Don’t underestimate the power of wind, especially when it comes to designing your post-frame building. As wind blows, it places a tremendous amount of pressure on everything in its path – and only properly engineered buildings will be able to handle it.
Code buildings are designed to withstand 90 mph of straight-line winds. But if you live in an area where winds will exceed that speed, or where they’ll be extended, you need to design your post-frame building accordingly.
There are stark differences between the types of wind as well. For example, a constant wind of 40 mph over five hours will create a different kind of pressure than a 105 mph wind gust that lasts half a second.
That’s why when designing your post-frame building, you need to plan for the types of wind events that are common in your location by including at least seven wind-protective design techniques.
Fighting back starts with drilling a deep enough hole for your column and anchor. We recommend the hole to be at least 4 feet deep, and possibly deeper if you expect extremely strong winds.
The next step involves creating a column anchor. Builders should fasten two pieces of wood to either side of a sturdy column to provide a strong hold. Once that’s installed and in the hole, filling the column hole will hold the anchor firmly in the ground.
Depending on the size of the building and wind conditions in the area, proper anchoring may include pouring concrete rather than refilling the hole with gravel or dirt.
2. Proper spacing between columns and girts – We’ll keep it simple: The more lumber you have in the ground, the stronger your structure will be. Same goes for the girt spacing – the closer the girts are to each other, the stronger the structure.
3. Proper truss to column connections – Don’t depend just on nails or screws to connect your trusses and columns. Create a tight connection with bolts to ensure resistance to pressure created by wind.
4. Proper truss with support bracing – When wind blows, it places pressure on more than just the side of the building it hits. Your building must be designed with support bracing so the wind load is transferred from the trusses, walls and columns on the windy side to the trusses, walls and columns in the rest of the structure. Even distribution of pressure is key for a long-lasting structure.
5. Proper steel sheathing fastening – The steel that panels a building’s sides is the first line of defense against wind. How the steel is attached to a building determines its reinforcement strength.
Our recommendation is to always use screws rather than nails to fasten the steel. Screws have over twice pullout resistance in comparison to nails, and thus provide twice as strong of a connection.
6. Prepare for prevailing winds – Determine which direction the prevailing winds will hit your building from, how strong they’re going to be, and design your building accordingly. To help you out, the United States Department of Agriculture Natural Resource Conservation Service created a tool specifically for that purpose.
7. Prepare for door openings – Wind places a lot more stress on a building when the doors and windows are open by pushing on the walls from the inside as well as the outside. Our initial advice would be to latch the doors shut when not in use, so your structure remains closed when wind blows.
However, if you need to access your building even on a windy day make sure you plan for it. In those cases, be sure that your building is engineered to withstand large amounts of internal pressure.
Whether it’s a sustained 40 mph wind or a brief 110 mph gust, the pressure of wind can create problems for any ill-prepared building. Follow our seven design tips to ensure your post-frame structure remains strong, no matter what the wind blows.
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