Build a Futon Frame
By Mark Johanson
Create a comfortable place for you to rest your feet, and for your guests to rest their heads, with this futon project.
Although still relative newcomers in the American home furnishings market, convertible futon sofas are starting to mature. The original inexpensive wood-pallet or tube-steel versions continue to hold a strong position on the lower end of the futon-frame spectrum, but innovative furniture makers and futon specialty shops have improved both the quality and styling of higher-end models. The futon frame shown here seeks to jump on the finer-futon bandwagon, combining simple efficiency with solid construction techniques and slightly more sophisticated styling.
The footprint of the plan is a loveseat-style sofa with an accompanying ottoman. Together they provide compact, comfortable seating that occupies less than 60 in. of wall space — compared with about 80 in. for a standard full-size bifold futon. But when butted together, the flattened sofa frame and the ottoman convert into a spacious, full-size bed.
The separate mattresses for the sofa and ottoman do not detract from sleeping comfort. And if you prefer, the ottoman frame can be topped with a piece of beveled glass to create a low coffee table. (The ottoman mattress tucks neatly behind the sofa frame.) Either way, this futon and ottoman set is appropriate for any decor, regardless of whether it’s casual or formal.
Because it is strong, springy and inexpensive, we used white ash to construct the furniture frames and slats. The mattresses (54 x 54 in. and 21 x 54 in.) and mattress covers can be ordered from any futon supplier and may even be in stock at larger futon stores. The only specialty hardware items needed are the nylon rollers that are attached to the backrest frame and move in routed grooves to create the conversion mechanism.
The gentle slope of the sofa arms adds a sense of flow to the overall design and takes advantage of the outstanding bending properties of ash. You can use several methods to bend wood. I opted to cut thin strips of ash and laminate them together in a bending form made from face-glued plywood. This method has excellent strength and results in a top laminate strip with contiguous grain. When form-bending with laminate strips, use polyurethane glue because it resists “creeping” and has a long open time.
To make the plywood bending form, cut three strips of 3/4-in. plywood to roughly 10 x 48 in. Face-glue and screw them together, making sure the edges are flush. Then plot out the curve for the arm (see illustration in the PDF below) on one face of the workpiece. Follow the cutting line with a band saw or jigsaw; then sand the cuts slightly so they’re smooth.
To make the 1-1/2-in.-thick arms, resaw (photo 1) and plane your stock into twelve 1/4 x 3 x 48-in. strips (six strips per arm). Plane or sand the strips so the faces are very smooth and flat to get a good, even glue bond. Line the inside edges of the bending form and the work surface with waxed paper; then apply a thin coat of polyurethane glue to one of the strips. (This will be the visible strip, so choose the one with the nicest grain.) Lay the strip into the form; then apply glue to another strip and butt the unglued face against the glued face of the first strip. Continue adding strips until you have six of them in the form. Clamp the strips together on one end. Then begin clamping the two halves of the form together, sandwiching the strips between them. Use plenty of clamps, tightening each clamp until both faces of the glued block conform with the edges of the form (photo 2). Allow the workpiece to dry overnight, strip the arm out of the form and then glue up the other arm.
Resaw the laminated arm strips slightly wider than their 2-1/2-in. finished width. Use a band saw with a pivot jig, or rip them on a table saw.
Make a plywood bending jig; then clamp the plies between the halves of the jig to make the bent arms.
Once you have both arms glued up, chisel off the glue squeeze-out; then joint the laminated edges until they’re smooth. Trim the arms to width on your jointer (photo 3) or by ripping them on your table saw. Do not cut them to final length yet.
Trim the edges of the arms on your jointer. Joint them until both edges are flat and the arm width is 2-1/2 in.
The sofa sides are joined with dowels and glue. Plane, joint and cut the front legs, back legs, side rails and side spreaders to size. The back legs should be left square on top at this point. Use a doweling jig as a guide for drilling the dowel holes in the parts (photo 4).
To make the side assemblies for the sofa frame and ottoman frame, join the side rails and spreaders to the front and back legs. Use a doweling jig and 1/2-in.-dia. x 2-in. dowels.
Lay one of the arms across the top of one side assembly so the arm overhangs the front leg by at least 2-1/2 in. The flat portion of the arm should be parallel to the rails and spreaders. Adjust the arm so the slope begins about 8 in. from the inside edge of the back leg. Mark trim lines on the arm, square to the top surface of the arm, 2-1/2 in. past the front leg and 3 in. past the back leg. Transfer the trim lines to the other arm; then square-cut both to length with a handsaw or power miter saw. Use the arms to mark cutting lines on the tops of the back legs (photo 5); then trim the tops of both back legs to match the arm profile. Label the arms and sides so you can keep track of which arm was traced onto which side.
Trace the profile of the bent arms onto the top edge of each back leg to create trim lines for the legs. Trim with a jigsaw.
