Standard Interpretations - Table of Contents|
| Standard Number:||1926.451(a)(1); 1926.451(a)(6); 1926.451(c)(1)(ii); 1926.451(c)(1)(iii); 1926.451(c)(3)|
August 4, 2000
Mr. Joseph D. Barbeau
Marsh USA Inc.
60 Colony Road
West Springfield, MA 01089
Subject: Use of Masonry Wire as Tie-in Points and 2" x 4" Lumber as Scaffold Bracing, 1926.451(a)(1), 1926.451(a)(6), 1926.451(c)(1)(ii), 1926.451(c)(1)(iii), 1926.451(c)(3)
Dear Mr. Barbeau:
This is in response to your letter dated July 20, 1999, addressed to the Occupational Safety and Health Administration in which you requested an interpretation on the use of number 9 masonry wire tied to U-shaped wire anchors with eyelets to secure a scaffold to a wall and the use of 2" x 4" lumber as a brace between the scaffold and the wall. Please accept our apology for the delay in responding to this inquiry.
There are several sections of the regulations that address your question. Under the general scaffold requirements, in 29 CFR 1926.451(a)(6), scaffolds must be designed by a qualified person (defined in §1926.450 as one who, by possession of a recognized degree, certificate, or professional standing, or who by extensive knowledge, training and experience, has successfully demonstrated his/her ability to solve or resolve problems related to the subject matter, the work, or the project) and must be constructed and loaded in accordance with that design. Under §1926.451(c)(1)(iii), it is the responsibility of the competent person (defined in §1926.450 as one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees and who has authorization to take prompt corrective measures to eliminate them) to use the necessary ties, guys, braces or outriggers to prevent a supported scaffold from tipping. Further, under §1926.451(c)(3), it is his/her responsibility to assure that the supported scaffold poles, legs, post frames and uprights are plumb and braced to prevent swaying and displacement.
Ties, guys, and braces for a scaffold must be installed according to the scaffold manufacturer's recommendations. If the specifications are unknown then the standards at 29 CFR 1926.451(c)(1) must be followed. These standards state that these guys, ties, and braces must be used when there is a 4:1 height ratio (beginning at 20 feet) for supported scaffolds. The location of the guys, ties, and braces depends upon the width of the platform. A platform width of three feet or less must have guys, ties and braces every 26 feet or less. When the 4:1 height ratio is reached guys, ties and braces are to be installed at each end of the scaffold and at horizontal intervals not to exceed 30 feet vertically.
The competent person must inspect the scaffold prior to each work shift or when something happens that could affect the structural integrity of the scaffold. During this inspection, the competent person must know the scaffold load rating and verify that each component is capable of supporting, without failure, its own weight and at least 4 times the maximum intended load applied. When used, guys, ties and scaffolds are considered a component of the scaffold.
Use of U-shaped wire anchors with eyelets
As described in your letter, the scaffold was secured to the wall with #9 masonry wire looped around the scaffold supports and through the eyelets of the wire anchors. You saw that several of the eyelets had opened up. You noted that the contractor indicated that the eyelets opened because the #9 wire was tied too tightly.
Since the anchors were used to secure the scaffold, they are considered "scaffold components" under the standard. Therefore, under §1926.451(a)(1), they must be capable of supporting "at least 4 times the maximum intended load applied." Even if tying the wire "too tight" caused the eyelets to open, that would indicate a load capacity that would probably be below what would be needed to meet the standard's strength requirements for scaffold components. In addition, irrespective of what caused them to open, once they were open, they were almost certainly incapable of meeting the strength requirements at that point. The fact that the eyelets failed before the wire failed underscores the weakness of the eyelets. Furthermore, the strength of the wire, as discussed below, is probably very limited. A competent person probably could not, therefore, approve the design of such an anchor.
Note also that when evaluating the capacity of the anchor, the extent to which the anchor is secured in the wall must also considered.
Use of #9 masonry wire to tie a scaffold to anchors
In your letter you stated that you had spoken with a wire manufacturer prior to submitting your questions to OSHA. The wire manufacturer that you had spoken with said that no testing data was available to support the use of the # 9 steel wire for tying-off a scaffold. Without such data, the qualified person designing or approving a scaffold system using such wire could not be assured that all components of the scaffold, including the wire, would meet the capacity requirements of §1926.451 (a)(1). Note that manufacturers of supported scaffolding usually have recommended guying, tying and bracing methods which normally would not include the use of such wire.
Published information on typical #9 wire confirms that it is likely to be inadequate for the use you describe. In "Pocket REF" by Thomas Glover, 1995, Sequoia Publishing Inc., Number 9 wire is listed as having a diameter of 0.148 inches. If we assume that this wire is made of A36 steel, which has an Fa = 21 ksi, the maximum loading for the wire would be:
P = 21,000 psi x 3.14 (.148 )(.148)/4 = 360 poundsThe above calculation for the masonry wire indicates that the wire would not support a typical load. Remember too that often the weakest link in the (tie-in bracing) system is the eyelets or the attachment points at the end of the wire. The eyelets, which are weaker than the wire, failed before the wire.
Use of 2 x 4 wood braces
With regard to the 2" x 4" lumber for bracing, the selection of the scaffold bracing must be included in the evaluation of the competent or qualified person when site specific condition and materials are considered. The competent person needs to know the quantity of tie-in brackets needed for a given scaffold load rating that will keep the scaffold from tipping and plumb. With particular regard to the use of 2" x 4" lumber, there is considerable variation in lumber quality (reflected in the various grades of lumber). The fact that the 2 x 4s split demonstrates that they were inadequate for use as bracing material. One way of avoiding that kind of mistake is to use a wood design manual to determine the allowable loading for the selected lumber.
We hope this explanation adequately addresses the concerns raised in your letter. Thank you for taking the time to provide us with your comments. If you need additional information, please contact us by fax at: U.S. Department of Labor, OSHA, Directorate of Construction, Office of Construction Standards and Guidance, fax # 202-693-1689. You can also contact us by mail at the above office, Room N3468, 200 Constitution Avenue, N.W., Washington, D.C. 20210, although there will be a delay in our receiving correspondence by mail.
Russell B. Swanson, Director
Directorate of Construction
Standard Interpretations - Table of Contents|