A few days ago, the remnants of Hurricane Noel traveled northward to New York and New England with wind speeds approaching 80 miles per hour in Massachusetts. The storm caused significant damages, especially there.
“As I watched television reports, all I could think about was the importance of looking out for hurricanes, no matter where you live,” said NJIT architecture professor Rima Taher, PhD, also a civil engineer. “Northeaster storms have hit the north Atlantic coasts with near hurricane wind speeds and the potential to damage property with severity equivalent to what people think can only happen in gulf waters.”
Today hurricane-proof building practices can be incorporated into residential or commercial construction. Taher spent two years studying the best designs of these designs as well as construction materials and methods needed to withstand extreme wind events and hurricanes. “Certain home shapes and roof types can make a big difference,” she said. Based on Taher’s article about the design of low-rise buildings for extreme wind events that appeared in the Journal of Architectural Engineering (March, 2007), more recommendations follow.
•A home with a square floor plan (or better a hexagonal or octagonal plan) with a multiple-panel roof (4 or more panels) was found to have reduced wind loads.
•Roofs with multiple slopes such as a hip roof (4 slopes) perform better under wind forces than gable roofs (2 slopes). Gable roofs are generally more common because they are cheaper to build. A 30-degree roof slope has the best results.
•Wind forces on a roof tend to be uplift forces. This explains why roofs are often blown off during an extreme wind event. Connecting roofs to walls matters. Stapled roofs were banned following Hurricane Andrew in Florida in 1993.
•Strong connections between the structure and its foundation and connections between walls are good. Structural failure is often progressive where the failure of one structural element triggers the failure of another, leading to a total collapse. Connections are generally vulnerable but can be inexpensively strengthened.
•Certain areas of a building such as the ridge of a roof, corners and eaves are normally subject to higher wind pressures. In the cyclonic home design, CSTB researchers proposed some aerodynamic features to alleviate these local pressures such as introducing a central shaft which would function by creating a connection between the internal space and the roof ridge considered to be the location of the largest depression. This connection helps balance pressures leading to a significant reduction in the roof’s wind loads.
•Roof overhangs are subject to wind uplift forces which could trigger a roof failure. In the design of the hurricane-resistant home, the length of these overhangs should be limited to 20 inches.
•The design of the cyclonic home includes simple systems to reduce the local wind stresses at the roof’s lower edges such as a notched frieze or a horizontal grid to be installed at the level of the gutters along the perimeter of the home.
•An elevated structure on an open foundation reduces the risk of damage from flooding and storm-driven water.