Recently, I had a request for a banner that was going to span a street. My first thought was mesh banner material. It is obviously perforated and would allow wind to flow through it instead of turning it into a big sail. The customer needed the banner to be printed on both sides. There in fell a problem.

Mesh banner stock typically comes with a liner on the back to keep the ink from bleeding through the holes and making a general mess of your printer. When printing the back side, the film would have to be removed and something would have to be applied to the front. Time would not allow for us to explore options as the event was in 2 weeks and the customer needed the banner yesterday.

We opted to print 2 banners and place them back to back. City ordinance requires banners spanning the street to have air reliefs. We had to cut wind slits, which I am strongly against, to meet code. Feeling like it was an unnecessary step, I started researching the pros and cons cutting wind slits into banners. I found a great article on SignAndGraphicsShopTalk (a yahoo group) and thought I would share it.

Why Wind Slits Are Not Recommended in Banners.


What is a wind slit?

It is slit cut into the banner with the intent of giving the wind a way to blow through the banner and reduce the stress on the banner or on how the banner is installed. Usually the cut is made in the shape of a half circle or half-moon.


How does someone determine when wind slits should be used?

1. It is important to ask why you believe wind slits should be used.  Many
times they are used as a panacea.  If a customer is concerned about the wind
it is easy to cut wind slits and send them on their way.  It is a very
visible and reassuring method to show the customer we took care of your
concerns.  But in reality you probably have not helped your customer.

2. How much wind stress will be reduced by the wind slits?

a) Calculate how many square inches in your banner and how many square
inches of wind slits.  If your banner is 36" x 96" that is 3,456 square
inches.  If you cut four wind slits that are 12" long each and a half moon in
shape you will have created a pass through for the wind that is approximately
58 square inches.  

There are 4 of these so that equals 232 square inches / 3,456 square inches
of banner area.  The maximum wind stress reduction from these wind slits is
about 6%.  If you are depending upon a 6% wind reduction keeping your banner
from blowing down you are more of a risk taker than I am.  

3. Perhaps the most important question in determining whether to determine
wind slits is:  Is this the proper banner material to use for this size, use
and installation?  Most times the wrong banner material is being used and
wind slits are the quickest remedy.

4. Will using wind slits offset the graphic image of the banner?  Who wants
6-10 or more cuts made in the banner they just paid hundreds or thousands of
dollars for?  I believe the answer to this is almost no one.


How else can I reduce the wind stress on the banner?

1. The best way is to use the correct material.

a) With many new materials it is much easier to use a better material.  This
could be from one of many types of mesh to a heavier material like an 18
ounce vinyl or heavy poly cotton.

b) Many of the trade magazines have run articles on very large banners that
are installed on the side of buildings.  These banners cover hundreds or
thousands of square feet.  I have yet to see one of these installations use
wind slits as the remedy to reduce wind stress.

2. The next best way is to install the banner correctly.  This subject could
cover many articles so we will not go into detail now but take this up at a
later date.  But suffice it to say many banners fail because the installation
is poor.

Why not use wind slits?

1. Detract from the graphics and reduces the impact of the message.
2. It is a poor method to deal with wind stress.
3. Because using wind slits will not replace using the proper banner
4. You are doing your customer a disservice if they believe this is the
proper method to  reduce wind stress.
5. The cuts in the banner can actually weaken the banner and propagate a

When to use wind slits.

1. When a customer is buying on price only.  But they should be informed the
wind slits are better than nothing but will most likely not make much of a

2. Remember if you still must cut wind slits cut them after the graphics are

I think there are many good points made in this article.

The first is know your material and application. Every job requires the right tools, just as every banner needs to suit the requirements of the customer. There are plenty of options out there, so limiting yourself to price is not always the best answer.

Second, wind slits are by nature ineffective. To be effective, one would have to make a banner that looks like swiss cheese. Not to mention the strength of a banner is the threads running through it, which are now all cut along each "stress reliever". One would be better off punching holes in it. And the actual stress reduction is minimal compared to the possibility of failure along those cuts.