Texas Moves To Strengthen coastal building codes

In early January, the Texas Windstorm Insurance Association (TWIA) agreed to replace its existing building code with upgraded versions of the International Residential Code (IRC) and the International Building Code (IBC). The final changes were expected to be published January 10, 2003. The implementation date has been tentatively set for May 2003. The TWIA program is a voluntary, state-run wind pool program along coastal Texas implemented for insurability purposes to increase protection from property damage.

On behalf of the Institute for Business and Home Safety (IBHS), Nanette McElman, P.E., IBHS building code manager, sent a letter to the Texas Department of Insurance strongly urging implementation of upgraded IRC and IBC codes rather than accepting them without amendment.

In her letter, McElman stated that the IBHS had reviewed the differences between the existing TWIA Windstorm Resistant Construction Code and the IRC and IBC 2000 with regards to windborne debris and roof resistance. Several technical differences were found that would affect the performance of a home during a high-wind event. For example, the TWIA code required additional opening protection that the IRC and IBC do not. Specifically, all exterior openings including non-glazed openings were to be protected from windborne debris, whereas Section R301.2.1.2 of the IRC 2000 states that structures located in windborne debris regions have the option of protecting only glazed openings from windborne debris or the structure shall be designed to resist internal pressures, McElman explained.

McElman wrote, “Although structures designed to internal pressures are structurally capable of surviving a design event, the openings are sacrificial, leaving the interior of the structure vulnerable to wind and rain.”

The existing TWIA code also required that asphalt shingles be rated for winds of 110 mph, but the IRC 2000 does not require asphalt shingles to be rated for high winds. The IRC 2000 allows for an exception that only requires additional fasteners in high wind areas. Mandating that asphalt shingles be tested in accordance with ASTM 3161, modified to 110 mph ensures not only acceptable fastening patterns and methods, but also ensures that the asphalt shingles will be more likely to perform in higher winds, McElman said.

The important upgrades for the IRC and IBC that were eventually accepted by all parties are: The elimination of design for internal pressures and the incorporation of wind-rated asphalt shingles (110 mph), McElman said. In Seaward areas (barrier islands), all openings (glazed and non-glazed) will continue to be protected. In Inland I areas (first tier counties), all glazed openings will be protected in accordance with the IRC and IBC. (No opening protection was mandated under the TWIA code.)

In terms of hurricane protection, structures built in Texas under the TWIA program on the barrier islands will continue to be built stronger than anywhere else in the country, other than in South Florida; and the first tier counties will be upgraded to be stronger than any other of its kind in the United States. These codes, it must be noted, primarily deal with new construction.