Quebec winters test the limits of your Velux skylights. Snow, ice, freeze-thaw cycles can turn your natural light source into a roofing weak spot.
This guide explains how to protect your skylights during the cold season without climbing on the roof every time there’s a storm.
Key points to remember
- Skylights create a thermal breakpoint that promotes the formation of ice dams during freeze-thaw cycles.
- Monthly visual inspection from the inside to detect excessive condensation, moisture stains or abnormal frosting
- Fall preventive maintenance (cleaning flashing, checking joints, proper insulation) prevents most winter problems.
- Snow removal at height should be entrusted to a professional – never climb on a snow-covered roof or use metal tools on glazing.
- Skylights over 20 years old need to be professionally inspected and replaced, ideally when the roof is replaced.
Why winter is hard on your skylights
Skylights create a thermal breakpoint where interior heat meets exterior cold. This temperature difference causes melting and refreezing cycles that wear down materials.
Snow naturally accumulates around skylights, especially on sloping roofs. When the sun warms the glazing, the snow partially melts, then refreezes around the edges. This is how ice dams form.
Waterproofing joints are particularly hard hit. Materials contract when it’s cold, expand when it’s hot, and this alternation creates tiny cracks where water can seep through.
Signs to look out for from inside
You don’t need to climb onto the roof to assess the condition of your skylights.
Excessive condensation around the frame indicates an insulation problem or snow accumulation blocking ventilation. Occasional droplets are normal, but if the water runs off regularly, there’s a problem.
Stains on the ceiling indicate infiltration. Yellowish or brownish discoloration indicates that water is coming through somewhere.
Frost on the inside of the glazing reveals a major thermal bridge – the insulation or seals are no longer doing their job.
Good preventive maintenance practices
Effective maintenance begins in the fall. Have your flashing and gutters gutters to ensure smooth drainage of meltwater.
Check the condition of caulking joints. Dry, cracked or loose joints should be repaired with a sealant adapted to the Quebec climate, ideally silicone or polyurethane.
Make sure the interior shaft is adequately insulated. Poor insulation lets heat escape, melting snow and creating ice dams. Leave at least 2 inches of air space between the insulation and the roof deck.
According to the Quebec Construction Code, 1 square foot of ventilation is required for every 150 square feet of attic space, divided between air intake and exhaust.
During winter, perform a monthly visual inspection from the inside.
When to call in a professional
Clearing snow from overhead skylights poses a major risk of falling. Professionals are equipped to work safely.
Call in an expert if snow accumulation exceeds 30 centimetres, if the ceiling around the well is sagging, or if seepage appears despite no visible damage. According to the RBQ, wet or icy snow weighs up to 4 times more than fresh snow.
Skylights over 20 years old deserve a professional inspection before winter. At this age, seals show signs of fatigue that may require complete replacement.
Common mistakes to avoid
Never climb onto the roof in winter to clear snow from your skylights. Snow-covered and icy surfaces are dangerous.
Do not use metal tools to remove ice. Metal scrapers will scratch the glass and damage the seals. Use a soft snow broom or telescopic rake from the ground.
Avoid overheating your home to melt snow. This practice creates ice dams and increases your heating costs.
Do not use de-icing salt near skylights. These products corrode metal seals.
Preserving the longevity of your skylights
With proper maintenance, a Velux skylight can last 20 to 25 years.
Keep a record of your inspections. Note dates, observations and actions taken.
Schedule a professional inspection every three to five years. An experienced roofer can detect early signs of wear and tear that you might otherwise miss.
When is the best time to replace a skylight? When you replace your roof. This approach allows you to renew flashings and sealants at the same time.
Need help with your skylights?
If you see signs of infiltration, or if your skylights are more than 20 years old, our team can perform a complete inspection. We respond quickly to any winter waterproofing problem in the Greater Montreal area.
Contact us at and we’ll be happy to answer your questions.
Frequently asked questions
How often should I check my skylights in winter?
A monthly visual inspection from the inside is all it takes. After each major storm, a quick glance will reveal any problematic build-up.
Is it normal to have a little condensation on the glass?
Yes, occasional drips are normal. On the other hand, if the water runs off regularly or if you see mold, this indicates an insulation or ventilation problem.
Can I use de-icing salt near skylights?
No. These products corrode metal joints and damage sealing materials.
How much does it usually cost to replace seals?
Costs vary according to accessibility and scope of work. Ask a qualified roofer for a quote.
When should a skylight be completely replaced?
After 20 to 25 years of use, or if you notice repeated infiltrations despite repairs, cracks in the glazing or deformation of the frame.
