Ontario homes live through four distinct seasons, each with its own demands. Roofs shed snow, foundations sit in wet clay, vinyl siding bakes in sun, and basements breathe damp air. I’ve crawled through enough attics in London and Sarnia to know that small oversights become expensive repairs when the weather swings. A seasonal maintenance routine protects resale value, helps insurance claims go smoothly, and makes your home more comfortable day to day. Whether you are booking a home inspection in London, Ontario, comparing home inspectors near me, or managing a commercial property with a preventative program, the rhythm of the seasons is your best tool.
Below you’ll find a practical, Ontario-specific maintenance calendar, plus the why behind each step. It’s based on what a local home inspector sees repeatedly during pre-purchase reports, mold inspection and testing, and commercial inspections.
Winter sets the stage: preparing before the first freeze
Most spring water problems start in the fall. Ontario soils, especially in the London and Sarnia corridor, move as they freeze and thaw. Gutters packed with leaves, downspouts dumping at the foundation, and exterior caulking that has failed all push meltwater into basements when temperatures swing above zero.
If you only do three things before the first hard frost, make them roof, drainage, and heat. A short story to illustrate the stakes: a family in north London replaced a furnace in October, then called for a home inspection in January because they noticed condensation streaks on bedroom ceilings. The culprit wasn’t the furnace. The attic hatch lacked weatherstripping, warm indoor air poured into a cold attic, and frost built up under the sheathing. When the January thaw arrived, the frost melted, dripped through the drywall, and left stains that looked like roof leaks. A thirty-dollar gasket would have prevented it.
Before winter, stand back from your house on a rainy day. Watch how water leaves the roof and moves across the lot. If you see sheets of water cascading from a valley, that’s a gutter capacity problem. If water sits against the foundation longer than ten minutes after the rain stops, you likely need grading improvements or longer downspout extensions. These fixes beat sump pumps working overtime in March.
Indoor air matters too. With windows closed and humidity rising, homes in Southwestern Ontario often tip into the 40 to 55 percent relative humidity range. That’s high for winter and invites window condensation and mold growth. A home inspector London ON will often recommend setting humidifiers to 30 to 35 percent when outside temperatures fall below minus 10 Celsius. It sounds dry, but lower humidity reduces frost on windows and protects attic sheathing from moisture.
Early winter: safety, heat, and air quality
Once the cold settles in, focus on the systems that run constantly. Safety checks around combustion appliances take minutes and can save lives. Confirm that your carbon monoxide detectors are less than seven years old, test them, and place at least one near bedrooms and another near the furnace room. Replace smoke alarm batteries even if they chirp happily today. Inspect the furnace filter monthly through the heating season. If you can’t see light through the filter, the blower is straining.
If your house has a high-efficiency furnace, keep the intake and exhaust terminations free of snow. A blocked pipe can shut the system down on the coldest night. I’ve responded to more than one panicked call where the fix was a broom and five minutes outside. Side note for homeowners in snow belts east of London: if drifting is common along your wall, consider a simple pipe hood or stand-off kit to keep those terminations clear.
Air quality often dips in winter. We close houses up, run showers and kettles, and sometimes dry clothes indoors. That sets the stage for condensation on exterior walls and window frames, and mold shows up on cold corners behind dressers. If you see persistent fog on the inside of double-pane windows, measure indoor humidity and adjust ventilation. Bathroom fans should exhaust to the exterior and move enough air to clear a mirror in ten to fifteen minutes. If a fan barely holds a tissue to the grille, the duct is likely clogged or undersized. For families dealing with asthma or persistent respiratory irritation, air quality testing London Ontario can be worthwhile, especially in older homes with mixed renovations.
If you live in or manage a building from the 1960s through the 1980s, be mindful of vermiculite insulation, resilient floor tiles, and acoustic ceiling finishes. Not every old material contains asbestos, but enough do that guesswork is risky. Asbestos home inspection and, when indicated, asbestos testing London Ontario can prevent expensive surprises when you plan a renovation.
Mid-winter: ice dams, attics, and moisture
Ice dams are a predictable Ontario problem when snow meets heat loss. They form where warm attic air melts roof snow, then the meltwater refreezes at the colder eaves. Water backs up under shingles and finds nail penetrations. I’ve seen immaculate roofs leak like sieves during a two-day thaw. Look for thick icicles only above certain rooms, usually bathrooms or kitchens. That often points to a localized heat source such as a loose bath fan duct blowing into the attic or missing insulation around recessed lights.
