Foundation Tar Coating

When tar coating makes sense, and our application process

Tar coating is appropriate in three main scenarios. First, targeted repair: your home was bituminous-coated 15 or 20 years ago, most of the perimeter is still sound, but a specific section — often an exposed corner or the portion under a downspout — is starting to fail. Replacing the whole foundation with Delta-MS would be disproportionate; a fresh tar coating localized on the affected section, after cleaning and filling active cracks, easily buys back another ten years. Second, the tight-budget renovation: you know the foundation needs attention, excavation is feasible, but a full Delta-MS membrane is outside the envelope. Tar coating alone will not last 30 years, but it protects the home right now and stays compatible with a drainage membrane if you decide to add that layer later. Third, the technical complement: on a new build where we are installing a French drain and a dimpled drainage membrane, a bituminous primer improves bonding and seals the concrete pores before the membrane goes on.

There are also situations where we will steer you toward a different method. If the water table is high and your foundation is concrete block with already-tired mortar joints, tar coating alone is not enough — hydrostatic pressure will find the joints. In that case, we recommend our Delta-MS membrane service instead, which creates a real drainage space between the wall and the soil. If foundation geometry is complex — re-entrant angles, multiple pipe penetrations, irregular shapes — sprayed elastomeric liquid membrane gives better results because it follows every detail without seams. And if you plan to stay in the home for 25 years or more, the extra investment in a long-life membrane pays back. Our free diagnosis tells you straight up which method fits your situation, without defaulting to the most expensive option.

Our application process runs in five documented steps. One, inspection and written diagnosis with photos: we assess the condition of the concrete, presence of moisture, the existing French drain, surface grading and any signs of infiltration inside the basement. Two, excavation of the affected perimeter — using mini-excavation where access allows, to keep landscaping damage to a minimum. The trench reaches down to the footing and is wide enough to work in safely. Three, wall preparation: pressure-washing to remove soil, fine roots and remnants of the old coating, hand-brushing of efflorescence areas, filling active cracks with polyurethane or epoxy depending on type, and application of a bituminous primer that seals the concrete pores and improves the bond of the main coats. Four, application of the liquid tar: two or three successive coats depending on the substrate, either with a long-nap roller or by airless spray. Spraying produces a more uniform film and better distribution into the concrete's irregularities; we use it as standard on larger jobs. Between coats we respect the manufacturer's drying times — generally four to eight hours depending on temperature and humidity. Five, final inspection, backfilling with compaction by lifts, restoration of grass and surface grading to push water away from the footing.

On the technical side, the bitumen we use is a cold-applied asphalt product, low-VOC, compliant with Quebec standards. It cures into a matte black film, slightly flexible, that bonds firmly to the concrete and stays watertight against liquid water. Its main limitation compared to modern membranes is that it does not create a drainage space: water travelling down along the foundation presses directly on the coating. For that reason, a tar coating only performs as advertised when there is a functional French drain at the base of the footing. If your drain is old, blocked or non-existent, we diagnose it first and propose a combined intervention — French drain repair or new installation at the same time as the tar coating. The 10-to-15-year service life holds up when drainage and surface grading do their share of the work; without that, even the best product wears out early. Written workmanship warranty, current RBQ, APCHQ, RECQ and Réno-Maître certifications, all verifiable online.