To mount the arms to the side assemblies, first drill a pair of dowel holes in the top edge of each leg. Insert dowel points into the holes, position the arms over the dowel points and press down firmly to mark centerpoints in the undersides of the arms. Bore these dowel holes with a drill press, using the bending form as a drill backer to help you orient each arm so the dowel holes will be exactly vertical (photo 6). Do not glue the arms on yet.
Use one half of the bending form as a drill backer to ensure that the dowel holes in the arms are vertical.
For its conversion mechanism, this futon frame uses 1-in.-dia. nylon rollers mounted to the backrest and fitted into grooves in the inside faces of the side assemblies. If you use futon roller hardware, make sure to read the instructions that come with it carefully — the required sizes, shapes and locations of the grooves may vary among manufacturers. The instructions also may require that you alter the width of the backrest frame to create gaps of a different size between the backrest and the side assemblies (as shown, there is a 1/2-in.-wide gap between each end of the backrest frame and the sofa side). An alternative to futon rollers is to attach fixed 1-in.-dia. maple dowels to the frame to slide (not roll) in the grooves.
Make a hardboard template to use as a guide for routing the grooves in the side assemblies. Draw the groove layout onto the template board; then carefully cut out the grooves in the hardboard with a jigsaw (photo 7). Smooth the edges of the grooves; then position the template over each side assembly in turn. Cut the grooves in at least three passes with a router and straight bit fitted with a template collar (photo 8). It’s always a good idea to make some practice cuts first on scrap wood.
Draw the roller-groove layout onto hardboard; then cut out the grooves to create a template.
Use a straight bit with a template collar to rout the roller grooves into the sofa-frame sides.
Front/back sofa rails
Plane, joint and cut the front and back rails to size. The back rail should remain square, but the front rail is cut with a smooth arc on the bottom edge. To lay out the arc, bend a strip of hardboard from the arc ends to the apex; then trace the arc formed by the hardboard onto the rail (photo 9). Cut the arc with a jigsaw and sand it smooth.
Lay out the arcs on the bottoms of the frame rails by bending a strip of hardboard into a smooth arc and tracing it on each workpiece.
Join the side assemblies to the rails with a pair of connector bolts and cross dowels at each joint, according to the manufacturer’s installation instructions (photo 10). Check the sofa frame to make sure it’s square.
Join the sofa legs to the front and back rails with connector bolts that fit into cross dowels inserted into holes in the rails.
Frames and ottoman
The futon seat and backrest are simply frames that contain 1/2-in.-thick slats. The backrest side rails extend past the bottom rail to capture the seat frame (which is not as wide) inside. The frames are pinned together with clevis pins secured with cotter pins. The clevis serves as a pivot at each joint. Mill the frame parts to size; then cut a 3/4-in.-wide x 1/2-in.-deep rabbet in the top inside edge of each front and back rail (photo 11). The ledges created by the rabbets will support the slats. Make the frame spreaders; then assemble the frames with the spreaders spaced as shown in photo 12.
Cut rabbets in the rails to support the ends of the slats in the backrest, seat and ottoman.
Assemble the frames for the seat and backrest, including the spreaders, using dowels and glue.
The ottoman is built using the same basic techniques used to make the sofa frame and the seat and backrest frames. The main difference is that the ledges for the slats are milled directly into the front and back rail of the ottoman. Build the ottoman, milling the slats for it, the backrest and seat frames in the process. Sand and finish all the futon frame and ottoman parts (photo 13). I used a dark mahogany gel stain with three thin coats of tung oil as a topcoat.
Once all of the parts are cut, but before the slats are installed, sand the wood to 150-grit and apply your finish.
Install the slats, spacing them on the ledges as shown. Use two 1-1/4-in. screws at each joint (photo 14).
Install the slats in the ottoman, backrest and seat by driving two screws at each slat end. Insert a spacer between slats for consistency.
Putting it together
Lay out drilling centerpoints for the clevis pins that join the seat frame and backrest frame; then make the connection (photo 15). Also plot out drilling points and mount the roller hardware in the ends of the backrest frame as shown in the drawing. Loosen the connector bolts holding the sofa frame together and separate the side assemblies so you can fit the seat and backrest between the frame arms. Slip the rollers into the grooves; then tighten the connector bolts to draw the sofa frame together (photo 16). Test the operation, making sure the seat rests solidly on the front rail of the sofa frame when the futon is set up as a couch. The seat and backrest should also be level and even with the top of the ottoman frame when the futon is converted to a bed.
Join the backrest frame and seat frame with a clevis pin inserted into guide holes at the ends of the frames. Secure with a cotter pin.
Loosen the rail-leg joints so you can fit the backrest/seat frames and rollers into the sofa frame, with the rollers aligned in their grooves. Retighten the screws at the leg/rail joints.
Once everything is set, you may want to attach strips of mesh-style anti-skid carpet pad to the seat and backrest slats to minimize mattress movement.
The compact footprint of a loveseat, the utility of a full-width ottoman and the convertible nature of a futon sofa combine to create comfortable, stylish seating that can be transformed into a full-size bed.