Why is finish grading so important?
Finish grading is not just an aesthetic issue. If improperly completed, improper finish grading can affect the performance of multiple building systems. When water is allowed to saturate the areas immediately surrounding a structure, movement will occur. This is particularly true in cold climate areas where frost heaving should be expected. With movement of the supporting soils, damage can occur to the concrete foundation, framing, plumbing, and drywall systems for starters. Insect infestation, rot, and mold can also be caused by improper grading issues.
^^ Backfill against wooden framing. ^^
How do I know if my grading is okay?
If you’re not sufficiently qualified to analyze your own grading issues, consider talking with a credible excavation contractor. If you’re looking at moving large volumes of runoff, it may be best to involve a civil engineer for professional assistance. A real benefit of working with a civil engineer is that once a design and specifications have been established, it’s easier to obtain equitable proposals for completing the work from multiple vendors. It’s possible, for example, that without established engineering specifications for your project, that if you consulted with three different contractors, you might arrive to three different solutions to the problem. Lack of design specifications makes comparing proposals very difficult.
^^ Example of landscaping company backfilling and mulching against wooden siding. ^^
3 Ways Grading Goes Wrong…
The addition of dirt and mulch materials around the foundation for landscaping is probably the leading cause of finish grading problems we see routinely. Often times the finish grade may be done properly by the builder, only to have a large amount of materials imported later for planting. This can create a “hump” in the grading right about where the eves from the house are depositing moisture. With this reverse grading, water heads toward the foundation potentially causing settlement and other issues.
The second condition we observe regularly is insufficient compaction. Consider if say four feet of material was removed from the earth to place foundation footings and walls. If replaced with proper mechanical compaction, you might expect the backfill to shrink no more than 5%, or 2.4”. This is a fair amount of settlement, even if the work is performed correctly. Consider larger fills, the failure to use the proper compaction equipment, or backfilling during adverse weather conditions and the settling can be much worse.
Lastly, using a well-defined grading plan and verifying that the proposed grading and drainage layout actually work with instruments such as site levels and lasers is of the utmost importance. You simply can’t “eyeball” complex grading and drainage areas and expect them to work properly. Be sure to hire a qualified contractor with sufficient equipment and experience in your area to handle your finish grading projects.
^^ Properly graded and compacted backfill with adequate separation between dirt and wood framing components. ^^