How to Roof a Shed: Choosing the Covering and Laying It Start to Finish
Match the roofing to the slope, get the drip edge and underlayment right, and a shed roof is a manageable weekend job.
- Intermediate
- 1 to 2 days
- Updated
The short answer
To roof a shed, check the deck is solid, pick a covering that suits the slope (asphalt shingles from about 4/12, metal panels from about 3/12 for exposed fastener panels, roll roofing from 2/12 with double coverage), install drip edge at the eaves, underlayment, then the covering from the bottom up, and finish the ridge or top edge. Work in dry weather, on a low, safe roof.
A shed roof is a good small project because it is low, short and simple: usually one or two planes with few details. The work is the same as on a house, just on a smaller scale, and the same rules apply. The covering has to suit the slope, the water has to be carried over each joint by overlap, and the edges need protection.
The key choice is the covering, and it depends on the slope. Many sheds have a low pitch, often between 2/12 and 4/12, and that rules some materials in or out. Standard asphalt shingles want a steeper slope than a flat shed gives, see how to shingle a low slope roof. Metal panels work well on sheds, and roll roofing is a low-cost option for very low slopes.
This guide walks through a typical job. If your shed is nearly flat, below 2/12, none of these is right, and you need a membrane system such as EPDM or a torch-on or TPO roof.
Tools
- Tape measure
- Chalk line
- Hook blade utility knife
- Roofing hammer or coil nailer
- Tin snips
- Drill with screw bit (for metal)
- Caulking gun
- Extension or step ladder, tied off
Materials
- Drip edge for eaves and rakes
- Synthetic underlayment or roofing felt
- Roofing: asphalt shingles, metal panels or roll roofing
- Roofing nails or metal roofing screws with washers
- Starter strip and ridge cap, or metal ridge trim
- Roofing cement or sealant for exposed fasteners
- Replacement sheathing if the deck is weak
Safety first
- Even a low shed roof can cause a serious fall. WorkSafeBC requires fall protection where a fall could be 3 metres (about 10 feet) or more, and any roof where a fall could cause serious injury calls for care. Keep the roof dry and use a tied-off ladder.
- Do not work on a wet roof, in the wind or in frost. Wet shed roofing is slippery, particularly metal and roll roofing.
- Check overhead before moving a ladder. Sheds are often close to fences, trees and power lines.
- Cut metal edges are sharp. Wear gloves and eye protection.
Step by Step
Step 1: Measure the roof and work out the slope
Slope decides what you can use. Measure the rise over a 12 inch run with a level and tape, for example 3 inches of rise in 12 inches is 3/12. Measure each plane's length and width, multiply for the area, and add about 10 percent for waste. See how to measure a roof and calculate squares for the method.
Step 2: Choose the covering that suits the slope
Common minimums are around 2/12 for asphalt shingles with special low-slope underlayment and installation, 3/12 for exposed fastener metal panels, and for roll roofing the BC Building Code floors of 3/12 for single coverage and 2/12 for 19 inch selvage double coverage. Every product also has its own limit, so use the higher of the code and the manufacturer's instructions.
Other factors are budget, appearance and life. Metal lasts longest, shingles are familiar and easy to repair, and roll roofing is cheapest but shortest lived.
Tip: If you are unsure, asking the supplier for the minimum slope of the exact product takes a minute and prevents a leaky roof.
Step 3: Check and repair the deck
Walk the deck carefully, pressing with a screwdriver. Soft, dark or crumbling wood needs replacing. The deck should be clean, dry and flat, since any bumps show through roll roofing and shingles. Countersink any proud nails. See how to inspect a roof deck.
Step 4: Install drip edge at the eaves
At the eave, the drip edge goes on the bare deck, under the underlayment. At the rakes, it goes over the underlayment. This ensures water flows over each layer. See how to install drip edge. Overlap pieces by about 2 inches.
Step 5: Roll out the underlayment
Start at the bottom and work up, so each upper layer laps over the lower one. On low slopes, more overlap is needed. Follow the product instructions, and consider a self-adhered membrane at the eave and for slopes below about 4/12. Keep the underlayment flat, with no wrinkles. See how to install synthetic underlayment.
