There is no dispute on the need for wind braces on any structure. There is often confusion on how and when those braces need to be installed.
The sooner that some sort of bracing is installed on a building, the easier it is to maintain plumb or vertical. For this reason, we stress the importance of tying off a building, both ways, as soon as the first section has been erected.
One detail that many over look is the total surface area of the hoops. It does not take very long to have the combined surface of a 4’x8’ sheet of plywood. For this reason, it is important to not rely for an extended period of time on your initial tie down ropes as your “bracing”. There have been instances where the combined surface area of the hoops is more than the entire gable end.
If you are doing a long building with long hoops, i.e. 30’ wide, it would be wise to install the bracing before the whole structure is assembled.
Wind bracing can be installed in two directions, one goes away from the end wall and one goes toward the end wall. Both ways are acceptable, provided that you do both. If you install them toward the end at one end, you must do the same at the other end. By doing the same concept at each end, you are essentially holding things in opposite directions.
When bracing goes away from the end, the load is referred to as “tensile load”. Cable is often used for this. The cable and the clamps used must be rated against stretching and breaking. This is a convenient system since you are not limited by a precise measurement. When using this system, it is important to end up at the ground, in the 4 corners.
When bracing goes toward the end, the load is referred to as “compression load”. Round tubing with flattened ends is most often used. It is important to make sure that the tubing is strong enough as to not bend as it is being compressed. This is the method which has been used the longest since the instinctive way to brace something it to “prop something against it”.
With either method of bracing, where you start and end is very important. For bracing to be effective, you must start at a point that is connected to the whole structure. This would be either the ridge or a row of purlins. Starting at a mid point of a hoop will give little reinforcement since the hoop can flex from side to side. The closer that bracing goes at 45 degree angle, the stronger it will be.
In the case of longer hoops with multiple rows of purlins, it is advisable to have a series of shorter braces than one long one. This means you would start at a certain hoop/purlin connection and go down and over for 3 or 4 hoops and anchor at that hoop/purlin connection. Go over to the same hoop you did the first brace on and repeat the process from the lower purlin. You would then be going down to the base or the next row of purlins. Remember that if at one end, if you are going left to right, on the other end you go right to left.
Where ever you end up, it is wise to have extra anchoring at that point.
For extra clarification, please watch our “installing wind braces” video on the website.