Cut a thick plywood sheet into a large rectangle, which will become the back of the finished hinged seat. A set square can be used to get the angles square, while a tenon saw, jig saw or band jaw can be used for cutting. Cut the length of the rectangle to the desired final width of your chair. This will be determined by how many people you would like to seat. Cut the width of the plywood to the desired final height of your chair. This will be determined by whether your chair has a high back that reaches roughly to shoulder height, or a normal chair back which can measure up to the bottom or middle of an average person's back when seated.
Cut more plywood into two squares that will become the sides of the chair. The length of the squares will be the finished depth of your chair. The height will be the approximate finished height of your chair seat. Chairs currently in your home can be used as a guide for the height and depth of the seat.
Cut a rectangle from plywood to form the front of the chair. The height of the rectangle will be the same as the height of the squares already cut. The length of the rectangle will be the same as the length of the back of your chair, minus the thickness of two pieces of the plywood used. Thus the front of your chair will be the same length as the back, once the two side pieces are attached to its side.
Assemble the pieces as they will appear on the finished chair. Position the large rectangle at the back, a square at each side and the remaining rectangle at the front. Each piece should be level at the bottom edge. Each side square will be fitted to the inside of the back piece.
Screw from behind the chair back to attach the side pieces. Three screws at each side should be enough to create a strong joint. Use screws that are twice as long as the thickness of the wood.
Sandwich the front of the chair between the side pieces and screw in place. Screw from the side of each piece to attach. Again, use three screws at each edge to form a strong joint.
Cut two rectangles of plywood that are the same size as the outer edges of the bottom of the chair seat.
Screw one of these rectangles to the bottom of the chair to form the chair base. Align the edges of the frame and the bottom of the chair to do this. Screw from underneath to attach the base.
Attach a piano hinge to the remaining piece of plywood, which will become the chair seat. The hinge ideally needs to be the same length as the chair sear. Screw in the hinge using each of the holes on the hinge plate.
Place the chair seat onto the frame of the chair, with the hinge at the rear. Center the seat on the chair base. The chair lid will overhang at the front slightly to create a lip to lift the lid.
Lift up the chair seat and hold it in place. Screw the other side of the hinge to the back of the chair to form the lift-up part of your seat. Use each screw hole on the piano hinge for a secure fixation.
Stain your finished seat and allow to dry.
Varnish the seat for a smooth finish.
Things You Will Need
- Thick plywood sheets
- Piano hinge
- Wood Stain
- When staining or varnishing your seat, cover the hinge to protect it.
- Decorative shapes can be cut into the back of the seat, such as Gothic arches or Hepplewhite-style shield backs.
- Countersink screws and cover holes with wood filler for a more professional finish.