Step 6: Install the roofing from the bottom up
For shingles, start with a starter strip and lay courses in order, see how to install starter strip shingles. For metal panels, start at the end and in the direction the manufacturer specifies, overlapping each panel as directed, using screws with washers in the flat of the panel or as specified. For roll roofing, see how to install roll roofing.
Keep everything square to the eave. A chalk line every few courses helps correct any drift.
Step 7: Finish the rakes, ridge or top edge
On a gable shed, finish with ridge cap over both sides. On a single-slope shed, the high edge needs a cap flashing or a trim piece that laps over the roofing and keeps water out. Seal any exposed fasteners with roofing sealant. Overhang the rakes by about 3/4 to 1 inch so water drips clear.
Step 8: Check the details and clean up
Walk around the shed and look at it from several angles. Check that every fastener is flush or sealed, that edges are tight, and that no nails are lying around for tires and feet. Add a gutter or keep the eave clear of splash if you want to protect the shed walls.
Shed Roof Slope Limits at a Glance
- Asphalt shingles: commonly 2/12 minimum with special installation, and 4/12 or more for standard installation. Confirm with the manufacturer.
- Exposed fastener metal panels: commonly 3/12 or more, and some products allow less with extra sealing, per the maker.
- Roll roofing: 2/12 or more with 19 inch selvage double coverage, and 3/12 or more for single coverage, which are the BC Building Code minimums.
- Membranes (EPDM, TPO, torch-on): for nearly flat roofs, and needing slight slope for drainage.
Shed Roof Ventilation and Condensation
An unventilated shed under a metal roof can drip with condensation on cool, humid Fraser Valley mornings. A synthetic underlayment, a vented ridge or a few soffit and gable vents reduce the moisture. If you store tools or wood in the shed, it is worth planning airflow, see attic ventilation basics.
Common Mistakes
- Choosing a covering the slope cannot use. Shingles on a near flat roof leak. Check the minimum slope for the product.
- Skipping drip edge. Water runs back under the edge and rots the fascia and deck.
- Laying underlayment the wrong way. The upper layer must lap over the lower one, or water runs behind it.
- Not repairing the deck first. Soft boards and bumps show through and fail early.
- Exposed fasteners with no sealant. Nail and screw heads on the surface leak over time.
- Working on a wet roof. Even a low shed roof is a fall risk when slippery.
When to Call a Professional
Call a roofer if the shed roof is nearly flat, if the framing is sagging or rotted, if the shed is tall or attached to a building, or if you are not comfortable with the work at height. Attached lean-to roofs also need proper flashing to the wall, see how to install step flashing.
Also check with your municipality if the shed is large, because permits and setbacks may apply, and a reroof usually does not need one but a structural change might.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Roof Repair service or the towns we cover.
How to Roof a Shed: Questions
What is the best roofing for a shed?
It depends on the slope and your budget. Asphalt shingles suit slopes of about 4/12 and steeper, metal panels last longest and suit slopes of about 3/12 and up, and roll roofing is the cheapest choice for very low slopes. Always check the minimum slope for the specific product you buy.
Can you put shingles on a low-slope shed roof?
Only above the minimum slope for the shingle. Standard shingles want at least about 4/12. Some manufacturers allow 2/12 to 4/12 with special underlayment and installation. Below 2/12, shingles will leak, and a metal panel made for low slopes or a membrane is the better choice. Follow the manufacturer's low-slope instructions exactly.
Do I need underlayment on a shed roof?
Yes for shingles and metal. Underlayment is a second line of defence if water gets past the covering, and metal roofs also need it to manage condensation. Synthetic underlayment is easy to work with on a small roof. Roll roofing is often laid directly on a clean deck, but check the manufacturer's instructions.
Do I need drip edge on a shed?
It is strongly recommended. Drip edge sends water clear of the fascia and the top of the wall, protects the deck edge, and is cheap. It goes under the underlayment at the eaves and over it at the rakes. Without it, water runs back under the edge and rots the wood.
How long does a shed roof take to install?
A small shed usually takes one to two days for a careful DIYer, including tear-off if needed, deck repair, drip edge, underlayment and the covering. Weather matters. Work only in dry conditions, and plan to cover the deck before the end of the working day so rain does not catch a bare roof.
Related Guides
All Specialty Roofing guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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