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Installing a Cupola

Construction How-To, Roofing June 27, 2014 Sonia



Top off your Roof

By Rob Robillard

I love the look of cupolas, and this article will show you how to install a decorative cupola on your roof.

I first had the opportunity to rebuild an 80- to 100-year old cupola in historic Concord, Massachusetts, and have since repaired several other cupolas of varying styles.

What Is A Cupola?

A cupola can be a decorative or functional architectural structure mounted on top of a home or barn and usually centered along the roof ridge line. In my neck of the woods all barns worthy of their salt have a functional cupola. When functional, a cupola is used to ventilate a building or roof area. They are often made from wood, copper or composite materials. They can come as a single piece or, if larger, two or three pieces.

Cupolas of various styles were integrated into English domestic architecture during the late

17th century and became part of the U.S. architectural design during the post-Revolutionary Federalist era. Many new homes use decorative cupolas as architectural details to enhance the exterior design.

A decorative cupola differs from a functional cupola in that the roofing material and roof sheathing does not need to be cut away to create a vent hole.

These types of cupolas should be installed with step flashing to prevent leaks.

The decorative cupola in this installation was built by a company called Walpole Woodworkers.

Cupolas generally have three major components: the base; the louver vents or windows; and the finial or weather vane.

How to Install a Decorative Cupola

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First step is to determine the cupola location. Measure and mark the center of where the cupola will be installed. If the roof is longer than your tape measure, pull two tape measures from opposite ends and determine where the centers of the two opposing tapes meet.

Measure left and right along the ridge line to determine the outer sides of the cupola.

Remove only the roof ridge shingles where the cupola will be located.

Remove only the roof ridge shingles where the cupola will be located.

Remove only the roof ridge shingles. I cut the center shingle out and then used a nail puller (cat’s paw) or a flat bar to remove the roofing nails and ridge cap shingles. The goal is to remove them in one piece so you can use them later for patching, if needed.

Use two pieces of wood to make a hinged angle finder. Use the angle finder on the roof ridge to determine the pitch.

Use two pieces of wood to make a hinged angle finder. Use the angle finder on the roof ridge to determine the pitch.

Cut and remove only the ridge shingles and/or ridge vent up to the outer edge of where the cupola will sit.

The cupola is made from composite material and arrived as a single piece.

The cupola is made from composite material and arrived as a single piece.

You may need to use the utility knife to trim the shingles back.  Use care not to expose the roof sheathing. If you do you will need to patch this spot with rubber flashing tape or flashing and shingles to prevent water intrusion.

Determine how the cupola will be oriented on the roof so you cut the correct sides to match the pitch.

Determine how the cupola will be oriented on the roof so you cut the correct sides to match the pitch.

Determine the Roof Pitch

On the ground, insert one screw into the ends of two 24-in. pieces of wood to make a hinge tool to copy the roof pitch. Bring this angle finder up to the roof and lay it over the area where you removed the ridge shingles.

Mark the centerline on the cupola and align the angle finder.

Mark the centerline on the cupola and align the angle finder.

Press the angle finder tightly to the shingles and then insert a second screw to hold it tight, locking the angle in place.

Scribe the roof pitch on the cupola. Cut the angle with a jigsaw.

Scribe the roof pitch on the cupola. Cut the angle with a jigsaw.

Once this is complete, use a level to mark a plumb line from the center of the ridge onto your angle finder. This plumb line will be your top reference line when tracing the cupola. Bring your angle finder off the roof to the cupola to be installed.

Shown is the cut base. If you have a steep roof greater than 9-12 pitch, you may need to install an extended base. Cut the opposite side of the base to match.

Shown is the cut base. If you have a steep roof greater than 9-12 pitch, you may need to install an extended base. Cut the opposite side of the base to match.

Mark the Cupola Base

Determine which sides will be the front and back of your cupola.

Bring the cupola to the roof and test the fit.

Bring the cupola to the roof and test the fit.

Measure and draw a center-line on the two opposing base walls on your cupola. These are the two sides that will straddle the roof ridge.

Use the ridge shingles that you removed, if in good condition, to make any necessary patches or to cover any roofing you removed.

Use the ridge shingles that you removed, if in good condition, to make any necessary patches or to cover any roofing you removed.

Using your angle finder, line up your plumb line on the center line and ensure that the bottom legs of your angle finder line up at the lower corners of the cupola. Doing this will ensure an accurate and symmetrical cutout.

Predrill holes in the 2x4 mounting blocks and apply silicone to the bottom of the prior to attaching them to your roofing.

Predrill holes in the 2×4 mounting blocks and apply silicone to the bottom of the prior to attaching them to your roofing.

Mark both sides of the cupola the same way and use a saw to cut out the angle along your marked lines.

Mount four sections of 2x4 blocks to fit flush inside the edges of your cupola. Drive the top fasteners into the ridge board.

Mount four sections of 2×4 blocks to fit flush inside the edges of your cupola. Drive the top fasteners into the ridge board.

If you have a steep roof, greater than 9-12 pitch, you may need to install an extended base.

When mounting the cupola, apply silicone only to the seams that straddle the ridge and are fastened to the mounting blocks.

When mounting the cupola, apply silicone only to the seams that straddle the ridge and are fastened to the mounting blocks.

Mounting Boards

Mount four sections of 2×4 blocks on the roof to fit flush inside the edges of your cupola. Predrill your holes in the block and apply silicone to the bottom of each block prior to attaching it to your roofing.

Mount all four blocks to the roof sheathing and drive the top fasteners into the ridge board.

Attach the cupola with two to three stainless steel screws driven into each block.

Attach the cupola with two to three stainless steel screws driven into each block.

Position the Cupola on the Roof

Once you are satisfied with the fit on the roof, attach the cupola with two to three stainless steel screws driven into each mounting block. Plug or patch the screw holes. On PVC cupolas, I use the Cortex screw and plug system.

Apply silicone only to the seams that straddle the ridge and are fastened to the mounting blocks. This will keep angled rainfall from getting under your cupola and affecting the 2×4 wood.

Leave the lower pitches’ roof edges open to drain any wind driven snow or moisture that may make its way under the louvers.

Use the ridge shingles that you removed, if in good condition, to make any additional patches or to cover any roofing you removed.