Madison McVeigh/CityLab

We can build homes to sit above flood waters so people can ride out the Harveys of the future, but it won’t be easy or cheap.

Three months after Hurricane Harvey churned through Texas, dumping 51 inches of rain and damaging an estimated 150,000 homes, the state’s most populous county took a bureaucratic step that has huge implications for how it will deal with the risk of future flooding.

On December 5, Harris County, which surrounds the City of Houston, approved an overhaul of its flood rules, expanding them from 100-year floodplains—which have a 1 percent change of flooding in a given year—to 500-year floodplains. The new rules (which don’t apply inside Houston city limits) will compel people building houses in some areas to elevate them up to eight feet higher than before.

Flooded neighborhoods in Houston on August 29, 2017, three days after Harvey made landfall. (David J. Phillip/AP)

“We had 30,000 houses that flooded” from Harvey, said county engineer John Blount, who put forward the rule changes. Before the floodwaters even subsided, hundreds of county employees fanned out to survey the damage. “We went to every one of those houses and figured out how much water got in them, and then we did a statistical analysis,” Blount said.

The data was geocoded, factoring in location and neighborhood conditions, and one result was the increased elevation rule. (The county is also buying out 200 of the most vulnerable homes and hopes to buy out thousands more, but those represent a small fraction of the homes inside the floodplain.)

Harris County’s new rules are the most stringent flood-related development restrictions anywhere in the United States, according to Blount. If a future Harvey-sized deluge comes, almost all the homes in the area will be safe, he said: “Had that same event happened, at the same location but [with houses] built to the new standard, 95 percent or more would not have flooded.”

For a structure, standing water is a fearsome enemy. Even a small amount of flooding in a home can exile its inhabitants for weeks and require costly repairs. After Harvey, tens of thousands of evacuees lived in hotels or with friends as workers in their homes tore out drywall to prevent the spread of mold, which can sicken residents. And more Harveys are coming: As my colleague Robinson Meyer reported, a new MIT study concludes that Harvey-scale flooding in Texas is six times as likely now as it was in the late 20th century, and will only get more likely as this century wears on.

A man tears out flood-damaged materials from a home in southwestern Houston on September 2, 2017. (Rick Wilking/Reuters)

More than a million people live in the 100- and 500-year flood zones across the Houston area, and hundreds of thousands more do in other U.S. cities, including Miami and New York. Harris County’s move conforms with the advice of building engineers, climate experts, and the insurance industry. If you live in an area that’s prone to flooding—or will be soon—getting off the ground is the best way to avoid recurring, expensive, and heart-rending damage to your house.

“There’s no real substitute for elevation. That’s your best bet,” said Tim Reinhold, senior vice president and chief engineer of the Insurance Institute for Business and Home Safety (IBHS), a research organization based in Tampa and funded by insurers.

Houses don’t have an engineered safety margin for avoiding flooding the way they do for wind resistance, Reinhold points out; even a few inches of water can be devastating. His advice: “Build that margin in by going higher.” The IBHS recommends elevating houses three or more feet above the 100-year floodplain.  

Yet three feet is nowhere near standard. The City of Houston requires one foot of elevation above the 100-year floodplain. Many jurisdictions in Texas and other states require none. What seems like a simple, obvious safeguard raises tricky questions: How high is high enough? Who has to pay for it? And at what point does it no longer make sense to build in a place at all?


From a distance, the house on the campus of Louisiana State University in Baton Rouge looks like a typical Spanish-style model from the 2000s, with a red-tiled roof, tan walls, and flowering bushes out front. Its appearance may be unexceptional, but the house is tougher than any other for miles around. It was built to withstand 130-mile-per-hour winds, lashing rain, flying debris, hail, and even a deep freeze.

No one lives in “LaHouse,” a project of the university’s agriculture center. Rather, it’s “a life-size exhibit that depicts various ways to achieve high-performance housing,” said Claudette Reichel, its director. Builders and contractors, student groups, and regular homeowners tour LaHouse to study its special features.