This is where a thermal imaging house inspection helps. Infrared scanning quickly shows heat loss patterns and hidden wet spots without opening up finishes. It’s not magic, and it requires the right temperature differential and trained interpretation, but it catches issues that a flashlight misses. During mid-winter home inspection Ontario appointments, I carry an IR camera for this reason. On one Sarnia bungalow, we traced a recurring bedroom ceiling stain to a warm chase where a plumbing vent penetrated an attic commercial building inspection with patchy insulation. A few batts properly fitted and a sealed boot cured the leak that had cost the owners three drywall repairs.
For finished attics, check for frost on roofing nails. A little sparkle on the coldest mornings is normal. Thick rime, however, signals high attic moisture. The common culprits are bathroom fans venting into the attic, missing air barriers around the hatch, or large gaps at top plates. Aim for a tight ceiling, consistent insulation, and balanced roof ventilation. If you see mold on the underside of the sheathing, plan for mold testing only if remediation requires lab confirmation. Often, visible attic mold can be addressed by correcting ventilation and air sealing, then applying a professional antimicrobial treatment.
Early spring: thaw watch and water management
The spring shoulder season is the busiest for a home inspector Ontario. Snow disappears, then the phones ring. Basements that stayed dry all winter suddenly smell musty. The soil is saturated, and footing drains face their highest load.
Walk the exterior as soon as the snow is mostly gone. Look for downspouts that shifted or disconnected under the snow load. Reconnect them and add extensions to carry water at least two to three meters away from the foundation. Rake mulch and soil back to maintain a positive slope away from the house. Check window wells. They should be clean, with covers intact and drains working. If a well fills like a bathtub during the first heavy rain, its drain may tie into a clogged perimeter system. That’s a good time to schedule a camera inspection of the weeping tiles.
Inside, watch for efflorescence on foundation walls, the white powdery bloom that salts leave as water evaporates. It’s a clue, not a crisis. A single horizontal line at the floor can be historic. Fresh, patchy deposits after every rain point to ongoing seepage. Dehumidifiers help control humidity, but they don’t solve bulk water intrusion. If your sump runs more than a few hours after rain stops, or if the pit starts clean and ends the season with silt, service the pump and consider a secondary unit with an alarm.
If you smell earth or a sweet, musty odor, think mold. Mold testing London Ontario should be targeted, not a fishing expedition. A competent mold inspection focuses on moisture sources, uses moisture meters and thermal imaging to locate wet spots, and only samples where results inform the plan. Broad air sampling without context tells you little more than the obvious: mold spores exist. You want to know where moisture is entering and how to eliminate it.
Late spring: roofs, siding, and exterior systems
Once the roof is dry and safe to approach, scan shingles for cupping, missing tabs, or nail pops. In London’s wind corridors, edges and rakes take a beating. Lift a couple of shingles gently to check the underlayment. If you see brittle felt and granules filling gutters after every rain, plan a roof replacement before the next winter. Proper flashing matters more than shingle brand. Valleys, wall intersections, and chimneys cause most leaks I write up during a home inspection London.
Brick and block need attention after winter. Tuck pointing that looked fine in September can crumble in March. Look closely at step cracks near corners and at lintels above windows. Rusting lintels expand and lift bricks, opening the way for water. Steel that has swelled needs grinding, coating, and sometimes replacement. Painted quick fixes often trap moisture and accelerate corrosion. For vinyl or fiber cement siding, verify that joints are sealed, flashing is sound, and caulking around windows remains flexible. Caulking is not decoration. It is a critical water control layer, and substitutes like silicone bead over old latex rarely adhere.
Decks deserve a serious check. Ledger boards should have proper flashing. Fasteners must be lag bolts or structural screws, not nails. In older neighborhoods, I still see decks anchored only by nails into soft rim joists. A crowd, a dance, and a little bounce can tear it free. If you own a rental or commercial property with public access decks, bring in a commercial building inspector to review loads, connections, and guard heights. Insurance carriers ask hard questions after an incident.
Early summer: cooling equipment, insulation, and shade
Ontario summers bring humidity and heat waves that expose weak air conditioning systems. Replace or clean filters at the start of the cooling season, clear vegetation two feet around condensers, and wash coils gently from inside out. If you notice ice on the refrigerant lines, resist the urge to chip at it. Turn off the system and run the blower to thaw, then book service. Low airflow or low refrigerant can both cause icing.
Attic insulation matters year round. In summer, poor insulation bakes second floors and drives cooling costs up. Ventilation keeps roof sheathing cooler, but the real comfort comes from continuous insulation with proper air sealing below it. If you plan a top-up, air seal first. Spraying foam around penetrations, sealing the attic hatch, and damming around fixtures does more than adding a few extra inches of loose fill. On a home inspection London Ontario, I often find a patchwork of old batts with gaps big enough to fit a hand. Infrared thermography on a hot afternoon makes these voids obvious. Sealing and leveling that layer can drop upstairs temperatures by several degrees on a sunny day.
