This is part of an ongoing series about moving to the country from a geek’s perspective.
The most critical factor in deciding whether you can build a home on a piece of rural property is determining whether you can build a septic system that will support it. Well, that’s assuming that electricity and water aren’t an issue, but whereas those utilities hopefully already exist at or near the property (or can be extended there if needed), it may not be possible to install a suitable septic system to support your planned home.
I’ll be honest: this city boy had no idea how a septic system worked until a couple months ago. I just assumed it was like a giant port-o-john that someone came and sucked out with a truck every once in a while. But it’s much more involved: all of the waste water from your house goes into a holding tank, where the poop and other nasty stuff sinks to the bottom, and the soaps and other fats float to the top. The water in the middle then flows out into a field of “fingers”, which used to be just pipes with holes in them run through gravel, but nowadays are typically “chambers” which serve the same purpose.
The upshot is that the bad stuff stays in the system and breaks down by itself, but most of the water flows back out into the ground. That field is usually about 60 by 100 feet for a typical 3-bedroom house, which means you need a good deal of area to put the system, and that area needs good drainage so that the whole thing doesn’t back up and fail. In Indiana, the county health department makes the determination of what type of septic system is needed for a particular piece of land and a particular size of home.
In order to make this determination, they need a soil test to be performed by a licensed soil scientist. The soil test involves digging several holes of a small diameter up to five feet deep. The scientist will inspect the color and constitution of the soil, at 6-inch intervals, all the way until either 5 feet or a “limiting layer”, which typically is bedrock or some other material that water can’t flow through. He’ll then write up a report with this info and send it to the health department.
If the “limiting layer” is too shallow (less than about 3 feet into the soil), you aren’t building a septic system there and you can’t build a house there. Well, at least not without spending $20k+ on a highly-engineered system. If it’s more than 42 inches or so, you’re good to go: you may end up needing to add some fill dirt to the top of your field, but there’s probably enough stuff there to work with.
However there are other factors that are involved, such as the permeability of the soil and whether there’s a natural water table. In fact it’s possible that the soil is too permeable, in which case water flows back into the ground too quickly without having time to be broken down by the natural microbes in your system.
At any rate, if your conditions are less than ideal but you still have enough soil to work with, you may need a mound system, which is about twice as expensive as a regular field system. While a regular system might run you around $5k, a mound system could be $10k. Many systems these days also have “perimeter drains” to help ensure water keeps moving correctly.
The upshot of all of this is that determining whether a septic system can support the type of house you want to build is probably the most involved and site-specific criterion you’ll be faced with, and it’s mostly out of your control. You don’t pick where you want the home to go and then fit a septic system wherever you can; you figure out where the septic system can go and then build the home next to it.
So, we’re faced with a chicken-and-egg problem: you don’t want to buy land without knowing you can build a suitable septic system, but the seller can’t just get a “generic soil test” since they don’t know what type of home the buyer will want and where on the land they want it. The solution to this is a contingent offer to buy: when you actually make a formal offer for the land, you’ll make it contingent on the soil test being acceptible for your purposes.
In our case, we had 10 days from the time the offer was accepted to have a soil test completed. Indiana has an online registry of available soil scientists so I just found one who was close-by and made an appointment. We showed him where we wanted to build the house, he took the necessary samples at several locations, and a few days later sent his report to us and the county health department. It cost about $250.
At that point, we called up the health department and spoke with them about the type of system we’d need. It all sounded pretty standard and reasonable, so we moved forward with the purchase.