With flood waters still receding across the Midwest and Hurricane Bertha officially opening the 2008 hurricane season in the Atlantic, builders across the nation are being reminded of the need to protect their new homes against high water. One option worth considering? Modular homes, even when elevated foundations are required or recommended.
One such example can be found at a beachfront site in New Bern, N.C., where this week Handcrafted Homes (www.handcraftedhomes.com) is building a modular coastal cottage. Handcrafted is a North Carolina-based firm that supplies houses to seven states from Delaware to Georgia, and according to Len Fairfield, general contractor for the New Bern project, placing a modular home on an elevated foundation is no harder than elevating any other house.
Foundations for Coastal Modular Homes
Fairfield speaks from experience. Most of Handcrafted’s product is set by independent builders, but Fairfield runs Handcrafted Homes’ only company-owned field operation. In the past four years, he has built more than 150 homes on scattered lots in coastal North Carolina’s Pamlico, Carteret, and Onslow counties. Almost all have been in the 130-mph coastal wind speed zone; many have been built in areas designated as flood hazard zones.
Often, building near the ocean means setting the house on a piling foundation. But for the New Bern project, Fairfield instead raised the grade at the site to 12 feet above sea level with engineered fill. “That got us out of the flood zone,” he says. Then he placed a Superior Wall prefabricated concrete foundation structure that rises 9 more feet above grade. The factory-built home is then firmly connected to that.
Regardless of whether a modular home is set on a perimeter foundation or pilings, however, Fairfield says each house comes with all the structural elements to both handle the coastal wind loads and attach to the foundation.
When a concrete perimeter foundation is used, the builder connects that foundation to the modular house by bolting a sill plate to the concrete and then running steel straps from the plate to the modular frame after the modular boxes are set onto the sill. The straps get help from OSB sheathing, Fairfield says. “We leave about 18 inches unsheathed at the bottom of the wall, and we attach that sheathing on site so it goes a few inches up the studs of the wall, down across the floor framing of the house, and then down to the bottom of the sill plate at the foundation,” he says.
The details vary slightly for a piling foundation. “We notch the top of the pilings out, run a double 2x12 band around and bolt that to the pilings with a plate and a bolt,” Fairfield explains. “Then the house sits down on top of that 2x12, it all gets nailed together, we set the metal straps, and then we nail on the OSB to lap over the bottom of the wall and the 2x12 band.”
Jane Yates, Handcrafted’s director of engineering, says the additional material in the 2x12 band offers better anchoring for the steel straps and the lapped-over sheathing than does a 1.5-inch sill plate, but she notes that the open foundation also makes for a greater wind uplift load. “With a pile foundation you have more to contend with on uplift, because the air is underneath the house trying to pick it up like a kite all the time.”
Perimeter foundation connections, by contrast, mainly have to cope with the house wanting to slide along the foundation sideways. But this is a load the anchor bolts, sheathing, and framing connections can readily be sized to handle.
In terms of design, this New Bern project also represents the first fruits of a collaboration between Handcrafted Homes and home designer William Poole (www.williampooledesigns.com). (Hanley Wood, the company that publishes BUILDER, licenses William Poole Designs home plans for its line of consumer home plans magazines.)
Island Design, Quality Control
With its classic “island home” lines and its careful interior and exterior detailing, the new dwelling is a prime example of the modular industry’s escape from the confines of plain, boxy designs. (To see the “Twin Gables” model being set this week in North Carolina, visit www.williampooledesigns.com/plans/Twin_Gables.) But while Poole wants to transcend modular’s past aesthetic reputation, he speaks highly of the modular industry’s construction quality control practices--methods which have a direct bearing on these homes’ abilities to withstand extreme structural challenges such as hurricanes or earthquakes.
“I am jealous of the reputation we’ve earned in 40 years of design work, and I am not going to let somebody that would not do a good job work on my designs,” says Poole, who says he visited many modular companies in his research. “But I found that the majority of modular companies are doing a superb job.” In contrast, Poole says he has been disappointed in the craftsmanship by some site builders using his designs; he describes the work on one stick-built multimillion-dollar home on the Virginia shore as “appalling.”
He says modular home building offers many quality control advantages. Employees work indoors in dry, sheltered conditions with continual supervision and frequent inspections. “There are 250 inspections on a modular home. There is someone looking on all the time, seeing that the workmen are doing it correctly,” he says. “You couldn’t possibly do that in the field. So you are assured of a better-built house.”
And Poole says the same careful standards are applied even to the lowest-priced models. “In visiting the factories, I saw that the lowest common denominator was made better than an expensive custom house was being built in the field. A $250,000 home is built better than the $3 million home I had designed out on the Eastern Shore — and better than some of the houses that I built myself, when I was in construction.”
Ted Cushman is a contributing editor to BUILDER magazine.
Learn more about markets featured in this article: Atlanta, GA.