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Best Foundation for a Detached Garage

The Best Foundation for a Detached Garage: A Complete Guide

A sturdy, reliable foundation is crucial when building a detached garage. The foundation you choose will determine how long your garage lasts and how well it withstands the bad conditions. 

In this article, we'll discuss the pros and cons of the most common foundation types for garages. With this guide, you'll learn the basics of each foundation type so you can make an informed decision. Let's dive in and explore your foundation options for a detached garage.

shelterlogic detached garage with roll up door and side entry on a concrete foundation

Key Takeaways

  • A concrete slab foundation is the most economical and fastest option but offers limited insulation and settling risks.
  • Perimeter foundations with footings and piers allow insulation and adjustability but have higher costs and complexity.
  • Stem wall foundations combine slabs and perimeter walls for added strength and moisture resistance.
  • Consider garage size, soil conditions, climate, budget, and aesthetics when choosing the best foundation type.

Concrete Slab Foundation

Concrete slab foundations are a simple and popular choice for garages and smaller structures like sheds. A slab foundation consists of a solid, monolithic slab of concrete that is poured directly onto the prepared ground. The slab extends out to form the footings that surround the perimeter of the building.

Slabs are often 4-6 inches thick and may include wire mesh or rebar reinforcement for added durability. This single-piece foundation lacks any joints for punctures or leaks, while the continuous footings provide stability around the edges. Concrete slab foundations perform well in areas with stable, well-draining soils.


  • Cost-effective - Concrete slabs are one of the most economical foundation options. They don’t require deep excavation or as much material as other types.
  • Fast installation - Slabs can be poured and cured relatively quickly compared to other foundations. This allows for faster completion of the garage project.
  • Durable - A properly poured concrete slab is extremely durable and can last for decades. The monolithic design resists cracking and settlement.


  • Limited insulation - Without space beneath, slabs provide minimal insulation. The garage floor will be cold in winter. So not recommended for cold areas.
  • Settling risks - Slabs may crack and settle over time if the soil underneath shifts. This can damage walls and floors.
  • Difficult to modify - Expanding or altering a simple slab foundation is very complex and costly.


Concrete slab foundations typically run $4 per square foot. A 24' x 24' detached garage would cost $4,000 - $7,000 for the slab.

Concrete Perimeter Foundation

Unlike slabs, perimeter foundations are constructed using an array of concrete footings and piers around the exterior walls. The footings provide continuous support below ground, while piers are poured footings that rise up above grade.

Once the footings and piers have cured, anchor bolts are embedded and wood or masonry walls are built upon the foundation. The interior floor is then added, often as a floating slab within the walls or over a gravel base. Perimeter foundations allow for space beneath the floor.


  • Allows insulation - The open space beneath lets you insulate utilities and floors for efficiency.
  • Prevents sagging - Individual footings and piers provide enhanced support to interior floors in large garages.
  • Adjustable - The height and spacing of footings can be adapted to suit frost depth and design.


  • Complex installation - Perimeter foundations require more excavation, materials, and labor to install.
  • Settling potential - The pier footings can shift and settle if soils are unstable, causing cracks.
  • Higher cost - The extensive materials, equipment, and labor involved drive up costs significantly.


$6 - $12 per square foot, so $14,000 - $28,000 for a 24' x 24' garage.

Concrete Stem Wall Foundation

Stem wall foundations are commonly used for detached garages and similar structures. This type combines attributes of slab and perimeter foundations for optimal stability. It consists of:

  • Continuous concrete footings around the perimeter, 12-24 inches wide
  • Short foundation walls (stems) cast atop footings, 8-12 inches wide
  • A center concrete slab that ties into the stem walls

The key benefit is a reinforced connection between the slab and the surrounding foundation walls. The slab anchors the walls and resists sideways forces, while the walls provide continuous support to prevent cracking and sagging.


  • Strength - The combined slab and stem walls offer a reinforced connection for stability.
  • Frost protection - The adjustable height of stem walls provides insulation and frost heave prevention.
  • Moisture resistance - Concrete construction prevents moisture issues in the garage interior.
  • Utility access - Some space beneath the slab allows for wiring, ductwork, or plumbing as needed.


  • Higher cost - More expensive initially than a basic slab foundation.
  • Heavy equipment - Requires machinery like backhoes for excavation and concrete delivery.


Between $8,000 - $24,000. More expensive than the slab but less than the perimeter.

