Things You'll Need
Dimensioned lumber to match existing joists
Screws, 3 inches long
Always wear eye and ear protection when working with power tools.
Keep children and pets away from any work area, particularly when you are creating holes in the floor.
Cutting a hole in the floor for a staircase may happen during new construction or while renovating an older home. When converting an attic or basement to finished living space, you may decide to replace a ladder with a stairway or to enlarge an existing stairway. Either process requires cutting away flooring. Avoid cutting through any beams or joists unless you are absolutely sure that they're not helping to support the house.
Lay out the location where your new staircase will go using a tape measure and a chalk line. Make the hole 3 inches larger in each dimension than you want the finished opening to be. Mark the corners of the hole with a pencil, then stretch and snap the chalk line between the corners, leaving a straight line marked in chalk.
Cut away the flooring and subflooring along the chalk lines.
Support the floor from underneath by placing 2-by-4 props from the floor pressed up against the ceiling on both sides of the hole that you cut.
Cut away any joists that are crossing your new opening using a circular saw.
Measure the length of the stairway opening, and cut two pieces of lumber that match the width of the existing joists and the length of the opening. For example, if the floor joists that you cut are 2-by-8s and the hole is 72 inches long, you need two 2-by-8s cut to 72 inches.
Install the two boards that you cut by fitting them into the opening and using 3-inch screws to screw them onto the exposed ends of the joists that you cut, thus creating a hole with sides that are formed by the boards rather than by cut joists and the openings between them.
Cut two more boards for the short ends of the opening, and install them between the ends of the first two boards that you screwed in, creating a framed rectangular opening in the floor.
Remove the supporting 2-by-4s from underneath.
Jagg Xaxx has been writing since 1983. His primary areas of writing include surrealism, Buddhist iconography and environmental issues. Xaxx worked as a cabinetmaker for 12 years, as well as building and renovating several houses. Xaxx holds a Doctor of Philosophy in art history from the University of Manchester in the U.K.