Flipping the Script on a Second-Story Addition

Here, the complex roof structure for the new second-story living space floats like an umbrella over the undisturbed existing roof. The house got through last week’s three-day nor’easter storm fine, says architect and builder Andy DiGiammo. “There was no damage from wind or rain.”

At this gable end location, the complex roof system is supported by two posts: one at the existing ridge, and one at the existing wall corner. The post bases are wrapped with Ice and Water Shield membrane to keep water out of the existing first story.

Two structural valley timbers and two structural ridge timbers converge at this central point in the roof, supported at the apex by a single post that penetrates the roof and extends down to a bearing point on the existing wall below. “Whenever I put an addition onto existing, I start with existing structural points that I want to hit,” says Andy DiGiammo.

Leaving the existing roof in place while building the new roof simplified the problem of staging the job, and made it easy to construct a stable working platform for the framers. The existing roof also provides a convenient walking and working surface, notes DiGiammo.

At some locations in the new roof structure, rafters bear on existing roof areas that will be left in place when the addition is complete. Meantime, the sheltered area under the new roof is a convenient workspace. DiGiammo plans to leave the existing roof intact until the upper roof and its supporting walls are complete and the area beneath the new roof is fully enclosed and dried in.

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