One aspect of new home construction people often don’t think about is lot grading.
It’s not a thrilling subject, but it’s an important one.
Lot grading involves sloping the dirt around a home and on a lot to ensure surface water flows away from the building’s foundation and toward a suitable outlet where it can safely be disposed of without effecting surrounding homes. A good grading plan with proper drainage is essential when building a new home. Poor drainage can lead to the ponding of rainwater on your lawn and in some cases a wet or flooded basement.
Planning for good drainage starts well before the construction of a new home. When a land developer is creating a new subdivision, an overall grading plan by a professional engineer is required as part of the planning process. This plan is submitted to the city for approval to ensure that the overall drainage incorporates proper design that takes drainage patterns of the existing land, as well as neighbouring lands, into account and all surface water created by rain and melting snow makes its way to the stormwater outlets. Eventually, all water flows from these outlets to a storm water management (SWM) pond. SWM ponds are the ponds constructed in new subdivisions to capture and retain the surface water runoff from a subdivision and prevent it from entering the sanitary sewer system or neighbouring streams and rivers.
Once a subdivision has been serviced by the developer and the builder is applying for a building permit for a home, they must submit individual plot plans for each lot as part of the application. These plans are prepared by the builder’s engineer or surveyor and they are based on the overall subdivision grading plan. They show in greater detail the specific grading design for each individual lot as well as where the house is located on that lot.
Lot grading plans identify how the land around the house should be sloped and to what degree, as well as location of any drainage swales, shallow channels generally located between lots that move water draining away from the home off the property to the appropriate storm water outlet.
Once the construction of the home is complete and the builder has performed final grading, the surveyor must confirm that it has been built to plan. The engineer responsible for the overall subdivision grading plan then can issue a final grading certificate to the city that certifies the lot has been graded in conformance to the original plan.
The final grading certificate, however, is not the end of the story. After purchasing a new home, it is the responsibility of the homeowner to maintain the approved grading plan. Any areas of settlement around the foundation or in drainage swales should be repaired. When constructing landscaping features such as fences, walkways, decks, patios and swimming pools, the effects to drainage should be considered. All too often problems can occur after this type of work is completed. Blocking flow routes and drainage patterns can lead to serious flooding that can affect neighbours. All new landscaping and construction should be carried out without disruption to existing drainage. When in doubt, consult your builder or a professional engineer or surveyor.
Peder Madsen is president of the London Home Builders’ Association and vice-president of CCR Building and Remodeling in London.