You might be surprised to know that even though a lot of land in Oklahoma seems flat, most of it is not perfectly so. In fact, we rely on it not being perfectly flat for a number of reasons. While it might seem like building on flat land is cut and dried, there's one big problem with this scenario - drainage.If you're going to build a house on your land, arm yourself with some understanding of how slopes will play into your decision.Imagine pouring out a glass of water on a perfectly flat table. Where does the water go? Nowhere. It stays in a puddle because the table is flat.
Now think about a house on a perfectly flat piece of land. When the ground gets wet, where does the water go? Nowhere. That leads to drainage problems with 2 kinds of liquid: Rain water and sewage (specifically septic systems). Let's start with the yuckier of the two.
Flat ground and septic systems
With your typical, tried-and-true, anaerobic septic system, you've got a tank with two pipes. The first leads from your house to the tank. The second leads from the tank out to smaller pipes in your yard. Those farthest pipes are usually situated near the surface. The final product in your sewage process, water, filters out through those holes and into the soil, while the solid stuff is eaten up by bacteria in the tank.
There's a catch. The deeper those pipes are, the less efficient the system becomes because it's more difficult for the water to filter out into the soil at greater depths. With a sloped yard, it's easy to keep those pipes near the surface while letting gravity do its thing. When we're talking about a perfectly flat piece of land, gravity is out of the question.
So what happens when the ground becomes saturated? Water can't properly move out of the septic system and eventually your septic system backs up. You can't flush the toilets until the ground dries up, which isn't pleasant.
The solution here is an aerobic septic system. An aerobic system uses a compressor to filter out the waste, much like a pool or aquarium filter would. In the middle of the night, a sprinkler head pops up and spreads that filtered water on your lawn. No gravity required.
A situation like this is very rare. Typically, you have a gently sloping lawn that would make an anaerobic septic system work easily. But remember that when you're looking at land to build your home on, drainage is something that you have to take into account.
Flat ground and rain water
I can tell which of my clients have had drainage problems before, because they seem obsessed with making sure the ground around the house gets graded correctly. They are right to be concerned.
When building a house on flat land, there's nowhere for the water to go when it rains, so like the table example above, it just sits there around the house. Even if it doesn't run inside, it de-stabilizes the soil under the foundation and can cause unwanted movement. You might have seen evidence of movement in houses: cracked bricks, cracked drywall, and worse.
If you're considering a piece of land to build your home on, take care to find a spot that isn't too flat, one that has some kind of slope within 20 to 30 feet of where your house will sit. That will make drainage a lot easier and will help you sleep better at night.
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