When Andrew James Gregor designed this custom renovation in the dry hills east of San Francisco, he wanted to keep the building’s profile low, while making the most of the site’s expansive views. He also needed to capture and store rainfall on the roof to help with irrigating the landscape.
Gregor’s solution was a series of nearly flat roofs stepping down the hillside, with wide eaves to shade the house. The eaves also had to direct rain back toward the house, with gutters at the wall-to-roof intersection directing the rain into a collection system.
Gregor chose LVLs for the rafter system. Wood I-joists would have been cheaper, he says, but LVLs offered the opportunity to build a roof that sloped in toward the house from the wide, overhanging eaves at every side. Unlike wood I-joists, whose strength depends on keeping each member’s top and bottom flange intact, LVLs can safely be ripped at the edge, as long as the reduced depth of each piece still satisfies the structure’s load requirements.
An architect by training, Gregor used the LVLs to accomplish a visual purpose. “One of the things that annoys me about flat roofs is that they pitch at different angles around the building, and the angle is really weak—like three degrees,” he says. “It ends up looking like a twist. So I designed this roof with a fascia that is absolutely level all the way around, and the pitch is all inside the roof.” By ripping the LVLs individually on a custom taper from 12 inches in the center to 8 inches at the wall plate, Gregor created a slope of 1/4 inch per foot in both directions. But at the fascia, the LVLs widen to full width to create a level visual line.
The most complex framing came at the corners, where sloping the overhang inward from both roof edges required tapered blocking and outriggers, assembled into a cross-hatched grid. “My crew called it ‘the diamond,’” Gregor says. —T.C.
Photos: Andrew James Gregor/Blue Dog Construction