Exterior waterproofing and membrane

This is the repair people put off until the third wet spring. It costs the most, it takes the longest and it involves a machine on your lawn. It is also the only approach that keeps water away from the outside face of the wall rather than managing it once it has arrived, and for a block or stone foundation, or a wall leaking in several places at once, it is generally the honest recommendation.

Step one: locates, and they are not optional. Before anyone digs, a locate request goes to Ontario One Call. It is legally required, it is free, and homeowners and contractors alike are told to submit at least five business days before digging (Ontario One Call, homeowners). Private services the utilities do not own, such as a gas line to a garage or a buried irrigation feed, are the homeowner's to declare. Build that week into your schedule.

Step two: clearing and excavating. Decks, steps, walkways, air conditioners, shrubs and interlock along the wall come out or get protected, and those costs belong on the quote rather than in a conversation on day two. The trench goes down to the footing, typically 1.8 to 2.4 m in an Ottawa basement, and it needs to be wide enough to work in safely, which means the spoil pile is larger than most people expect.

Step three: cleaning and repairing the wall. The exposed wall is scraped and washed. Cracks are filled, deteriorated parging is cut back and replaced, block joints are repointed where needed, and any old tar coating that has failed is removed rather than covered over.

Step four: the waterproofing itself. A liquid-applied rubberized membrane or a peel-and-stick sheet membrane goes on the full height of the wall, carried down over the footing joint, which is where a great deal of water actually enters. A dimpled drainage board then goes over the membrane. Its job is to give water a free path down to the drain instead of sitting against the wall, and to protect the membrane while the trench is backfilled.

Step five: new weeping tile and backfill. New perforated pipe is laid at the footing in clear stone, wrapped in filter fabric, and tied to the sump or the storm connection. The trench is backfilled in lifts, and the finished grade is set to fall away from the house. Reinstatement of sod, interlock or a deck is the last step and the one most likely to be quoted vaguely, so get it specified.

How long it takes. One wall on a straightforward site is usually three to five working days. A full perimeter is commonly two to four weeks depending on access, weather and how much hardscaping has to come out and go back. Add the locate week at the front. Nothing about this work is fast, and rain days extend it.

What it costs in Ottawa in 2026. Indicative ranges only. Exterior waterproofing tends to be priced by the metre of wall, and a common Ottawa band is about $150 to $300 per linear foot, which is the imperial unit the trade still quotes in. A full-perimeter job on an average detached house frequently lands somewhere between $20,000 and $42,000. The drivers are depth to footing, whether a machine can reach the wall or the dig has to be done by hand, what is in the way, the condition of the wall once it is exposed, and reinstatement.

What makes an Ottawa house different. Champlain Sea clay is the reason this repair is both necessary and delicate here. Clay holds water against a wall rather than letting it drain away, and it is sensitive material that loses strength when it is disturbed (NRC, Geotechnical properties of Leda clay in the Ottawa area). That has two practical consequences: backfilling with free-draining granular material rather than the clay that came out makes a real difference, and excavating hard against a neighbouring foundation on a narrow older lot needs care and sometimes an engineer. In the mature inner suburbs, Alta Vista, Manor Park and parts of Nepean among them, the constraint is often simply that a mature tree or a two-metre side yard means the machine cannot get there.

Who should do the work. No provincial licence covers waterproofing itself. What matters is that the contractor carries liability insurance and WSIB coverage, books the locates, and works to a written scope. A City of Ottawa building permit is needed where the work becomes structural, for example underpinning or replacing a section of wall, and structural design work in Ontario has to come from a licensed professional engineer, verifiable in the PEO directory.

What to ask before you hire. Which membrane product, sheet or liquid, and what is its warranty. Is drainage board included. Is new weeping tile included and what is it connected to. Who books the locates. Exactly what reinstatement is in the price, in writing, including sod, interlock and the deck. How will you backfill and with what material. What is your warranty on the wall, how long, and is it transferable. Get at least three quotes, and compare scopes rather than totals.

One honest caution. A contractor who offers to dig only the corner where the water shows, on a wall that is leaking in several places, is selling you a partial answer at a full price. Ask them to explain why the rest of the wall is sound.