How to Build Sheds | A Practical Step-By-Step Sequence

Building a shed takes planning, a foundation, and a framed shell, but the exact rules vary by city.

For the full breakdown, see our best Built Sheds guide.

Whether you need extra storage or a workspace, the process for how to build sheds comes down to one thing: preparation. Get the local rules and foundation right, and the rest is a logical sequence of framing, roofing, and finishing. Here’s the order that works, plus the building-code traps that stop projects cold.

Step 1: Check Permits and Local Code Before You Buy Lumber

Your city or county sets the rules on shed size, height, and placement, and skipping this step is the most expensive mistake you can make. A permit can be required even for small structures, so a quick call to your local building department saves you from a forced teardown later.

Seattle’s rules show how specific these codes get. The city requires no permit only if your shed is 120 square feet or less, single-story, not attached to another structure, and used for storage or similar unoccupied purposes. New York City allows backyard sheds up to 120 square feet without permits, but caps height at 7 feet 6 inches and requires flammable-material sheds to sit at least 3 feet from the property line. Many other U.S. cities fall in the same general range, requiring permits for sheds larger than 120–200 square feet.

Before you draft plans, confirm your local setbacks, height limits, lot coverage, and whether your foundation type affects permit status. Seattle, for instance, exempts only sheds on a simple concrete slab, pier blocks, or soil — a foundation choice that directly impacts compliance.

Step 2: Set the Foundation and Build a Square Floor

Your foundation depends on regulations, soil type, and whether the ground is level, so match it to your site conditions rather than copying a neighbor’s setup. Deck piers with support beams running lengthwise, then floor joists and plywood sheets on top, form a common and reliable base.

When you frame the floor, square matters more than anything else. Check the outer frame by measuring the diagonals — if they match, the frame is square. Internal joists typically sit at 400mm or 600mm centres with galvanized joist hangers, and the deck gets plywood sheeting on top. Get this step right, because every wall you build afterward depends on a true floor.

Step 3: Frame Walls, Then the Roof

Build each wall flat on the floor deck, starting with the two longest walls. Use 2×4 or 2×6 top and bottom plates, then stand the walls and secure them before adding the roof structure. This on-deck method keeps everything aligned and is far easier than trying to frame walls in place.

For the roof, assemble the frame before placing it. Secure rafters to a ridge beam and the top plate, and for wider apex roofs, add collar ties to prevent the roof from spreading under load. Larger spans may also need purlins for extra support. The roof decking is typically 11mm or 18mm OSB3 or exterior-grade plywood, chosen to match your finish and span design.

Step 4: Weatherproof, Finish, and Install the Door

Once the shell is up, the sequence is: install the door, add siding and trim, then finish the roof with your chosen material. Flash window and door rough openings before installing them — this weather barrier is what prevents leaks and rot over the shed’s life.

For roof finishes, common options include bitumen shingles, EPDM rubber for flat or low-slope roofs, or corrugated bitumen, metal, or plastic sheets. A breathable roofing membrane or mineral-surfaced felt goes underneath, with horizontal laps of at least 150mm and side laps of 100mm. Follow the manufacturer’s instructions for overlaps and fixings.

If you are buying a pre-built unit instead of framing from scratch, a solid product roundup can help you compare options before you commit.

FAQs

What size shed avoids a building permit?

Many cities exempt sheds up to 120 square feet from permit requirements, but this threshold varies — some use 200 square feet, and height and setback rules still apply. Always confirm with your local building department, since foundation type and whether the shed is attached to another structure can also change the requirement.

What is the cheapest shed foundation?

Pier blocks or a simple concrete slab are the most economical options for small sheds, and some codes explicitly permit these types. Pier blocks work well on level, well-draining soil, while a slab suits heavier structures. Your local frost depth and soil conditions determine which one is durable for your area.

Can I build a shed without a permit if it’s under 120 square feet?

Not automatically — it depends on your city’s specific code. Some jurisdictions exempt sheds up to 120 or 200 square feet, but others require permits regardless of size, especially in environmentally sensitive areas or if the shed sits close to property lines. Verify your local rules before building to avoid fines.