Exterior Waterproofing near you

Water needs an opening and a force to move it, whether gravity, wind pressure or wicking. That's why leaks cluster wherever the wall is interrupted.

Behind the cladding, a water-resistive barrier covers the sheathing and carries any water that gets past the finish down and out. It only works if every piece is lapped so the upper layer overlaps the one below, like shingles, and if it's tied into the flashing at every opening. A barrier that is torn, reversed or tucked behind a flashing instead of over it can channel water straight into the wall.

Flashing is the metal or membrane that turns water back outside where the wall is interrupted: over window and door heads, under sills, at the base of walls, where a roof meets a wall and on top of parapets. Many chronic leaks come down to one flashing that was left out, installed backwards or covered over in a later renovation. Caulking helps at the surface but can't stand in for flashing; sealants are covered on the exterior caulking page.

A balcony or deck built over a bedroom, a garage or an enclosed room is really a small flat roof that people walk on. It needs a continuous waterproof membrane, a slope that carries water to an edge or a drain, and careful flashing where it meets the wall and the door sill. Depending on the design, the membrane may be a sheet product, a liquid-applied coating or a built-up system, often protected by pavers on pedestals, decking on sleepers or a traffic-rated surface.

Most failures start at the edges: the joint with the wall, the door sill, railing posts screwed down through the membrane, and drains or scuppers clogged with leaves and ice. When the walking surface has to come up to reach the membrane, it's worth rebuilding those details rather than patching the one obvious spot. Rot or corrosion found underneath needs a qualified contractor or engineer before new waterproofing goes on.

Clear water repellents are the product most homeowners picture when they think of waterproofing brick or stone. Penetrating repellents soak into the surface and reduce how much rain it absorbs while, in principle, still letting vapour out. Film-forming sealers and paints sit on top and can stop the wall from drying. Either kind can trap moisture and salts if water is already getting in behind it, and the result can be flaking and spalling after a few winters.

A repellent never replaces fixing cracked joints, failed caps, missing flashing or overflowing gutters. Where one is justified, a mason or envelope specialist should confirm the wall can dry, choose a breathable product suited to that masonry and try it on a small area first. The brick repair and masonry pages explain why old, soft brick deserves extra caution.

Water often travels along framing, membranes and pipes before it shows, so a ceiling stain may start some distance from the actual opening. A good diagnosis combines inspection inside and out, moisture readings, infrared imaging when conditions suit it and, where needed, controlled water testing that wets one detail at a time until the leak appears. Sometimes a small opening in the cladding or the interior finish is the only way to see what's going on.

In a condominium, the balcony usually isn't yours alone to repair. The Condominium Authority of Ontario explains that balconies and other exclusive-use common elements are owned by the corporation even though owners use them exclusively, and that most owner-proposed changes need board approval and a formal agreement under the Condo Act. In Quebec divided co-ownerships, balconies are typically part of the common portions, often reserved for one unit's use, and the declaration of co-ownership says who looks after them.

Before hiring anyone to seal, tile or re-membrane a condo balcony, read the declaration and by-laws and talk to the board or property manager. Unapproved work can damage the building's membrane, get in the way of the corporation's own repairs and leave you paying to undo it. For a house or plex in Quebec, make sure the contractor holds RBQ subclass 7.0, which covers insulation, waterproofing, roofing and siding.