Blow, ye summer winds. David Helms' home is ready for you.
Helms, founder and president of Signature Built Homes, is less than a month from finishing his 11,000-square-foot home in a brick-streets neighborhood in west St. Petersburg. Already, he contends, thanks to a unique combination of innovative storm-resistant construction materials and techniques, his home is hurricane-proof.
He says it has already been vetted by engineers to withstand winds of up to 300 miles per hour.
Helms, 50, started Signature Built Homes in St. Petersburg seven years ago. Since then, he has constructed an estimated 20 houses, all in Pinellas County. In addition to his own home (with its five bedrooms, eight baths and a room solely for a Wii gaming system), he has three others for clients in Tierra Verde, all under construction.
They range in size from 4,000 square feet to 17,000 square feet with a Kevlar-coated safe room, six-car garage and boathouse.
Helms says he has been using hurricane-resistant techniques and materials for years, but his own home, started last July 5, is the first with such a combination of hurricane-resistant techniques, thanks in part to a flat-roof design.
Helms said the key was "starting from the ground up." The idea is to create an impenetrable "structure envelope" that will resist hurricane winds and rain. The home is far enough from water to be safe from storm surge.
The walls are made from insulated concrete forms, polystyrene blocks 12 inches tall, 8 inches thick and 4 feet long filled with 3,000-pounds-per-square-inch concrete mixed with Helix steel fibers, then strengthened by vertical and horizontal reinforcing bars.
Twenty of these concrete-filled foam blocks create a cube called a "Powerwall" that weighs the same as one single traditional concrete block — 40 pounds — but is, obviously, much larger. A standard concrete block is 8 by 8 by 16 inches.
Helms says Signature Built is the first Tampa Bay area builder to use Helix in residential construction. The rust-proof, steel-fiber additive is made of twisted, toothpick-sized metallic wires that lock into place like screws, Helms says. When the Helix-concrete mixture is poured into the foam cubes, the concrete remains moister and cooler than regular concrete poured into block walls, Helms says. This extends the curing time, which increases the strength of the concrete, up to 5,000 pounds per square inch, or psi.
The result is a concrete wall strong enough to withstand winds of up to 250 mph. Traditional concrete-and-block walls are rated for 130 mph, Helms says.
Once the walls are up, a coat of waterproof polymer-based Coraflex is applied. Coraflex is a colored stucco — an "orange gold," Helms says — that won't crack, is impervious to wind-driven rain and never needs painting, Helms says.
A building's roof is often the weakest part of the structure in a hurricane, Helms says. Winds can catch a single shingle or tile and begin peeling the roof off bit by bit. Or the winds can catch the edge of a sloped roof and lift the entire covering.
With that in mind, on the Tierra Verde projects, instead of traditional felt paper, Helms is using a special kind of waterproof sheathing panel that is sealed with tape to provide a secondary water barrier because of the conventional design of the roofs.
On his home, Helms is using a Sealoflex system, a liquid membrane applied directly to the roof deck that is then extended up and over parapet-style walls that rise above the roofline. The membrane eliminates the need for exterior roof covering and strengthens the roof to withstand winds exceeding 300 mph, the manufacturer claims.
In addition, the underside of the roof deck is insulated with Icynene foam insulation that is sprayed on. The Icynene glues the roof to the rafters, creating a watertight seal and eliminating the need for roof vents, Helms explains.
Helms also uses HurriQuake Disaster Resistant Fasteners, which prevent shearing and roof panel uplift in high winds. These fasteners won Popular Science magazine's Innovation of the Year award in 2006. Their barbed bottom section, fat middle, twisted top shank and large head make them highly resistant to wind shear and uplift.
The other weak spots in many structures are the windows and doors, which often give way to high winds and wind-driven debris. Helms uses double- or even triple-impact glass as well as 2- by 8-inch timbers to strengthen window and door openings with 10-inch lag bolts and J-bolts, which are put into place with concrete.
To further create a watertight seal, openings then are sealed with a Sealoflex coating system. Sealoflex is also used to seal the perimeter where walls and foundations meet, a touch not required by standard building codes, Helms says.
The process also provides a strong pest barrier, he adds.
The house and its blueprints have undergone preliminary review by engineers from the Institute for Business and Home Safety, a nationwide organization based in Tampa that promotes hurricane-resistant construction.
Although the home cannot receive its final certification under the institute's "Fortified . . . for Safer Living" program until it undergoes third-party inspection, the house's design plans provide for protection against winds of at least 200 mph, spokeswoman Wendy Rose said. The institute's minimum standards for certification are 150 mph winds. Details are at disastersafety.org.
Another benefit of creating a "structural envelope" of protection is energy efficiency, Helms explains. "Energy efficiency is part of it. That comes hand in hand with it."
"The Styrofoam Powerwall blocks were green long before building green was popular," Helms says. So is Icynene. "We're green without even trying."
His home will have other energy-efficient touches, such as multiple air conditioning systems and several tankless water heaters.
In many cases, the additional hurricane protection doesn't necessarily boost the construction costs. For example, some hurricane-resistant materials cost less in labor to install than conventional materials. A Signature Built home ranges from $180 to $380 per square foot.
"I feel we're competitively priced against other custom builders in town — probably in the middle of the road," he says.
Fred. W. Wright Jr. is a St. Petersburg-based freelance writer.