighborhood are just a few factors to consider.
It’s best to avoid lots in flood plains if possible, but we can still work with them if needed. If your lot is located in a flood plain, it’s important to raise the finished floor of the home above the flood elevation point. This could potentially limit the number of options that are available to you.
The lot’s soil is, in most cases, the deciding factor on what foundation should be used. Every home we build requires a soil report. This report recommends what type of foundation to use based on what is called the soils reactivity. If the soil is “reactive,” this means it’s prone to quite a bit of expansion and contraction. Like the elevation of the home site, this could potentially limit the type of foundation you can use.
The neighborhood also plays a deciding factor. In some neighborhoods, a certain type of foundation is required, which obviously limits the options.
Here are several types of foundations typically used in home construction:
- Block and Beam – Usually on older homes like you may find in the Houston Heights
- Conventional Reinforced Slab – Uses structural steel and sits “on-grade” meaning it sits directly on the ground
- Post-Tension Slab – One of the most common slabs found in today’s home building. It uses cables that are tensioned after the pour to help reduce cracking.
- Pier and Beam – This type of foundation provides a crawl space and is commonly found in homes built in the flood plain to raise them above flood elevation
- Structural Slab – A structural slab allows the foundation to “float” on a pier system and is used in highly expansive soils.
The majority of the homes we build use either a Post-Tension slab or a Structural Slab. Below is a more in-depth look at both:
Post-tensioned slabs use cables to run through the center of the slab. The cables are very similar to reinforced steel, but are designed by a structural engineer.
The cables are made with high-strength steel wires wound together and placed inside a plastic sleeve. At each end of the cable an anchor is embedded into the slab edge. When the cables are tightened, the wires will stretch, applying pressure to the slab. After tightening the cables any excess cable is removed and the anchor is covered with grout for corrosion protection.
There are several reasons why a post-tension slab is preferred over a conventional foundation:
- Allows construction on expansive soils
- Slabs and other structural components can be thinner
- Reduces shrinkage cracking
Structural slabs use drilled piers placed below the “active zone” of the soil to minimize heaving due to expansive soils. Reinforced beams are then poured and sit on top of the piers so the foundation essentially “floats” on the piers.
A structural slab typically outperforms any other foundation system because it allows the soil to move vertically. Without a pier system the slab is more susceptible to heaving, which can damage the foundation.
Like most things in life you get what you pay for. The structural slab is a more expensive option, but reduces the risk of foundation failure.
The foundation typically takes two to three weeks to install due to engineering inspections, city inspections, and weather.
The cost of the slab will vary widely depending on the slab type, size, pier depth, and the number of piers specified by the structural engineer. It can typically range between $5.00 and $25.00 per square foot.
Once the foundation is installed, the framing can begin.
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