Loft space can easily be converted to a room or storage area. Putting down flooring in attic space requires paying attention to issues involving the loft that affect livability of the house. These issues include insulation, electrical wiring and plumbing in the attic floor area. Putting down a floor will take careful thought and planning, but the additional space gained will be worth the effort.
Construct an attic access that is either a hatch door or staircase. Frame the opening of the access by driving nails downward from the attic side into the ceiling of the room below. Use nails that are a minimum of 4 inches to outline the cutout. Define the opening for cutting by using a carpenter's square and chalk. Cut through sheetrock or plaster, along with floor joists, with a circular saw.
Construct a box frame to secure the cutout. Build the framing to follow the exact shape of the opening. Use boards the same depth as attic rafters. Install the framing with 4-inch stainless steel screws. Build a staircase leading up to the attic at least 42 inches wide, if you have room. Install a pull-down staircase if there is not enough room for stairs.
Re-route wiring, water pipes and drain lines before you install sub-flooring. Run new wiring in conduit, and disengage the old wiring at the breaker box and at outlets or lights. Attach the conduit low on rafters to avoid penetration by new nails for the flooring. Route plumbing through rafter areas by fitting pipes closer to the ceiling of the room below.
Install insulation to the full depth of the rafters before you add flooring. Don't skimp on insulation, even if you will insulate the walls and ceiling areas of the new attic room. Insulate the floor to create a dead air space, and keep heat from below from escaping to the attic, while the floor rafters are open.
Use 4-inch stainless steel nails to secure ½-inch plywood over rafters for the sub-flooring. Cut the plywood flooring to fit into all nooks and crannies of the loft floor space to conserve heat in the room below. Install carpet or wood flooring, if you will construct an actual room in the loft, at the appropriate time during construction.