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Building a new home gives us a chance to create something brand new with the goal of having no problems. After all, that’s one of the motivations for building a new home in the first place. You shouldn’t have to wrestle with frequent repairs like you would on an older home. One of the more common problems in older homes revolves around improper yard drainage. With a poorly designed drainage plan, a home can have standing water, basement leaks, flooding, pests (i.e. mosquitoes) and many other potential side effects. Let’s take a look at some of the basics of lot drainage from a professional builder’s perspective to help ensure your new home comes with zero problems.
Yard Water Drainage 101
Each new community built today comes with an overall water drainage plan designed by a civil engineer, showing where the storm water should flow. So for each drop of rain that hits the ground, there is an overall plan for how it should be managed to prevent problems. This community plan includes sizes and locations of storm drains, elevations for all points within the community, swales which direct accumulated surface flow water…etc. Then each individual lot within that community is designed to fit within the overall water drainage plan so that all of the yards work together to prevent flooding or ponding of water.
Building Lots Requiring Special Considerations
When you are evaluating potential lots to build on, there are some key items to look out for that have the potential for drainage trouble in the future. These items are not deal breakers, but they will need special attention to avoid potential yard drainage problems.
- Low Elevation – The lowest lot in the community can be a problem. All of the homes uphill will drain down and hopefully through or past the lowest lot. As long as the design of the community is correct and the design is followed properly by the developer/engineer/builder, there shouldn’t be any problems.
- Rock Under Surface – When rock exists below the surface, it can create an impervious barrier that prevents rainwater from percolating down into the ground. This will create excessive surface runoff which can lead to higher volumes of water in drainage pipes, swales and streets.
- Adjacent Bodies of Water – It’s important for the civil engineer designing a subdivision or individual lot drainage plan to consider adjacent bodies of water carefully. What is the high water elevation for the body of water? Meaning, during a typical storm how high will the water rise? Once the engineer knows this answer, they can determine what the effect will be of that raised water level on any given individual lot.
- Rising Backyard Elevation – When the backyard slopes upward from the back of a home, there is a need to manage the water that will ultimately run down the slope of the backyard toward the home. This can be accomplished with what is called a horseshoe swale (basically a depression in the ground that collects the rainwater and directs it around the house toward the front/street). The other option is to slope the backyard to a drain that will then carry the water off the lot. The only problem with this solution is that the drain needs to be kept clean in order to operate properly. Things like leaves, tree debris, toys, animal nests…etc. can cause blockage that can lead to clogs.
Design and Implementation Keys to Success
The building lot for a new home requires just as much attention as the house plan design. A qualified civil engineer should review the existing, undeveloped lot along with its surrounds before creating what’s called the engineered plot plan. This plot plan will show where the house sits on the lot, the proposed elevation of the basement and first floor, final grade elevations, and any storm drains required.
Once a proper design has been completed and approved by the local building department the house can be built. This is where the implementation begins. The house absolutely, positively must be set to the elevation chosen by the civil engineer. This will ensure the grading around the lot will work as proposed. Some people use the old cliché, “it all starts with the foundation.” Actually, most builders will tell you a slightly different variation to this slogan, “it all starts with the elevation of the foundation.” If the house is built too low, there can be major issues with water leaking into foundations, undermining slabs and driveways, standing water,…etc.
After the home is built, the original engineered plot plan still must be followed or redesigned with any proposed changes. Homeowners regularly get into trouble when they add fences, landscaping, pools, storage buildings…etc. These items have the potential to completely change the drainage of a lot and cause major problems if the water is dealt with accordingly.
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