While the most populated city of the Coastal Bend area of Texas, Corpus Christi, was spared the brunt of Hurricane Harvey, the coastal towns of Port Aransas and Rockport saw the force of the high winds and storm surge that came with the Category 4 hurricane. Bautex had the opportunity to visit the Coastal Bend of Texas ten days after the area was hit so hard by Harvey. While clean up and repair were well underway, utilities were only partially restored. The destruction from Port Aransas to north of Rockport was immense and gave us insight to the power of hurricanes and what that means for buildings in hurricane zones. Our observations, conversations, and tours of previously constructed projects located in the area led to the following lessons learned.
Wind and Water Damage
Every building we passed suffered damage from wind, water, or both. The wind loads in Rockport were over 130 mph, slightly exceeding the design code of 120 mph for Inland I category. This resulted in most roofs suffering some amount of damage, many roof failures and a considerable amount of complete structure failures. The age of the building, proximity to open water or fields, and location to other structures and trees were the major factors in how the high winds affected the structure. Older buildings with no wind protection fared the worst.
Wind debris caused damage where structures failed or tree limbs were torn off. In both cases the debris became missiles. These impacts were clearly shown through 2x4 sized holes in walls of buildings, windows and doors broken from flying debris, and building materials and limbs still protruding from structures. The danger from this flying debris cannot be understated and makes FEMA 320/361 and ICC 500 missile debris impact testing critical for building materials along the coast.
Water damage was rampant wherever we travelled as evidenced by the mountains of insulation, drywall, and furnishing being removed from every building. Some of this damage came from storm surge, especially in Port Aransas, but much of the water damage came from roof and window failures.
What Types of Structures Failed and Why
Town after town the total structural failures we saw indicated that building types with the highest number of complete loss buildings were wood framed or pre-engineered metal buildings. Both types of structures are susceptible to rot/rust from cyclical wet and dry cycles as well as salt air conditions. Both of these types of systems are lightweight assemblies and depend on the sheathing, whether wood or metal for shear resistance. Once their roofs were compromised, the wind pressures forced failures of the sheathing, which contributed to partial and total collapses. The rot and rust of connections clearly added to the structural failure.
Recommendations for Rebuilding
Clearly, Hurricane Harvey’s destruction was disastrous for the Coastal Bend of Texas, but the losses can be used as a learning experience for the construction industry to build better. There is not a single answer to rebuilding or redesigning structures along the coast. The design has to be looked at holistically and not as individual design aspects or materials. The roof matters, the walls matter, the windows matter, the finished floor elevation matters but when designed together and constructed as an assembly they can create a hurricane resistant structure that will stand up to fierce storms like Harvey.
Building at finished floor elevation well above the storm surge model can protect a building from the onslaught of rushing seawater into the structure. This can be done by building on pilings and in some cases by bringing the building pad up a few feet with fill material.
Using resilient wall systems to build in hurricane areas can protect both the structural integrity of the building but also eliminate the chance for flying debris to penetrate the walls. Concrete wall assemblies like Bautex should be considered for the inherent strength against high winds but also for the lab tested resistance to wind-borne missile debris. These types of walls do not reply upon sheathing for shear strength and are far less likely to suffer catastrophic failure.
Roofs have to be designed with low pitches to minimize the amount of wind pressure on the structure. Connections to the wall assembly should be designed to be robust and if possible to exceed the prescribed code. Having an adhered weather barrier on the roof sheathing will add protection against water penetration should the roofing material become compromised during the storm.
There are other design details that should be considered including window and door protection, exterior finishes that don’t have an air gap to allow high winds to pull them off the wall, and air and moisture barrier systems that are fully adhered should all be considered in looking at rebuilding or new construction along the coast.
As a Texas-based company, Bautex is committed to solution-based wall designs that help along the Texas coast. To read a more detailed analysis of lessons learned from Hurricane Harvey, the full article can be found here. To find out more about Bautex and how The Bautex Wall System can be used as part of a robust windstorm design go to bautexsystems.com.