The plex — duplex, triplex, fourplex — is one of the most popular gateways to real estate investment in Montreal: you live in one unit, rent the others, and the market pays the mortgage. But behind this appealing model often lies a century-old structure, with technical particularities all its own. A poorly assessed plex can turn a good investment into a money pit. Here are the pitfalls to know before you sign.
A plex is not bought like a house: you are not buying just a roof, you are buying a return — and every deficiency nibbles at it.
A structure loaded with history (and wear)
The plexes of Montreal’s central neighbourhoods are frequently 70, 100 years old or more. Brick masonry, exterior staircases, flat roofs, period plumbing and electrical: all elements that have a lifespan, and that often reach the end of the line at the same time. The issue is not age in itself, but knowing what remains to be done, when, and at what cost.
Pitfall 1 — Masonry and staircases
Brick and mortar take a century of freeze-thaw. Watch for deteriorated mortar joints, bursting brick and, more serious, the bulging wall that signals cladding separating from the structure. Exterior staircases (rusted metal, rotten wood) are both a cost and a safety issue.
Pitfall 2 — The flat roof
The flat or low-slope roof, typical of the plex, depends on a membrane and good drainage. Blisters, ponding water, loose flashings and a membrane at the end of its life are classics. Re-roofing a plex is anything but trivial on the budget side.
Pitfall 3 — Period plumbing and electrical
This is often where the worst surprises hide: corroded galvanized piping, Poly-B plumbing, old wiring, or a Federal Pioneer electrical panel. Multiplied by the number of units, these systems represent costs — and sometimes insurability issues.
Pitfall 4 — The basement and moisture
Foundation cracks, deficient drainage, infiltration, and the absence of a backwater valve (sewer backup) are frequent. In a multi-unit building, a basement water incident affects everyone.
Pitfall 5 — What you cannot see in the rented units
A plex particularity: tenants occupy the premises. Access to some units may be limited at the time of the inspection, which creates blind spots. This has to be taken into account — and you have to know how to deal with this reality.
We read the plex’s technical condition and its impact on value and return; we do not set market value (an act reserved for chartered appraisers, OEAQ). Our report informs your decision and your negotiation, it does not replace a certified appraisal.
The angle that matters: return
For a plex, every deficiency is a deferred expense that weighs on the return. That is why the exercise comes close to a building condition assessment: we translate the condition of the components into coming costs, so you buy with full knowledge — and have arguments to negotiate.
500+ projects carried out in Quebec, including plexes and income properties
Our approach
Boreon documents the real condition of a plex, sorts the deficiencies by severity, and translates it all into clear strategic information. Thermography is integrated into our inspections, our inspectors are InterNACHI-certified, we hold professional liability insurance, and the schedule is agreed in advance based on complexity. We cover Montreal and Greater Montreal — West Island, South Shore, Laval and North Shore.
Key takeaway
A Montreal plex combines aging masonry, a flat roof, period systems and an at-risk basement — all costs that weigh on the return. Before buying, have its technical condition and coming expenses read: that is what distinguishes a good investment from a money pit.
Shopping for a plex in Montreal? Have its technical condition assessed by Boreon — to buy and negotiate with your eyes open.
