Building a Shed Foundation (2024 Guide)
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A sturdy foundation helps your backyard shed withstand the elements without sagging, shifting, or collapsing over time. Though many homeowners outsource this project to a professional, it is possible to do it yourself. Our helpful step-by-step guide will walk you through the different shed foundation options, how to build one yourself, and when to hire a pro.
How To Prepare
Consider the preparation process before you begin. You’re not ready for a hardware store trip until you know what you need to get started.
- Apply for building permits: Check with your local permit office to see if you need one to begin construction. You may also have to get a city or county inspection to approve the final foundation and/or shed.
- Determine shed location: Consider your local climate and where on the property you’ll install your shed foundation.
- Climate: Wet or snowy regions may require a deeper foundation for stability or a layer of gravel for better drainage. You should also consider the extra weight of snow and the natural flow of water.
- Soil type: Your soil type can affect what you need to build. For example, clay expands and shrinks according to rainfall. You’ll need a proper base to support a concrete slab or blocks on top of clay-heavy soil.
- Utility lines: Hitting a utility line can be dangerous and costly, so call 811 to have your county mark underground utility lines before you start digging. You may have to choose a skid foundation if utility lines run through your work area.
- Frost line: Colder areas have deeper frost lines. Check with local building codes to determine how far you must dig when installing posts.
- Landscaping: Keep permanent landscaping in mind when mapping out where you want your shed to go. You want 3–4 feet of clearance between your shed and existing structures, including fences and trees.
- Consider shed size and type: Smaller sheds may not need a foundation. You also won’t want a permanent foundation if you eventually plan on moving the shed to another location. Instead, consider one that you can easily deconstruct.
How To Choose a Type of Shed Foundation
There are many things homeowners should consider before choosing a foundation type. Beyond budget, consider:
When building a shed, you have several foundation types to choose from. Some are more budget-friendly than others. Your choices may also be limited by the climate and slope of your site—or by your level of skill. Use the table below to compare the different types and narrow down your options:
| Type | Cost Range per Square Foot | Sloped Sites? | Frost-Proof? |
|---|---|---|---|
|
Concrete blocks |
$15–$30 |
Some slope is OK |
No |
|
Concrete piers |
$6–$12 |
Yes |
Yes |
|
Concrete slab/ concrete pad/ concrete foundation with footers |
$5–$25 |
Yes |
Yes |
|
Deck blocks |
$12–$25 |
Some slope is OK |
No |
|
Floating concrete slab on-grade foundation |
$4–$8 |
Yes |
Yes, but may require additional work |
|
Gravel pad/gravel base/gravel foundation |
$800–$2,000 total |
Yes |
Yes, but may require additional work |
|
Pavers |
$8–$50 |
No |
No |
|
Permeable concrete pavers |
$10–$30 |
No |
No |
|
Post and beam |
$6–$12 |
Yes |
Yes, but may require additional work |
|
Screw piles |
$15–$30 |
Yes |
Yes |
|
Skid foundation |
Varies—cost of pressure-treated lumber depends on location and seller |
No |
No |
*Cost data via Angi, Fixr, HomeGuide, and Lowe’s.
How To Build a Shed Foundation
Building a post and beam foundation is one of the easiest and most DIY-friendly options for sheds. This type of foundation is also durable and works well in areas with uneven ground or frost concerns. Our step-by-step guide will walk you through the process, from marking out the site to installing the floor frame.
Step 1: Lay Out the Shed Area
The first step is to choose a location for your shed. Ideally, you’ll want a spot close to being level that doesn’t collect water when it rains. You need at least 3 feet of clearance if you’re building near a fence, or at least 4 feet if your shed is larger than 160 square feet.
Use mason lines and batter boards to lay out the exact dimensions of your future shed.
Step 2: Square the Area
You need to measure 3 feet along one mason line and 4 feet along a corresponding line to ensure your area is perfectly square. The distance between the two should be 5 feet if your work area is square. You’ll need to adjust your string if it’s not. Do this with every corner. Remember that adjusting a line on one side will affect your other corners.
