The following info covers pluses and minuses of installing a cupola.


Cupola on 45′ and 34′ domes

40' dome - ladder on left to access loft under cupola.

40′ dome - ladder on left to access loft under cupola.


Cupola area with beam poured ready to accept top five panels.

Cupola area with beam poured ready to accept top five panels.


34' dome cupola legs formed up. Window dormers not installed.

34′ dome cupola legs formed up. Window dormers not installed.

5.50 cupola overhang Kaufman picture assembly 407

45′ Dome Cupola Overhang Panels Being Installed.

Question:  When does Ai recommend installing a Cupola?  Ai recommends that a cupola be built only if a loft is desired. A cupola added on top of the larger domes, 40′, 45′, or 48′  creates enough headroom so a third floor loft can be built. A ships ladder is installed to access the loft from the second floor. For example in a 40′ dome with a cupola, a third floor can be built so one can stand in the loft and see out the windows.

If your property is zoned RC1 or R1, the panels in the top of the cupola can be elevated to increase the pitch to make the dome roof acceptable to your building department. Call Ai at 321-639-8777 for more info.

For additional light on the second floor:

  1. max out the number of window dormers and door dormers instead of installing a cupola. A door dormer can be installed on the second floor if there is a first floor standard entryway below it.  To receive additional light on the second floor instead of installing a door in the door dormer (which results in a balcony railing being installed), install a tall window for light.
  2. On site install solar tubes in the prefabricated panels.  Ai recommends prior to installing solar tubes, assemble the dome kit with the additional dormers and see if lighting from the dormers is adequate.  Dome owners are surprised how the light from dormers radiates easily in the dome.

A cupola can be installed in a  22′ or 27′ domes.  In all domes, Ai recommends the installation of an exhaust fan in top center of the dome.  If a cupola the vent would be in top center of the cupola.  Also vents can be installed in the top of some second floor walls. The interior wall ducting for the fan can run thru the vertical second floor wall and second floor joist and vent out under an entryway or dormer.  Second floor window dormers are not available in the 22′ or 30′ domes.

Does a cupola change the structural integrity of the geodesic dome?   No. In hurricane areas install impact resistant glass in the cupola windows to prevent the glass breaking from the force of the winds or debris being slung into the glass.

Because of window costs and the installation steps involved in the assembly of the cupola, your dome construction budget might increase from $5,000 - $10,000 for a cupola. The following is an overview of the Cupola Construction.

The top five component panels of the dome make up the cupola top with overhang panels (eave panels) added on site.

  • The topside exterior of the five pentagon panels of the cupola is prefinished steel reinforced concrete. These panels have seven inch thick E.P.S. insulation.

  • The overhang/eave panels consist of 3 1/2″ thick E.P.S. wrapped in steel mesh. The underside of the eave panels have prefinished concrete.

  • The topside and edges of the eave panels are stuccoed onsite.

The actual cupola assembly instructions consist of six pages. The subcontractor and four laborers take two to three days to build and assemble the cupola. Yes some form of hoisting mechanism is needed to lift the cupola panels to the top of the dome. The cupola is made by installing the top five panels on top of a five-sided concrete wall that contains the windows.

  • The first step is to form and pour a concrete beam around the top opening which reinforces the opening.

  • Next, set 2×4 window frames in place on top of the beam.

  • Then form and pour a concrete column at each of the five corners.

  • Finally, install the five panels and there C1 extensions on the top of the wall and concrete the seams.

  • At anytime thereafter you may install the windows and finish the interior.

If I do not install a cupola on the dome, how does the hot air and moisture get exhausted from the dome? In a vertical wall near the top of the dome, in bathrooms, at stove, microwave, clothes dryer and at top of the dome install exhaust fans that can be turned on to exhaust hot air and moisture. Use galvanized ducting for the exhaust fan ducting. It extends thru interior walls, through the floor joist and vents out under an entryway or dormer.

Third Floor Loft Heights And Square Footages

Please see the floor planners in the back of the Stock Floor Plan Booklet for loft heights and square footages. The outline of the third floor loft matches that of the cupola. The 22′, 27, 30′, 34, & 36′ domes cannot have a third floor loft.

Dome Size Loft Maximum Sq.Ft. Height in Loft Ceiling Height under Loft
40′ 112 sq.ft. 5′ 6″ 7′ 6″
45′ 142 sq.ft. 6′ 10″ 8′
48′ 170 sq.ft. 8′ 1″ 8′