Do you need extra room in your home for an occupant, or have you always wanted to turn the basement into something more than just a storage space? To do so, the basement will have to undergo some significant renovations to become a livable space. Here are the basic steps for turning a basement into a comfortable room.
Most importantly, ensure that the basement will be as dry as possible. Slope the ground around the house away from the foundation, so water runs away. Make sure downspouts carry water well away from the house. If you’re still having basement water problems, dig a ditch around the house down to the footing and install drainpipes, sloped to carry water away. Coat the foundation exterior with waterproofing material before filling in the ditch again. Inside, as extra precaution against flooding, install a drainage ditch next to the foundation wall. Direct the ditch to a sump and sump pump at the low end of the basement slab.
Then you will need to construct actual walls, as basements usually just have the foundational walls showing. Some homeowners attach furring strips (1-by-3 lengths of wood) to the concrete foundation walls and then attach drywall to that. That's the hard way. The easier way is to build a 2-by-4 stud wall on the basement floor and then raise it into place. Use pressure-treated wood for the sole (bottom) plate. Build the wall with just a top plate, not adding a cap (double top) plate at this time. That way, when you raise the wall, it will clear the ceiling joists. After the wall is up, install the cap plate. Carefully measure the stud lengths and plate thicknesses in advance so all will fit exactly. Space the wall out 3 or 4 inches from the foundation wall. Once the wall is up, slip the cap plate in place between the top plate and the bottom of a floor joist. It should fit just snugly enough to hold the wall in place. Plumb and align the wall at this time.
To anchor the wall at the top, drive decking screws up through the top plate and the cap plate into a ceiling joist. To anchor the sole plate to the floor, buy or rent a powder-actuated fastener to shoot hardened nails through the plate into the concrete slab. You can also glue the sole plate to the floor.
Then you will need to do wiring and the lighting to make the space brighter. While the studs and ceiling joists are exposed, drill holes for all wiring, pull the wire through, and connect all outlets and switches. Do the same in the floor joists and install all lighting boxes. Install a ceiling fan for getting some air circulation in the room and some lights for added brightness, due to the basement’s below ground level.
Then there is the ceiling installation. Box in and drywall any exposed pipe, ducts, and other obstacles that you cannot move. Alternatively, leave all ducts and piping exposed and paint them bright colors, as if part of the basement decor. You must meet minimum ceiling height requirements. Ask your local building inspector what they are. If a pipe or girder is too low, you may have to build a wall around it. Turn the space into a closet. Install drywall on the ceiling.
If you want to minimize noise coming through the floor from above or below, install two layers of drywall. After the first layer is up, run aluminum resilient channel strips perpendicular to the joists. Then hang a second layer of drywall from the channel, with screws going only into the channel, not the joists. That way, sound won't travel through the screw to the floor above. The 3/4-inch dead air space between the two layers will significantly reduce sound transmission.
The basement will also need insulation to keep a steady temperature. Place batt insulation in the stud walls, with the vapor retarder facing the warm side of the room. If your basement is going to be heated, you don't need insulation between the floor joists; let the warm basement air help heat the floor above. Do not cover the exposed foundation wall with a plastic vapor barrier thinking this will stop moisture in the concrete from moving into the room. The moisture will only condense on the plastic and run onto the floor. Similarly, do not staple plastic over the stud wall. Moisture vapor has to pass through the wall. If your basement is too humid, use a dehumidifier to remove water vapor.
Then you will probably want to install finished flooring over the concrete foundation flooring to make for easier movement around the room and better insulation. There are many types to choose from, and they are each installed differently. These include:
- Ceramic tile: Tile flooring can be laid directly on a slab, if the surface is smooth and dry.
- Vinyl tile: You can also lay this directly on the concrete, but it will be a hard and possibly cold floor. Any moisture will pop it loose. It is preferable to lay it on a plywood subfloor.
- Carpeting: This too can be glued directly to a slab, but putting it on a subfloor is better.
- Laminated wood: It can be "floated" on the concrete floor by first putting down the plastic sheeting, then laying the laminate so it ends up wedged in place between the sole plates of the surrounding stud wall.
- Hardwood floor: This type of flooring must be placed on plywood subfloor as described above because it is most susceptible to expansion and contraction from moisture and heat changes.
Some moisture will inevitably either collect on the concrete floor or work its way through the floor from the ground underneath. To prevent moisture from subsequently working its way into your finished floor, cover the slab with 6-millimeters of plastic sheeting and tape down all seams. Over the plastic, lay sleepers, which are 1-by-4s or 2-by-4s that are spaced apart 16 inches from the center of one board to center of the next. Instead of nailing them down, cut them to fit snugly between the walls. Place spacers every 3 or 4 feet between the sleepers to keep them aligned. Over the sleepers, lay down 5/8-inch plywood subfloor. Use drywall screws to attach plywood to sleepers.
For bedroom furnishings, amenities like an armoire are a good alternative to knocking out a wall to put in a closet space or putting up hanging racks for clothing. Consider putting the bed away from the support beam as well, just in case of inclement weather. Make sure to have plenty of electrical outlets for iPods, laptops, TV, video game consoles, and other electronics. You may have to revisit the outlets currently in the basement or the power source for the house and consider upgrading them if you plan to use the basement as a living space.