Monday, September 11, 2017

DESIGNING ROOFS: Don't Get Carried Away

Can you count how many different roof types
are visible on this house?
(1890s-era Queen Anne Victorian
on Military Street in Port Huron, Michigan).
Victorians could get away with this,
but you may not be able to.
Every day I see more new traditional-style homes topped by tortured, often incomprehensible roofscapes. Variety is good. Surprise is good.  Bedlam isn’t.

You can’t design an interesting roof simply by melding a bunch of disparate roof shapes together. Even if you’re after a picturesque effect, the elements have to be deliberately composed, and with a touch of restraint at that. Even the most flamboyant Victorian houses will, on close inspection, reveal basically simple roof shapes enlivened by carefully-controlled accents such as turrets and dormers.

If you’re into the Grand Teton school of roof design, it’s especially critical to think through your roof scheme very carefully—it’ll probably be the most visible part of the building. With that in mind, here’s a quick rundown of common roof shapes, followed by some suggestions and caveats for combining them:

Classic gambrel-roofed Dutch Colonial home
featuring the English-style "dustpan" dormer.
•  A gable roof is the most familiar type, having two sloping planes with a triangular gable wall at each end. By contrast, a hip roof slopes on all four sides, yielding corner “hips” that climb toward the center. A flat roof has little or no pitch. A shed roof is sort of like a tilted flat roof—it slopes in one plane only.  A gambrel (commonly seen on barns) has two different pitches: steep on the sides, and shallow on top. A mansard has a very steep pitch on all four sides and a flat roof on top, often concealing an attic story inside.

Once upon a time, bargeboards
were a favorite location for ornament.
Not so much today.
A few technical terms may be useful here: Roof slope (properly called pitch) is described in inches of vertical rise over horizontal run—a “4-in-12” roof, for example, has rafters that rise 4 inches in every 12 inches of horizontal distance. The peak of a roof is called the ridge. The lower edge is called the eave. The sloping side edge on shed, gable and gambrel roofs is variously known as the rake, the verge, or the barge—pick your favorite. And now some game rules:

Mansard-roofed Victorian, circa the 1880s.
•  Limit yourself to just one or two roof shapes. For picturesque roofs, the two most compatible shapes are gables and hips; they were a favorite on late Victorian houses such as Queen Annes. Flat roofs, too, will combine with almost every other type, though they won’t always produce an intelligible style.

Other roof shapes are much more difficult to combine successfully. Sheds, hips, gambrels and mansards will usually get into a stylistic brawl when any two are combined. If you pine for one of these shapes, it’s safest to use it exclusively. If you’re adding onto an existing building, the rules are even simpler—copy the pitch, massing and details of the roof that's already there.

Frank Lloyd Wright's Robie House, Chicago, c. 1909:
Now that's a real roof overhang.
•  Use powerful proportions.  If you want overhangs, make them generous—at least two feet or so.   Use heavy barge rafters to prevent the sloping roof edge from looking papery. If you're planning  to have a fascia (a trim board behind the gutter), make it substantial as well.  Avoid fussy elements such as narrow sub-roofs and tiny dormers; they usually end up looking like Snoopy’s doghouse.  When in doubt, make elements bigger than they need to be.

•  Unless you’re absolutely sure of the effect you’re after, avoid combining different roof pitches. More often than not, varied pitches look disorganized or, worse, like a construction error. Stick to a uniform pitch, and rely on the size and arrangement of roof masses for effect.

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