Earthquakes, hurricanes, and tornados continue to wreak havoc on our wood frame houses and buildings. We will never be able to completely protect against the worst case scenario, however our codes are continually improving so that we can make our buildings stronger. A big part of this improvement has been the addition of connection hardware. Whereas most connections used to be secured by nails, connections needed to establish shear and diaphragm strength are now secured by hardware. Most of this hardware is fastened with nails and in many cases a large number of nails. For example, where a small framing clip may take 12 nails, a four foot strap may take 32 nails, depending on the particular size and type of connector.
Because of all the additional hardware nailing, nail gun manufacturers have come out with positive placement nail guns that are specially made for nailing on hardware. There are different styles but they all use the same nails which are different
from standard nail guns. The nails are hardened and come in four sizes which are.131 X 1-1/2",
.148 1-1/2", .148 X 2-1/2", and.162 : 2-1/2". The guns use two methods to find the nail holes in the hardware. One style uses a probe that is placed in the hole, and then the gun directs the nail. In the other style, the nail protrudes so that the nail is placed in the hardware hole before firing the gun.
You need to make sure you use the right nail for the hardware. Each piece of hardware has its own nail requirements. If you use too big a nail you can fracture the steel around the nail hole, and if you use too small a nail you will not develop the appropriate strength needed. Hardware manufacturer specifications note the requirements. For example on the web at strongtie. com, Simpson Strong-Tie Company lists all their hardware with the amount and size of nails needed. There is also a convenient nail replacement chart which lists some nail size substitutions. This is helpful when you are installing hardware that was designed for standard nails but you are using positive placement gun nails. You can find this chart at strongtie. com/ products/connectors/nails. asp.
Quality of installation is probably the most important part of framing to withstand the forces of nature. APA (formerly the American Plywood Association, now the Engineered Wood Association) confirmed this fact when it conducted a study of the construction failures in the aftermath of Hurricane Andrew. In the houses they investigated, roofs were the most common failures. Those roof systems most often failed due to lack of proper sheathing nailing.
Wind — and earthquake-resistant framing are important skills for lead framers, and essential to those in susceptible parts of the country. Building codes, along with the designs architects and engineers create to meet code requirements, specify the framing for wind and earthquake resistance. The lead framer must take that information, along with data from connector manufacturers, and ensure that those requirements are met.
Roof failure as a result of Hurricane Andrew
