by Peter
Marzbanian
My company recently completed the renovation of a 30-year-old
raised ranch in Vineyard Haven, Mass., on Martha's Vineyard.
The job transformed a nondescript house that would have been at
home in suburbia into an architecturally unique residence
appropriate to its resort-island setting.
From the beginning, it was clear that one of the most
technically challenging parts of the job would involve the end
of the house facing the street — a drab gable with two
garage doors. Determined to make this elevation into a
welcoming entry, architects Geoffrey Koper and Katie Hutchison
had designed a 4-foot-deep addition with a 2-foot-deep bay
window seat. The bay's four windows, set among trimmed panels
and crowned with a shingled gable, would become one of the
home's nicest architectural features.
But the garage doors posed a problem. The client didn't want to
move them, because doing so would mean extending the
foundation. Instead, most of the small addition would have to
hang off the existing house. The question was how to support
it.
No longer ho-hum, this raised ranch was
transfigured by an architect-designed whole-house remodel and
addition.
Before
After
The Plan
Had we been building the house from scratch, the answer would
have been straightforward: Change the direction of the home's
floor joists at that end of the house so they cantilevered from
the house to carry the weight of the bay. But on an existing
house, this would have required a major structural redesign
— which everyone wanted to avoid.
Instead, structural engineer Paul Donohue devised an ingenious
way to support the bay — using steel, LVL, and solid wood
— that didn't entail tying into the existing floor
frame.
A pair of T-shaped tubular steel goalposts would be bolted to
the house at each end of the bay (see illustration). The posts'
steel columns would transfer the structural load down to a
4-foot concrete knee wall extending from the existing home. An
LVL header would link the tops of the two posts, and the space
between the LVL and the house would be spanned with
joists.
The wall and roof frame would further tie the addition to the
existing home.