GRADING AND DRAINAGE PLANS
In episode 2626552 of things you need to have ready before building, we discuss grading and drainage plans.
Rainfall is one of the things that necessitates Civil Engineering plans, and the logical question is; how is all the excess water dealt with?
When it rains, rainwater should normally flow away from a building where proper grading and drainage have been set up; however, where that is absent, water will flow towards that property and can damage the building's foundation. Therefore it is necessary to properly plan and implement a good grading and drainage plan.
What is a Grading and Drainage Plan?
It is not enough to focus on the roof, windows and other openings in a building to manage water in-flow into the building. It is equally necessary to prevent the in-flow of water on the property, and that is the job of a proper grading and drainage system. In fact, a construction permit will not be given in many cases, unless a grading plan is tendered.
Grading is simply the process of shaping the building's landscape in such a manner to direct the surface runoff away from the building. The runoff should be chaneled towards a lane, street or an approved drainage system. The grading plan reveals the slope of the landscape in increments, as well as the property in question, the current grades of the landscape, the proposed location and the dimensions. Also included in the plan are land development criteria, drainage swales, easements and fences.
A grading plan directs the construction project to allow proper surface drainage, whie putting in perspective neigbouring buildings and lots. The plan regulates the relationships between the building to be graded and adjoining properties. The plan also helps the builder with specific details required to inspect and manage the grading process, thus minimizing errors and callbacks.
Laws on Drainage
There are laws in most American cities regulating construction procedures which cover grading plans. A city- approved grading plan is usually required to obtain a construction permit, and that plan must be consulted to begin grading activities, whether the building is a single family unit, row-house or semi-detached residential properties.
Establishing and Implementing a Drainage Plan
The goal of a drainage plan is the elevation of the soil and the building's landscape. In creating the grading plan for a residential or commercial building, two factors should be considered.
First, water should move down and away from the building's foundation. And again, the water should be channeled away from the property and into a storm drainage system.
Consequences of Poor Grading Systems
If your land isn't properly graded, it would not just affect your building but neigbouring lands and property as well. When it rains, your building's foundation will be in danger of moisture damage since rainwater will flow towards your building instead of away from it. Also, hydrostatic pressure could build against the wall or base of the building. (Hydrostatic pressure is the weight of the water pushing the wall).
Again, various other issues could result, such as soil erosion, structural damage, and cracks in the foundation.
The negative impacts of an improper grading system extends to the neighbouring property. Where surface runoff flows into the adjacent property, soil erosion or flooding could result. Where this happens, the contractor or building owner is liable for such damage, leading to extra costs.
In order to prevent any of these situations from ensuing, it is pertinent to carefully follow the grading plan while preparing the finished grade. Other alternatives include grading slopes to channel water out of the building or constructing swales to redirect groundwater. You could also determine soil level by adding or removing specified amounts of soil from the site.
Who Creates a Grading Plan?
A licensed civil engineer or architect must supervise the creation of a grading plan. Before obtaining a construction permit, the design must also be approved and signed by an architect or civil engineer. In some cities, it is required that the design itself be done by a civil engineer, especially in cases where the grading project involves a property of 2,000 cubic yards.
However, where the grading plan is for a complex project, even if it involves less than 2,000 yards, the local planning department stipulates that a civil engineer prepares the grading plan. Generally, engineers are more skilled and knowledgeable on the techniques that the grading plan requires, although architects can create good grading plans.
Supervision of Grading Projects
While inspecting and planning the final grade, certain guiding principles should be followed. First, the grading process should be done during the dry season so as to prevent soil erosion and regrading the land later. Again, the earthwork excavated from the site should be used to prepare the final grade. The remaining earthwork should be covered or sprayed with hydraulic mulch to prevent excessive runoff or soil erosion.
The foundation should also be protected with proper backfilling, especially if the grade is below the foundation or is near the wall cladding. This protects the foundation from moisture later, and also get rid of termite paths to the building.
Finally, the site supervisor should carefully monitor the activities of the grading crew to ensure that the grading plan is properly followed throughout the entire project.
To help you create your grading and drainage plans, our team of professionals at JPC Design Consortium are available to help you. Let's help you get started on your project! Contact us right away.