Yes, with the scope planned for the season. Cold changes how adhesives cure, how membrane handles and how much roof can be opened in a day, so the assembly and the sequence are chosen accordingly. What stops work is not the calendar but active precipitation, wind and a substrate that cannot be made dry.
What does cold actually do to the materials?
Every component behaves differently below freezing, and a scope written for July does not simply transfer to January.
- Adhesives and primers have minimum application temperatures. Solvent and water-based products cure slowly or not at all in the cold, and some cannot be used below a stated threshold at all.
- Self-adhered membranes depend on pressure-sensitive adhesive that loses tack as temperature drops. In cold conditions they need warmed material, a primed substrate, and firm rolling, or they are replaced by another attachment method.
- Single-ply sheets stiffen and hold roll memory, so they need relaxing before they will lie flat, and heat welding on TPO or PVC requires the equipment reset for ambient conditions and every seam probed.
- SBS modified bitumen is the more forgiving material in the cold, particularly torch-applied, which is one reason it is so common on Ontario winter projects. Rolls still have to be stored warm and handled carefully, because cold bitumen cracks when it is flexed.
- Sealants and mastics skin over and cure slowly, and applying them to a cold or frosted surface produces a bond that lets go in the spring.
The practical rule is that the substrate has to be dry, frost-free and above the product's stated minimum, not merely the air.
Which assemblies suit a winter installation?
The specification is where a winter project is won or lost. Torch-applied or hot-applied SBS modified bitumen works well in the cold, and mechanically fastened assemblies work in almost any temperature because the attachment does not depend on chemistry. Adhered assemblies are the ones that need scrutiny, since the adhesive dictates the working window.
Where a building will not tolerate hot work, the answer is usually a mechanically fastened system rather than an adhered one, with the fastener pattern designed for the wind uplift demand of the roof zone and increased density at perimeters and corners. On some buildings a hybrid is used: mechanically fastened base layers with a torch-applied cap.
Insulation, cover board and vapour control layers are all installable in cold weather provided they go down dry and are not left open to snow. What cannot be done in winter is drying out a wet assembly, so anything found saturated comes out rather than being left to dry.
How do snow and ice change the site?
They add a whole workstream before roofing begins. Snow has to come off the work area each morning, cleared with plastic tools and a residual layer left rather than a metal blade in contact with membrane. Ice is removed by melting or by hand, never by chipping down to the surface. Frost forms overnight on an exposed deck and on new insulation, and it has to be removed before anything is bonded to it.
Access and safety tighten as well. A frozen membrane and a snow-dusted parapet edge is a serious fall hazard, so guardrails, travel restraint or fall arrest at every open edge and controlled access zones matter more, not less, under the Occupational Health and Safety Act and the working-at-heights requirements enforced by the Ministry of Labour, Immigration, Training and Skills Development. Snow-covered skylights are treated as holes in the roof, because that is what they are.
Daylight is the other constraint. Short days shrink the productive window, which is one of the reasons a winter project is sequenced into smaller daily sections.
How is the building kept dry through the work?
The same way it is in summer, only with less margin. The crew opens only what can be closed in and made watertight the same day, with a temporary water cut-off at every stop point, so nothing is ever left open overnight. In winter those daily sections are deliberately smaller, because a squall arriving mid-afternoon is not a forecast event and a partly open deck over occupied space is not recoverable.
Drains are kept clear and functioning through the work, which in winter means checking that they are not frozen below the strainer. Meltwater has to be able to leave the roof, particularly at the tie-in between new work and the existing membrane, where a dam of ice will push water under the temporary seal.
Materials are stored warm and brought up in the quantity that will be used, because a pallet of membrane left on the roof overnight is a pallet of cold, stiff, hard-to-handle membrane in the morning.
What actually stops the work?
Weather events, not the season. Work stops for active precipitation, for wind that makes handling sheet material or operating a crane unsafe, and for conditions where the substrate cannot be brought to a dry, frost-free state. Those days are lost and they have to be allowed for in the schedule rather than treated as surprises.
Sustained deep cold restricts which products can be used but rarely halts a properly specified project on its own. Where a forecast turns partway through a day, the crew stops opening new area and closes what is open, which is why the daily section size is set conservatively at the start.
When does waiting for spring make more sense?
Often, if the roof can wait. A roof that is dry, drained and not leaking is better replaced in a season with longer days, no snow clearing and the full range of products available. A winter project carries more weather days, more preparation per unit area and more constraint on the assembly.
Waiting stops making sense when the roof is already letting water in, when insulation is saturated and continuing to deteriorate, when a wind event has taken membrane or cap flashing off, or when the building is putting product, tenants or production at risk every time it rains. In those cases the choice is not summer versus winter. It is a controlled winter replacement versus repeated emergency work through to spring, with interior damage accumulating in between.
A middle path exists too. Stabilise now with a properly built temporary repair through our emergency roof repair service, use the winter to scope, tender and order material, and put the crew on the roof early in the season. Our post on choosing the season for commercial roofing compares the seasons directly.
How should a winter project be scoped?
Honestly, and with the season written into the documents. A winter scope should name the assembly and attachment method chosen for cold installation, state the daily tie-in requirement, allow for snow clearing and frost removal as work rather than as goodwill, and carry weather days in the schedule. It should also carry unit prices for wet insulation and deck replacement, because a winter tear-off frequently uncovers more saturation than a summer one.
The condition assessment behind it matters even more in winter, since the roof is harder to read under snow. Where a flat roof inspection was done in the autumn, the scope rests on evidence. Where it was not, expect the tear-off to reveal more than the drawing shows.
How we plan and run a full replacement, in any season, is set out on our flat roof replacement and commercial roof installation and replacement pages. To have a winter roof assessed and scoped, call 416-456-0777.