Remove pillows and cushions that are not attached to the sofa. Set these to the side.
Clear any furniture near the center of the room, and lay down a sheet to create a workspace.
Move the sofa to the workspace, positioning it on top of the sheet. The sofa should be in the center of clear, open space that allows you enough room to move all the way around it comfortably.
Remove upholstery staples along the back side of the couch with needle-nosed pliers.
Cut into the fabric on the back side of the couch, making a large slit. From here, cut all the fabric away from the back of the couch. Cut away fabric from the arms and lower portion of the couch if you plan to reupholster the entire piece of furniture; if not, remove only the fabric on the back side of the couch to reupholster this area alone.
Remove and dispose of the foam batting.
Cut away the frame for the back of the couch using a hacksaw. Take care not to damage the lower portion of the frame. You may leave a portion of the frame in place, if desired, to keep a low back on the daybed. Attach a 2-by-4 along the top of the remaining frame, and nail it into place to create this effect.
Place foam batting over the exposed wood. Secure the batting to the frame with a staple gun and staples.
Measure the unupholstered area of the sofa, recording measurements for height, width and depth. Use the measurements to determine how much fabric you need, after adding approximately 6 inches to the measurements to provide a little extra room.
Place the fabric over the foam batting, allowing 2 to 3 inches of overlap on either side.
Pull the fabric tight across the batting, and staple it into position along the back side of the couch.
Trim away the excess material, and follow the same upholstering procedure if you are doing the arms or the entire sofa.
Unzip the fabric cover, or cut away the fabric on the sofa chair cushions and re-cover the batting with new material if desired. Or simply replace the cushions on the seats of the sofa.
Move the daybed into its desired position, remove the sheet, dispose of debris collected there, and then vacuum the entire area.