HOMES AT RISK - Roof Flaw Puts Homes in Jeopardy
Published Sunday, June 11, 2000, in the Miami Herald - BY PETER WHORISKEY

Tens of thousands of South Florida homes were built with a roof flaw that will render them unsafe in the next major hurricane. The roofs may fly off.

A growing body of wind engineering research, begun after Hurricane Andrew wrecked 49,000 homes and killed 15 people eight years ago, is now yielding one of its most important lessons. A standard roof construction method, prescribed by local building codes from 1962 to 1994, has left many of the 300,000 homes built during that period with roofs attached with nails that are too short and too few.

The deficiency of nails means that the roofs offer less than half the resistance they should have to withstand South Florida's high winds, say experts who have tested the connection.

Sustained winds as low as 95 mph, or a relatively weak hurricane, can cause the plywood base of these roofs -- the layer beneath the tiles and shingles -- to pull away from the roof frames and fly away, leaving behind gaping holes and opening the homes to wind and rain. The flaw has been cited as one of the leading causes of wreckage during Hurricane Andrew's thunderous gusts.

"If a major hurricane hits South Florida, a large percentage of exposed houses again will lose plywood roof sheathing," said Tim Reinhold, an engineering professor at Clemson University, who has conducted wind simulation tests on the panels.

"Even homes that were built according to the code at the time do not have enough nails for those kinds of winds. It's that simple."

After Hurricane Andrew, reformers singled out several aspects of the South Florida Building Code as contributing to the destruction -- the permitted use of staples instead of nails, for example, and of pressed board instead of wood. In engineering circles, however, the debate over the dangers of these practices continues. The recent research on roof plywood nailing, by contrast, has turned up some of the most unequivocal results.

Today, even representatives of the American Plywood Association, the trade group in which the construction practice appears to have originated, now disavow its use in South Florida and other hurricane-prone areas. ``We were shocked and appalled that it was being used in South Florida,'' said Ed Keith, a senior engineer at the organization. ``We had no idea.'' How did builders and building regulators get something so simple so wrong?

The Herald examined that question and found:

NAILING BY THE NUMBERS
It took a while after Andrew to understand the problem. Determining the correct number and size of nails to attach plywood roof sheets to roof frames may seem a simple matter.

From 1962 to 1994, the local building code prescribed 33 two-inch nails per plywood panel. Since then, the building code has prescribed 45 or more 2 1/2-inch nails per panel.

The importance of getting these numbers right wasn't completely understood after Hurricane Andrew, however, and it wasn't until recently that researchers fully understood the devastating effects of the old, flimsy nailing requirement.

The new findings -- including studies at Clemson University, Virginia Tech and the National Association of Home Builders Research Center, and work by Miami engineers Fred and Peter Berlowe -- have two significant ramifications in South Florida.

First, they cast a very different light on the causes of the vast wreckage of Hurricane Andrew. While the loss of plywood roof sheathing has long been recognized as one of the leading causes of damage, many have blamed the destruction on carpenters too lazy or too rushed to drive all the nails prescribed by the building code. The new findings suggest that the building code itself, as much as or more than shoddy workmanship, caused the plywood roof sheathing to lift away from roofs.

"We and many other people gravitated very quickly to the conclusion that workmanship was the major factor," said Jay ndell, a National Association of Home Builders researcher and the lead author of the most comprehensive study of Hurricane Andrew damage, completed last year.

Unlike the impressionistic reports after the storm, that study was based on a scientific sample -- of 500 homes. "And to a certain extent, workmanship was a problem. But a much bigger factor was certain aspects of the building code itself." The study, which was funded by the U.S. Department of Housing and Urban Development, was reviewed by a five-member peer panel that included representatives of Clemson University, Johns Hopkins University and one of the plywood association's biggest members, the Weyerhaeuser Corp. Second, the new findings raise serious questions about the safety of tens of thousands of homes.

About half of South Florida's existing single-family homes -- more than 300,000 -- were built during the 32-year period from 1962 to 1994, when the code dictated too few nails for attaching roof plywood. While some of the roofs built then were sheathed with traditional tongue-in-groove boards, which required more nails than plywood, and some were attached with staples rather than nails, many of the roofs built then are likely to have been made with plywood attached with too few nails.

