Not sure if you have a slab on grade foundation or a raised foundation? Perhaps you were filling out a form on a foundation repair website and they asked what kind of foundation you have – and, maybe, you weren’t entirely certain. There’s no such thing as a stupid question or dumb Google inquiry. This article outlines the difference between slab on grade and raised foundations.
Dalinghaus Construction Inc. has over 100 years of combined foundation repair experience. We’ve serviced thousands of foundations – slab on grade and raised.
This article covers the definition of a slab on grade foundation and a raised foundation, as well as their various pros and cons. By the end of this article, you will know what kind of foundation you have and how to mark any future foundation repair paperwork. You will also learn the primary types of repairs required for each type of foundation.
What is a Slab on Grade Foundation?
A slab on grade foundation, also referred to as a slab foundation, is 4-6 inches thick and is anchored via footings (underground concrete columns) that support the foundation.
Generally, these foundation footings are 18-inches to 2-feet deep, outlining the perimeter of the foundation. Slab foundations are often poured in one-fell-swoop over tied rebar or mesh with a base layer of sand to ensure proper drainage (with a vapor barrier).
Slab on grade foundations are perfect for warm, wet climates where there is no freeze-thaw cycle.
Post-tensioned foundations are a type of slab on grade foundation. The post-tensioned foundation system relies on extreme stress and utilizes steel cables (in lieu of rebar or steel mesh) pulled taut after the concrete slab has cured.
While your typical grade slab foundation is 4 to 6 inches thick, the concrete slab for post-tensioned foundations is generally 8 inches thick and utilizes 3000 PSI concrete.
Common types of slab on grade repairs:
- Carbon fiber staple/wrap crack repair
- Underpinning (push pier & helical pier
Slab on Grade Foundation Pros:
- Quickly poured/cured
- There is no crawl space for mold or critters, where moth and dust doth corrupt
- The foundation could be your hipster floor if you wanted to have it stained or scored
- They keep your house cool in the summer
Slab on Grade Foundation Cons:
- No crawl space = no storage
- Cracks (there are 5 Characteristics of Concrete Cracks to watch out for)
- Don’t hold up well in colder climates without glycol tubing
- If sewage and/or drainpipes need maintenance, this requires cutting into the foundation
What is a Raised Foundation?
A raised foundation is an elevated foundation that creates a crawl space between the home’s subfloor and the earth’s grade. Generally speaking, these crawl spaces have between 18-inches to 4-feet of clearance. Stem wall foundations, pier-and-beam foundations, and cripple wall foundations are perfect examples of raised foundations.
Raised foundations work well in cold climates. Moisture mitigation through irrigation is an important aspect of keeping raised foundations free of water damage and wood rot.
Common types of raised foundation repairs:
- Carbon fiber staple/wrap repair (for stem walls and footings)
- Underpinning (push pier & helical pier)
- Post and pad replacement
- Seismic retrofitting
Raised Foundation Pros:
- Protection from flooding, environmental hazards
- Easy access to wiring, plumbing, and other systems
- A significantly cheaper option than a basement foundation
- Aesthetically makes your home look taller
- Offers some storage
Raised Foundation Cons:
- Collects significant moisture
- Requires you to lose weight for DIY plumbing and electrical work
- Susceptible to mold, mildew, and rot
- Attracts spiders and snakes
Choose the Right Foundation Repair Contractor
In this article, you learned the definition of a slab on grade foundation and a raised foundation, in addition to understanding their pros and cons.
Dalinghaus Construction Inc. has serviced thousands of foundations in Southern California and Arizona. Again, there’s no such thing as a stupid question. We’re happy we were able to sum up the differences between slab on grade and raised foundations.
If you’re ready to begin receiving bids on your foundation repair project, be sure to read our article Why Hire a Licensed, Insured, & Bonded Foundation Repair Contractor to ensure you only hire qualified foundation repair contractors.
If you live in SoCal or Arizona and would like to book a free foundation inspection through Dalinghaus Construction Inc., click on the button below –