Until recently, crawl space foundations were the favored type of foundation, but in recent years slab foundations have become increasingly popular. While there are advantages and disadvantages to each type of foundation, the choice ultimately comes down to a combination of personal preference plus site-specific considerations regarding where the home is being built.
Slabs hold an advantage over crawl space foundations in geographic regions that are wet, but not prone to flooding. A slab can help to prevent mold growth because of the vapor barrier it provides. In addition, homes on slabs are lower to the ground, eliminating the need for stairs or ramps. The concrete also blocks insects and other pests from inhabiting the area under the home. Financially, slab installation tends to be cheaper and quicker than crawl space foundation installation. Slabs typically last around 50 years which is about the same as a properly cared for crawl space foundation, but in comparison a slab is typically stronger and more durable.
Tree roots, earthquakes and shifting soil can all damage slabs. If a concrete slab takes on damage, it can be difficult and expensive to repair. Concrete floors are additionally hard on the feet and back which can make comfort an issue. Lastly, any duct work or plumbing under a slab foundation can be difficult and expensive to access.
Crawl Space Advantages
Crawl spaces can work well in dry climates, climates prone to flooding and in sloping sites. These foundations work better in earthquake-prone locales and with soils that are more prone to sliding. In addition, crawl space foundations provide easy access to plumbing and wiring and a way to easily check for termites and other vermin. A well-insulated crawl space can provide good ventilation and offer a storage area. In addition, wood is typically the material of choice for crawl space foundations, making them more comfortable to walk on.
Crawl Space Disadvantages
Crawl spaces need a certain amount of TLC in order to properly insulate. In humid locations, poor insulation can lead to mold and rodent issues. Crawl space foundations take longer to build and can be more expensive than a slab foundation. On average, they can cost up to $25,000 in comparison to the max cost of $12,000 for a slab.
Both slab and crawl space foundations offer a range of advantages and disadvantages, but ultimately it comes down to a few key points. Where are you building the house? Will the site be on a slope, prone to shifting soil, or earthquakes? Is the region dry, humid, or prone to flooding? Is budget a consideration? Are you considering ductwork, electrical runs, or plumbing lines under the slab and, if they break, how will you repair them? All these factors need careful consideration before choosing between slab-on-grade vs crawlspace.
For Further Reading:
• “The Advantages & Disadvantages of a House Built on a Slab Vs. a Crawl Space”, an article at SfGate.com: https://homeguides.sfgate.com/advantages-disadvantages-house-built-slab-vs-crawl-space-36388.html
• “Buying a House on a Concrete Slab: Advantages and Disadvantages” at Investopedia.com: https://www.investopedia.com/articles/investing/013017/pros-and-cons-buying-house-slab.asp
• “Slab or Crawlspace”, and article at Houzz.com: https://www.houzz.com/discussions/2304109/slab-or-crawl-space