The back of LaHouse Resource Center, with raised foundations visible (Courtesy of LSU AgCenter)

Those include the foundation. Around the back of the house, visitors can see that it’s been raised a few feet off the ground. The master bedroom is hoisted on piers; another part of the house rests on a concrete-block perimeter “stem wall,” and a third part on a “slab cap” over a filled-in stem wall. Regardless of the method used, the extra height is enough to clear most floods (and to get major discounts on flood insurance). LaHouse has other keep-dry features, like insulation that doesn’t soak up water. But for homeowners wanting to minimize the risk of getting inundated, “by far the best thing to do is elevate,” said Reichel.

Unfortunately, doing so is uncommon in the South. “Everyone still builds on a slab,” said Mike Barcik, senior engineer for technical services at the Southface Institute, a sustainable building nonprofit in Atlanta.

Nationwide, according to Census data, 59 percent of new single-family homes are “slab-on-grade,” as it’s known in the construction industry. The technique is pretty much what it sounds like: Concrete is poured into a mold set shallowly into the ground, forming a slab several inches thick. Because a ground freeze can crack the slab, the method is mainly used in warmer climates. It’s straightforward and cheap. But it results in a house with a low elevation, which is obviously not ideal in a flood zone. “I don’t understand why you would ever build a house on a slab on grade that could be in a flood-prone area,” Barcik said.

Climate change means that the definition of “flood-prone area” will have to be revised. In greater Houston, many of the Harvey-swamped locales were not designated as high-hazard flood zones. And conventional home insurance does not cover flooding. Homeowners who live in a 100-year flood zone are required to buy insurance through the National Flood Insurance Program (part of the Federal Emergency Management Agency). These homeowners must either elevate, relocate, or demolish their home if it has been “substantially damaged” by a flood—that is, if it needs repairs costing more than 50 percent of the house’s market value, minus the value of the land. FEMA may provide funding to elevate, but only up to $30,000, a fraction of the likely cost.

Owners whose homes sustained a lower level of damage aren’t required to take these drastic measures, so many storm victims dread a “substantial damage” assessment. After Hurricane Katrina, thousands of New Orleanians successfully appealed to have the assessment lowered, then repaired their houses as-is. And many people living in floodplains don’t buy flood insurance, so aren’t eligible for FEMA’s help to fortify their homes.

Since 1978, more than 30,000 properties around the country have been flooded so often they’ve been designated “severe repetitive loss properties” (SRLPs) under the NFIP, according to the Natural Resources Defense Council, an environmental group. Analyzing homes that had flooded multiple times, NRDC found that:

the vast majority of properties we looked at have not taken steps to protect against future floods, like putting their home on stilts or pilings or relocating to higher ground. The data we received from FEMA show that 75% of the 30,000 properties we examined have not taken action to reduce their vulnerability to flooding or received assistance to do so.

Widely criticized as “broken,” the National Flood Insurance Program is burdened by $25 billion of debt and faces an uncertain future. Rates have been going up and could keep rising. With storms expected to become wetter and more intense in years ahead, many Americans will have to choose between paying more for insurance, or taking their chances; elevating their homes at their own cost, or moving somewhere else.


Building a house with a raised foundation isn’t cheap. “If you’re starting with a home that’s slab-on-grade right now, and want to raise it by using fill, it could be $13,000 to $14,000 to do that just one foot,” said Gary Ehrlich, the director of construction codes and standards for the National Association of Home Builders.

The fill method—trucking in soil and resting the slab on top of it—is cheaper than the pier-and-beam or stem-wall options. But it’s not adequate for raising a house’s height by several feet. The eight-foot-elevated homes now required in parts of Harris County would carry significant added costs, which builders would pass on to homebuyers.

But those costs pale compared to elevating a home after it’s been built, a strategy of last resort for some owners of Houston homes that predate the city’s 1985 elevation requirement. Adam Bakir, a Houston builder and remodeler, does one or two home elevations a year. The job is akin to major surgery. Workers tunnel under the house, Bakir said, then raise the whole thing on jacks—the slab and the house that rests on it.

Since Harvey, Bakir has received more than 20 inquiries about home elevation. If potential customers ask for a cost estimate, he’ll tell them: between about $75 and $100 per square foot. “If you have a 2,500-square-foot house, which is typical,” he said, “the upper end of it would be about $250,000. The lower end, around $180,000.”  

Not surprisingly, most owners balk at those figures. So their houses remain close to the ground—and unprotected from the next flood.

