By all accounts, investigators have worked extensively to improve the ability of buildings and other built entities to withstand extreme weather conditions following Hurricane Andrew in 1992.
Collectively, the Building Performance Assessment Team assembled by the Federal Emergency Management Agency (FEMA) formed in September, 1992 spent more than 1,500 man hours conducting site surveys, preparing documentation and assessing damages. The goal was to ensure that observed failures be corrected to protect people from future hurricanes using recognised standards of design and construction.
The resultant report released last week, Building Performance: Hurricane Andrew In Florida, contained six general recommendations, as well as further specific recommendations in the areas of roof cladding and roof framing systems, exterior wall openings, light wood-frame buildings, masonry buildings, manufactured homes and modular buildings, accessory structures and the repair/retrofit of partially damaged buildings.
What went wrong?
On the positive side, the assessment team found that from the viewpoint of the primary structural systems of buildings (systems that support the building against lateral and vertical loads experienced during a hurricane), masonry buildings and wood-frame modular buildings generally held up relatively well.
Predictably though, in an event which destroyed 1,951 mobile homes and 985 fixed structure homes and caused damaged to 23,000 residential buildings, that is where the good news ends.
Indeed, plenty went wrong. Exterior architectural systems such as roofing, windows and doors often failed to withstand Andrew’s force. The breaching of the ‘building envelope’ (doors, windows) due to debris not only caused damage from a direct point of view but allowed an uncontrolled build-up of internal air pressure that contributed toward deterioration of building integrity. Numerous accessory structures, such as light metal porch and pool enclosures, carports and sheds were destroyed by the wind and added further debris, while the loss of roof material and roof sheathing and the failure of windows and doors exposed buildings to further damage from wind and rain.
To varying degrees, the report’s authors say, problems occurred for all types of roofs. Damningly, while some of the damage was simply an inevitable result of high winds and ‘missile’ (debris) impact, most of the damage has been put down to the failure of method of attachment, inadequate design and substandard workmanship.
Worse, problems associated with design and workmanship, along with the misapplication of various building materials, were also named as a significant factor in many observed structural failings of buildings.
Finally, there was the mismanagement and disorganisation on the part of the authorities, which investigators say led to inadequate county review of construction permit documents, a shortage of inspectors and inspection supervisors and the inadequate training of supervisors and inspectors.
What comes next?
In addition to the aforementioned areas of concern, the assessment team says general improvement is needed in a number of key areas.
First, the demonstrated failure of workmanship in some areas shows that a better understanding is needed in terms of proper construction techniques which take into account high-wind and flood load consequences. This would largely be achieved through a state or local government certification scheme, which would incorporate specific continuing education requirements.
Second, there is the expansion of the South Florida Building Code, which should include prescriptive design elements for lateral load transfer.
Third, contractors need proper guidance with regard to correct methods of transferring loads. Permit drawings for construction should including a narrative that explains a building system’s safe transfer of loads, and should be submitted with a complete load transfer part plan-checklist that is specific to the building type in question.
Finally, there are the failures in the inspection process. Much could be achieved, the report’s authors say, through a multifaceted certification scheme for inspectors and supervisors that focuses on specific areas of design and construction. Inspectors who perform framing inspections, for example, would be specifically trained and certified in that area. Requirements for increased participation in the inspection process from licenced designers would also help, as would better inspector supervision, especially in developments where large tracts of repetitive design occur.
When Andrew struck, significant flaws in the design and construction process were laid bare, but as both Andrew and, later, Hurricane Katrina have shown, extreme weather events are a part of life in Florida.
By learning the lessons and making improvements, builders can design better, sturdier dwellings that stand up more effectively when these events happen.