Ontario winters are among the most punishing in North America for residential structures — freeze-thaw cycles, ice dams, condensation, and frozen pipes are common realities for GTA homeowners. The consequences of skipping winter prep range from nuisance (a leaky window seal) to catastrophic (a burst pipe that floods two floors). This checklist covers what to do before winter sets in (October–November) and what to monitor through the season, with GTA-specific context throughout.
Pre-Winter Prep: Exterior (Do Before First Frost)
Exterior tasks are weather-dependent — complete them before temperatures drop consistently below freezing. In the GTA, that window is typically October through mid-November. The following supply-grid covers the two essential phases of pre-winter preparation.
🏠 Do Before First Frost
- Clean gutters completely — late November after all leaves have fallen is ideal, not October
- Re-seal all failed exterior caulk around windows, doors, and trim (caulk fails after 5–7 years)
- Disconnect and drain ALL exterior garden hoses — leaving hoses connected causes hose bib freeze damage ($80–$250 to replace)
- Drain and winterize exterior irrigation systems — blow out with compressed air or call an irrigation contractor
- Inspect downspout extensions — water must drain at least 1.8 m (6 ft) away from the foundation
- Deck: remove all furniture and planters, drain planters completely, inspect boards and fasteners for next season
🔧 Do Before Heating Season
- Replace furnace filter — change at season start, then every 30–90 days through winter
- Book furnace or boiler annual inspection — call in September before the November rush fully books contractors
- Test all smoke and CO alarms — CO risk rises significantly with increased heating system use
- Check attic insulation and ventilation — inadequate attic ventilation causes ice dams and mould
- Locate and test main water shut-off valve — must be accessible and operational in case of a burst pipe
- Check window weatherstripping for gaps — a failed window seal causes condensation and mould in GTA winter
⚠️ Don't Forget the Hose Bibs
This is the most commonly skipped task in GTA pre-winter prep. A garden hose left connected traps water in the hose bib (the outdoor tap) — when temperatures drop, the water in the bib expands, splits the fitting, and leaks inside the wall. Repair costs $80–$250 plus possible drywall damage. Takes 30 seconds to disconnect a hose. Do it before the first hard freeze.
During Winter: 5 Things to Monitor Through the Season
Preparation before winter is essential, but the season itself requires active monitoring. These five steps cover the highest-risk issues GTA homeowners encounter from December through March.
Watch for Ice Dam Formation After Heavy Snowfall
Ice dams form when heat escapes through the roof, melts the snow above, and the meltwater runs down and refreezes at the cold eaves — forming a ridge of ice that forces water back under shingles and into the building. Signs to watch for: large icicles hanging along the eaves, and water stains on interior ceilings near exterior walls (often mistaken for a plumbing leak).
Prevention: Ensure the attic floor is well-insulated so heat stays in the living space rather than escaping into the attic. Ensure the attic has adequate cross-ventilation so the attic air stays cold and snow melts evenly rather than concentrating at the ridge. These are the only permanent fixes — the root cause is always inadequate insulation or ventilation.
Safe removal: Lay calcium chloride de-icing product in a mesh stocking (an old nylon works) across the dam perpendicular to the eave — it channels a melt path through the dam. Never use a hammer, axe, chisel, or pressure washer on ice dams — you will damage shingles and void your roof warranty. Professional ice dam removal costs $300–$900 in the GTA.
Prevent Frozen Pipes During Cold Snaps
The highest-risk pipes in GTA homes are those on exterior walls, in unheated garages, and near rim joists in the basement — areas where insulation is thin and outdoor temperatures directly affect the pipe temperature. During sustained periods below -15°C (common in GTA January and February), let kitchen and bathroom faucets trickle overnight if they are located on exterior walls. Even a slow trickle prevents the pressure buildup that causes pipes to burst.
If a pipe freezes: shut off the main water valve immediately to limit damage. Apply heat with a hair dryer starting at the faucet end and working toward the frozen section — never use an open flame, a heat gun at close range, or a blowtorch. A burst frozen pipe causes $5,000–$50,000 in water damage — the cost of prevention is $5/month in extra water from a slow trickle.
Insulating exposed pipes in unheated areas (foam pipe insulation, $5–$15 at any hardware store) and keeping the heat on even when away from home (minimum 15°C) are the two highest-impact preventative measures. Refer to our guide on basement renovation and waterproofing for pipe exposure issues in older GTA homes.
Manage Condensation on Windows
Window condensation in GTA winter is not a window problem — it's a humidity problem. It occurs when indoor air is too humid for the outdoor temperature. When it's -10°C outside and 22°C inside, the dew point is easily reached at the cold glass surface. The ideal indoor winter humidity range is 30–40%. Above 40%, expect condensation on single or older double-pane windows. Frost on the inside of glass means humidity is far too high or the window seal has failed.
Run an HRV (Heat Recovery Ventilator) — standard equipment in post-2003 GTA homes — to exchange stale humid indoor air with fresh outdoor air while recovering heat. If you don't have an HRV, a dehumidifier in the main living area manages humidity effectively. Do not ignore persistent window condensation — it rots window frames, grows mould in wall cavities, and causes paint failure on interior trim. The fix is cheap; the damage from ignoring it is not.
Protect Deck and Outdoor Structures
Wood and composite decks handle Ontario winters well if treated correctly. The most common winter deck damage in the GTA is not from snow load but from two preventable causes: improper de-icing products and metal shovels.
