Planning a shed, pergola, garage slab or coop

Outbuildings look like small projects, and small buildings still have the same needs as large ones: a flat, well-drained base, a frame that is square, a roof that sheds water, and a permit in many places. The size often decides what you need to do. A small shed on a gravel pad is simple; a garage slab is a serious pour.

This planner follows the order of work from the rules and the site to the finish. You can skip steps that do not apply to a kit shed or a pergola.

Step 1: Check the rules and choose the site

Many places require a permit above a certain size (often 100 to 200 square feet) and set minimum distances from the property lines and other buildings. Choose a level, well-drained spot, away from trees and with room to work. Call 811 before you dig.

Step 2: Build the foundation

A small shed sits on a compacted gravel pad with a border, or on concrete blocks. A garage, workshop or large shed is better on a concrete slab, poured over a compacted base with a vapor barrier. Check the shed maker's foundation instructions, since some warranties require one.

Step 3: Frame the walls and floor

Wall framing is studs at 16 or 24 inches on center between top and bottom plates, with doubled studs at openings. Frame the wall flat on the floor and tip it up. The sizes depend on the span and the loads, so follow your plans or a span table.

Step 4: Sheathe, roof and side it

Plywood or OSB sheathing stiffens the frame and gives the siding something to fix to. Work out the number of sheets from the area. The roof needs underlayment, flashing and a covering such as shingles or metal panels, and the siding goes over house wrap.

Step 5: A pergola, a coop or other structures

A pergola is posts, beams, rafters and slats on footings, and the spans matter more than the looks. A chicken coop is about floor area per bird, ventilation, nest boxes and predator-proof openings. Both follow the same logic of foundation, frame and cover.

Before you start

• The permit and setback rules for the size of building you plan.
• Call 811 before you dig.
• A level, well-drained spot with room for the delivery and the work.
• The weather window for the foundation and the roof.
• Power, if you want lights or tools inside: that needs a licensed electrician.

Mistakes that cost people money

• Building on soft, wet or sloping ground without a proper base.
• A foundation that is not square or level, which makes every later step harder.
• No gap or flashing at the base, so the walls rot from the bottom.
• Skipping the permit and being asked to take it down.
• Roofing without underlayment or flashing at the edges and openings.

Frequently asked questions