"They're all at risk," said J. Daniel Dolan, a wood engineering professor at Virginia Tech, who advises homeowners to retrofit their homes for safety's sake. "You'll see major damage in the next major hurricane."

INDUSTRY GROUP'S ROLE
Plywood association promoted the old method of nailing roofs Figuring prominently in every aspect of the flawed construction practice is the American Plywood Association, a marketing group based in Tacoma, Wash., that represents the nation's largest plywood manufacturers, including Georgia Pacific, Louisiana Pacific and Weyerhaeuser.

The association promoted the old nailing method as far back as the 1950s; the old method entered the South Florida Building Code in 1962 after the association wrote to the code committee regarding "more liberal use of plywood" -- and the committee initiated a code change as a result. After Hurricane Andrew, the plywood association defended the nailing standard.

"There is no evidence that the nailing schedule under the current building code was inadequate," according to a January 1993 press release from the association.

At the same time as that press release, however, the association also recommended upgrading the nailing standard to require more and longer nails "to add an extra measure of safety." The change, to 45 or more 2 1/2-inch nails per panel, more than tripled the uplift resistance of plywood roofs, and was adopted soon afterward in Miami-Dade, Broward and elsewhere around the country.

In response to recent questions from The Herald, representatives sought to distance themselves from the use of the old nailing standard in South Florida. Keith, the senior engineer at the plywood association, said the association never intended the old standard for high-wind areas. "It never should have been adopted into the South Florida Building Code; it was a minimum recommendation," Keith said.

``Building codes are not our responsibility.'' The American Plywood Association routinely gets involved in helping to write local building codes, however. Did the association ever warn building officials that the standard was insufficient in hurricane-prone regions? `

"I don't know, but I don't think anyone said, `You can't have this for high-wind areas,'" Keith said.

In South Florida and around the country, building code committees rely on industry marketing organizations for technical expertise. The local committees typically do not have the budget or the staff to conduct testing for every conceivable type of construction.

"Like it or not, we have to rely on these groups," said Jose rani, an engineering professor at Florida International University and a member of the Miami-Dade County building code committee that oversees the South Florida Building Code. "There is no way in the world we could afford all the research that would be needed otherwise. Unfortunately, few of these groups are without some bias. They want to sell their products."

THE PITCH FOR PLYWOOD
Cost-cutting appeal resulted in changes to building codes The American Plywood Association's promotion of the nailing method dovetailed with its promotion of plywood itself. In the early 1960s, most home roofs were made of wooden boards, usually tongue-in-groove one-by-sixes or one-by-eights.

By tradition and by code, the wooden boards required many nails. Every time a roofing board crossed a roof truss, carpenters were supposed to drive in two or three 2 1/2-inch nails. The plywood manufacturers liked to advertise that plywood didn't need as many nails, and, as a result, using plywood would ``drastically'' cut home builders' expenses for nails and the required labor.

A 1958 brochure told builders that using plywood instead of boards could save 11 hours of labor and 12 pounds of nails on a typical small house. ``Suppliers were saying, `Why don't you switch to plywood?' or `If you want to save some money, go to plywood,' '' said Lenny Miller, president of Pasadena Homes, a home builder noted for its attention to construction strength. ``The labor was less expensive with plywood.''

A key step in the marketing campaign was making sure that local building codes permitted the cheap and efficient use of plywood in roofs. The organization worked toward this goal throughout the United States. The association has ``taken the lead . . . in obtaining virtually every building code approval of plywood,'' the organization, then known as the Douglas Fir Plywood Association, boasted in a 1962 trade industry ad.

On Dec. 16, 1959, the Miami-Dade County code committee received a letter from the association, according to meeting minutes, ``re: Revision of South Florida Building Code to allow more liberal use of plywood.'' On the basis of the letter, the committee initiated an amendment to the South Florida Building Code, minutes show.

Until then, the code had dictated that typical roofs, if they were to be sheathed in plywood, had to be covered in sheets that were five-eighths of an inch thick and attached with 33 nails 2 1/2 inches long. The next edition of the South Florida Building Code reduced the minimum thickness of roof plywood from five-eighths of an inch to half an inch and reduced the nail length from 2 1/2 inches to two inches.

