Whether you are buying your first home or your fifth, a pre-purchase inspection is your best line of defence against costly surprises. But what exactly does an inspector check? What should you pay attention to? This complete guide walks you through the 8 major building systems that every thorough inspection should cover, along with the red flags that should make you think twice before signing.
1. Foundation and structure
The foundation is the backbone of any building. It supports the entire weight of the structure, and problems here can be among the most expensive to fix. During a pre-purchase inspection, the inspector will carefully examine the foundation walls, both from inside (basement) and outside, looking for cracks, signs of water infiltration, spalling concrete, and structural movement.
Red flags to watch for:
- Horizontal cracks in the foundation walls (possible lateral pressure)
- Stair-step cracks in concrete block foundations
- Evidence of water seepage or active leaks in the basement
- Uneven or sloping floors (may indicate settlement)
- Doors and windows that stick or do not close properly
- Rubble stone foundations in older homes (pre-1950)
2. Roof and cladding
The roof is your home's first line of defence against the elements. In Montreal, where we experience harsh winters with heavy snow loads, freeze-thaw cycles, and intense summer heat, the roof takes a beating year-round. The inspector will evaluate the shingles or roofing membrane, flashing around chimneys and vents, soffit and fascia condition, gutters, and attic ventilation.
Red flags to watch for:
- Curling, buckling or missing shingles
- Multiple layers of roofing (indicates past cover-ups)
- Damaged or missing flashing around penetrations
- Sagging roofline (potential structural issue)
- Ice dam damage visible at eaves
- Inadequate attic ventilation leading to moisture buildup
3. Plumbing
The plumbing system includes all water supply pipes, drain pipes, fixtures, the water heater, and related components. The inspector will check for leaks, test water pressure, examine pipe materials, assess the water heater age and condition, and look for signs of past or present problems. In older Montreal homes, galvanized steel or even lead piping may still be present.
Red flags to watch for:
- Low water pressure (may indicate corroded pipes)
- Galvanized steel or lead piping (costly replacement ahead)
- Water stains on ceilings or walls below bathrooms
- Water heater past its expected lifespan (10-12 years)
- Slow drains or gurgling sounds (possible sewer line issues)
- Signs of amateur plumbing work
4. Electrical
The electrical system is critical for both safety and functionality. The inspector will open the main electrical panel to check the wiring, breakers, grounding, and overall condition. They will also test a sampling of outlets, check for proper GFCI protection in wet areas, and look for any code violations or safety hazards.
Red flags to watch for:
- Knob-and-tube wiring (pre-1950 homes)
- Aluminum wiring (1965-1975 era, fire risk at connections)
- Federal Pacific or Zinsco panels (known safety issues)
- Double-tapped breakers (two wires on one breaker)
- Undersized electrical service (60-amp in a modern home)
- Missing GFCI protection in kitchens, bathrooms, and exterior outlets
5. Heating, ventilation and air conditioning (HVAC)
Montreal's climate demands a reliable heating system. The inspector will evaluate the furnace or boiler age and condition, test the thermostat, check ductwork or radiators, examine the heat pump or air conditioning system if present, and verify that the system is operating correctly. They will also check ventilation systems including bathroom fans, kitchen exhaust, and the HRV (heat recovery ventilator) if applicable.
Red flags to watch for:
- Furnace or boiler past its expected lifespan (15-20 years)
- Cracked heat exchanger (carbon monoxide risk)
- Absence of a heat recovery ventilator (HRV) in newer homes
- Disconnected or damaged ductwork
- Non-functional bathroom exhaust fans (moisture buildup)
- Signs of improper combustion (soot, scorching)
6. Insulation and energy efficiency
Proper insulation is essential in Quebec's climate, where winter temperatures regularly drop below -20°C. The inspector will check insulation levels in the attic, walls, and basement, evaluate the vapour barrier, and use infrared thermal imaging to identify thermal bridges and areas of heat loss. This is one area where FLIR cameras prove invaluable.
Red flags to watch for:
- Insufficient attic insulation (less than R-50 in Quebec)
- Vermiculite insulation (may contain asbestos)
- Missing or damaged vapour barrier
- Cold spots visible on thermal imaging
- Condensation on windows (indicates excessive indoor humidity)
- Drafts around doors, windows, and electrical outlets
7. Exterior and grounds
The building exterior and surrounding grounds play a crucial role in keeping water away from the foundation and maintaining the building envelope. The inspector will evaluate siding condition, grading and drainage patterns, driveway condition, balconies and decks, stairs and railings, and any retaining walls.
Red flags to watch for:
- Negative grading (ground slopes toward the foundation)
- Missing or clogged gutters and downspouts
- Rotting wood on balconies, decks, or siding
- Crumbling or damaged driveway near the foundation
- Loose or missing railings on stairs and balconies
- Trees planted too close to the foundation
8. Interior finishes
While interior finishes are often cosmetic, they can also hide or reveal underlying problems. The inspector will look at walls, ceilings, and floors for signs of moisture damage, check doors and windows for proper operation, examine kitchens and bathrooms for functional issues, and look for any signs that cosmetic renovations may have been done to conceal problems.
Red flags to watch for:
- Fresh paint in isolated areas (may hide water stains or mold)
- New flooring over old (may conceal damage)
- Musty odours (indicates hidden moisture or mold)
- Water stains on ceilings or around windows
- Cracks in drywall above doors and windows (settlement)
- Improperly installed tiles or fixtures in bathrooms
What happens after the inspection
After the on-site inspection, you will receive a detailed report within 24 hours. This report will document every finding with photographs, descriptions, and prioritized recommendations. Use this report to:
- Negotiate the price — Major findings can justify a price reduction or repair credits.
- Request repairs — Ask the seller to fix specific issues before closing.
- Plan your budget — Know what maintenance and upgrades to expect in the first few years.
- Walk away if needed — If the inspection reveals deal-breaking problems, you can withdraw your offer (if your offer was conditional on inspection).
- Protect yourself legally — The report serves as proof of the property's condition at the time of purchase, which is valuable in any future hidden defect claim.
A thorough pre-purchase inspection is not just a formality — it is your most powerful tool as a buyer. It gives you the information you need to make a confident, informed decision about one of the biggest investments of your life.