Even for homeowners who can afford to elevate, it’s hard to know how high to go. Sure, the city says 12 inches today, but what will it say tomorrow—and when it comes to extra clearance, how much is enough? Officials who hope to set elevation minimums face the same problem on a larger scale, balancing neighborhood flood risks against the capacity of regional infrastructure. In New Orleans, elevation requirements jumped after Katrina, but recently went back down again, based on updated FEMA maps that take into account new levees and drainage improvements. (Which, given the performance of the city’s pumps during several recent flooding events, seems optimistic.)

Workers put the last touches on new elevated homes in New Orleans’ Lower Ninth Ward in February 2007, about 18 months after Hurricane Katrina. (Bill Haber/AP)

The changing mandates can seem arbitrary, even to officials. Michael Centineo, New Orleans’ former floodplain administrator, told the Louisiana Advocate: “You’re talking huge sums of money that was put into that [elevation] program and then ... eight years later, they’re telling you now you can build lower. So, that’s the crazy part, right?”


There are other challenges to elevating homes besides the expense and unpredictable regulations. Access becomes more difficult, especially for wheelchair users. (You can install an elevator, but of course, it will cost you.) Crawl spaces can develop moisture problems and invite termites. Aesthetics can be an issue. A single-family house elevated several feet may look ungainly, propped up on piers (especially if neighboring homes are at a conventional height). As with houses in general, elevated-home designs vary from quite nice to very bad.

An existing house being elevated to comply with federal flood-insurance regulations in Toms River, New Jersey, in 2013 (Wayne Perry/AP)
New houses in the Breezy Point neighborhood of Queens, New York. Built after a fire swept through the neighborhood during Superstorm Sandy, they sit on elevated concrete foundations. (Mark Lennihan/AP)

The evidence suggests, however, that elevation works. Recently, the Los Angeles Times analyzed how newer vs. older homes weathered Harvey. Elevation requirements “proved widely effective in their biggest test to date,” wrote the Times’ Ralph Vartabedian and Ben Welsh. “The brunt of [the damage] appears to be borne by older houses—sometimes just doors away from newer, unscathed real estate—that predate federal and local anti-flooding regulations.”

In addition to mandating higher elevations, Harris County has abolished slab-on-grade building, even on top of fill, in the 100-year floodplain. All new houses there will have to be on pier-and-beam foundations or concrete piers.

“It’s a huge change,” Blount said, but the Greater Houston Builders Association has expressed its support for the measure. “No one wants to be building houses in an area that’s known for flooding,” Blount said. “It’s not good business and it’s not good government to have residents flood.” Even so, the new rules won’t stop developers from trying to have flood maps revised to exempt areas on their edges, as New York Times reporters found happened in The Woodlands in Harris County.

Stricter regulations could prompt pushback from builders if rolled out more broadly. Region-wide, they would push up home prices and make housing less affordable. Then again, someone has to pay in the end. It’s just a matter of who—builders? homebuyers? taxpayers?—and how.

John Jacob, director of the Texas coastal watershed program at Texas A&M University, believes that elevating homes is essential if Houston wants to solve its water quandary. “Water seeks the low spots; we need to seek the high spots. It is just that simple,” he wrote in a post-Harvey blog post. “Elevation needs to be our watchword.  Elevation needs to be the metric by which we gauge all new development as well as all redevelopment.”

Jacob himself lives in an older city neighborhood called Eastwood, on a high lot, in a house perched above a four-foot crawl space. The house is new, built in 2015. He estimated that elevating it added $5,000 to a cost of about $300,000—not nothing, but a lot less than he would have paid 10 or 20 years down the line.

Jacobs said the house doesn’t look strange because of the added height. “It’s not like houses on stilts. You’ve got vegetation and those kinds of things. It doesn’t look too weird at all.”

During Harvey, a little extra height would not have saved the homes of people who had to wade through waist-deep water and be rescued by boat. But it could have made a big difference for many others, Jacob said.

“I went out mucking as a volunteer,” he said. “Most of these places we went to had just one to two feet in the house. Had their lot been elevated, or their house, you could have lost a car, and it would have been a hassle. But that’s a lot different than having to fix your house.”

However, the most effective means of elevation that Jacob recommends doesn’t involve a special kind of foundation. The surefire way to keep a home or a neighborhood high and dry is simple: Don’t build it in a floodplain.

“What we ought to do,” he said, “is build in the right place.”

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