Concrete masonry walls convey the impression of strength and solidity — so much so that people may prefer sheltering in a commercial building than in a wood frame building if they think there's a windstorm on the way. But in reality, the simple fact that a structure is made with concrete block doesn't mean that the building can hold up to high winds. The building's safety depends not just on the materials, but on the construction details — and typical block buildings are far less capable of withstanding high winds than are buildings designed and built to the latest construction standards.
For a graphic example, look no further than this test (below), performed at the wind testing facility of the Insurance Institute For Business and Home Safety (IBHS) Research Center in Richburg, South Carolina. On the left, labeled "Common," is a typical strip-mall building with the ordinary details found at older strip malls around the nation, including relatively modest amounts of rebar. On the right is the "Better" building, which incorporates details drawn from current National Concrete Masonry Association (NCMA) guidelines, including bent rebar reinforcement for corner connections in the wall-top bond beam, and vertical rebar in grouted block cores spaced no greater than 8 feet apart in the clear wall sections, as well as at both sides of wall openings. The "Better" building also has continuous attachment for roof flashing, and rooftop mechanicals that are positively connected to the roof structure rather than simply laid on 2x4 sleepers. Under the pressure of a 135-mph wind, the "Common" building takes only a few minutes to experience the typical failure, while the "Better" building maintains its structural integrity and an intact enclosure. For a closer look at the IBHS testing and recommendations, see: Commercial Building Wind Demo.