PRACTICAL. RESPONSIVE. EXPERT ENGINEERING CONSULTANTS SINCE 1985

It appears the U.S. Federal Occupational Safety and Health Administration, OSHA, has managed to thoroughly twist a well written scaffold regulation to the point where many scaffold erectors, users and compliance officers will be totally confused.  I am referring to a recent Letter of Interpretation that addresses the stability of scaffolds, and more specifically the method for tying a supported scaffold to an adjacent structure so the scaffold doesn’t fall over.

U.S. Federal OSHA periodically issues Letters of Interpretation in response to inquiries from concerned citizens.  Typically, the letter addresses a question the writer may have regarding a specific regulation (standard).  The question normally involves a particular circumstance that may not be directly addressed by the applicable standard.  OSHA responds with its’ interpretation of what OSHA thinks the standard requires.  It is important to understand that a Letter of Interpretation is exactly that, an interpretation by the agency, and is not a change in the standard or its’ applicability.  OSHA cannot change the standard except through the rule making process.  However, the letters OSHA issues do influence the standard of care that one might use for a specific instance.  As with other industries, the impact these letters can have on scaffold matters can be substantial.   Such is the case with a Letter of Interpretation issued by OSHA on March 26, 2010 which addresses the use of #9 wire to tie a scaffold to an adjacent structure for stability.

The questioner asked:  “Do OSHA’s standards permit an employer to double wrap #9 gage steel wire in order to guy, tie or brace a scaffold?”  OSHA’s answer is nothing short of amazing since the scaffold standards, as rewritten in November, 1996, are performance standards as opposed to the original specification standards.  This means that the existing standards allow reasonable options to achieve the result prescribed in the standard.  For example, access is required for all scaffold platforms.  There are a number of options available to the scaffold designer.   Another example, and the focus of this article, is the requirement that all supported scaffolds shall be stable and not fall over.  This can be accomplished by making the scaffold base big enough so it won’t fall over, tying it to an adjacent adequate structure, or guying it.  If you choose to tie the scaffold to the adjacent structure, OSHA prescribes the maximum vertical and horizontal spacing, which happens to be 30 feet horizontally and no more than 26 feet vertically (and less depending on the scaffold width).  Other than that, the tie design is the responsibility of the Qualified Person who designs the scaffold.  The standard, as written, does not tell the scaffolder what to use for the tie, does not tell the scaffolder how much load is on the tie, and does not provide design criteria.  This is not an oversight in the standards; this standard is a minimum requirement and therefore does not, and should not, provide design criteria.  In fact, it would be impossible to provide design data since the circumstances for each scaffold are unique.  Furthermore, the scaffold standards are not instructions.  If you don’t know how to determine the tie load for your scaffold you better get a qualified designer to help you.  This Letter of Interpretation is not the answer.  Here is why.

The letter correctly points out that the referenced section, 29 CFR 1926.451(c), does not “specify whether #9 gage wire is a permissible method of compliance.”  This isn’t surprising since there are unlimited devices and materials that can be used as a scaffold tie.  Unfortunately, from here the letter takes a decidedly wrong turn in that it describes 4 conditions (the letter incorrectly states 5 conditions) that must be met in order for the scaffold to comply with 29 CFR 1926.451(a)(1), which is the standard that specifies that a scaffold and its’ components must have a 4 to 1 safety factor.  Therein lies the problem since OSHA never specifies what load it is using to establish the 4 conditions.  Instead, OSHA dangerously requires that:

  1.  “The #9 wire shall have a minimum tensile strength of 40,000 psi.”  This is a useless requirement, since no loads are specified.  You could use duct tape for a tie if you could show that it is strong enough.  (In theory, OSHA has to prove it would not work!)  And how do you determine the wire tensile strength in the field?  Furthermore, if I use wire with lower tensile strength, is it wrong?  (See #2)
  2. “The #9 wire shall be in a U-loop form (i.e. double-wrapped) around the pole and both wires shall be tied to an eye bolt, which is attached to a masonry wall.  At the eye bolts, both wires shall be twisted to a minimum 5 wraps to get the ultimate strength.”  This is unbelievable!  The requirement “At the eye bolts, both wires shall be twisted a minimum of 5 wraps to get the ultimate strength,” gives the impression that more twists are better, when in reality more twisting will weaken the wire.  What size eye-bolt?  Is it an open 3/8” eyebolt from Home Depot (Capacity = 160 pounds) or a forged eyebolt?  Is this eyebolt screwed into the mortar or should an anchor be used?  What strength is the anchor?  What happens if the wall isn’t braced?  Will it fall over?  How do you count those wraps on the tie?  Is 4 wraps no good?  And will it be stronger if I use 6 wraps?  Furthermore, there is a footnote attached to this requirement that refers to an earlier Letter of Interpretation that declared that single wrapped #9 wire was no good.  That letter was wrong when it was issued years ago and is still wrong; unfortunately OSHA still thinks it is correct.  What about the height or location or shape or size of the scaffold?  Is the load on the tie at the top of a scaffold 300 feet tall the same as the tie load on one that is 30 feet tall?
  3. “Scaffolds shall not be covered with a tarp or any plastic material.”  Does this suggest that if I enclose the scaffold in plywood or screening I will be okay?  I know the answer to that is no but it is sure misleading because it suggests that all open scaffolds are the same.  Is a 3 tier scaffold in a building basement the same as a 3 tier scaffold on top of a cat cracker in a refinery?  I think not!
  4. “A 2×4 timber, putlog or scaffold member shall be placed securely between the masonry wall and the scaffold to protect the scaffold from tipping due to compressive loads.”  What bending stress timber would that be?  Does length have anything to do with it?  Instead of the 2×4 can I use a scaffold tube and screwjack or must it be a 2×4 when wire is used as the tension tie?  Since I’m being told how many wraps on my wire perhaps I should be told how many nails in my “securely placed” 2×4.

Come on OHSA, what were you thinking?  This is embarrassing not only for you but also for all of us in the industry.  The Scaffold Industry Association, SIA, has an alliance with OSHA where we work on issues.  We are here; where were you when this question was raised?  Believe it or not, there are members of the SIA who really do understand scaffolds and are concerned about the correct way to install and use scaffolds.  Having an enforcement agency publish a letter like this is an insult to qualified scaffold designers and a disservice to the individual who asked the question.  The answer to the original question is really quite simple and is found in 29 CFR 1926.451(a)(6):  “Scaffolds shall be designed by a qualified person and shall be constructed and loaded in accordance with that design.”  Let the qualified person decide how to connect the scaffold to the wall.  This is how we address the variables in tie design.  Unfortunately, this OSHA letter dangerously misleads the uninformed worker, and the compliance officers, to think that #9 wire can always be used as long as it has 5 wraps.  This is a dangerous precedent that could ultimately destroy the concept of performance standards.

Simply put, if you cannot design scaffold ties, if you don’t want to learn how to design scaffold ties, and you don’t want to have a qualified person design your scaffold ties, you shouldn’t be in the scaffold business.  And that is not my opinion—the OSHA standards specify it.  No interpretation is required to understand.

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