Montréal-Nord: plexes on clay, high water table and thaw
Montréal-Nord is a flat basin of Champlain Sea clay, bordered by the rivière des Prairies to the north and cut through by Gouin Boulevard. The building stock came in waves: brick plexes of the 1950s and 1960s between Gouin and Charleroi, poured-concrete bungalows of the 1960s and 1970s toward the east, and recent infill projects. On this ground, water pools, the water table rises to within a metre of the surface in spring, and every thaw opens its run of corner cracks. Our Ahuntsic yard puts us ten minutes from any street in the borough.
Brick plexes: the stair-step crack that follows mortar joints
On a 1950s plex in Montréal-Nord, the classic pathology shows up at the basement window: a stair-step crack dropping from one corner, following the mortar joints of the concrete block, and weeping as soon as snow melts against the brick. The local clay holds meltwater from planting beds and walkways, and the outer wall takes the load. We measure it with the calibrated crack gauge: under 2 millimetres and stable from October to April, a flexible polyurethane injection is enough; beyond that, or if the opening moves, structural epoxy comes in after stability is verified.
What plex owners forget: the foundation wall often carries two or three units, and the seepage shows up in the lower unit while the upper-floor owner sees nothing. The diagnosis therefore covers both basements when the building is divided, with written readings handed to both parties. In a neighbourhood where plexes change hands often, a report of a stabilized crack is worth what an inspection quote is worth at purchase.
High water table and drainage: the pump that works from thaw on
In the flat streets between Gouin and the river, the sump pit tells the real state of drainage: a pump cycling every twenty minutes in April points to a clogged or absent French drain — common before 1970, when several streets never had a perimeter drain at all. The standard repair runs a trench at the footing, a 4-inch drain in clean stone, a continuous slope to the cleanout, and a permeable backfill that cuts the water off before it pushes against the wall. The water-disposal by-law forbids tying that drain into the combined sewer without a check valve, and the municipal inspection checks the point.
The calendar matters as much as the method: in clay, a trench opened at thaw fills with water and swells under every machine pass. We book Montréal-Nord drainage jobs from June to October, when the water table drops and the clay is workable; injections, on the other hand, run year-round from the interior, without opening the ground. Matching the right move to the right season is half the job on this soil.
Rebuilds and junctions: new concrete against old block
Rebuilt lots after demolition present a textbook case: today's poured-concrete foundation glued against the neighbour's block wall, or against a retaining wall holding up a raised next-door yard. New concrete and old block do not settle at the same rate, and the junction becomes a straight vertical crack line that lets air and water through. The remedy varies: a cut control joint with a flexible sealant when the movement is seasonal, or segmental underpinning when the old wall follows the fill sliding down.
These junctions also call for a read of the survey certificate before digging: several Montréal-Nord yards carry drainage easements or shared walls left over from the original subdivision. Our assessment includes that read, with the planned excavation depths, because a trench that bites into the neighbour's easement stops dead mid-job. An hour of checking paperwork beats an excavator parked for three days.
Our services in Montréal-Nord
Frequently asked questions
My crack weeps only in spring: is it urgent?
A crack that weeps at thaw but stays dry from June to November gets measured first: on the gauge, if it stays under 2 millimetres and stable between October and April, a flexible polyurethane injection closes it and adapts to the seasonal play. The risk is not one spring of water, it is the cycle repeating: every thaw washes out the mortar, rusts any rebar, and widens the opening. Treat it before it turns structural.
Is a French drain mandatory in Montréal-Nord?
The building code does not force a drain on an existing foundation, but any new drain must meet the building chapter on perimeter drainage: continuous slope, an accessible cleanout, discharge to the storm sewer or the pit with a check valve. In practice, a house that runs a pump every April has failing drainage, and the seller must declare it in a transaction. Fixing the drain before listing avoids the last-minute renegotiation.
Can a crack be injected in a plex party wall?
Yes, and it is the borough's most common case: the injection runs from the more accessible basement, no excavation, and the sealed wall serves both units. The legal label follows the wall: on a shared footing, the expense splits under the registered agreements, and our written report, with measurements from both sides, serves as the common document for both owners. Two signatures on a clear quote beat a lawsuit over a one-sided bill.
A foundation to assess?
A job in Montréal-Nord ? Three photos and the build year are enough for a first firm opinion. Or call 438-544-6364.
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