Keep an eye on paving and patios. Frost heave and spring saturation shift slabs, which throws water toward the house in summer thunderstorms. Re-level pavers to maintain slope away from walls and re-seal joints if ants and grass have taken over. Yard grading is not glamorous, but it’s the cheapest exterior fix that actually works.
Mid-summer: indoor air, pests, and plumbing quirks
Closed houses combined with cooking, showers, and perhaps a basement workout area can push relative humidity into the 60s. That’s the threshold where mold growth accelerates. Run bathroom fans during and 20 minutes after showers. If your fan vents into the soffit, confirm that the duct runs to an exterior cap, not just into the attic cavity. Foam-sealed rigid duct is best. Flexible duct draped across insulation collects condensation and sags.
Consider an indoor air quality spot check if you’re noticing persistent odors, new allergies, or if renovations disturbed old materials. Air quality testing London Ontario can identify particular irritants, but again, context is key. A competent assessor will ask about humidity, ventilation rates, and potential sources such as new furnishings or paints that off-gas in heat. If you’re in the Sarnia area dealing with river valley humidity, a dedicated dehumidifier in the basement set to 45 to 50 percent helps prevent musty smells.
Summer is also pest season. Carpenter ants follow wet wood. If you see piles of frass that look like fine sawdust near baseboards, investigate for leaks. Mice don’t need an invitation. Inspect weatherstripping at doors and the garage entry, seal gaps around utility penetrations with steel wool and sealant, and tidy storage that allows inspection of baseboards and corners. Pest problems often point to moisture or food sources in the wrong places.
Laundry rooms deserve a pass mid-summer. Pull the dryer, clean the vent, and check the duct run to the exterior. Long, convoluted runs clog fast and add heat and humidity to the house. Kinks behind the dryer are common. A smooth-walled metal duct with the shortest path out is worth the trouble.
Early fall: roofs, heat, and storm readiness
Fall is the time to button up before another freeze. Book furnace service early and have a qualified technician check heat exchangers, safety switches, and combustion. If you have a fireplace, clean and inspect chimneys, especially if the liner is masonry. Dryer and bath fans share a simple test. Turn them on and step outside. You should feel a strong exhaust stream. If not, clean or replace.
Gutters need attention before the first heavy leaf fall, then again after. Screens help but don’t eliminate maintenance. Pay special attention to valleys that empty into gutters at 90 degrees. They overflow easily and dump water against siding. If you’re building or renovating, install kick-out flashing where rooflines meet walls. It is a small detail that prevents big rot.
Exterior caulking and paint protect trim from winter. Scrape, prime, and paint soft spots before they swell with moisture and burst in March. Examine the bottom edges of wood and composite trim, the weakest points. Seal entry thresholds and add weatherstripping where a slip of paper pulls through easily.
If you manage a retail or office building, schedule a commercial building inspection or at least a roof and HVAC review before the heating season. Rooftop units need belt checks and filter changes. Flat roofs collect leaves, and roof drains clog. One mid-November rain with drains blocked can flood a top floor tenant. The cost of a preventive walk-through is trivial compared to a wet office or a server room failure.
Late fall: the last line before snow
The final push is about freeze protection. Shut off exterior hose bibs from interior valves, then open the exterior taps to drain. Insulate any exposed pipes along unheated garage walls or in crawl spaces. Stock salt or sand, and check outdoor lighting for safe paths in the dark.
If you haven’t looked at the attic since spring, peek again on a cold night. The house has shifted with humidity and the season. Make sure the hatch is closed tight, insulation hasn’t drifted away from eaves, and no new staining has appeared around penetrations. That quick check catches the odd small roof failure before it becomes a winter project.
Septic systems in rural parts of Middlesex and Lambton counties need a different rhythm. Pump at the interval recommended for your household size, typically three to five years. Fall is a good time because the ground is accessible and you don’t risk frost-damaged lids. Direct roof water away from tank and bed areas to reduce saturation.
Where a professional adds value
Homeowners can handle most of this checklist with a flashlight and a free Saturday, but two areas consistently benefit from a professional eye: hidden moisture and complex systems. A home inspector Ontario who uses moisture meters, thermal imaging, and has construction experience reads subtle patterns that reveal problems before they become expensive. For example, a faint seasonal ceiling line may suggest a framing bow that traps warm air, not a roof leak. I’ve seen owners chase a leak for years when the fix was better attic air sealing above a bathroom.
