How to Add a Balcony to a House

Sketch the size and shape of your proposed balcony and make note of its required length and width. Measure and cut 2-by-10 inch, pressure-treated lumber to the width of the balcony with a circular saw to form the ledger. Drill holes through the wall and the timber at 1-foot intervals. Bolt the ledger to the wall through the holes with 6-inch lag bolts.

Cut two pieces of 2-by-10 inch, pressure-treated lumber to 2 feet in length. Place the first timber vertically on the wall beneath the left edge of the ledger. Drill holes through the timber and into the wall. Secure the timber to the wall with 6-inch lag bolts. Repeat with the other timber on the right side of the ledger.

Screw the joist hangers to the timber ledger so there is one joist hanger on either end of the ledger and an additional joist hanger every 1-1/2 feet along the length of the balcony. Cut two lengths of 2-by-10 inch, pressure-treated lumber to the length of the balcony. Cut additional lengths of timber to the balcony length to fasten one timber to each floor joist.

Attach the timbers to the floor joists with a hammer drill and long screws. Cut a piece of 2-by-10 inch, pressure-treated timber to the width of the balcony. Screw this timber to the ends of the floor joists with long screws. Reinforce the joints with 6-inch wide L-brackets.

Measure 2 inches from the bottom of one vertical timber attached to the wall to the outer edge of the balcony. Cut two 2-by-10 inch, pressure-treated timbers to this length to form the knee braces for the balcony. Bolt one knee brace to either side of the balcony with heavy-duty gusset plates on either side of the joints.

Cut sheets of 1-inch-thick plywood to the length of the balcony and 3 feet in width. Apply wood glue to the top of the floor joists. Screw the plywood to the top of the floor joists to form the balcony subfloor. Cut four pieces of 2-by-2 inch, pressure-treated timber to 2-1/2 feet in length. Screw one 2-by-2 inch piece vertically into each corner of the balcony with mounting brackets.

Measure the distance between the side and front corner support posts. Cut two lengths of 2-by-2 inch, pressure-treated timber to the distance between the back and front support posts. Cut one piece of 2-by-2 inch, pressure-treated timber to the distance between the two front support posts. Screw the timbers between the support posts with L-brackets to form the handrail. Repeat this process to mount a second handrail 1-1/2 feet from the balcony floor.

Varnish, stain or paint the balcony and the handrails as desired. When the varnish or other treatment is dry, lay the balcony floor. This can be made from any material you wish, such as ceramic tiles, a concrete slab or even wooden decking. Allow the flooring material to set or dry thoroughly before using the balcony.