How to Build a Cupola

Cupolas can be built to suit the size of the roof.

Cupolas were used in the days before roof vents to provide ventilation for barns, stables and houses. They are the square, vented structures on the rooftops of older buildings. Cupolas are used today as decorative additions to homes and other structures. A 24-foot, two-car garage with a conventional roofline would require a cupola with a base measurement of 24 to 30 inches, according to Amish Country Products and More. A 60-foot roofline could support two 20-inch cupolas on the sides and a single 36-inch cupola in the center.

Things You'll Need

• Ladder
• Table saw
• Cedar lumber, 2 inches by 6 inches by 8 feet
• Cedar lumber, 2 inches by 2 inches by 8 feet
• Plywood, 2 feet by 4 feet, 1/2 inch thick
• Measuring tape
• Flashing
• Regular and L-shaped brackets
• Tin snips
• Tar
• Putty knife
• Stainless steel screws
• Plywood
• Jigsaw
• Louvered vents
• Caulk
• Brick mold
• Carpenter's square

Instructions

1. 

   Checking the fit before cutting the actual piece can save time and money.

   Determine the roof pitch--the amount of slope--by calculating how many inches of drop for every foot of horizontal run, according to Ask the Builder. When you have the correct pitch, transfer it onto a scrap piece of plywood the same size as the cupola. Make cuts and take the pattern onto the roof to check the fit.

2. Cut the 8-foot lumber into 4 equal pieces, a little less than 2 feet each, using a table saw. Cut two 45- degree angled pieces to ride the roof ridge. The two straight pieces will run horizontal with the roof. Together they will form a box-shaped base for the cupola. The overall size of the cupola will be 2 feet by 2 feet by 3 feet tall.

3. Sand the eight pieces of cedar, then miter the ends at 45 degrees.

4. Build the sill, then wrap it with flashing and tar it in place with the putty knife. Use the tin snips to make cuts on the flashing.

5. Secure the base with L-shaped brackets. Check to be sure the base is square. Attach it with roof tar and stainless steel screws. Cut a small piece of plywood to place on top of the box to make a flat base.

6. Cut a hole in each piece to mount a louvered vent. Use L-brackets to mount the box on the sill base.

7. Cut out the curved piece from the plywood to use as a template for the other three pieces. Cut the three pieces. The four sections will look like an octagon. They should be 18 inches tall. Secure them with the flat L-shaped brackets on the inside and use silicon caulk on the outside.

8. Screw the sill to the corner posts. Drill pilot holes and drive a 4 3/4-inch screw into each post, two on each side of the miter joint.

9. Assemble the brick mold frames between the posts. Pre-drill and countersink the holes before driving in the screws, according to Woodworking Plan Finder.

Tips & Warnings

• Marine-grade plywood should be used, according to Runner Duck Resources.

References

• Amish Country Products and More
• Ask the Builder
• Wordworking Plan Finder
• Runner Duck Resources