Improving Lot Grading

Proper lot grading is one of the most important things you can do to prevent water from getting into your home. Since 2011, the Town of Slave Lake has had a Bylaw that requires all homes in neighbourhoods to be graded in accordance to an approved lot grading plan. 

Lot grading starts at your basement wall. Good eavestroughs, downspouts and extensions help make your outdoor drainage system better, but it can’t make up for poor lot grading. Walk around your home and ensure there is a minimum slope from the wall. This includes under stairs, steps, and decks. The dirt or sod should slope down from the wall at a continuous angle for at least 1.5 to 2 metres (5 to 6 feet). If the surface is decorative rock, bark, or another porous material that lets water through easily, take the measurement from where the underlying dirt begins. 

To have a proper slope, the soil at your basement wall should be higher than the ground several feet away. You should have a positive slope of 5% for a minimum distance of 3 m or to the side property boundary whichever is less. Use a slope gauge (see Diagram A and Diagram B) to see if the angle of the slope is adequate. 

Homemade Slope Gauge 

It’s easy to make a slope gauge. Cut a 2x4 into one five foot length and one six inch length. Place the shorter piece vertically on end. Place the longer piece horizontally on top. Nail or screw the end of the horizontal piece onto the end of the shorter piece. Tie or place a level on top of the horizontal piece and you are ready to go! See Diagram B.

Place the long end of your slope gauge against the basement wall and the shorter end on the ground. The horizontal board should be level. If it is not, add soil at the basement wall until level is achieved. 

Use this process as a guide for backfilling all the way around your home. Pack down the soil with a shovel or your foot. Check every 1.5 to 2 metres (5 to 6 feet) with your slope gauge to make sure the angle is still right. 

It’s important to backfill underneath your stairs, steps, and decks as well. Use the same angle as around the rest of the house, even if the bottom stair or step is less than five feet from the basement wall. 

BE KIND TO YOUR NEIGHBOURS

The sloping of your lot must follow the same rules as downspout extensions (see Chapter 3). Water should be directed to the back alley or the street and not into your neighbour’s yard. This can be tricky when the space between houses is narrow. One solution is for you and your neighbour to create slope down towards a common property line. This creates a common swale that can then channel water towards the alley or the street. See drawing below. 

Your property may not allow for this solution. (i.e. you may have a retaining wall or high ground at the property line). In such cases, you can create an internal swale (a slope from the house and a slope from the high ground meet in the middle of the of the yard) and channel water towards the alley or the street. See drawing below. 

In some cases, a neighbour’s property may have approved grading, but be lower than yours. A retaining wall along the property line is a good solution to this problem and can be done in front of an existing fence or other feature you don’t want disturbed. The wall allows you to create an internal swale that can safely channel water away. 

It is always best if neighbours can discuss and resolve lot grading issues together.