Paper Towels vs. 2x4s

© 2004 Door & Access Systems
Publish Date: Fall 2004
Author: Barbara Kelkhoff
Page 70


Paper Towels vs. 2x4s
By Barbara Kelkhoff, The Chamberlain Group
Chair of the DASMA Door Operator Committee

When testing a garage door opener’s reversing mechanism, should you use a 2x4 or a roll of paper towels?

In a recent issue of the ASHI Reporter, the monthly magazine for the American Society of Home Inspectors, an article recommended the 2x4 approach as cited in DASMA Technical Data Sheet (TDS) 167. However, in response to that article, DASMA received a comment from a home inspector who argued that a roll of paper towels is a better test method.

The Paper Towel Argument

He identified himself as an “instructor for a nationally known school for home inspectors” and said he has tested more than 1,890 garage doors.

“When the 2x4 method has been used,” he argues, “I have seen doors come off track, metal doors bending, and operator arms bending as well.” He says a test with a roll of paper towels is “the best way is to simulate … body pressure response.”

He concludes, “Unless you have a better test, I think you should retract the information (on testing using a 2x4) in DASMA TDS #167. We tell our students not to do the 2x4 test.”

The Facts

While the home inspector makes a good case that a roll of paper towels shows compression, this test might not result in a safety reversal at the correct height. The safety reversal system must always be tested using a 2x4 laid flat on the ground.

But the first thing to remember is to regularly test the system. The inherent reversal system should be tested monthly, or after any adjustments or repairs are made to the door or operator.

The following steps for proper installation and testing are defined by Underwriters Laboratories (UL 325) and the Consumer Product Safety Act. To ensure the proper operation of the inherent reversing system, the proper installation of both the door and operator is essential.

1. A garage door opener is installed on a door that is balanced and properly reinforced to handle the opener.
Note: Increasing force settings should never be used to compensate for a door that is not balanced or does not move smoothly.
2. The garage door opener is connected to the door as directed by the manufacturer’s installation instructions.
3. After installation and after any adjustments, the reversal system is tested using a 1.5" solid object or a 2x4 laid flat on the garage floor. Conduct this test monthly to ensure proper operation throughout the life of the system.

Using other items, such as a roll of paper towels, might indeed verify that the operator reverses. But the test must also verify that the operator can reverse when the door is all the way down to 1.5" off the floor. A roll of paper towels might not compress to 1.5". That’s why a 2x4 must be used to set and test this safety system.

Continually Educate

This story illustrates the importance of constant education. Garage door opener safety systems are continually changing; thus, we must continually educate.

The inherent reversal system has been required since UL 325 was written in the mid-1970s. From 1982-1992, approximately 60 children between the ages of 2 and 14 were trapped and killed under automatic garage doors, according to the Consumer Product Safety Commission (CPSC). External entrapment protection was then required for residential operators in 1993, more than 10 years ago. At that time, the manufacture of garage door openers also became regulated under the federal laws of the Consumer Product Safety Act.

Our industry is getting larger every day. New installers are constantly joining our industry, and every week, new inspectors are inspecting garage doors for the first time.

Our job of education never ends. We all must do our part to educate consumers, our own company employees, and other professionals about the dangers and the proper installation and testing of residential doors and openers. As we learn of new requirements or issues, we must diligently pass on that knowledge to all those affected by our industry.

The Value of TDS

Even though this inspector disagreed with our Technical Data Sheet, I’m glad that TDS is available to anyone on the Internet. These documents have been closely reviewed by DASMA-member experts, and we work hard to make sure each TDS contains accurate, up-to-date, and helpful information.

DASMA now has about 70 TDS documents that contain a wealth of information about all DASMA products. To freely access any TDS, simply point your browser to and click on Publications.