Constructing a Shed Base on Your Lawn

Installing a sturdy shed base is one of the most important steps when putting up a new storage shed in your backyard. Rushing through this foundation stage can lead to a poorly built shed that is uneven, difficult to assemble, and vulnerable to moisture damage over time. Building your shed on a proper base distributes the structure's weight evenly, keeps floors level, and prevents sinking, cracking and shifting over the years of use. For homeowners with grassy yards, constructing a shed base directly on the lawn can be a convenient and affordable option.

Compared to poured concrete and gravel foundations, a framed wooden base built right on top of grass allows you to get your shed up quickly without heavy equipment or expensive materials. But there are still some key considerations when planning a shed base on your yard's grassy surface. Follow the steps in this guide to correctly build a shed foundation directly on your lawn.

Choose the Right Spot on the Lawn

Not all areas of your yard may be suitable for supporting a shed base and structure. Before building, evaluate your entire lawn to determine the best location.

• Pick a flat, level section of the yard without dips or bumps.
• Avoid low, wet spots where puddles form when it rains.
• Select a site with well-draining soil - not pure clay or sand.
• Stay at least 6 feet from property lines and utilities.
• Consider convenience for unloading materials and using the shed.
• Account for door clearance - don't have the doors blocked by trees or structures.

Also have any underground utilities marked before you dig or build to avoid damage. Call 811 for utility locating services.

Avoid Slopes for Stability

Sloped areas often seem like convenient spots to tuck a shed, but even slight hills can cause problems. Slopes put extra pressure on shed walls and floors, leading to cracking and instability over time.

For maximum strength, always build your shed base on flat, level ground. Use a long level on the site to confirm it is free of any pitch or slope.

Remove the Grass and Soil

Once your shed site is chosen, prep the area by removing the grass and digging down roughly 6 inches. First take away the sod using a flat shovel or sod cutter. Stack the strips of sod off to the side.

Next, loosen and shovel out the topsoil until you reach the harder packed ground underneath. Discard rocks, roots and debris as you dig. The goal is to create a flat, packed earth base for the foundation.

Add a Gravel Sub-Base

For better stability, some sources recommend adding a 2-4 inch layer of gravel before compacting the soil. The gravel helps prevent settling and provides additional drainage under the shed base.

Add Fill Dirt and Compact It

To make up for the 6 inches of soil that was removed, bring in compactable fill dirt . Spread it out across the shed site, raking smooth. Then use a hand tamper to compress the soil, packing it down tightly.

Compacting is crucial for stability and preventing settling issues. Make sure to tamp until the fill dirt is densely compressed . Add more dirt and tamp again if needed to account for lowering from compacting.

Prevent Future Sinking

No matter how well the ground is compacted initially, some minor settling of the shed's base can happen over time. To allow for adjustment, some builders leave a 1/8" gap between the shed floor panels and the foundation frame.

Assemble the Base Frame

Construct a rectangular frame around the perimeter of the shed site using pressure-treated 2x6 or 2x8 lumber. Cut the boards to length then fasten together at the corners with 3-inch deck screws.

Space floor joists 16 inches on center across the inside of the frame and secure them with joist hangers and screws. You can use 2x6s or 2x8s for the joists depending on shed size and weight.

Add Support Blocks

For additional reinforcement, glue and screw treated 4x4 support blocks under the joists every 4-5 feet around the frame's perimeter. This helps prevent bowing under the shed's weight.

Add Gravel and Level the Frame

Once the frame is complete, spread a 4-6 inch layer of compact gravel across the middle, leaving the outer edges clear. Shovel and rake it flat, then tamp down with the hand tamper.

Check for level as you go. Place a 4-foot level on the joists and use shims under low spots. Adjust and add gravel until the frame is perfectly level.

Tip: Add Foundation Blocks

For extra support under shed walls, place concrete foundation blocks under the rim joists where the wall studs will sit.

Add Deck Boards or Plywood

With your gravel shed base prepped and level, put down 5/4 pressure-treated decking boards across the joists, screwing them into place. Use at least 3 screws per board.

3/4" CDX plywood sheeting can also work for the floor. Cut sheets to fit between the joists and fasten securely with screws every 6 inches.

Allow Space for Expansion

Wood decking and plywood will expand and contract with changes in moisture and temperature. Leave a 1/8-1/4" gap between boards and the foundation frame to allow room for expansion.

Install Landscape Fabric

To prevent grass and weeds from growing up in the gravel base, unroll a landscape fabric across the gravel, letting it drape over the edges. Secure the fabric with gravel or landscape staples.

The fabric will block vegetation while still allowing drainage through the gravel. Leave overlapped seams unsecured for moisture to escape.

An Alternative Weed Barrier

Some builders use 6mil plastic sheeting instead of fabric for the weed barrier. Plastic also works but may not allow as much water permeability as landscape fabric.

Set and Anchor the Shed

With the platform frame, flooring and fabric in place, you're ready to set the shed onto the new base. Get helpers since sheds can be heavy and awkward. Lift and lower carefully onto the frame.

Before securing the shed, check that it's centered and square on the base. Finally, anchor the shed to the floor frame using the manufacturer's corner brackets, hurricane ties or foundation clips.

Seal Gaps for Weather Protection

After securing the shed, seal any gaps between the floor panels and foundation frame with weatherstripping or silicone caulk. This helps prevent moisture intrusion, insects and rodents.

Once your shed base on grass is built, be sure to do periodic maintenance to maximize its longevity:

• Re-tamp the ground if any settling occurs under the shed.
• Re-level the shed right away if it becomes unleveled.
• Control weed growth by re-applying landscape fabric as needed.
• Watch for signs of moisture damage inside the shed.
• Re-adjust or shim the base if gaps appear between the floor and frame.