What Size Cupola and How Many?

What Size Cupola and How Many?

In the world of post frame (pole buildings) cupolas are relatively small, usually square, structures placed on top of the ridgeline. While they are primarily aesthetic, with side louvers they can also be functional vents.

The cupola is a development during the Renaissance of the oculus, an ancient device found in Roman architecture, but being weatherproof was superior for the wetter climates of northern Europe.

CupolaMy own and only personal cupola experience is with the one mounted on the top of our post frame house along the South Dakota side of Lake Traverse. Our building has a footprint of 4824 square feet and the peak of the roof is 44 feet above grade. We put a four foot square cupola with glass sides on ours, with four pairs of different colored lights so they can be changed depending upon the season. My bride has far too much fun changing the bulbs to match her mood….er I mean the season!

Now there is a “science” (keep in mind, it was created by a cupola manufacturer who wants to sell more and larger cupolas) to cupola selection.

To select the “right” size cupola for a building, a good rule of thumb is 1.5 inches of cupola for every foot of unbroken roof line (measured along the ridge). Using this theory a 24 inch cupola would only be good for 16 feet of ridge line, 36 inch would cover 24 feet, and 48 would do 32.

For ridgelines greater than 32 feet, they recommend an inch of cupola for every foot of ridge. This would place two 24 inch cupolas on a building up to 48 feet long, two 36 inch for 72 feet and two 48 inch for 96 feet.

In my humble opinion, the two cupola sizing seems much more realistic than the single cupola.

I had always been educated to size the cupola to the building width, where cupolas were most often sized with an inch of cupola for each foot of building width across the gable end.

In the end, beauty is in the eye of the beholder – see a cupolaed building you like the looks of? Email it to your Hansen Pole Buildings’ Designer to get sizing and quantity ideas which will meet your needs and budget.

28 thoughts on “What Size Cupola and How Many?

  1. Ally Saltonstall


    I have a 40×60 pole barn for my horses and am looking to add a cupola or two for ventilation. I am unsure of what size would be appropriate. Any help would be greatly appreciated!

    1. Christine Castelli

      Hello, we are converting an old barn to a livable property and the size is 50 x 24 and I would like a cupola for natural light, what size should we get?

        1. How about for an 80×160 arena? The long side of the arena is quite visible given the terrain of the land, even though the arena is well set back from the road. So I am considering aesthetics of the side view 🙂

          1. I would probably place a 48″ cupola at center, then a 36″ cupola 40′ from each endwall.

  2. Sanford Holden sr

    I have a 60 by 100 by 20 foot high to the bottom of rafters pole barn for hay storage.
    I’m looking to put vent fans in some cupolas to create airflow I’m interested in your opinions on what size and how many.

    1. admin Post author

      I would probably start with two 48″ vented side cupolas spaced evenly on your 100′. You might get enough exhaust from them alone to avoid having to add powered fans.

  3. We are building a barndominium to look like the original old barn on our farm. We have one problem and that is we have a fireplace that doesn’t come in the center of the ridge line. We were wondering if we could still cover it with a cupola even though it’s not centered.

    1. Could you? It is possible, although it is likely to look strange. You would also have to either build it onsite, or (if using a prefabricated cupola unit) create a base to support it being not centered upon the ridge.

    1. The smallest commercially available cupola is typically 24″ x 24″, we would suggest using it as opposed to something smaller.

  4. Good afternoon,

    We are building a 45′ wide x 90′ long building long building and were wondering how wide our cupolas should be. If we just did one, I think it would be too big (about 11.25′ wide according to the guidance.

    I think two would look better than one since it’s such a long building. Would you cut the width of the building in half (45′) and calculate it from there for each cupola at 5.6′?

    Thanks for your input and expertise!

  5. I have a cabin with a 24 ‘ ridge line, a 12″ pitch, a 9′ ridge ht and 10’ high walls. i realize the cupola should be around 30″ wide. How high should it be?

  6. I have a 40′ long pole buiding, 30 foot wide and 14′ to the bottom of the gutters. What size coupla would you recommend

  7. We have a 30 x50 pole barn that has 50 feet of unbroken roofine and ten feet to the bottom of gutter. the roof pith is 6/12. I was thinking two cupolas at 30 “but I’m really not sure. What size would you recommend?

  8. I got a 253 ft long ×40 building with a 20ft x20 ft wing on a side wall .it is like 88ft from one end . Wondering how msnt cupolas I need.

  9. Dolores Schmidt

    my garage is 42′ long, has 3 garage doors What size cupola’s would be recommended? and how many. I also need to factor in that there are
    2 skylights already on the roof

    please advise
    Dolores S

    1. admin Post author

      Without knowing how wide your buildings is, we would normally suggest one at the center of your roof’s length, with size to be determined by width of your building.

  10. My barn is about 45 feet long and 40 feet wide. There are three evenly spaced ridge line vents that I would like to replace with cupolas. What size would you recommend?

    1. If you are going to place 3 of them up there, I would put a 36″ at dead center and 24″ ones halfway between the big one and each endwall.

  11. How does one calculate the size and number of cupolas in a barn with a ridge vent? Will the addition of a cupola make a difference? It is a ten horse barn, 70’ x 35’. The barn is well insulated, walls and roof.

    1. Without an enclosed non-conditioned dead air attic space there is no Code requirement for ventilation. If you have insulation at ceiling level, then your ridge should provide a minimum of 588 square inches of net free ventilation area (this can be combined between ridge vent and cupola venting). For horse barns, there is never such a thing as too much ventilation.


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