by Andrew P.
As an architect and builder on the New England coastline, I work a
lot in my own interpretation of the shingle style. The tradition
employs a lot of low rooflines, where the roof springs from the
first-floor wall, and consequently, I often wind up using various
kinds of dormers to create usable space under those low
Utility with Flair
One dormer I frequently use is the "Nantucket dormer" — a
sort of hybrid between a shed dormer and a doghouse dormer. We call
it a Nantucket dormer because it's rumored to have been developed
on Nantucket Island, where it's a common roof feature on many
homes. But you can also find this dormer style used throughout New
England on old houses.
Figure 1. A Nantucket dormer provides the
headroom of a shed dormer with visual appeal of two doghouse
dormers. Here, it is used to define one side of an entire house,
where a plain shed dormer would have been too boxy.
I like this style because it allows me to get the practical utility
of a shed dormer, for enclosing space, along with the visual
interest and traditional look of doghouse dormers. From the
exterior, it looks pretty much like two closely spaced doghouse
dormers. However, the Nantucket dormer creates a larger clear space
on the inside, defined by the area under the two doghouse roofs
combined with the shed roof that connects them.
A typical use for this method is to open out a piece of usable
space in a room over a garage. It's useful wherever you want to
build a large dormer into a roof but would rather not have a big,
clunky-looking shed dormer. I've even used this element on a
grander scale, as shown in Figure 1, in which one whole side of the
second story of the home is framed out as a double set of
hip-roofed dormers joined by a center shed roof.
The framing for these dormers can be a challenge for my field
crews. But in principle, it's fairly simple: We frame the dormer
opening in the roof by doubling up the rafters of the main roof
system (Figure 2). The outside walls of the doghouse dormers rest
on those doubled rafters. We frame up the front wall and side walls
of the dormer, then we install the center, shed part, of the dormer
roof, running the shed rafters back to tie into some kind of
support — either all the way across the main roof to mate
with the main roof rafters for the other side of the house, or else
to some interior supporting structure like a bearing beam or wall.
Again, we double the shed rafters on the ends of the center shed
Figure 2. The trick to framing a Nantucket
dormer is establishing the valleys for the two doghouse dormers
(plan illustration top). The outside valleys meet the main roof,
while the inside valleys meet the lower-pitched shed roof that
joins the two doghouse dormers. While essentially a shed dormer in
plan, the visual effect is closer to a pair of doghouse dormers
At the elevation where the lines of the main, steep-pitched house
rafters and the lower-pitched dormer shed rafters cross, we run
headers across from each doubled shed rafter to its counterpart
doubled main house rafter. Those headers are intended to catch the
ends of the doghouse dormer ridge boards, which we install next.
With the locations of those ridges defined, we can then place
valley rafters for the intersection points where the doghouse roofs
meet the main roof, as well as where the doghouse roofs join the
center shed roof.
Usually I keep the dormer walls short, to accommodate the various
pitches and to keep the dormers from visually dominating the roof.
To gain sufficient ceiling height in the indoor room, I let the
ceiling follow the plane of the rafters. So inside the house, the
cut-up shed-and-doghouse roof planes are revealed, making for some
interesting interior spaces.
I didn't invent this form of dormer — it has been around for
a long time. It's an interesting and useful roof form that I can
add to my bag of tricks, just to keep things lively.
Architect and builder Andrew P. DiGiammo owns and
operates a custom design/build firm based in Assonet, Mass. Photos
by the author.