Slab and crawl space are the most popular foundation choices, but each one has key features that can make all the difference in the construction of your home
Spending all your time deciding between a contemporary or cottage-style home? Before building your dream home, it’s also important to choose the right foundation type.
There are many types of foundations. While homeowners who live in moist areas often pick slab foundations, crawl spaces are better for homes built on shifting soil. Be sure to understand the features, pros, and cons of these two popular foundation types so you can make the best decision when you have a new home built.
What’s the Difference Between a Slab Foundation and a Crawl Space Foundation?
A slab foundation is a raised slab that the house is built on top of. In comparison, a crawl space foundation has exterior concrete walls (and sometimes interior support walls) that elevate the house 18 inches or more above grade, creating an accessible area beneath the house used for plumbing and wiring.
What Are the Pros and Cons of a Slab Foundation vs. a Crawl Space Foundation?
There are some advantages and disadvantages to each type of foundation. Here’s a detailed list of pros and cons to help you decide which foundation is best for your home.
Pros of a Slab Foundation
Better for moist climates as it prevents mold growth in the home
Less subjectable to insects and pests
Faster to construct
Sturdy and strong since slabs are 24 inches thick
Requires less maintenance
More energy efficient since it insulates the flooring of your house by preventing cold air from flowing underneath, unlike crawl space foundations
Durable—it can last for 50 years or more
Comfortable to walk on
Cons of a Slab Foundation
Cracks easily with shifting soil
Floods more easily
Tree roots can damage it. Homeowners are advised not to plant trees too close to the foundation—no less than 50 feet away
Repairs can be more expensive
No basement storage
Plumbing fixtures and electrical wiring are embedded in the concrete, and they’re not flexible if you want to do any future renovations
Pros of a Crawl Space Foundation
Works well on sloped sites
Preferable in areas prone to earthquakes
Better with shifting soil
Recommended for dry climates
More suitable for flood-prone areas
Easy access for plumbing, electric, and HVAC maintenance
Easy access for termite inspection
Can be used as a storage area
Flexible remodeling options
Durable if well executed
Raises the home aesthetics and the value of the house
Cons of a Crawl Space Foundation
More expensive than a slab foundation
Construction takes longer than a slab foundation
Crawl space foundations must be ventilated to reduce accumulated moisture
Cold is transferred through the floor joists and subflooring to the living areas above and sometimes can freeze pipes if not well insulated
Requires more TLC to prevent mold, rodents, and insect infestations
Likely to require structural repairs
Less energy efficient
Floors are not strong enough for heavy pieces of furniture
What Is the Difference in Cost Between a Slab Foundation and a Crawl Space Foundation?
A concrete foundation will cost between $4 to $14 per square foot with an average of $5,200 to $13,000. Crawl space foundations can cost $5 to $16 per square foot or $7,000 to $21,000 on average. This makes the cost of a crawl space foundation double the cost of a slab foundation for the same home.
Which Is Better: Slab Foundation or Crawl Space Foundation?
As much as it can be tempting to go with the most affordable option, there are many factors that could determine the best foundation for your home.
Sloped or Low-Grade Lot
A crawl space foundation is a better choice for both sloped or low-grade lots since there is limited digging for walls. Plus, the foundation can be designed to level the home’s flooring. However, in the case of slab foundations, they fit flat lots.
For a damp climate, a concrete slab foundation is better, but if your house rests on a flood-prone area or sees a lot of rain, a crawl space is ideal. A crawl space foundation that is well-protected is less likely to get flooded, unlike a slab foundation, which can transfer water through the slab.
When groundwater freezes the soil, it can expand and thaw, causing the foundation to crack or shift. This is why a crawl space foundation is more suitable to stabilize and drain excess groundwater in the foundation if you live in freezing conditions.
If you're considering building a home, you should always consult a local foundation contractor to determine the best and safest foundation for your home.