Rolled roofing is the inexpensive, fast option that turns up on garden sheds, detached garages and the occasional porch roof across the GTA. It has a place, and on the right building it does a perfectly respectable job. It also gets used where it should not be, usually on a low-slope section of a house, and that is where it tends to fail. This guide explains what the product is, how it is installed, how long it realistically lasts in an Ontario climate, and when a proper membrane or shingles are the better choice.
What Rolled Roofing Is, And What It Is Not
Traditional rolled roofing, often called mineral-surfaced roll roofing, is essentially a long, wide asphalt shingle. A base mat of fibreglass or organic felt is saturated and coated with asphalt, then surfaced with ceramic-coated granules on the exposed side. It is commonly sold in rolls roughly 36 inches wide that cover about one roofing square (100 square feet) once laps are allowed for, and it is heavy enough that a single roll is a solid carry.
The term causes confusion because several very different products arrive on site in rolls:
- Mineral-surfaced rolled roofing: a single-layer, nailed product with cemented laps. This is what most people mean, and what this article is about.
- Modified bitumen membranes: SBS or APP polymer-modified sheets installed as a two-ply system, torch-applied, heat-welded or self-adhered. Also sold in rolls, but a much more robust roofing system.
- Single-ply membranes: EPDM rubber or TPO sheets, used on flat and low-slope roofs.
- Underlayments: felt, synthetic and self-adhered ice and water membranes that go under shingles and are never meant to be the finished surface.
When a quote says “roll roofing” for a house, ask which of these it means. The difference in lifespan and performance between a nailed mineral-surfaced sheet and a two-ply modified bitumen system is large. For low-slope house roofs, the flat roofing systems page covers the membranes that do that job properly.
Where Rolled Roofing Works
Rolled roofing is at its best on small, simple, unheated buildings with enough slope to drain properly. It is light, quick to install, and inexpensive, and when it wears out it is easy to strip and replace. Good candidates include:
- Garden sheds, wood storage and small workshops that are not heated.
- Detached garages with a modest pitch where appearance is not a priority.
- Temporary coverings on outbuildings awaiting a permanent roof.
- Low-value structures where a short service life is an acceptable trade-off for low cost.
In each case, the building can tolerate the occasional small leak without damaging finished interiors, and the roof is easy to access for maintenance. That is the key: this product suits structures where failure is an inconvenience, not a ceiling repair.
| Structure | Is rolled roofing suitable? | Better option if not |
|---|---|---|
| Garden shed with moderate slope | Usually yes | Shingles if you want a matching look |
| Detached unheated garage | Often acceptable at adequate pitch | Shingles or modified bitumen for longer life |
| Attached garage under living space | Not recommended | Two-ply modified bitumen or single-ply membrane |
| Low-slope rear addition or kitchen extension | No | Two-ply modified bitumen, EPDM or TPO |
| Porch roof tied into the house wall | Rarely, flashings become weak points | Modified bitumen or shingles, depending on pitch |
| Dormer roof on a main house | No | Membrane for low slope, shingles above minimum pitch |
Installation Methods: Exposed Nail And Concealed Nail
How rolled roofing is fastened decides a lot about how long it lasts. Manufacturers publish minimum slopes and lap requirements for each method on the wrapper and in their application instructions, and those limits should be followed.
Exposed-nail method
Sheets run parallel to the eave, each lapping the one below. The nails go through the lap, along the bottom edge of each upper sheet, and the lap is sealed with asphalt lap cement. The nail heads stay visible and exposed to weather. It is the fastest and cheapest way to apply roll roofing, and the least durable: every nail head is a potential leak, and the lap seals rely entirely on cement that ages and hardens.
Concealed-nail method
Starter strips are installed along the eaves and rakes first. Each sheet is then nailed along its top edge, where the next sheet will cover it, and the overlapping lap is cemented down without any nails passing through the exposed surface. This keeps fasteners out of the weather and generally allows use on somewhat lower slopes than the exposed-nail method, within the manufacturer’s limits. Where roll roofing is the right call for a building, this is generally the better method.
Double-coverage (selvage) roll
Some products are made with a wide unsurfaced selvage edge, so each course overlaps the previous one by about half its width. That gives two layers across the whole roof and better tolerance for low slopes. It costs more in material and labour than single-coverage sheets but still falls well short of a properly installed two-ply membrane.
| Method | How it is fastened | Strengths | Weaknesses |
|---|---|---|---|
| Exposed nail | Nails through visible laps, cemented seams | Fast, low cost | Exposed nail heads, short life, wind lifts laps |
| Concealed nail | Nails covered by the next course, cemented laps | Fasteners protected, cleaner look | Laps still depend on cement |
| Double coverage (selvage) | Wide overlap gives two layers | Better on lower slopes | More material, still a nailed single-sheet system |
| Two-ply modified bitumen (for comparison) | Fused or self-adhered base and cap sheets | Continuous waterproof membrane | Higher cost, specialised installation |
Deck preparation and cold weather
Like any roof, rolled roofing needs a solid, dry, clean deck with no nail pops or high edges, a metal drip edge at the eaves and rakes, and proper underlayment where the manufacturer calls for it. Temperature matters too. Cold roll goods crack if unrolled stiff, so crews cut sheets to length and let them relax flat in mild weather before fastening. Lap cement also sets slowly in the cold. As autumn nights cool, the practical installation window for this product narrows; work done on a chilly October afternoon needs more care than the same job in early autumn.
Fasteners and laps are where shortcuts show. Galvanized roofing nails long enough to penetrate the deck properly, set at the spacing printed in the instructions, hold far better than whatever is left in the truck. Lap widths and the amount of cement are specified by the manufacturer for each method, and skimping on either is the most common reason a young roll roof opens up after its first winter. On sheds, the deck itself is often thin or old board; replacing soft sections before the new roof goes on avoids nails that never grip.
