Best Season for Roof Replacement: When New Shingles Can Seal

The best season for roof replacement is the warm stretch from late spring to early fall. The reason is not comfort for the crew. It’s the thin strip of sealant on every new shingle, which needs heat from the sun to bond. A roof put on in warm weather seals in its first sunny days. A roof put on in the cold can sit unsealed until spring. That said, the calendar is only half the answer. The other half is whether your old roof can wait.

The part that decides the season

Every asphalt shingle has a strip of sealant across it. It sits just above the cut-outs, where the shingle above lies on top of it. Owens Corning describes it as a factory-applied strip of thermally activated sealant. Direct sun activates it, and the shingle bonds to the course below.

Until that happens, the nails do all the work. IKO puts it plainly: before the sun activates the sealant, only the roofing nails hold the shingles in place. A strong wind in that window can lift an edge and fold it back. You might not see it from the driveway, but you’ll find the shingle on the lawn after the next storm.

How fast the strip seals is not the same on every slope. Owens Corning lists the factors: location, roof slope, which way the roof faces the sun, and the average daily temperature during and after the job. The Asphalt Roofing Manufacturers Association, ARMA, says the same about slope, orientation and the sun the shingles get. So a south slope in Stayner can seal days before the north slope of the same house.

Cold weather: where the line sits

IKO says asphalt shingles start to stiffen when the temperature stays below 10 degrees Celsius. Roofers prefer a shingle that bends, and a stiff one is harder to lay flat.

Owens Corning’s cold weather bulletin draws its line lower, at air and surface temperatures at or below 4°C. Below that line, its instructions add steps:

• A gap at the joints. Field shingles go on with a small gap at each end joint, so they do not buckle when they expand in warmer weather.
• Hand sealing at the edges. Every shingle along the whole roof perimeter is hand sealed with dabs of asphalt roof cement. The bulletin says this protects against wind uplift when it is too cold for the strip to activate.
• Extra care in handling. The bulletin asks for extra care with shingles below that line.

ARMA warns that cold shingles may crack when handled, and adds two more steps. Store the shingles indoors so they stay warm until they go on. Consider open metal valleys, because woven valleys make the crew bend shingles that may crack.

A cold roof is not a bad roof. It takes more steps to protect it until it seals. If you’re quoted for November, ask how the edges will be handled.

Spring: wait for the ice to leave

Spring is the start of the good stretch, but the first warm week is not always the first good roofing day. Lake-effect snow off Georgian Bay can sit on a shaded slope well after the lawn is bare. Under it, the eaves may still carry ice.

ARMA warns about nearly invisible ice or frost on a roof deck in cold months, and it advises waiting until the surface is free of ice and frost. That matters on a tear-off. When the old shingles come off, the wooden deck is open, and the crew is standing on it.

Spring also shows you what the winter did. Look at the ceiling under the roof after the snow melts. A brown ring there can trace back to a fault somewhere else on the roof, such as the eaves where ice dams sat all winter. On a new shingle roof, 705 Roofing puts ice and water shield at the eaves and in the valleys, and the deck is inspected once the old shingles are off.

Summer: the shingles seal fast

In warm weather, the sealant strip has what it needs. IKO notes that shingles are more flexible when it’s warmer. A roof put on in July has weeks of sun ahead of it before the first cold snap.

There are trade-offs. On the hottest days, soft shingles scuff more easily underfoot, and the crew works around the heat. IKO says some roofers start early and take a break at midday. If you want a summer date, call us early in the year.

Fall: the deadline is the first cold weeks, not the first snow

Fall is the season most people pick, and it works if the roof goes on while the days are still warm. A shingle put on in September has warm, sunny days to bond before the November wind off the bay.

The risk is a roof that goes on in the last weeks before the cold. The Owens Corning bulletin says shingles put on in cold weather may not seal until warmer temperatures come back. On a north slope, that can mean a whole winter of nails only, under snow load and wind. That is the case for the hand sealing at the edges described above.

Cottage owners have one more thing to think about. A cottage that sits empty from Thanksgiving on has nobody there to see a lifted shingle or a drip after the first storm. If the cottage roof needs replacing, plan it for a time when someone is around for the weeks after.

Winter: possible, but not on every day

A roof can be replaced in winter. IKO says roofers in colder parts of North America have adapted to working through it: they hand seal shingles and keep them warm before they go on. It also says many roofers slow down over winter.

On price, IKO says roofers who work in winter may build the cost of the extra steps into their quotes. Some may offer an off-season discount instead. Ask what is included, not just what the number is.

The bigger limit is the day itself. Our roof replacement page covers which cold, icy or wet days are not safe for a tear-off. A crew can’t leave a deck open to a snow squall halfway through the job.

When the season should not decide it

The season matters most when you have a choice. Some roofs do not give you one:

• Water inside. A wet stain on the ceiling, or a drip in the attic after rain, will not wait for June. Book a roof repair to stop the leak first. The full replacement can then go into the right season.
• Soft spots in the deck. Go up into the attic with a flashlight after a rain. Shine it along the plywood near the eaves and around the chimney. Dark, wet wood means water is getting through now.
• Shingles on the ground. One or two after a windstorm can be repaired. Many, from more than one slope, point to a roof near its end.

If none of these apply, you have time. Use it to get the inspection and the written quote done while the old roof is still dry, so the job can go on the calendar in the warm stretch.

From the ground, you can check one more thing with a pair of binoculars. Look at the shingle edges along the bottom row. Edges that curl up, or a row that looks lifted, can mean the shingles are no longer bonded and the wind has a grip on them.

What changes once the roof is open

Whatever the season, the deck is the one thing nobody can see before tear-off. 705 Roofing strips the roof down to the wooden deck, and any soft or rotten plywood is replaced before the new roof goes on. Our page on roof plywood replacement explains how that part of the job works. More plywood means more time with the deck open, and that’s one more reason to book the job for dry, warm weeks.

If you have big icicles every winter, look at the attic too. Warm air leaking into the attic melts the snow on the roof, and the water refreezes at the cold eaves. Our attic insulation and ventilation page covers the vents that work with a new roof.

Questions about timing a roof replacement

What is the best month to replace a roof?

There is no single month. Pick a date when the days are warm and the roof has sunny weeks ahead of it before the cold comes. Around Georgian Bay, we’d aim for late spring through early fall.

Can a roof be replaced in winter?

Yes, on the right days. In cold weather, Owens Corning’s instructions call for hand sealing every shingle along the roof perimeter. ARMA advises warm storage and waiting until the deck is free of ice and frost.

Will a roof put on in late fall leak before it seals?

The risk the shingle makers name is wind, because only the nails hold the shingle until the strip bonds. Owens Corning’s answer is hand sealing every shingle along the roof perimeter.

Is roof replacement cheaper in the off-season?

Not always. IKO says roofers who work in winter may price in the extra steps, and some offer a discount to keep busy. Compare what each quote includes.

The one thing we cannot see from here

We can tell you here what each season does to a new shingle. It cannot tell you what your deck looks like under the old roof, or whether the valleys have been leaking for a year. A roof visit settles that, and it is the best way to decide whether your roof waits for spring or needs work now.

We work in Wasaga Beach, Collingwood, Stayner, Barrie, Midland and Simcoe County.