If you're considering adding an in-law quarters addition to your home so that your parents, in-laws or even adult children can "move in" without completely invading your space, you're probably excited to get started. However, it's important not to get ahead of yourself when planning to add an in-law suite. To ensure you don't end up making costly (or simply annoying) mistakes, consider these factors before you start building that addition.

Can your septic system handle the additional load?

If your home is connected to a septic system rather than a public sewer, you'll want to make sure your tank is large enough to handle the additional load from extra people moving in. Generally, contractors base the size of a septic tank on the number of bedrooms in a home. A home with 3 bedrooms, for example, will generally be fitted with a 1,000 gallon tank. A home with 4 bedrooms will need a 1,250 gallon tank in order to hold the average amount of water and waste generated by 4 people. If you add an additional bathroom and kitchen to your home in the form of an in-law quarters, you might exceed the capacity of the tank, resulting in flooding.

To find out whether or not this will be an issue for you, contact a septic service and ask them to come out and look at your tank. Based on the size of your tank, the conditions of your leech field, and whether or not all of the bedrooms in your home are occupied, they can tell you whether you'll need to upgrade your tank when you build your addition, or if the tank you have is large enough to accommodate the extra water usage.

Is your current furnace up to the challenge?

If you have a forced air heating system, your HVAC professional will need to add additional duct work to bring heat into the extension. Similarly, new pipes will have to be run if you have a boiler-style heating system. Depending on the current size and layout of your home, the furnace or boiler you have may not be able to generate this additional heating power. Have an HVAC contractor come out to give you an opinion now, rather than waiting until the extension is built and finding out that you suddenly have to come up with the cash for a larger furnace. If you have central air, make sure your AC unit is up to the extra capacity, too!

Sometimes, it is less expensive to install a separate heating and cooling system in the extension, rather than replacing the furnace and AC units and running new ducts. If the in-law quarters are small, a small electric heater and window AC unit may suffice. Talk to your contractor about this possibility as well.

How will the occupants access the new extension?

The beauty of this style of home extension is that those who live in it have their own entryway and don't have to disturb the occupants of the rest of the home when they go in and out. However, it's important to consider how the entrance to your new in-law quarters will be accessed. Specifically, how will the occupants get from the driveway to the door? You may need to build a new pathway fro, the driveway through the backyard, or you may even need to build a second driveway to accommodate the additional cars. Plan this out the landscaping now, so your loved ones are not left tip-toeing through flower beds to get to their door.

Adding an in-law suite to your home is a great way to accommodate loved ones. Just make sure you take the time to consider how it will affect your septic system, HVAC system, and landscape planning before you dive in to the building process.