Determine the desired dimensions for the rectangular frame and cut pieces of 2" x 10" lumber to the correct lengths for the four sides. The rectangular frame in this project measured 11-1/2’ x 4-1/2.’
Note: The key to success with this loft is keeping everything on the level. Always check level before securing any of the boards or posts for the loft frame.
Measure and mark a level line 3-1/2’ up from the floor along the back wall. Line up one of the 2” x 10”s on this line and screw into the wall studs. Use the same process to line up and attach the side pieces to the support walls, remembering to drive screws into the studs. With three sides secured, nail the fourth 2” x 10” into the ends of the two side pieces.
Measure and cut eight 2” x 8”s to fit snugly inside the rectangular frame (54-1/8" for this project). Space the joists evenly and install them using metal joist hangers at the wall sides (Image 1) and nailing through the frame into the end of the joist on the other side (Image 2). If building a larger frame than used in this project, install more joists to make sure the floor has enough support.
Even with walls partially supporting the sides, the loft frame needs support. Measure and cut two 4" x 4" posts to the total height of the loft wall (from the floor to the top of the knee wall). Position one post inside the corner of the frame, make sure the frame is level, then mark the top and bottom of the frame on the post. Cut a notch in the post the same width and depth as the frame lumber so the post will fit flush against the frame.
Note: To notch the posts, use a hand saw or circular to make several cuts in the notch space, then remove the material with a chisel.
Position the posts on the inside of the frame and fit the notches over the frame. For this project, Karl positioned one post at the corner, but installed the other three feet in from the corner to leave room for the stairs. Check for level and plumb, then install by driving screws through the frame into the post. These posts sit inside the frame and will not be visible in the completed loft.
Measure and cut sheets of oriented strandboard (OSB) to serve as the loft flooring. Install by nailing through the top of the OSB down into the joists and frame.
The frame for the curved part of the loft will consist of three 2” x 8”s, attached at an angle to give as much support as possible to the curve. The exact dimensions will depend on the size of curve desired. For this project, the frame for the curve will extend 2 feet from the main loft frame. Measure and cut 2" x 8" lumber to the desired dimensions, mitering the edges of the boards. Nail the extension together.
Position the angled frame on the front of the rectangular frame, flush with the top of the frame. Make sure the frame is level with the main frame, then nail one end of the angled frame flush with the edge of the main frame. Adjust the other end of the angled frame so that it’s flush with the main frame, check for level, and nail in place. Measure the inside of the frame at both ends and adjust until it extends a uniform distance from the main frame.
Cut two 4" x 4" posts the same height as the top of the frame. Position them inside the front corners of the frame, check for level and plumb, and attach using screws.
Use screws to attach a small piece of 2" x 8" lumber to the center of the angled frame, keeping this board flush with the top of the frame. Position a 4" x 4" support post against this board and check for plumb. Nail through the post and into the board and frame. Attach the post by driving screws through the frame and board into the post.
Fit sheets of OSB over the angled frame, nailing through the OSB into the frame. Notch one sheet of OSB to fit around the support post. Make sure the OSB extends far enough past the frame to create the curve.
Cut the curved floor. Draw the desired curve onto the OSB, making sure it extends past the curved loft frame. Cut out the curve with a jigsaw.