Ottawa breaks buildings in specific, repeatable ways. A hundred and twenty freeze-thaw cycles a year, a sixty-degree annual temperature swing, sensitive marine clay under much of the city, and a housing stock spanning 1890 to last spring. After enough inspections here, the same eleven findings account for most of what matters.
1. Grading that slopes toward the house
The most common finding in the city and the cheapest to fix. Soil settles against a foundation over the years until the ground falls back toward the wall, and every rainfall and every spring melt is then directed into the basement. Cost to correct: often a few hundred dollars of soil and an afternoon. Cost of ignoring it: the interior waterproofing quote you will get instead, at $8,000 to $20,000.
2. Clay sewer laterals with root intrusion
Anything built before about 1970 in Ottawa was very likely served by vitrified clay tile, joined every metre or so, buried under a lawn with a mature tree on it. Roots find the joints. Alta Vista, the Glebe, Old Ottawa South, Westboro and Nepean are all prime territory. A sewer scope costs $200 to $400; a lateral replacement runs $12,000 to $20,000 and takes your front yard with it.
3. Attic insulation that is not doing its job
Not usually absent — displaced. Wind-washed at the eaves, compressed under stored belongings, disturbed by a previous electrician and never put back, or simply installed to a 1975 standard. Infrared shows this instantly in winter and almost nothing else does. Correction is inexpensive; the ongoing cost of not correcting it shows up on the gas bill every January and in ice dams every February.
4. Bath fans venting into the attic
Astonishingly common, including in brand-new construction. The fan runs, the moisture goes into the attic, and in an Ottawa winter it condenses and freezes on the underside of the sheathing. Come the March thaw it rains inside the attic. Homeowners then report a "roof leak" that no roofer can find.
5. Ice damming and its consequences
Heat escapes into the attic, melts the snow on the roof, the meltwater runs to the cold eave and refreezes into a dam, and subsequent meltwater backs up under the shingles. The damage shows up at the soffit, in the wall below, and on interior ceilings. It is an insulation and ventilation problem wearing a roofing costume, and fixing the roof without fixing the attic guarantees a repeat.
6. Foundation movement in Leda clay
Much of Ottawa sits on Champlain Sea sensitive marine clay, which shrinks in dry summers and swells when wet. Foundations move with it, particularly near large trees that draw moisture from the soil. The signature is seasonal: doors that stick in August and free up in November, diagonal cracking that opens and closes. Distinguishing this from ordinary shrinkage cracking or from genuine structural failure is one of the more consequential judgments an Ottawa inspector makes.
7. Aluminum branch wiring
Homes built roughly 1965 to 1977 — a defined band across Nepean, Gloucester, older Orléans and parts of Kanata. Aluminum expands and contracts differently from the terminals it is connected to, and connections loosen and overheat over decades. It is manageable with proper remediation (approved connectors or pigtailing, done by a licensed electrician), but it is an insurance question first and a safety question second.
8. Knob-and-tube surviving behind renovations
In the Glebe, Sandy Hill, Hintonburg, Centretown and New Edinburgh, a house that was "fully rewired" in 1985 frequently still has original circuits in ceilings and exterior walls. Two dangers: the wiring has no ground, and it must never be buried in insulation — which is exactly what happens when someone blows cellulose into an attic without checking.
9. Poly-B supply piping
Grey plastic supply pipe used widely from about 1985 to 1997, so it is all over Kanata, Barrhaven, Orléans and Gloucester housing of that era. It fails at fittings, often without warning. Many Ontario insurers now surcharge, restrict or decline coverage on homes that still have it. Whole-home replacement typically runs $6,000 to $15,000.
10. Basement moisture and finished basements built badly
Ottawa basements sit above the dew point in July and below it in January, and the finished basements built over uninsulated concrete in the 1970s and 80s were designed for neither condition. Framing directly against concrete, no vapour control, carpet on slab. The result is the musty smell that half of the calls we take start with.
11. Radon
Invisible, odourless, and the leading cause of lung cancer in Canadians who have never smoked. Health Canada’s 2024 Cross-Canada Survey found roughly one in five Canadian homes at or above the 200 Bq/m³ guideline, and Ottawa Valley geology is not at the mild end of that distribution. It cannot be inferred from the neighbour’s result, the house’s age, or anything visible during an inspection. It has to be measured, and the good news is that mitigation is reliable and costs $2,500 to $4,000.
How these cluster by neighbourhood
| Area | What we find most |
|---|---|
| Glebe, Sandy Hill, Hintonburg, Centretown | Knob-and-tube, stone foundations, clay laterals, unpermitted renovation work |
| Alta Vista, Nepean, Bells Corners | Root intrusion in laterals, aluminum wiring, aging services, 1960s insulation levels |
| Kanata, Barrhaven, Orléans (1985–97) | Poly-B piping, failed sealed window units, first-replacement roofs |
| Riverside South, Findlay Creek, Half Moon Bay | Insulation coverage, bath fan venting, HVAC balance, settled grading, sump performance |
| Manotick, Greely, Carp, Osgoode, Dunrobin | Well flow and quality, septic condition, wood stove clearances, oil tanks |
Frequently asked
What is the most common problem found in Ottawa home inspections?
Grading that slopes toward the foundation, followed closely by attic insulation deficiencies and bath fans venting into the attic. All three are inexpensive to correct and expensive to ignore.
Is aluminum wiring a deal-breaker in Ottawa?
No, but it is a condition to negotiate around. Proper remediation by a licensed electrician makes it acceptable to most insurers. Find out what your insurer requires before your condition period expires.
Why do so many Ottawa basements smell musty?
Because Ottawa basements are above the dew point in summer and below it in winter, and a great many were finished with framing directly against uninsulated concrete and no vapour control. The smell is a moisture and assembly problem, not a cleaning problem.