Slab vs. Crawl Space Raised Foundations – The Complete Guide

Budget is only one factor in the process of choosing a foundation. See how two of the most popular options – slabs and crawl spaces – stack up in the most important categories.

On This Page:

What is a Slab Foundation?

A slab foundation is a layer of poured concrete that averages six inches in thickness, and that professionals install directly on the ground – often including an initial layer of rock or gravel for drainage. The slab and footings are poured at the same time.

Footings are columns of concrete that extend from the slab into the ground to anchor the foundation. They typically run two feet deep into the ground. There are various footing styles and insulation options to fit the needs of the home and demands of the environment.

Slab on Grade versus Floating

Slab on grade styles – also known as monolithic – have basic footings, a rock layer for drainage and wire mesh for reinforcement. For monolithic styles, installers pour the footings and slab at once so that they form one unit. These are best for environments that don’t freeze.

Floating slabs have either no footings or detached footings that the installers pour separately from the slab itself – resulting in a surface that “floats” and is not anchored into the ground. They have a base drainage material, much like monolithic ones, and they have wire mesh and rebar reinforcements. They are best for small structures like sheds, not for residential homes.

Note: You can technically refer to floating slabs as “monolithic” in the sense that the installers pour the concrete block all at once, but the industry makes a distinction between the two because of the detached or absent footings.

Conventional Foundations

Conventional foundations – also known as T-Shaped – are styles that have more heavy-duty reinforcements and footings. The footings run deeper than the frost line and extend out further than the perimeter of the home underground and into the yard. The structure involves stem walls, which are walls that extend upward from the footings, and a concrete block poured between them.

This style works best in frost-prone areas.

Raised Slab Foundations

A raised slab foundation is a cross between a slab and a crawl space. The installer builds a base structure of footings and a perimeter wall to support the home. Then, they fill the entire crawl space with rock or soil for drainage and cap it with a layer of concrete. These types are:

• Resilient in extreme weather and flood-prone areas
• Resistant to moisture and pests
• Good option for coastal properties

What is a Crawl Space

A crawl space is an elevated foundation that uses footings and block walls around the outside to support the house. These raise the home one and a half to four feet from the ground. Cinder or concrete blocks extend from the footings and close the space off except at ventilation areas. Often, homeowners layer the blocks with brick for aesthetic purposes.

Pier & Beam vs. Slab

Pier and beam foundations are elevated styles that are more similar to crawl spaces than slab. For this style, wooden or concrete “piers” elevate and support the home a foot or more from the ground. These are great for flood-prone and earthquake-prone areas.

Raised Foundation

A raised foundation is the physical structure of the footings and walls or piers that support the home to create the crawl space. Pier and beam styles fall into this category because they elevate the home using wooden or concrete “piers.” Raised styles are warmer and more comfortable than slabs because the subfloor doesn’t make direct contact with cold, hard concrete. They’re best for easy access to piping, and in flood-prone or earthquake-prone areas.

Slab Foundation or Crawl Space – Which is Better?

Construction Cost

Most Affordable: Slab

Sloped Land

Best for Slopes: Crawl Space

Moisture Resistance

Resists Water: Slab

Energy Efficiency

Most Energy Efficient: Slab

Pest Control

Fewer Pest Problems: Slab

Cost to Seal & Maintain

Lowest Maintenance Costs: Slab

Cost of Repairs

Slab repairs cost $500 to $6,000+.

• Can be expensive because piping systems are under or inside the block and difficult to access.
• Underpinning, extensive fixes and mudjacking costs over $8,000.

Read our guide to cracked foundations for details as to the causes and remedies for such damage.

Crawl space repairs cost $150 to $3,000.

• Problems are easier to identify and address because of easy access.
• More complex repairs, such as flood damage and encapsulation system damage, can run up to $15,000.

Most Affordable Repairs: Crawl Space

Earthquake-Prone Areas

Best for Earthquake Zones: Crawl Space

Storage

Greatest Storage Allowance: Crawl Space

Resale Value & ROI

Overall, both types perform well for resale and ROI. However, they will perform differently depending on the following factors:

• Is it the best style for the environment around the home?
• Is it consistent with other homes in the neighborhood/area?
• Is the foundation low- or high-quality compared to others in the area?
• Are homebuyers in your area looking for age-in-place features?
• Are homebuyers in your area looking for energy efficient features?

Highest Return on Investment: Tie

Slab vs. Crawl Space vs. Basement

A basement is another foundation option to consider. They have significant advantages and disadvantages compared to crawl spaces and slabs.

Basements:

• More expensive at $18,000 to $30,000 during new construction and $30,000 to $70,000 for adding post-build.
• More accessible for repairs than slabs.
• More storage than crawl spaces.
• Adds usable/livable square footage.
• Best for resale value because of added square footage.
• Can garner 70% ROI when remodeled or finished, according to the
• More prone to flood damage.
• More vulnerable in earthquake-prone areas.

FAQs

What’s Better – Raised Foundation vs. Raised Slab?

A traditional elevated foundation is typically better for an average home than a raised slab. A raised slab is a type of foundation that completely blocks up the crawl space area and isn’t common throughout the United States. They are most useful in coastal regions and extremely moist environments because they don’t trap moisture. They’re also a good solution for flood-prone areas that are too moist for typical raised foundations.

Slab vs. Foundation – What Works Best for a Garage? 

Most of the time, the best foundation for a garage is a poured concrete slab with footings and walls. Garages bear a lot of weight and the full foundation needs to support that weight and resist shifting soil. In most cases, a simple slab without substantial footings or stem walls won’t be supportive enough and will be vulnerable to cracking.

What’s the Best Foundation For a House? 

The best foundation for a house depends on regional factors. Slabs, crawl spaces and basements each excel in different situations. After you’ve weighed the pros and cons, get in touch with a certified foundation professional near you. They can help you figure out how to get the most value for your investment. If you consult with a professional foundation installer, you’ll guarantee yourself a secure, efficient and regionally-appropriate foundation.

^Top

No Comments Yet

You can be the first to comment!