Shovelling: Use a plastic deck shovel or a stiff-bristle broom. Metal shovels gouge wood grain and scratch composite decking surfaces. Leave a thin layer of snow rather than scraping to bare boards if using a metal shovel is unavoidable.
De-icing: Use calcium chloride (CaCl₂) only. Do not use rock salt (NaCl) or sand on wood or composite decks — NaCl damages wood fibres, draws moisture into the material, and accelerates corrosion of metal fasteners (joist hangers, screws, post bases). Most composite decking manufacturers explicitly permit calcium chloride and specifically prohibit rock salt in their warranty terms.
For full guidance on preparing your deck before winter, see our fall deck prep guide. If your deck needs refinishing before next season, our deck staining guide covers the full process.
Monitor Basement Moisture Monthly
GTA basements in winter face a specific moisture dynamic: cold concrete walls attract condensation from warm indoor air, and freeze-thaw cycles in the surrounding soil create hydrostatic pressure against foundation walls. Check your basement monthly through the winter for: new efflorescence (white salt deposits on concrete walls), active water staining on the slab floor, or mould growing on stored items, walls, or framing.
Run a basement dehumidifier when relative humidity exceeds 55%. Most GTA basements benefit from continuous dehumidification October through April. If your basement shows active water infiltration in winter — water seeping through wall cracks or the floor-wall joint — this is hydrostatic pressure from frozen and thawing soil, and the problem will worsen with each freeze-thaw cycle. Address it before spring. See our full guide on basement renovation and waterproofing for waterproofing options and GTA contractor costs.
💡 Weatherproofing: Where GTA Homes Actually Lose Heat
Sealing air leaks before winter typically saves 10–15% on GTA heating bills — more than upgrading to a more efficient furnace in most cases. The three biggest air leak sources in Toronto-area homes are: the attic hatch (add weatherstripping to the frame and glue a layer of rigid foam insulation to the attic side of the hatch itself), pot lights in the ceiling below the attic (seal with fire-rated spray foam from the attic side — standard pot lights are major air leaks), and rim joists in the basement (cut rigid foam board to fit each joist bay, press it in, and seal all four edges with spray foam). These three fixes cost under $150 in materials and can each be done in an afternoon.
Typical GTA Winter Home Maintenance Costs (2026)
The table below reflects current GTA contractor pricing for common winter-related maintenance and repair tasks. DIY costs for tasks like filter replacement and weatherstripping are not included — those are materials-only and represent significant savings.
| Task | Low | High |
|---|---|---|
| Furnace inspection and tune-up | $100 | $200 |
| Gutter cleaning (fall) | $100 | $250 |
| Hose bib repair (if frozen) | $80 | $250 |
| Ice dam removal (professional) | $300 | $900 |
| Frozen/burst pipe repair (accessible) | $300 | $800 |
| Attic insulation top-up | $800 | $3,000 |
| Weatherstripping kit (DIY) | $30 | $80 |
Note: All costs are approximate GTA contractor rates as of 2026. Burst pipe repair costs above assume the pipe is in an accessible location. Water damage remediation (drywall, flooring, mould remediation) from a burst pipe is separate and can range from $5,000 to $50,000+ depending on extent. Furnace repair costs if the furnace fails are not included — a furnace tune-up is the preventative investment that avoids a $2,000–$6,000 emergency replacement call in January.
Frequently Asked Questions: Winter Home Maintenance Ontario
What should Ontario homeowners do to prepare their home for winter?
Complete exterior tasks by November: clean gutters after leaves fall, re-seal exterior caulk, disconnect and drain all garden hoses, and inspect downspout drainage away from the foundation. Inside: replace the furnace filter, book an annual furnace inspection (do this in September — contractors are fully booked by November), test smoke and CO alarms, check attic insulation and ventilation, and locate your main water shut-off valve. The earlier you plan, the better your chance of booking reputable tradespeople before the seasonal rush.
How do I prevent frozen pipes in a GTA home?
Focus on pipes on exterior walls, in unheated garages, and near rim joists. During sustained cold below -15°C, let faucets on exterior walls trickle overnight. Insulate exposed pipes with foam pipe insulation. Keep the heat on at minimum 15°C even when away. If a pipe freezes, shut off the main water and apply a hair dryer — never an open flame. Prevention costs pennies; a burst pipe costs thousands.
Should I cover my deck for winter in Ontario?
No — covering a deck generally traps moisture and can cause more harm than good. Remove furniture and planters, inspect the structure, and use only plastic shovels and calcium chloride (not rock salt) through the season. Snow load on a properly built deck is not the issue — ice accumulation under dripping eaves and improper de-icing are the common culprits for winter deck damage.
What is an ice dam and how do I prevent one on my GTA home?
Ice dams form when heat escapes through the roof, melts snow, and the meltwater refreezes at the cold eaves. Prevention requires adequate attic insulation and ventilation — these are the only permanent solutions. For safe removal, use calcium chloride in a mesh stocking laid across the dam. Never use a hammer or pressure washer on ice dams.
How often should I change my furnace filter in Ontario winter?
Change your filter at the start of heating season, then every 30–45 days for a 1-inch filter during continuous winter operation, or every 90 days for a 4-inch media filter. Homes with pets or construction dust should change more frequently. A clogged filter strains the blower motor and risks heat exchanger overheating — a $15 filter protects a $3,000+ appliance.