For mold and asbestos, evidence beats fear. Mold inspection should center on moisture. Mold testing has a role when you need to confirm that a remediation cleaned the air to normal background or when you have a medical reason to identify species. Asbestos testing London Ontario is essential before sanding old floors, cutting into plaster, or removing old duct tape and pipe wrap. Lab turnaround is typically a few days, and it can save thousands in change orders mid-renovation.
Commercial buildings layer in their own complexity. Roof types vary, tenant improvements hide penetrations, and HVAC systems interact in ways that shift pressures and temperatures across suites. A commercial building inspection focuses on life safety, roofs, building envelope, and mechanical systems, with a priority list for capital planning. If you own a plaza or small office in London or Sarnia, that plan helps pace spending without surprises.
Two quick seasonal checklists you can tape to the utility room door
Spring priority checklist:
- Clear downspouts and extend discharge 2 to 3 meters from foundation Test sump pump and float, add backup or alarm if frequent runs Inspect attic for wet sheathing or frost residue after first thaw Rake soil to achieve 5 to 10 centimeters of fall per meter away from house Service AC, replace filter, and clear condenser coils
Fall priority checklist:
- Clean gutters and verify downspout connections before leaf drop Seal attic hatch, check insulation at eaves, and ensure clear soffit vents Service furnace, test CO and smoke alarms, and verify fan exhaust outdoors Shut off and drain exterior faucets, insulate vulnerable interior pipes Inspect roof flashings, especially at chimneys, walls, and valleys
London and Sarnia specifics: clay, wind, and water
London’s soils vary street by street. Many neighborhoods sit on heavy clay that holds water against foundations. That means grading and downspout extensions do more work than foundation coatings alone. I often recommend longer extensions than people like for aesthetics, because the numbers are blunt. Moving 20 millimeters of rainfall off a 150 square meter roof means 3,000 liters of water. That volume dumped at a corner will find the path of least resistance. Put the extension in for the wet months, hide it for the barbecue.
Wind hits harder on the west and south sides of many London homes. Shingles lift, siding rattles, and caulking dries. Focus your fall exterior check on those exposures first. In Sarnia and along the lake, salt and wind age metal faster. Inspect fasteners, railings, and exterior light fixtures for corrosion and seal penetrations through siding. The river valley brings humidity. Keep basement dehumidifiers set and running from late spring to early fall, and make sure condensate drains don’t backflow.
For those searching home inspectors London Ontario or home inspection Sarnia, ask whether the inspector includes thermal imaging, moisture scanning, and a roof walk when safe. Home inspectors highly rated in our area rarely skip those steps. They also understand common local construction details such as split-level floor transitions, cantilevered bay insulation gaps, and early 2000s brick veneer ties that missed studs.
Bringing it all together
Seasonal maintenance isn’t a heroic weekend twice a year. It’s a rhythm of small checks and quick fixes that match the weather. Pay attention to water and air, the two forces that do most of the damage when they wander where they shouldn’t. Use pros where they add clarity: a targeted mold inspection when odors or stains won’t resolve, asbestos testing before you open old materials, a thermal imaging house inspection when stains or comfort issues puzzle you, and a commercial building inspector when tenant spaces or flat roofs need an objective look.
If you want a simple rule of thumb, follow the water. In winter, stop it from freezing where it can pry things apart. In spring, push it away from your foundation. In summer, keep it out of the air you breathe. In fall, give it a clear path off the roof and down the hill. That cycle keeps Ontario homes healthy and makes the next home inspection London go from a list of surprises to a short set of notes.
1473 Sandpiper Drive, London, ON N5X 0E6 (519) 636-5710 2QXF+59 London, Ontario
Health and safety are two immediate needs you cannot afford to compromise. Your home is the place you are supposed to feel most healthy and safe. However, we know that most people are not aware of how unchecked living habits could turn their home into a danger zone, and that is why we strive to educate our clients. A.L. Home Inspections, is our response to the need to maintain and restore the home to a space that supports life. The founder, Aaron Lee, began his career with over 20 years of home renovation and maintenance background. Our priority is you. We prioritize customer experience and satisfaction above everything else. For that reason, we tailor our home inspection services to favour our client’s convenience for the duration it would take. In addition to offering you the best service with little discomfort, we become part of your team by conducting our activities in such a way that supports your programs. While we recommend to our clients to hire our experts for a general home inspection, the specific service we offer are: Radon Testing Mold Testing Thermal Imaging Asbestos Testing Air Quality Testing Lead Testing