Reverse sloped driveways may be considered a necessity in high-density neighbourhoods, where there is no room for external garages. Reverse sloped driveways, however, create a significant flood risk as they can direct overland stormwater flows into homes. Water that enters homes through reverse sloped driveways can cause damage, and can also contribute to sewer backup problems if this water enters basement floor drains.

Catch basins are located at the bottom of reverse sloped driveways to drain water to the municipal storm sewer system. When there is a surcharge in the municipal storm sewer system, stormwater can be forced back into catch basins, where it will then flow into basements, garages and weeping tiles. Your municipality may recommend installing backwater valves into reverse sloped driveway catch basins to reduce stormwater backup.

As this type of backwater valve is located outside of the home, it is susceptible to blockages from debris and ice, and will require periodic inspections and maintenance. If downspouts or weeping tiles are connected to catch basins, they should be disconnected before a backwater valve is installed. Talk to your municipal government to see if they recommend this option, and ask for information on proper installation of this type of backwater valve.

Ensuring that reverse sloped driveways do not have a constant slope into the home from the street can also reduce the chances that water will enter the home. A 15 cm high-point between the surface of the street and the point where the reverse-sloped driveway begins to slope down toward the home can reduce the chances that overland flooding will enter the home through the reverse sloped driveway.

In some cases, the reversed sloped driveway catch basin may be connected into the home’s weeping tile system or sanitary sewer lateral, which would increase sewer backup risk for both the home and the neighbourhood. If the catch basin is connected to the sanitary sewer, talk to your municipal government about connecting it to the proper municipal sewer system. Identification of which municipal sewer system sloped driveway catch basins are connected to should be part of the detailed plumbing investigation of the home (see Option 3).