Why Do Roofers Sometimes Hand-Seal Asphalt Shingles in Cold Weather?
Asphalt shingles do not rely only on nails.
They also use factory-applied sealant designed to help adjacent shingles bond together.
Under suitable warm conditions, heat helps that sealing process occur.
Ontario does not always provide those conditions.
GAF identifies cold-weather, fall, and winter installation among the situations where manual hand-sealing may be required.
That does not mean shingles cannot be installed in cooler weather.
It means installation technique has to respond to the conditions.
What Does “Hand-Sealing” Mean?
Hand-sealing involves applying the manufacturer-specified amount of approved roofing cement beneath the shingles in designated locations and pressing the shingles into place.
The purpose is to create secure bonding when normal heat activation may be delayed.
GAF’s technical guidance also emphasizes using only the specified amount because excessive roofing cement can cause problems such as staining or blistering.
Why Doesn’t the Factory Sealant Always Activate Immediately?
Self-sealing shingles depend on sufficient:
- Heat
- Sun exposure
- Roof orientation
- Surface temperature
GAF notes that sealing time can vary based on roof slope, orientation, and sun exposure.
A roof installed during warmer weather may seal relatively quickly.
A shaded roof installed during a cold Ontario period can behave differently.
Cold Shingles Are Also Stiffer
Temperature affects handling.
GAF warns that shingles can become brittle in very cold conditions and require more careful handling to avoid:
- Cracking
- Breaking
- Distortion
This is another reason cold-weather roofing should not be treated like a July installation performed with gloves on.
Hand-Sealing Is Also Used in Other Situations
Manufacturer instructions may call for hand-sealing:
- During certain repairs
- On extremely steep roofs
- In high-wind situations
- After installing some roof accessories
- When factory sealant has been contaminated
The exact method depends on the specific shingle.
Does This Matter for Roof Repairs Too?
Yes.
A contractor replacing a small number of shingles during cooler weather needs to think about how the repaired pieces will seal.
This is especially important when repairing an aging roof because surrounding shingles should be handled carefully.
What Should a Homeowner Ask?
If roofing work is planned during cooler weather, ask:
- What does the manufacturer require at this temperature?
- Will manual sealing be necessary?
- How are shingles being stored before installation?
- What precautions are being taken to prevent cold-weather damage?
A professional contractor should be able to answer those questions.
Ontario Weather Changes the Installation Method—not the Need for Proper Workmanship.
NanoTech Exteriors evaluates weather, material condition, and manufacturer requirements when performing asphalt-roof work so the solution is appropriate for the actual conditions—not simply the calendar.