Scaffold Questions Answered

By David H. Glabe, P.E. / June 20, 2013

While Suspended Scaffolds (scaffold platforms supported by non-rigid means such as ropes or chains) have been used for many years, there is still confusion about what a safe suspended scaffold is. Here are a few questions that are asked about these scaffolds.

Do suspended scaffolds have to be designed?
Yes, all scaffolds, including suspended scaffolds, have to be designed, and they have to be designed by a qualified person.

What is a “qualified person”?
A qualified person in an individual who by degree, certificate or professional standing, or who by extensive knowledge, training and experience, can demonstrate an ability to solve or resolve the problem at hand. In this case the qualified person would have to have knowledge of suspended scaffold construction and use.

Isn’t qualified person and competent person the same thing?
No; A competent person is one who can identify a hazard and has the authority to eliminate that hazard.

Does the qualified person also inspect scaffolds?
A qualified person can inspect a scaffold as long as she is a competent person.

Does a suspended scaffold always have two suspension ropes to hold up the platform?
No. A suspended scaffold can have one rope, two ropes, or multiple ropes.

Are cantilevered beams always used to support the suspension ropes?
No; There are several choices when it comes to supporting the suspenson ropes. Besides beams that protrude out from the face of the building, parapet clamps, whcich clamp to an adequately strong parapet, a roof hook that can be attached to the same adequate parapet, and a direct connection, can be used to support the suspension rope.

What is a direct connection?
A direct connection is a secure point that the suspension rope can be connected to. For example, a hook welded to a beam, can be used provided that it has been designed by a qualified person.

What is a P.I.?
A PI is a private investigator. It is also a Permanent Installation as it applies to scaffolding. A PI is purpose designed for a particular structure or building and is typically a suspended scaffold that is used for building maintenance.

Are there any differences between a Permanent Installation and a temporary two point suspended scaffold?
Yes there are differences. A temporary suspended scaffold is never intended to be left on the job after the work is completed, even if the work takes a number of years to complete. A PI is intended to always remain on the building for which it was designed and constructed. Consequently, a temporary suspended scaffold must comply with the OSHA standards for Construction whereas the PI must comply with the OSHA General Industry standards. Additionally, a PI is typically more robust and rigged differently than a temporary set-up.

Is a Competent Person required to design a suspended scaffold?
No; A competent person does not designs any scaffold—a Qualified Person designs scaffolds. A qualified person is one who can demonstrate an ability to design scaffolds, typically based on knowledge gained through education, experience, and expertise.

Do all suspended scaffolds have to be designed by a qualified Professional Engineer?
No, although you certainly want to have a person who is qualified to design a suspended scaffolds. The complexity of the installation may require a person who has knowledge of physics, engineering principles and knowledge of the industry.

Why do suspended scaffolds rank high in the number of scaffold deaths?
I have no idea. There is a 6 to 1 safety factor on the suspension ropes (or at least there is supposed to be), over-speed brakes, a 4 to 1 safety factor on the platform and hoist, personal fall arrest systems for the workers and tiebacks. Frankly the number of deaths should be zero. Apparently some workers just don’t have adequate training or don’t care.

I have guardrails on suspended scaffold platform. Why do I have to wear personal fall arrest equipment?
The guardrails are there so you don’t walk off the platform and the fall arrest equipment is there in case the platform drops out from under you, taking the guardrails with it.

What is a tieback?
A tieback is a rope that is attached to the rigging to ensure that the rigging doesn’t move or get displaced. Therefore, the tieback must be of the same strength as the suspension rope and must be taut. The anchor must be rated at the capacity of the hoist, with the proper safety factor.

I attach my tieback rope to anchors attached to the building. Are they strong enough ?
I sure hope so. It is hoped that the building owner has the data on the anchor including its’ strength. Therefore ask the building owner what the allowable load on the anchor can be. Building anchors must be inspected annually by someone who knows what he/she is looking at and the anchors must be load tested by a qualified engineering/testing company every ten years.

I am going to work off a suspended scaffold that has been installed under a bridge over troubled waters. It is supported by about 100 suspension ropes. Do I still have to wear personal fall arrest equipment?
Nope. Unless you want to.

I have been told that the counterweight for my cantilevered beams that support the suspension rope on my suspended scaffold have to be non-flowable. Can I use Jell-O™?
I don’t think so. I tried taking Jell-O™ through security at the airport and I was told it is a liquid. I disagreed—took three days to get through security.

How far out can I extend/cantilever a rigging beam?
It all depends on several things: First is the load that needs to be supported. For example, 1,000 pounds is a typical suspension scaffold load; the beam has to be strong enough to support that load. Second, the type of material the beam is made from is a factor. Third, the shape of the beam is a facto. A square beam will behave differently than an “I” beam. Fourth, the stiffness of the beam is a factor. The further the beam sticks out, the more it wants to roll over. Fifth, the backspan, that is the distance the beam sticks back into the building. For example, if you had a cantilever of ten feet and a backspan of 2 feet, there may be several issues.

Tags: Scaffolding Resources

Previous Post Is It Supported?
Next Post Shoring…Are You Protected?

David H. Glabe, P.E.

See what David H. Glabe has to say about construction engineering and the scaffolding industry.