Every major catastrophe seems to have its success stories. With Hurricane Michael, one stand-out example was the so-called "Sand Palace," a high-end custom concrete house on pilings that survived with little damage in Mexico Beach. But a house doesn't have to be a costly custom project to ride out a hurricane in style. Case in point: Six small Habitat for Humanity houses in nearby Panama City that came through Hurricane Michael essentially unscathed, even as the homes around them lost their roofs and suffered significant structural damage.
The six houses were part of the "Habitat Strong" program, an above-code construction program modeled on the recommendations of the "Fortified Home" program developed by the Institute for Business and Home Safety (IBHS), an insurance industry non-profit that advocates for more resilient building practices. Framed by local builder Eric Anderson (Compass Homes of Northwest Florida), the houses boasted beefed-up roof details and an engineered design featuring a continuous foundation-to-ridge load path. But according to IBHS, the added features that contributed to the buildings' exemplary performance added only a modest amount to the affordable structures' cost.
From one house to the next, components and details may vary, said IBHS Market Development Manager Alex Cary, herself a licensed builder in Alabama. But the concept of a continuous load path is consistent, she explained in a JLC interview. "It [the Fortified standard] just says that it has to be an engineered design," said Cary, "because there's a million ways to skin that cat. There's a myriad of straps and connectors, and usually the loads are specific to that structure, and there's a number of factors that go into that — including the design wind speed for that location, and the exposure category, so what's around that home, like homes and trees and things that are around to slow that wind down."
In this case, Builder Eric Anderson applied the same construction details that he typically includes on his market-rate houses. "I build above code," says Anderson.
To resist uplift, Anderson installed the "Go-Bolt" system (www.go-bolt.com), developed by a Florida builder after Hurricane Andrew. Go-Bolt adapts the reinforcing concept often used in concrete masonry block construction and applies it to stick framing. The method relies on threaded rod connectors that run all the way from the foundation to above the top plate, tied to anchors embedded in the concrete at the foundation, and fastened down over the top plate with three-inch washers and nuts. "I've got them within 8 inches of the corners, within 8 inches of every opening, and then spaced every 6 feet within the rest of the wall," said Anderson.
Anderson fully sheathes his stud walls using Windstorm OSB panels from Norbord, which allows continuous sheathing from the base to the top of the wall with a single long sheet of OSB. At the top of the wall, he specs nailing 2.5 inches on-center into each of the double wall plates. The plate at the base of the wall also gets nails at 2.5 inches on-center. Sheathing is nailed at 4 inches on-center, in the field as well as at the joints. On the Habitat projects, Anderson uses galvanized 8d nails, hand-driven by volunteers. On his regular jobs, his crew uses gun nails, but they follow the same tight nailing pattern.
Roof trusses are secured to the wall plates using Simpson H10A connectors. The Habitat houses have hip roofs, sheathed with 5/8-inch CDX plywood nailed at 4 inches on-center. The entire roof is covered with peel-and-stick bituminous membrane and roofed with 24-gauge steel roofing. The roofs are unvented, said Anderson, and insulated with spray foam (as are the walls).
In the aftermath of Hurricane Michael, everyone involved in the Habitat houses has gone into emergency response mode. Eric Anderson's personal house was not badly damaged, he says, although he lost the tabs on about 20% of his roof shingles. Since the storm, Anderson has lost four employees who had to move because their homes were condemned. But he has taken on 60 new employees, and on November 20 he said, "I have 150 jobs." All of it is mitigation work: gutting homes and repairing or replacing roofs in order to keep water out.
The Bay County, Florida, Habitat for Humanity chapter, which built the six houses, took a heavy hit in the storm. Their new office and Habitat ReStore (the source of most of their funding) were destroyed. Architect Victoria Williams (www.vbadesign.us), a Habitat board member who designed the houses, also lost her office.
Eric Anderson expects to be doing muck-out and basic repair work for at least six months and reconstruction for another three to five years, at least. But given the widespread destruction, the road back for Bay County won't be easy, he said: "In the next six to twelve months, we'll probably lose 20 to 30 percent of the population" as people migrate away in search of jobs and viable housing.
