Wind braces for structures

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.

You’re in a Windy Area? We can help

We have many structures in very windy locations from coast to coast. This is probably the most common comment we get from people who reach out to us. We have experience and extra steps we take to help ensure your structure doesn’t end up as an expensive kite. We have been diligent in our articles and instruction manual to help these situations, but ultimately it’s up to the customer to heed these warnings.

One of the things that is stressed in our assembly instructions is the importance of tying your frame off in both directions as soon as you have the first section of ridge installed. This is typically done with rope coming down from the ridge as an inverted “V”. The sooner this is done, the easier it is to hold everything plumb.

It is worth noting / stressing, that this is not a long term replacement for the wind braces. The wind on the collective surface of all the hoops is capable of exerting a tremendous amount of force.

When one does the math, there are actually cases where the wind pushes with more force when there is no cover on the building then with a cover!

A 20’ x 48’ x 12’ high structure with 4’ spacing has the same amount of hoop surface as an 8’ x 14’ wall. This is an example why the ropes used to hold the frame straight is not intended as a wind brace.

Once the hoops are all installed and the purlins attached, it is important to install the wind braces before proceeding. The purlins are what tie all of the hoops together and then by angling the wind braces down from the rows of purlins, you would be bracing the whole structure.

In photos on our website,you will see our smaller structures have fewer wind braces than the larger ones, which accounts for the above math mentioned. This has been developed with our experience, as well as the engineers who have assessed our structures.

There are different notes on placement, direction and location that will help your structure survive the wind as well. We do our best to go over all the scenarios with you when you’re discussing your purchase with us. The more details you can give us the better. Obviously we aren’t able to account for everything you may encounter, but it is our intention and mission to set you up for success as best as possible. We don’t want your greenhouse to end up flat or blown away anymore than you do! And this is also why we reiterate,

There’s no such thing as too many anchors!

You’re in a Windy Area? We can help

We have many structures in very windy locations from coast to coast. This is probably the most common comment we get from people who reach out to us. We have experience and extra steps we take to help ensure your structure doesn’t end up as an expensive kite. We have been diligent in our articles and instruction manual to help these situations, but ultimately it’s up to the customer to heed these warnings.

One of the things that is stressed in our assembly instructions is the importance of tying your frame off in both directions as soon as you have the first section of ridge installed. This is typically done with rope coming down from the ridge as an inverted “V”. The sooner this is done, the easier it is to hold everything plumb.

It is worth noting / stressing, that this is not a long term replacement for the wind braces. The wind on the collective surface of all the hoops is capable of exerting a tremendous amount of force.

When one does the math, there are actually cases where the wind pushes with more force when there is no cover on the building then with a cover!

A 20’ x 48’ x 12’ high structure with 4’ spacing has the same amount of hoop surface as an 8’ x 14’ wall. This is an example why the ropes used to hold the frame straight is not intended as a wind brace.

Once the hoops are all installed and the purlins attached, it is important to install the wind braces before proceeding. The purlins are what tie all of the hoops together and then by angling the wind braces down from the rows of purlins, you would be bracing the whole structure.

In photos on our website,you will see our smaller structures have fewer wind braces than the larger ones, which accounts for the above math mentioned. This has been developed with our experience, as well as the engineers who have assessed our structures.

There are different notes on placement, direction and location that will help your structure survive the wind as well. We do our best to go over all the scenarios with you when you’re discussing your purchase with us. The more details you can give us the better. Obviously we aren’t able to account for everything you may encounter, but it is our intention and mission to set you up for success as best as possible. We don’t want your greenhouse to end up flat or blown away anymore than you do! And this is also why we reiterate,

There’s no such thing as too many anchors!

Photos & Video: Purlins, Windbraces & Crossties

IMPORTANT wind braces are the longer pipes, purlins are the shorter ones, Cross ties are optional, and they are the longest pipes you will get (pictured below, not here)

Installing Purlins

 

How to install windbraces video is on our YouTube Channel

Below are examples of structures with cross-ties, bars going across the peak for larger structures. These are optional to reinforce the structure. Please see the supplemental Cross-Ties page in the installation guide as well as additional notes below the photos

We’ve had a number of questions regarding cross ties being missing from orders. This isn’t the case, and is done on purpose because the last cross tie interferes with the end cover, so we ship the orders “short” on cross ties to compensate for this. We are sorry for any confusion this has caused and are happy to help you with any other installation questions you may have.

Cross ties, also known as collar ties, are a horizontal bar in a structure which ties the left and right side together. They are usually 3’ to 4’ down from the peak. The purpose of cross ties is to add load strength to the structure. Many people look at cross ties as a nuisance because of lost head space but they have a three fold benefit.

  • By forming the triangle at the peak you create benefit for the dead load which is usually snow load. The top can not come down when the sides can not spread.
  • By tying the left and right sides together, you create strength for the live load, commonly referred to as wind load. When the wind blows from the left, the right side holds it from pushing inward and vice versa.
  • Most importantly, it decreases the rocking motion which can stress a building over time.
  • The cross tie can also supply a very useful support area for things that need to be suspended.

It is important to remember that when you spread out the load you create strength.Photos & Video: Purlins, Windbraces & Crossties