Building for High Wind Events

building-high-wind-resistanceSummer is upon us and with it comes the storm season. From hurricanes to tornadoes and all the high-wind events in-between, the Atlantic storm seasons get worse as climate change increases sea temperatures. There is a pervasive myth that building for tornadoes and hurricanes isn’t possible, but for lower impact systems like EF-0, EF-1 and EF-2 (similar to hurricane wind speeds) which make up 95% of high wind events, you can construct homes that will weather the storm and save money and lives.

While it’s more difficult to build structures that resist higher impact storms from EF-3 to EF-5, modern technologies and a better understanding of shear and uplift forces is making it possible to construct homes that survive even violent storms.

Use Taller Sheathing Panels

High winds travel through the load path of a structure, so designs that connect the roof, walls, and floor and provide a continuous load path will enjoy better resistance to high winds. One way to achieve this is through longer wall sheathing panels.

With proper engineering, shear walls can be constructed to withstand the combined shear and uplift forces that homes experience during high wind events. According to the APA: “The most effective way to provide lateral and in some cases uplift load continuity is to attach adjacent wood structural panel wall sheathing to one another over common framing.”

Taller OSB sheathing panels save on labor with the installation of hardware and cutting and installing the blocking at horizontal joints. There is also a reduction in the metal hardware required. Ken Jolliffe from Norbord: “The biggest charm for builders when using Windstorm or TallWall to satisfy shear and uplift in hurricane-prone areas is that they eliminate blocking and intermediate metal connectors and reduce air-infiltration which all add up to substantial cost savings and faster construction.”

Tie Gable End Walls Back to the Structure

Where gable ends meet the wall below is often one of the weak points which get damaged during high wind events and failures at this join are quite common. You can eliminate the gable using a hip roof or, if gables are unavoidable, opt for balloon framing. (Standard for Hurricane Resistant Residential Construction, SSTD 10-93 Section 306.4.2).

A number of advanced and inexpensive anchoring systems and ties have been developed that strengthen the connection between wall and gable. Some nailing patterns also provide added wind resistance.

Sill plates

Another effective way to increase capacity is to extend the structural wood panel sheathing at the bottom wall to the sill plate intersection. From the APA: “The connection of the wall sheathing panel to sill plate is extremely important because this is the connection by which the hold down capacity of the sill plate anchor bolting is distributed into the structure above. At this location, the panel can overlap the sill plate by the full 1-1 ½” of the sill plate depth. It is wise to use all of this depth as it permits the use of nail-to-edge distances of up to ¾”, yielding the maximum possible uplift of the nailed joint.”

Tags: , , , , , , ,