How Long Rolled Roofing Lasts
Expect a short service life. On a sheltered shed with a decent slope, rolled roofing installed with concealed nails may give a number of years before the granules wear off and the laps open. On a sun-exposed low slope, or with exposed nails, it can be considerably shorter. Manufacturers’ published expectations and warranty terms for these products are modest compared with shingles, and that is a fair reflection of what a single nailed sheet can do through Ontario freeze-thaw cycles and summer heat.
The typical failure pattern is predictable:
- Granules wear away in high-traffic or high-exposure areas, exposing asphalt to UV.
- Laps harden and pull apart as the cement ages, and wind lifts the edges.
- Exposed nails back out with seasonal movement, opening small holes.
- The sheet cracks along stress lines, especially near ridges, rakes and over deck joints.
- Water reaches the deck, which then softens and rots.
For a shed, this is a manageable cycle: tear off and replace every so often. For a house, it means repeated leaks into finished space, which is why it is a poor choice there.
Repairing or replacing an existing roll roof
Many GTA garages already have an old roll roof, and owners ask whether it can be patched. Small lifted laps can sometimes be re-cemented and nailed by a roofer, which may buy a season or two on an outbuilding. Once the granules are gone over large areas, the sheet is cracking, or the deck feels soft underfoot to the roofer, patching only delays the inevitable. At that point the honest recommendation is to strip it to the deck, replace damaged boards, and decide whether to reinstall the same product or step up to a membrane or shingles. Layering a new sheet over an old one is a poor idea: it hides rot, traps moisture and makes the next tear-off heavier and more expensive.
Why It Is Not A Substitute For A Proper Membrane On A House
The appeal is easy to understand. A homeowner has a low-slope rear addition, the shingles there keep leaking, and rolled roofing looks like a cheap fix that “suits low slopes”. The problem is that a nailed single sheet with cemented laps is not a waterproof membrane. On a nearly flat roof, water lingers on the surface, and any lap or nail hole becomes a leak path. Snow sitting on the roof through the winter and the meltwater it releases test those seams continually.
Low-slope house roofs need a system designed to hold water out even when it sits briefly on the surface. In Ontario that usually means a two-ply modified bitumen system, an EPDM membrane or a TPO membrane, installed with proper flashings at walls and edges. Shingles are another option on sections that meet the manufacturer’s minimum slope, using the extra underlayment the building code and manufacturer require for lower pitches. Confirm current code requirements with your municipality for your specific roof.
Rolled roofing also turns up as a patch over failing shingles on a main roof. That covers the symptom briefly and makes the eventual repair harder, because the area must be stripped completely. If you have a recurring leak, a proper roof repair visit should find the cause rather than cover it.
Rolled Roofing Compared With Modified Bitumen And Shingles
The table below compares the options most often considered for low-slope and outbuilding roofs. Costs are broad installed estimates for typical GTA jobs and vary with access, size, deck condition and detailing.
| Option | Best suited to | Service life expectations | Typical installed cost (estimate) |
|---|---|---|---|
| Rolled roofing, exposed nail | Sheds, temporary covers | Short | Often $3 to $6 per sq ft |
| Rolled roofing, concealed nail or double coverage | Sheds, unheated garages | Short to moderate | Often $4 to $7 per sq ft |
| Two-ply modified bitumen | Low-slope and flat house roofs | Much longer when well detailed | Often $10 to $18 per sq ft |
| Architectural shingles | Roofs above the minimum shingle slope | Long, per manufacturer terms | Often $5 to $10 per sq ft |
Small jobs carry a minimum charge for setup, disposal and travel, so a tiny shed roof often costs more per square foot than the table suggests.
When Modified Bitumen Or Shingles Fit Better
A few simple questions usually decide it:
- Is there living space below? If yes, choose a proper membrane or shingles, not rolled roofing.
- What is the pitch? Very low slopes need a membrane. Moderate slopes above the shingle minimum can take shingles, which also match the main house.
- Does it tie into a wall? Wall junctions need proper base and counter flashings, which membranes handle far better.
- How long will you own it? If replacing the roof every handful of years is fine, a roll product on a shed may be the smart budget choice.
- Does appearance matter? A detached garage visible from the street often looks better in shingles that match the house.
On a garage or outbuilding that sits next to the house, matching the main roof sometimes makes sense when both are due. When the house is due for a roof replacement, a garage or shed roof can often be done in the same visit.
Signs Your Low-Slope Roof Needs Attention
Whatever is on a low roof, the early signs of trouble usually show up inside the building or at the downspouts:
- Water stains or damp patches on a ceiling below a low-slope section.
- Dripping inside a garage or shed after rain.
- Granules or bits of black sheet washing out of the downspouts.
- A musty smell in an addition or garage, especially as autumn rain sets in.
Do not climb up to check. Low roofs feel safer than they are, especially when autumn leaves are wet. Book a professional inspection and let the roofer assess the surface, seams and flashings.
How long does rolled roofing last?
Can I use roll roofing on a flat roof?
Is rolled roofing OK for a shed?
Can it go over old shingles?
Can it be installed in cold weather?
Is modified bitumen the same thing?
Choosing Rolled Roofing For A Shed, Garage Or Addition?
If you are deciding what to put on a shed, a garage or a low-slope part of your home, The Roof Technician can look at the structure, the pitch and what sits below it, and recommend the system that will actually hold up. Have a general question first? Our FAQ page may help.
Call us today at (416) 826-0040 or request a free estimate.
Advising on sheds, garages and low-slope additions across Toronto and the GTA.