Some of the most appealing interior spaces are those created
under a roof that has been sensitively fitted with dormers.
Nestled at treetop level, these spaces are formed by the
sloped, sheltering surfaces of the primary roof and the walls
of the dormers, which admit daylight.
Adding dormers to a roof to meet space requirements has the
advantage of keeping the primary roofline lower than would be
possible with an additional full story. This can reduce the
apparent mass of the building and help ground the home to the
Whether you're retrofitting dormers or including them in a new
home, there are a number of design considerations to keep in
mind. In order to create dormers that are both functional and a
visual asset inside and out, you need to choose an appropriate
dormer that's properly scaled and located. Dormers incorporated
merely for a picturesque effect or to crudely maximize
habitable floor space often fail to meet these criteria and may
seem inauthentic. Successful dormers add pleasant living space
while harmonizing with the overall building elevation and
There are three basic types of dormer, described by the
dormer's relationship to the primary roof: built-out dormers,
which are the most prevalent; partially built-out/partially
cut-in dormers, which are less common; and cut-in dormers,
which are fairly rare. Built-out dormers can be further
characterized as either fully or partially nested within the
primary sloped roof. A fully nested dormer is completely
encompassed by the primary roof, since it sits some distance
above the primary eaves line, which is continuous. A partially
nested dormer is created by extending the exterior wall plane
of the main building vertically to form the wall of the dormer,
thereby interrupting the primary roof eaves line.
The variety of roof types found in primary roofs can also be
found in built-out and partially built-out dormers. In general,
it's best to select a dormer roof type that's compatible with
the primary roof. This doesn't mean it has to be the same roof
type, but it should relate to the style or vernacular of the
building as a whole. It's best to narrow your selection of
dormer types used in any one roof: Too many different dormer
types will create an unfortunate muddled jumble.
Dormer Placement and Scale
Placing dormers is about achieving balance and texture on the
exterior while satisfying interior space requirements. A
blocklike symmetrical building may invite somewhat methodical
dormer placement; window and door locations on the walls below
generally guide dormer locations above. In this scenario,
multiple single dormers may enliven the roofscape, staccato
fashion, while softening the building's apparent mass.
By contrast, a longer, asymmetrical building may allow for more
flexible dormer placement. If you're no longer restrained by
the strict rules of symmetry, you can place combinations of
continuous and non-continuous dormers to complement or
counterbalance a more rambling footprint. Dormers can be used
to highlight the horizontal line of the building or to create a
local symmetry that enhances the elevation.
When placing dormers, pay attention to the hierarchy of forms.
Dormers that are out of scale with the rest of the house may
appear overwhelming and no longer secondary to the primary
roof. In the other extreme, dormers that are too small may
appear lost within the roofscape, and more of a blemish than a
benefit. Use dormer placement and scale to enhance and clarify
building function and massing.
Continuous Shed Dormer
The shed dormer is a versatile option. When elongated, as shown
at right, it's a good choice for continuous headroom and
maximum daylight. Though sizeable, this dormer is comfortably
nested within the main roof thanks to the entry extension, the
slight setback from the lower wall, and the fact that it
doesn't extend the full length of the house. Also, the dormer
window size and style relate well to the windows on the rest of
An Unfortunate Dormer
Here, interior space has been maximized at the expense of
exterior massing and charm. Because the shed dormer isn't
subordinate to the main roof, it creates a towering, awkward
three-story building. The sides of the dormer as well as its
face are in the same plane as the walls below, which partially
accounts for its unfortunate boxiness; the low slope of the
dormer roof completes the boxy effect.
A Varied Dormer
Here, three different dormer types — hip dormers, a shed
dormer, and a partially nested hip dormer — are all
expertly balanced on the gambrel-roofed house. Dividing what
could have been a continuous shed dormer into separate distinct
entities reduces its mass and overall scale without sacrificing
headroom or daylight. The decision to terminate both ends of
the dormer with hip roofs accomplishes a couple of things: For
one, it helps keep the dormer subordinate to the main roof,
since the hip roof cheek walls consume less area than those of
a shed dormer. Second, the hip roofs slope back toward the
center, which further distinguishes the hip ends from the
linking middle section of roof. This allows the observer to
"read" distinct rooms within: bedroom, hall, bedroom, for
example, or bedroom, hall, bath.
The separate partially nested hip dormer is formed by extending
the exterior wall plane up through an interrupted eaves line.
This dormer's placement, roof, and window configuration reflect
the neighboring fully nested dormers, helping it to fit in and
to tie together the overall elevation.
Mansard With Partially Cut-In Doghouse
This mansard-roofed house is punctuated with discreet
non-continuous gable dormers. Due to the fairly steep slope of
the lower portion of the mansard, these dormers are less about
gaining headroom and more about introducing daylight with
style. Since the overall building is symmetrical, the dormers
are symmetrically placed too. These dormers are partially built
out from the main roof and partially cut in. If they had been
entirely built out, the windows would have been moved out
farther toward the exterior. This would have resulted in large,
exposed cheek walls, and the dormers would have appeared
bug-eyed. By cutting them in partially, that problem is
Fully Cut-In Dormers
dormers above had been fully cut in, as here, they would have
still admitted daylight, though less than in the example above
due to shadows from the cheek walls. The fully cut-in dormers
appear oddly contemporary for such a classic house. The cutouts
suggest skylights more than dormers; plus, there's no headroom
gain. These simply lack charm.
Built-Out Doghouse Dormers
Small, fully nested gable dormers on either side of a central,
larger gable element provide a fair amount of headroom and
daylight to this attic. The dormers are located in logical
relationship to the windows and volumes below, contributing to
a hierarchy of base, middle, cap. They also help to break up
the mass of what is otherwise a blocklike building, much like
the mansard example at top.
The eyebrow dormer is a classic shingle-style feature. As in
this example, it is traditionally a small curved-topped element
folded into the roof much the way our eyes are folded into
eyelids and brows. It provides a peekaboo of light and
ventilation. It is not the right choice if your objective is to
gain significant headroom. It is a quiet, beloved detail.
Gable Dormer, No Cheeks
This gable dormer, which has no sidewalls, is a great
counterpoint to the gable roof on the ell of the main volume.
Had this been a doghouse dormer instead, it might have looked
slightly isolated within the length of the roof. It would have
become more of a "mini me" than its current incarnation, which
is more like a sibling or mate to the ell gable.
These elegant barrel-shaped dormers provide dynamic sculptural
relief to the otherwise severe blocklike massing of this
building. They may well play a more important role on the
exterior elevations of this building than as functional devices
to add headroom and daylight to the attic.Katie Hutchisonis an architect and owner of Earthlight
Design in Salem, Mass.