How grading and drainage work

Grading and drainage work together to move water away from your home and into the city’s stormwater system.

Learn how to maintain drainage on your property.

On this page:

  1. How grading woks
  2. Subdivision grading
  3. How water moves across your property
  4. Common drainage features

How grading works

Grading is the slope or shape of the ground on your property. It helps direct water away from your home and toward safe places to drain.

Good grading helps:

  • move water away from your home and other buildings
  • direct runoff to a safe outlet, such as a catch basin or swale
  • prevent pooling, damp basements and drainage issues with neighbours

Over time, soil can settle and change how water flows. Check your yard after heavy rain. You may need to fill in low spots or adjust the slope.

Subdivision grading

Subdivision grading plans are designed by engineers and approved by the city to make sure water drains safely across neighbourhoods.

  • the builder or developer maintains grading for 2 years after city approval
  • homeowners shouldn’t alter grading during this period
  • after 2 years, the homeowner is responsible for keeping their property graded correctly

How water moves across your property

Every yard drains differently depending on how it was built and graded.

Back-to-front drainage

  • the highest point is near the back of your lot
  • water flows through side-yard swales and out to the street at the front

Split drainage

  • the highest point is beside your house
  • some water flows toward the street
  • the rest flows to the back, where it’s collected in a swale or catch basin before draining into a storm
Diagram showing example lot grading with slopes, drainage direction, and how water should be directed across a yard toward storm infrastructure.

Property grading example. Image source: City of Guelph

Common drainage features

Drainage features help move water through your yard and into the city’s stormwater system. Drainage features on a property line must be maintained by both neighbours.

Keep them clear to help prevent flooding and protect nearby properties.

Illustration of an infiltration trench showing a gravel-filled pit beneath grass. The trench allows rainwater to soak into the ground instead of running off the surface.

Infiltration trench or gallery

  • an underground gravel-filled pit that helps rain soak into the ground
  • usually found at the back of newer lots
  • keep the area above it clear of heavy items, soil build-up or paving
Diagram showing a ground slope rising away from a house foundation so that water drains outward from the building.

Positive slope

  • the rise of soil away from your house that directs water away from your foundation
  • can flatten as soil settles — build it back up if needed

 

Diagram of a basement window with a surrounding window well, showing drainage, gravel, and how water is kept out of the window area.

Window well

  • a curved metal or concrete wall around basement windows
  • keeps soil back and lets water drain away from the foundation
  • check for leaks and make sure the well is sealed
Image of a side-swale showing a shallow, grassed channel along a property line designed to direct stormwater runoff away from a house toward drainage infrastructure.

Drainage swale

  • a shallow, grassy channel that carries rain and melting snow away from your home
  • usually runs along property lines or at the back of a lot
  • keep it clear – don’t fill it in or block it

 

Diagram of a rear-yard catch basin: shows a grate at ground level that leads into an underground box and pipe to collect surface runoff water toward the storm sewer.

Rear-yard drain or catch basin

  • a grated drain that collects water and moves it underground
  • found at low points between homes
  • keep the grate free of leaves and debris