What Is A Slab-On-Grade Foundation?

Looking for information about slab-on-grade foundations? If so, don’t hit that back button because you’re on the right page.

In this expert guide, we’ll review slab-on-grade foundations, how they work, and why they may be the perfect choice for your home.

By the end, you’ll understand slab-on-grade foundations, their benefits, potential downsides, and how they compare to other popular foundation types.

What Is A Slab-On-Grade Foundation?

A slab-on-grade foundation is a common foundation type that involves a flat, solid concrete slab poured directly on the ground. Slab-on-grade foundations are popular because they’re cost-effective and relatively easy to build. The slab serves as both the floor of your home and its foundation, providing a sturdy base right at ground level.

Also, slab-on-grade foundations are the preferred option for residential buildings in places with mild climates with no significant risk of ground freezing.

Fun fact: Often, you may hear the terms “slab-on-grade” and “slab foundation” used interchangeably. The truth is that both refer to the same thing. So, if you hear someone talking about “slab-on-grade” or “slab foundations,” know they are talking about the same thing.

Why Is It Called Slab-On-Grade?

In the construction industry, the word “grade” refers to ground level.

When builders mention “slab-on-grade,” they mean that the concrete slab is poured right onto the prepared ground lot. There is zero space between the ground and the foundation, so the process is simple and efficient.

This lack of space between the ground and the slab is a defining feature of the foundation. The direct contact helps eliminate voids and provides a solid base for the building above it.

In sum, slab-on-grade foundations provide a simple, efficient method that reduces complexity during construction and makes maintenance easier.

What Does A Slab-On-Grade Foundation Look Like? 

• A slab-on-grade foundation is flat and solid: A typical slab-on-grade foundation has a flat and solid appearance. Some individuals describe it as a large, flat piece of concrete your structure sits upon. The flat slab is the most visible part of the foundation.
• A slab-on-grade foundation is clean and uniform: The uniformity of slab-on-grade foundations provides a polished look. You won’t see beams, piers, or crawl spaces, making slab-on-grade foundations look organized and neat. If you want a minimalistic design, slab-on-grade may be a suitable option for your project.

How Do Experts Build A Slab-On-Grade Foundation?

Preparing The Ground

The slab-on-grade installation process begins with preparing the ground. Specialists start by clearing the area of any vegetation, debris, and old structures.

After that, they level the area, ensuring it is even and free of depressions or large bumps.

Next, experts test the soil to check for moisture content and type; this is an unskippable step because it helps decide the best compaction method. If needed, experts add sand or gravel to boost stability and drainage.

Following the prep work, experts thoroughly compact the soil with heavy machinery such as compactors or rollers. This step helps increase the soil’s density and reduce the risk of settlement issues in the future.

On top of this, proper drainage systems must be installed to prevent water accumulation, which may weaken the soil structure.

Pouring The Concrete

After thorough prep work, the experts will pour the concrete all at once, creating a solid and uniform base.

Typically, the slab is around four to six inches thick.

Before pouring, the specialists will dig a grid of trenches around the perimeter and within the foundation area. These trenches act like a waffle grid, adding extra stability and support to prevent cracks.

The trenches, also called footings, are usually broader and deeper than the slab, often extending below the frost line to prevent shifting during freeze-thaw cycles.

Reinforcements To Maximize Strength

Reinforcements like wire mesh may be placed within the trenches and the slab area to further increase stability and strength.

Experts will also place steel rebar throughout the concrete to reinforce the slab.

Certain foundations use post-tension systems with a woven grid of cables for similar benefits.

What Are The Benefits Of Slab-On-Grade Foundations?

Slab-on-grade foundations offer several benefits due to their affordability and energy efficiency. Here are some of the main reasons why homeowners should consider slab-on-grade foundations:

• Cost-effective: Slab-on-grade foundations are one of the most budget-friendly options because they require fewer materials and labor than other foundation types.
• Energy efficient: Since there’s no air space beneath your structure, there is less opportunity for air to enter or escape. So, your home will be warmer in winter and cooler in summer.
• Pest-resistant: Pests such as termites and rodents often find their way into homes via basements or crawl spaces. A slab-on-grade foundation removes these entry points, making them a relatively pest-free option.
• Easy to construct: Compared to other foundation types, a slab-on-grade foundation is relatively easy to construct. That means you can move into your new home sooner.
• Minimal maintenance: Fewer components translate to fewer things that can go wrong. You won’t have to worry about frequent maintenance of a slab-on-grade foundation, saving you time and money.

Are There Any Drawbacks To A Slab-On-Grade Foundation?

Like everything, slab-on-grade foundations have their downsides. For example, they aren’t suitable for cold climates and settlement issues may be a concern.

• Issues in cooler climates: A slab-on-grade foundation isn’t ideal for colder climates with a high risk of the ground freezing due to frost heave. Frost heave happens when the soil beneath the slab freezes and expands, exerting upward pressure on the foundation.

As a result, this can lift and shift the slab, causing cracks and structural issues. Over time, the movements can compromise the home’s integrity, and you’ll have to deal with costly repairs.

In cold climates, we recommend using foundations that extend below the frost line, like crawl spaces or basements.

• Limited storage space: Crawl spaces and basements offer additional storage space, while slab foundations don’t. If you need extra room for storing belongings, this may be a deal-breaker.

• Can be expensive to repair: While initial installation costs are low, repairs can be high. This is because the home’s plumbing and wiring are usually embedded in the slab. Gaining access to them for repairs often means breaking up the slab.

• Possible settlement issues: If the soil is not compacted correctly, the foundation may settle unevenly, resulting in structural problems. Of course, this can happen with other foundation types as well.

Comparing Slab-On-Grade Foundations To Other Popular Foundation Types

Another popular option is pier and beam foundations, which involve placing piers into the ground to support the building and lift it slightly off the ground.

Pier and beam foundations offer easier access to electrical systems and plumbing, as well as enhanced ventilation — but they are usually more expensive to construct than slab-on-grade foundations.

Basement foundations provide additional storage and living space, but they are usually the most expensive to construct. On top of that, basement foundations require more maintenance than slab-on-grade, as moisture and flooding are common problems.

Crawl space foundations lift your structure off the ground, providing easy access to utilities. However, they are prone to moisture and pest problems.

Let Quality Foundation Repair Help You!

Are you worried your slab-on-grade foundation might have a problem? Quality Foundation Repair is a reliable foundation repair service in Austin, Texas, and its surrounding areas, such as Pflugerville, Georgetown, Cedar Park, and Round Rock.

We offer personalized solutions, including foundation inspections, crawl space repair, and house leveling.

For more information, call (515) 548-7891 for Austin or (512) 354-7637 for San Marcos. Contact us and get a free estimate today.