Moore, Okla., is certainly no stranger to tornado sirens, but you wouldn’t guess that by looking at the number of shelters it has.

Emergency shelters and safe rooms aren’t required by code in Moore, and when the milewide tornado that struck Monday tore through the town, only about 1 in 10 new homes had one, according to a report from The New York Times.

Public shelters are also in short supply. “Even if you want to go to a safe place, there’s not enough,” says Anita Wagoner, director of sales and marketing at Oklahoma City–based Home Creations, who spoke with BUILDER on Tuesday.

City officials have resisted mandating shelters, which typically range from $2,000 to $6,000 for residential units, arguing that it would make housing too expensive in a market where the average home value has been $107,900 over the past five years, according to the Zillow Home Value Index.

“This is the worst tornado that there’s ever been. To say that every new home must have a tornado shelter and that’s $5,000 each … that would be really difficult for all people to be able to afford and to have a house at all,” said Robert Crout, president of the Central Oklahoma Home Builders Association, in an interview with BUILDER on Wednesday.

“We offer [shelters] as an option, but we haven’t made them standard because people aren’t willing to pay for it,” Wagoner says. “Right now they will. In April and May they will. But sometimes we’ll have a special, and customers will opt instead for the eye candy. People just don’t see the need until they see the tragedy.”

What the builder does provide as standard is homes with more safety features than code requires. Every Home Creations house is equipped with J-bolts, OSB around the entire perimeter of the home, and tornado straps anchoring the top plate of the home to the rafters. Those features add $2,000 to $3,000 to the cost of the home, and enable it to withstand winds up to 160 miles per hour, which Wagoner says probably would qualify as an EF3 on the Enhanced Fujita scale. But because storms are evaluated based on what they destroy, “we avoid saying they’ll withstand a tornado. We just say they’re more structurally sound.”

There’s been talk, Wagoner says, of tightening the building code to include requiring these kinds of features, but so far that hasn’t happened.

But for a storm like the one that struck on Monday, even higher building standards wouldn’t be enough; a storm shelter or safe room would be homeowners’ best bet for safety, and even there, opinions diverge about what’s really safe.

“If there’s an F4 or F5, it doesn’t matter what you do to a home; you have to be underground. Even above-ground storm shelters are not safe,” Wagoner says.

While that attitude is widely shared, shelter manufacturers say that’s no longer true, and that public perception just hasn’t caught up with improved engineering. “Technology has caught up to the point where you can be safe above ground,” says Marty Strough, CEO of Berryville, Ark.–based Storm Rooms of America.

The Texas Tech University Debris Impact Testing Lab certifies above-ground shelters as capable of withstanding EF5 storms. "If the shelter has been tested as an F5, it's good for a 250 mile per hour tornado," says Larry Tanner, a research associate at the National Wind Institute and Debris Impact Testing Lab.

The lab also recommends indoor shelters above cellars only accessible from the outside, since residents are less likely to use outdoor shelters and often encounter flying debris while trying to reach them.

For builders debating whether to purchase a prefabricated shelter or to build or install one themselves, Strough, who operated a home building business for 36 years before entering the shelter business, advises companies to check first with their insurance provider. “General liability policies look at that as a specialty, and building a shelter is something they’re going to charge a lot more money for. I don’t know of any general liability policy that will pick that up."

He recommends using premade units and having installers take on the “huge amount of liability” that installing shelters entails.

Claire Easley is a senior editor at BUILDER.