It paralleled the American Plywood Association's recommended standard. Estimated savings in current dollars: $105 per home. Estimated reduction in resistance to wind uplift: about half. None of the members of the committee at the time could be reached for comment. Most have died. What is known, however, is that the pitch worked.

By the 1970s, plywood had become the standard material for roofs in South Florida. HOW WIND, ROOF INTERACT Plywood association's standard on uplift pressure is questioned It may be impossible to know whether the plywood manufacturers were aware that their nailing instructions would make homes vulnerable to hurricanes.

But basic engineering references available to the American Plywood Association's engineering staff as far back as 1960 suggested that its nailing recommendations were inadequate in hurricane-prone areas. When wind passes over a roof, it typically pulls upward on the roof, the same way that air rushing over the wings of an airplane lifts it into the sky.

Standard references dating back to the 1960s issued warnings about these uplift effects on home roofs. Consider the Uniform Building Code, the building code in effect in much of Washington state, the home of the plywood association.

The 1961 Uniform Building Code required that most roofs in hurricane-prone regions such as South Florida be strong enough to withstand wind uplift pressures of between 50 and 80 pounds per square foot.

The Uniform Building Code at the time also indicated that attaching a plywood roof according to the association's instructions was not enough to withstand such winds. According to the Uniform Building Code's tables, the association's roof nailing method could be counted on to hold between 42 and 47 pounds per square foot. Other basic references at the time contained similar information. By 1968, the engineers at the association showed an enhanced understanding of wind uplift effects. They announced then that they had tested a plywood roof in a simulated hurricane wind exerting 60 pounds of uplift. For the test, however, the plywood was nailed not according to the standard association recommendations, but with more and longer nails, as a diagram published with the announcement showed.

"The APA either knew -- or should have known -- that their basic standards were no good," said Fred Berlowe, a Miami professional engineer, who with his son, Peter, studied the issue on behalf of an insurance company that in 1995 considered suing the association for hurricane losses.

The Berlowes were among the first to recognize the significance of the flawed nailing pattern. "Any competent engineer at the time would have had all the basic information right in front of him -- at his desk," Fred Berlowe said.

WHAT ANDREW REVEALED
Structural damage attributed to loss of plywood sheathing Hurricane Andrew proved how dangerous a poorly attached roof could be. Signs of this phenomenon were impossible to miss. One of the iconic images after the storm was a house shorn of plywood sheathing, its naked triangular roof trusses pointing forlornly skyward.

Others simply lost one or two sheets, but the damage that followed typically destroyed the home. Crandell, of the National Association of Home Builders Research Center, counts the loss of plywood sheathing as the leading cause of home structural damage in Hurricane Andrew.

A PROBLEM ONCE AGAIN
Rebuilding after hurricane was by the old nail-poor standard After the hurricane, countless homes were rebuilt according to the old nailing standard. The code would not change until two years after the storm, as the debate over building codes lagged in a political fray. This added to the problem: What can be done with all the homes nailed with too few nails? One remedy is already available, but it affects only a small percentage of homes annually.

When a home is being retiled or reshingled, roofers are supposed to add extra nails, if necessary, to bring the roof up to the current, safer standards. Whether roofers are complying, however, is difficult to know. Few inspections are conducted to make sure that the plywood layer is being nailed correctly.

The reason for this is a practical one: To allow for a nailing inspection, the plywood has to remain exposed while the roofers wait for an inspector. During this interval, the house is not watertight and, as a result, is vulnerable to rain. Inspectors in Miami-Dade and Broward typically opt to take the roofers' word for it.r>
"We are not required by code to do the inspection," said Flavio Gomez, chief of the Miami-Dade Building Division. "The thinking was that we can't hold up the job when the roofs are open to the rain."

Another option: Homeowners who can access the crawl spaces beneath their roofs may add adhesives that will bolster the homes' grip on the roof plywood. Few people seem to be aware that their homes may need the upgrade, however, and local building officials are not promoting the issue.

"Most people have no idea that they need it and that it could save them in a hurricane," said Reinhold of Clemson University. Without retrofits, countless homes in South Florida and other hurricane-prone areas are vulnerable for the destruction that follows when the roof is opened. ``When the next one happens, no matter where it happens, we'll see the same thing -- lots of homes where the plywood has just been lifted from the roof,'' said Peter Berlowe, an engineer and lawyer who has studied the issue.

``It's basically a ticking time bomb."