Step 3: Install Posts
Installing posts may be the hardest part if you have rocky soil. Otherwise, it should be fairly simple. Either way, we recommend investing in a post-hole digger rather than relying on a shovel.
You can rent a gas-powered post-hole digger, also called a power auger, from many hardware stores. This will make the process much faster than using a manual post-hole digger. While the manual tool is easier to handle by yourself, it will take significantly longer to dig the holes. A power auger can be more challenging or even impossible to handle alone, but the work will go much faster.
The holes should be 4 feet apart and 12 inches below the frost line. Pour at least 4 inches of crushed stone before pouring the concrete at the bottom of each post hole. Place your post on top of it and ensure it’s square. Once the first layer of concrete has cured, pour additional concrete to secure the post in place. Add temporary bracing to the post as the second layer of concrete cures.
Step 4: Trim Posts and Attach Post Brace Brackets
It’s difficult to dig post holes that are perfectly level with one another, so even them out at the top instead. Determine how high you want your shed floor to be and mark one post to use as a guide for the others. Trim the tops with a saw as needed. Next, attach post brace brackets and install 4-by-4 runners.
Step 5: Build Floor Frame
Construct a floor frame on top of your 4-by-4 runners using 2-by-4 planks. Measure each side twice to guarantee the frame is square. Then secure the frame to each 4-by-4 one corner at a time. Have somebody hold the frame as you screw down each corner if possible. This makes the process faster while ensuring a more accurate final product.
Step 6: Lay Down Plywood
Once you’ve completed your floor frame, you can lay down plywood directly on top. Ensure it’s flush with the frame before nailing it down. Don’t move on until you double-check that the foundation is level. If it is, your foundation is complete, and you can begin framing your shed.
When you’re ready to move onto building the shed itself, check out the video below where general contractor Tom Silva demonstrates how to frame the walls of a shed. We also have videos that cover other steps in the process, such as installing shingles and running underground power to a shed.
How To Hire a Professional
Even experienced DIYers with detailed how-to guides sometimes need a hand with projects like shed foundations. If leveling ground, pouring concrete, or handling heavy materials feels daunting, hiring a pro is a smart choice.
You can expect to spend between $50 and $100 an hour in labor costs alone if you hire a professional. The amount of time it takes depends on your chosen type and size of foundation, so make sure to ask for a time estimate when getting a quote.
Ensure you get at least three references and check that the contractor is properly licensed and insured before choosing a professional. It’s also important that the contractor has everything they need to complete the job. They may know how to do the work but may not have the necessary resources, such as specialized equipment or a helper, to make the leveling process easier.
Our Conclusion
With the right knowledge and some basic tools, building a shed foundation is well within the reach of most homeowners. Start by researching local building codes and factoring in climate and soil conditions. Then consider your needs and budget. It may not be necessary to build the sturdiest foundation possible. Though large sheds typically involve pouring and leveling concrete, smaller sheds may just need to be raised slightly off the ground. Finally, don’t hesitate to hire a professional if you’re short on time or feel the project is beyond your skillset.
FAQ About Building a Shed Foundation
What is the best foundation for a shed?
The best foundation for a shed depends on several factors, including your budget, climate, soil conditions, and the size of your shed. However, if you don’t mind a bit of work and have the budget, a concrete slab is the best permanent foundation for many homeowners in terms of stability and durability.
What is the cheapest way to build a shed foundation?
The cheapest way to build a shed foundation is often a gravel pad. It requires minimal materials and can be a DIY-friendly project. If your shed is very small and the ground is mostly level, you might even get away with using just pavers or concrete blocks placed directly on the ground.
What are the benefits of a shed foundation?
The benefits of a shed foundation include stability, longevity, and functionality. A solid foundation helps protect your shed from the elements and keeps it structurally sound. It also ensures a level floor so that doors open smoothly and items can be stored more securely.
What is the frost line?
A frost line is the depth to which the ground freezes during winter—which varies by location. The soil above this line will expand and contract as temperatures fluctuate, putting pressure on shallow foundations and the structures above. Building a shed foundation below the frost line makes it more stable.
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