Now that you understand the main detached garage foundation types, let's go over the key factors to weigh when choosing the ideal foundation for your specific garage project.

concrete foundation

Choosing the Best Garage Foundation Type

Foundations for garages tend to be simpler than for homes, but you still want to select the optimal design for your needs. Here are important considerations when deciding which foundation is right for your detached garage build:

Garage Size and Usage

The scale of your garage and how you plan to use it can help determine the necessary foundation. Larger detached garages will require extra stability to prevent settling and cracks over decades of use. If you plan to use the garage space for heavy storage, vehicles, or workshops, opt for a stronger foundation upfront.

More modest, 12' x 12' storage sheds may only need basic slab foundations. But medium to large garages for parking cars, RVs, and boats are better served by stem walls or perimeter foundations. Slab foundations alone may not offer adequate support for big garages long-term.

Soil and Climate Conditions

Knowing your soil type and frost line depth is key for proper foundation design. Loose, sandy, or marshy soils are prone to shifting and require deeper footings. Clay-based soils can potentially expand and contract a great deal with moisture changes through the seasons.

In northern climates, all foundations need to extend below the local frost line to prevent heaving during freeze-thaw cycles. Frost lines typically range from 12-48 inches. In warmer southern regions, frost depth is less crucial.

Make sure your foundation type suits both soil qualities and frost considerations in your area.

Budget Availability

Foundation costs vary widely based on the labor and materials involved. In general, concrete slab foundations are the most budget-friendly, while extensive perimeter foundations with deep footings and numerous piers cost exponentially more.

However, weaker foundations may lead to repairs down the road that ultimately cost more in the long run. Focus on finding a design within your budget that still meets structural needs. Stem wall foundations are a good middle-ground option.

Aesthetic Preferences

Perimeter and stem wall foundations leave the interior floor visible within the garage, rather than burying it under a slab. This allows you to incorporate decorative concrete finishes, pavers, tiles, or stained concrete as a finished floor.

If your garage floor will be visible, you may prefer perimeter foundations for greater design flexibility. Slab foundations permit fewer decorative options.

Once you weigh these variables, you can zero in on the ideal garage foundation type to suit your specific detached garage project. You can read our detailed guide for detached garages for more information.

duramax imperial metal garage in dark gray with roll up door and side entry swing door on a patterned concrete floor

Final Words

A quality foundation is the bedrock of any successful detached garage project. Taking the time to research and select the ideal type for your needs, climate, and budget helps prevent issues from cropping up years down the road. Extra care during design, prep work, and the build process results in a stable, long-lasting foundation.

If you're in the planning stages for a detached garage, our detached garage buyer's guide is a great next step. It covers how to choose the perfect garage type, size, location, and materials to bring your vision to life.

With the right homework and planning upfront, you can equip your detached garage with a sturdy, durable foundation primed to stand the test of time. Careful structural decisions now will keep your garage secure for generations of vehicles, tools, and treasures to come.


Can I build a garage without a foundation?

While it is possible to build a garage without a traditional foundation, it is not recommended. A solid foundation ensures the stability and longevity of the garage structure.

What is the best type of garage foundation?

The best type of garage foundation depends on various factors such as the soil conditions, local building codes, and the specific requirements of your project. It is recommended to consult with a professional to determine the most suitable foundation for your needs.

Why is the foundation important for a garage?

The foundation is the most important part of any structure, including a garage. It provides a stable base for the entire building and ensures its structural integrity.

What are some common issues that can occur with a garage foundation?

Some common issues that can occur with a garage foundation include settling, cracking, and water damage. Regular inspections and maintenance can help identify and address these issues. 

What is a concrete foundation?

A concrete foundation is a type of foundation for a garage that is constructed with concrete as the main material. It provides a strong and durable base for the garage.

What should I consider when building the garage foundation?

When building the garage foundation, you should consider factors such as the soil conditions, local building codes, the size and weight of the garage, and the overall design and purpose of the structure. Consulting with a professional can help ensure that the foundation is built correctly.

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About The Author

Andy Wu - Resident Expert

Andy Wu - Resident Expert

Andy Wu is the resident backyard products expert and hails from Atlanta, Georgia. His passion for crafting outdoor retreats began in 2003.

As a fellow homeowner, he founded Backyard Oasis to provide top-quality furnishings and equipment, collaborating with leading manufacturers.

His main focus is on sheds and generators!

In his spare time he like to hike the tallest mountains in the world and travel with his family.

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