What you need before you start

A shed roof is simpler than a house roof because sheds are usually small and often have just one slope. Before you cut anything, you need to know three things: the width of your shed, how much overhang you want (usually 12 to 18 inches on each side), and what pitch — the angle — you want the roof to have. A 4:12 pitch (the roof rises 4 inches for every 12 inches it runs horizontally) works well for most sheds and sheds water reliably without being steep enough to be awkward to work on.

Gather your materials before you start framing. You will need lumber for rafters (usually 2x6 or 2x8 depending on span and snow load in your area), a ridge board, collar ties, plywood or OSB for sheathing, roofing felt, and shingles. You will also need nails, screws, a circular saw, a level, a tape measure, a speed square (to mark rafter angles), a hammer or drill, and safety equipment including a harness if you are working at height.

Key Takeaways

  • Measure your shed width and decide on pitch before you cut any rafters — mistakes here mean cutting new lumber.
  • Rafters are cut with a bird's mouth notch where they sit on the wall plate, and a plumb cut at the peak where they meet the ridge board.
  • Sheathing goes on before roofing felt and shingles, and it must be nailed every 6 inches along rafters and every 12 inches in the field.
  • Shingles overlap in rows from bottom to top, with each row offset so seams do not line up vertically.
  • Flashing at the edges and any penetrations (like a vent pipe) prevents water from running under the shingles.

Cutting and installing rafters

Rafters are the angled boards that form the frame of your roof. For a straightforward shed, you will have two rafters per pair — one on each side of the ridge board. Use a speed square to mark the cuts: the plumb cut (the angle at the top where the rafter meets the ridge board) and the bird's mouth (the notch where the rafter sits on the wall plate). The bird's mouth is crucial — it lets the rafter rest flat on the wall instead of perching on a corner.

Cut your first rafter as a template, then test-fit it before cutting the rest. Once you know the angle is right, cut all your rafters to match. Space them 16 or 24 inches apart (center to center) depending on your local snow load — your building department can tell you what is required in your area. Nail or bolt each rafter to the ridge board with at least three fasteners per connection, and find the bottom end to the wall plate with three nails minimum.

Add collar ties — horizontal boards that connect rafters on opposite sides — about one-third of the way down from the peak. These prevent the rafters from spreading apart under load. For a small shed, one collar tie per rafter pair is usually enough.

Sheathing the roof frame

Once the frame is solid, cover it with plywood or OSB sheathing. Start at the bottom edge and work your way up, staggering the seams so they do not all line up in the same column. Leave a small gap (about 1/8 inch) between sheets to allow for expansion. Nail sheathing every 6 inches along rafters and every 12 inches in the middle of the sheet.

The sheathing must be continuous — no gaps or soft spots — because it carries the weight of snow and wind and provides a solid base for shingles. If you find a rafter that is warped or sagging, fix it before you sheath, because sheathing will not straighten it out.

Installing roofing felt and flashing

Roofing felt (also called tar paper) goes on top of the sheathing and under the shingles. It acts as a secondary water barrier if shingles are damaged or wind-driven rain gets under them. Roll it out horizontally from the bottom edge upward, overlapping each row by 4 to 6 inches. Nail it down with roofing nails or staples every 12 inches or so — it does not need to be perfect, just held in place.

Install flashing at the edges where water could run under the shingles. At the eaves (bottom edge), use drip edge flashing, which hangs over the gutter and directs water into it. At the gable ends (the sloped sides), use gable flashing or straightforward fold the felt over the edge. If your shed has a vent pipe or chimney, install flashing around it before you shingle — this is the most common place leaks start.

Laying shingles from bottom to top

Shingles go on in rows from the bottom of the roof upward. Start with a starter course — a row of shingles with the tabs cut off — along the bottom edge. This gives the first row of full shingles something to sit on and creates a watertight overlap. Nail each shingle with four nails, placed about 5/8 inch above the tab cutouts so the nails are covered by the next row.

Each row of shingles overlaps the one below it by about 5 inches. Offset the seams — the vertical lines where shingle edges meet — so they do not line up from row to row. Most shingles have a pattern built in; follow it. The offset usually means starting the second row with a half-shingle, the third row with a full shingle, and so on.

Work your way up the roof, nailing as you go. When you reach the peak, cut the shingles to fit and nail them down. The very top row can be sealed with roofing cement under the tabs to keep wind from lifting them.

Finishing the peak and edges

At the peak, the shingles from both sides meet. Cut the shingles so they overlap slightly, and seal the seam with roofing cement. Some roofers use ridge cap shingles — special shingles made for the peak — which look neater and last longer than field shingles bent over the peak.

At the gable ends, trim the shingles flush with the edge of the roof or fold them over the edge flashing. Make sure no felt or sheathing is exposed — exposed edges let water in. If you have a gutter, make sure the shingles overhang it by about 1/2 inch so water drips into the gutter, not behind it.

Common mistakes and how to avoid them

The most common mistake is not securing the ridge board well enough. It carries the weight of both sides of the roof, so it must be bolted or heavily nailed to a post or beam underneath. A ridge board that sags will cause shingles to buckle and leak.

The second is rushing the sheathing. Soft spots, gaps, or uneven nailing will show up as bumps in the shingles and as places where water can pool. Take time to nail it properly.

The third is skipping flashing. Flashing is not glamorous, but it is where most leaks start. Do not assume shingles alone will keep water out at edges and penetrations — they will not.

Frequently Asked Questions

What pitch should my shed roof be?

A 4:12 pitch (4 inches of rise per 12 inches of run) is standard for sheds and works well in most climates. In areas with heavy snow, a steeper pitch like 6:12 or 8:12 sheds snow faster. In dry climates, a flatter pitch like 2:12 is acceptable. Check your local building code — some areas have minimum pitch requirements.

How far should the roof overhang the walls?

Twelve to 18 inches is typical. More overhang protects the walls from rain but makes the roof harder to frame and more exposed to wind. Less overhang is cheaper but offers less protection. Check your local code — some areas have minimum overhang requirements for weather protection.

Can I use metal roofing instead of shingles?

Yes. Metal roofing is more durable and sheds snow better, but it is more expensive and requires different fastening and flashing techniques. The framing and sheathing are the same; the difference is in what goes on top. Metal roofing is a good choice if you want the shed to last 40+ years with minimal maintenance.

Do I need a building permit for a shed roof?

Most jurisdictions require a permit for any structure over a certain size (usually 100 to 200 square feet). A permit means an inspector will check that the framing is adequate for your local snow and wind loads. It costs money and takes time, but it protects you if something goes wrong and ensures the roof will not fail under weather stress.

What should I do if I find a leak after the roof is done?

Leaks usually come from flashing, not shingles. Find where water is dripping inside, then look at the roof above that spot. Check for gaps in flashing, missing shingles, or shingles that have lifted. Small leaks can be sealed with roofing cement; larger problems may need a section of shingles removed and replaced.