How to Design an Underground Room

Measure the space that you want to convert into an underground room. If you don't already have a basement that you're going to convert, record the desired dimensions of the room. Bear in mind that the dimensions for a room you must construct from scratch should include the exterior walls.

If you're building a safe room, FEMA suggests making the room between 8 and 14 square feet with walls that are 8 feet tall. Otherwise, the dimensions of your garage are a good guide for creating the room. The space beneath the garage can serve as a good location for an underground room if you don't have a basement, according to FEMA. Plan to give each person who'll occupy the room at least 20 square feet of space. An individual may need more space, however, depending on the purpose of the room or if she uses a wheelchair.

Use the measurements to draw the schematics of the room to scale on graph paper.

Devise a way to get into your underground room. If the room is in a basement, you may have stairs that already lead down to the room. If you have a large crawl space that you're converting into a room, consider the benefits of entering the room from a door on the side of the home versus constructing a staircase within your home that leads down to the area. When an underground room isn't part of a home, FEMA advises installing an entry hatch above ladder rungs installed into at least 8 inches of reinforced masonry.

Consider different ventilation systems. Air doesn't flow as freely in underground rooms, and neglecting to install a ventilation system will make oxygen scarce. FEMA suggests installing an HVAC unit in an underground room with a ceiling exhaust fan. Also include ductwork or a hardened ventilation pipe to prevent windborne debris from flying into the room. When installing ductwork or ventilation pipes, remember to also install an insect and rodent screen.

Base the interior design and lighting on the underground room’s intended use. For example, if the space will become an office or a craft room, design it with plenty of storage options. For areas that will serve as a spare bedroom or entertainment room, consider adding a small powder room. If the room will double as a safe room during a storm, create a space to keep an emergency supply kit, food, water and even an in-wall safe with important documents and emergency money.

Use the scale drawing of the underground room to test different furniture layouts cut from paper. Remember to include the locations of doors, closets and any fixtures you plan to install.

Consider your power options. You can connect the underground room's power to your home's electrical system. In addition, or as an alternative, you can furnish power with a generator, particularly if you use the area as a safe room. For backup electricity, you can also use solar options recommended by your power company.