Standard Interpretations - (Archived) Table of Contents|
February 7, 1994
Mr. Peter J. Natwick
Flying Eagle, Inc.
P.O. Box 77050
Seattle, Washington 98133
Dear Mr. Natwick:
This is in response to your November 17 letter requesting a interpretation of equivalency from the Occupational Safety and Health Administration (OSHA) for your "Roof Creeper Kit Apparatus." I apologize for the delay in responding to your inquiry.
As you know, OSHA neither approves nor endorses products or work practices, but when provided with adequate information, it can offer an opinion as to whether or not they afford compliance with certain regulations. We have reviewed the product patent information, test results and pictures enclosed in your letter and it appears that if the "Roof Creeper Kit Apparatus" is securely attached to the roof according to your instructions, the platform would comply with the intent of the standard. Therefore, OSHA would consider the proper use of the "Roof Creeper Kit Apparatus," without additional nails or rope supports, to be a de minimis condition and no citation would be issued.
If we can be of any further assistance, please contact me or Mr. Dale Cavanaugh of my staff at (202) 219-8136.
Roy F. Gurnham, Esq., J.D.
Office of Construction and Maritime
November 17, 1993
Mr. Roy Gurnham
Director of Construction and Maritime
Department of Labor - OSHA
200 Constitution Ave. N.W., Room N-3610
Washington, DC 20210
Dear Mr. Gurnham:
I am seeking a Letter of Interpretation for Equivalency Rating on my patented (US #5050705) "Roof Creeper Kit Apparatus" into paragraph 1926.451(u)(2) of OSHA Construction Standards.
In your correspondence with Victor Saleeby of SIA, you indicated that this product appears to fall into the category of Roof Bracket Scaffold. I met with Mr. Saleeby on November 6, 1993, and demonstrated the uniqueness of the mechanics on my production prototype that earned a patent.
It is my belief that nailing is not necessary on my product because it is at least as effective as nailing, and provides equivalent safety based on the test data enclosed with this letter.
The benefits that would accompany an Equivalency Rating are many.
1. First, and obviously, using this unit on its own would prevent the puncturing of usable roofs, which is a common problem in the construction and maintenance industries.
2. It would allow painters instant positioning on roofs over plastic drops.
3. It would give workers a solid spot to execute a tear- off of old roofing material on pitched roofs.
4. It would offer better positioning to those workers involved in pressure cleaning or applying stain or fire retardant sprays to roofs, all of which compromise the traction available after treatment.
5. It would enable chimney sweeps better access to roofs in wintry conditions.
6. Of notable benefit it would offer firemen, whose special need for speed in positioning for tools in rescue or in transit across roofs requires a heavy duty yet light footed effective portable positioner.
Recently the Seattle Fire Department tested this unit in a training session and were impressed with the concept and construction of my prototype. They also requested a metal model of reduced size that would clip on and nest between two rungs of a roof ladder for storage and clip out to reposition a fireman's outboard foot when ventilating a roof using a chain saw. Note the improved posture of the fireman's outboard foot using this type of device in the photos that accompany this letter.
In detail, here is how the device works.
The framework on the standard model is wide enough (22") to span the distance between two common truss rafters or to stand over one at all times. The area beneath the frame and within the contact points is approximately five square feet.
When, for example, a fireman with gear weighing 250 pounds is working a roof, each foot exerts about 500 pounds per square foot of pressure on the roof as he walks. My device under this load exerts only 50 pounds per square foot on the roof. A local truss engineer said truss structures in this climate of light snow load were engineered to accept a construction load of 175 pounds per square foot. Five square feet would therefore allow 875 pounds. This unit has been tested to 1200 pounds by a certified lab. The Seattle Fire department indicated that a truss roof, when engulfed in flame, weakens to destruction in only five to seven minutes. A full sized model would allow positioning on a roof with 35% of its original strength remaining. Firemen fall through roofs all too often.
The length of the framework is 30", which meshes well with standard 10" exposure of cedar shakes. The longer frame members flex under a live load, which is the key element of the patented gripping action. A physics grad student examined the mechanics of the grip and concluded that "the amount of flex [of the frame] is squared in the deceleration formula."
The hooks are oriented proportionally across a 150 radian in relation to the longer frame rails and the interior surfaces are beveled to enhance the action. The central single hook point is beveled on both surfaces to exert force against upper and lower double hook points.
The contact points are small enough to enable good penetration into a variety of roof surfaces under a light load, assisted by the bevels. The parabolic shape of the hook recess ensures that a greater load encounters increasing deceleration from the resistance of the roof material and encourages a splay between the two tines of each hook.
As this action is occurring at each corner (the force of which is squared by the load weight flexing the frame), the result is an eight-vectored outward engagement of the outer hooks against the sheer of the roof surface. Note that the beveled surface of the upper hook is perpendicular to the surface it is mounted to. The previous down-the-hill vector of gravity vs. roof pitch has been effectively transformed into a perpendicular ten directional bite into the sheer of the roof surface, regardless of roof pitch.
When a very large load or shock is placed on this unit, the grip is maximized, the penetration is stabilized, and the frame creates a deceleration, high-centers and compresses the region of the applied roof structure while pinching the shingles against each other, preventing them from pulling out. The shingles below the upper feet are actually forced uphill, which discourages them from being torn from position. A large load also increases the moment the adjuster leg places on the two central single tines, which impressed the lab technicians as they approached the limits of their testing.
This feature was demonstrated at this year's Washington State Governor's Safety Fair with an upright piano placed on two units onto dissimilar, different pitched roof sections.
I have spent hundreds of hours testing these principles as an inventive tradesman in evolving this design. Within the range of materials this device is designed to work on, I have found no situations where I felt that nailing the unit down would provide needed additional safety.
As with any new concept, skepticism is encountered. Much effort has been put into the Instructions for Use and the Warnings that accompany this product to ensure that all users would be as safe as their own personal judgment allows.
Enclosed with this letter are the latest drafts of the Instructions for Use and the Warnings that accompany the product, a copy of the patent, lab test findings, pictures, and production samples of one upper and one lower foot.
If you have further questions, feel free to contact me by phone at (206) 781-8819, which includes a 24 hour voice mail.
Thank you for your attention.
P. J. Natwick
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