Ontario Lot Grading and Drainage Requirements

In most cases, yes, in some form. While the exact requirement is set municipally rather than by a single province-wide rule, most Ontario municipalities require an approved lot grading plan as part of the building permit for a new home, especially in serviced areas, subdivisions, and infill. The plan shows proposed elevations, slopes, swales, high and low points, and where water is meant to go, and depending on the municipality and project it may need to be prepared or stamped by a qualified professional such as a professional engineer or an Ontario Land Surveyor. On top of the plan, many municipalities also require a final grading certificate after construction to confirm the lot was built as approved. Confirm the specific submission requirements with your local municipality before you finalize your foundation elevations, because grading and building height are tied together.

A lot grading certificate is the after-construction confirmation that the finished grading was actually built to match the approved grading plan. It is typically prepared by a qualified professional who surveys the completed elevations, confirms that water slopes away from the building and reaches the approved outlet, and certifies that the lot conforms to the design. Many Ontario municipalities require this certificate before they release your grading deposit or security and close out the file, so it is often the last box to tick on a new build. The sequence is design it, build it, prove it: the plan says what you will do, the construction does it, and the certificate proves it was done. If your municipality requires a certificate, budget for it and schedule it after final grading, not as an afterthought once you have already moved in.

It varies by municipality, project type, and whether you are in a subdivision or an infill situation, so there is no single number. Many municipalities collect a grading deposit or security as part of the building permit process, often in the range of a few thousand dollars per lot, and some deduct their review fees from that deposit. The deposit exists to make sure the final grading is actually completed as approved rather than left “mostly done” with a few low spots, and it is generally held until the grading is certified and the municipality is satisfied. The practical advice is to treat the deposit as a real line item in your budget, understand exactly what conditions release it, and plan the final grading and certification so you get it back promptly instead of leaving money tied up for a year.

Not freely. Your finished grading generally has to match the approved grading plan and the wider drainage concept, because changing it can push water onto a neighbour, create a new low spot at your own foundation, or break the outlet the whole street depends on. Filling in a swale because it looks odd, raising a patio, or adding hardscape without a drainage plan are common ways homeowners accidentally create flooding and end up regrading at their own cost. On top of the municipal side, if your lot is within a conservation-authority regulated area, altering grade or placing fill can require permission under Ontario Regulation 41/24. Before you reshape anything, check the approved plan, confirm whether you are in a regulated area, and if you are unsure, ask your municipality – a quick call is far cheaper than a regrade or a dispute with a neighbour.

A conservation authority gets involved when your lot is within a regulated area – typically near wetlands, watercourses, valley or stream corridors, shorelines, or hazardous lands. In those areas, grading, placing fill, or altering drainage can require permission from the authority. As of April 1, 2024, conservation-authority permissions across Ontario are administered under a single new regulation, Ontario Regulation 41/24, which replaced the old individual authority regulations and narrowed some of the triggers, including reducing the regulated area next to provincially significant wetlands. Because that clearance can count as Applicable Law for your building permit, a permit can stall until it is provided. The safe move is to contact your local conservation authority early, confirm whether your property is in the regulated area, and get written confirmation if no permit is required, so it does not surprise you mid-project.

The governing principle is that finished grade must slope away from the building so water cannot pond against the foundation, and the general rule of thumb builders use is a fall of a few inches over the first several feet away from the wall – enough that a hose or a heavy rain visibly runs away from the house rather than toward it. The exact grades on your lot come from the approved grading plan, which balances the slope away from the building against the swales and outlets that carry the water off the property, so you should not simply pick a number. What matters most is that there are no low spots or reverse slopes near the foundation, downspouts, window wells, or below-grade entrances, since those are where the water that causes basement problems collects. When in doubt, follow the plan and confirm the finished elevations with whoever certifies your grading.

Downspouts should discharge away from the foundation walls and toward the approved drainage path for your lot, not straight down beside the basement wall. Roof water is a surprisingly large volume in a storm, so a downspout emptying at the foundation can overwhelm the soil and the perimeter drainage and become a direct cause of a wet basement. The right destination depends on your lot: it may be a splash pad and a slope toward a swale, an extension that carries water well away from the wall, or in some serviced areas a connection defined by the municipality. Avoid dumping roof water onto a neighbour or into a spot that has no clear outlet. If you are unsure where your roof water is supposed to go, the approved grading plan or your municipality will tell you, and getting it right is one of the cheapest ways to protect the house.

Grading and drainage are site work, so the right people are an experienced excavation and site-work crew who understand how the grading plan, the foundation elevations, the swales, and the outlets fit together – not just someone with a machine who can push dirt around. On a new build, the grading should be coordinated with whoever set the foundation elevations, because the two have to agree, and it should be finished in a way that will actually pass the municipality’s grading certificate. Doing it right the first time is far cheaper than regrading after a wet spring or after a neighbour complains. In the Simcoe County and Georgian Bay area we handle the excavation, rough grade, drainage, and final grade with our own crew, so the site is set up to certify cleanly and keep the basement dry, and we are happy to price it from the lot.