Designing Effective Rooftop Fall Protection Systems

Introduction

Hi, my name is Justin, and I’m with Pro-Bel Enterprise. Today, I’ll be going over the basics of fall protection design. First things first, let me tell you a little more about myself.

I’m a Junior Designer for our fall protection and I also work in Business Associate Development. Which essentially means it’s my job to arrange our free design service for any eligible projects, and that includes most projects within North America.

I’ve arranged designs for projects for everything from retrofitting small schools and new construction projects like apartments and airports to large scale projects for name-brand hotels.

If you have a project and you’re confused about fall protection, I’m happy to answer any questions and I can arrange a consultation, if need be, for no charge. Most projects will be eligible for free designs, so there’s no harm in reaching out!

Pre-Design Preparation

First, you need to know your scope. For this demo, we’ll be doing a hospital that only requires fall protection, not suspension. We will be making one that covers window washing systems in the future, so stay tuned. Until then, we have resources on Pro-Bel's website, and our contact information is in the bio if you have any specific questions.

Alright, now that we know our scope is only fall protection, it’s time to review the relevant information in the drawings.

To design for fall protection, we need the elevations, roof plans, Isometric, structural plans, and details for the fall protection if they were included.

Most regions follow the same guidelines for fall protection, but Canada and some states have slight tweaks to their requirements. You need to confirm if the region you’re working in follows standard protocol for fall protection or not.

Structural Considerations

The structure of the roof will determine both the placement of the anchors and what type of base they’ll require. For wood structures, the anchors can usually be placed anywhere. For cement, they can be cast in place pretty much anywhere on the roof. But for steel, they can only be placed on the beams, which can make it a bit trickier if there’s a lot of interference on the roof.

Elevation Review

Review any elevations that would alter the drop distance. If the roof plan doesn’t encompass all the roofs on the building, you’ll need to merge them together in a separate document to begin the design. Calculate the drop distance on all elevations to make sure all the faces require fall protection.

Parapets

The required height for a parapet, which eliminates the need for tie-back anchors, is 42” from the finish of the roof. This varies in some regions, but that’s the standard requirement for most states.
When a parapet is under 42” and rooftop work is expected to occur within 6 feet of the roof edge, safety & tie-off anchors are needed.

Once you’ve reviewed these factors, it’s time to create a design. You should separate all the roof plan into a new document to begin the design process. If the different roof elevations aren’t on one document, they need to be merged. Have any relevant documents such as the roof details, elevations, landscape if applicable to the roof, isometrics, overall building section and any other plans that would impact the roof.

Fall Protection Design Tutorial

Here’s the document I’ve prepared for the tutorial. This building only wanted fall protection, no window washing or facade maintenance. And before I start, I need to put out the disclaimer that this should be done by a professional. I’ve put my contact information in the description and me or a separate regional designer can prepare an OSHA compliant design.

This brief tutorial is just going to go over the basics of how fall protection design operates.

This area is part of the lower roof merged with the roof plan. It’s 13ft from the ground which means it needs fall protection.

Fall Restraint Requirements

Since we can’t rely on fall arrest for this height, we need fall restraint. The minimum distance is 8 feet 9 inches, but I prefer to put it 10ft back while getting a feel for the building. The first anchor will go here. The maximum span for a cable is 30 feet so we’ll need to measure out the lines so they're within 30 feet. After that, we need to add another anchor so the worker can reach this side of the roof. Next, you need to consider the corners. They should be within 6f, of the center anchors. This is because the worker’s lanyard reaches 6ft, and there’s an additional 2ft of arm reach.

Corners are usually one of the more difficult design concepts for people learning fall protection, so it should be reviewed by a professional. Me or any other professional designer can be contacted to review your design work or to compose the design for you which is a free service for any eligible projects.

Now because this roof has a wall, we’ll be adding wall anchors along it and measuring them out to be within 30 ft apart.

Designing Anchor Points Around Obstacles

Next, we must create a design that works around these obstacles. The hazard zone is 6 ft from the edge, but since there’s equipment prevents us from going 6ft back we have put it closer to the edge.

I’ll substitute the wall anchor here for two roof anchors so they can be connected to the anchors we’ll have to place in the hazard zone. Before determining where in the hazard zone the anchors need to be placed, we need to check what anchors can be placed further than 6 feet to see where the optimal position is for the anchors aligned along the edge.

Now, we adjust the anchor placements, the design is within the needed distancing, and all areas of the roof in this section are covered.

Tie-back Anchor and Horizontal Lifeline Placement & Requirements

Since there’s less interference at the bottom, we can just place them down following standard guidelines.

The worker can only reach 6 feet from this point, so we’ll need to add two more anchors to reach the bottom portion of the roof. This second anchor can be moved to have a further reach and reduce the cost of the fall protection system.

And we’re going to stop one of our cables here, because our maximum allowable cable distance for a single cable is 300 feet – so instead, we’re going to have a termination point here with shock absorber over here. It’s a good spot for it since it’s not near any mechanical equipment that the worker would have to traverse around.

This upper corner of the building is a bit unusual since they have a snow screen, meaning that this screen itself is only 5 feet tall. We could potentially attach equipment to it, but it’s not designed for that purpose, and the clients have said they don’t want to design it to take any of our weight. So in that case, we’re going to have to use roof anchors on the perimeter between the snow screen wall and the building edge. So, in that case, we’re going to be centering one of our anchor tools using this square tool… and there, we can see it’s lined up perfectly to the perimeter and roof edge now. Then I can do the same on the other side… And because I know that the span is 47’’, I can’t get away with just one, so I’ll need to place three anchors to have the cable length reach.

So, from here, we have a couple of options. We can continue in this straight line, which will use a cable system that’s actually inside the hazard zone, meaning there’d be no attachment in these spots. So, any person working on the roof would have to either attach to this point down here or somewhere up top and go along. They wouldn’t be able to safely attach to this one on the corner because once they’re along here, they’ll be in a hazard zone and won’t be able to safely work. So, that option leaves us with two choices. We can tell them that’s the situation and to snap onto a cable from far away, or we can add an extra anchor or two along here and have it come along like this.

And so, these would allow me to have an access point here, or here, to attach to the cable, because my fall hazard zone is now within 6 feet of the building edge. Anything in this zone here is a no-go. However, with these new anchors, the worker can stay out of the fall hazard zone.

Then we’re going to align these anchor points here and distribute them evenly. To be sure, we’re going to measure between the anchors to ensure that it’s within the 30 foot rule, and it looks like it is. On the other side, we’d have to have a cascading anchor with one out here, and one back here, which isn’t a great design. So instead, in this area, I’m going to take one of my anchors and bring it down. Then I’m going to measure 14’’ here, place the anchor here, and align them all vertically for the best access. Now, the worker can safely run my cable both ways!

So, some other challenges… For this building, we’re going to assume that this lower portion of the building here is almost the same height, at least within 12 feet of the roof. So what that means is that we need to terminate the cable system before this roof extension starts and introduce anchor systems instead. The reason for that is because I don’t have enough space because of the mechanical equipment to introduce an additional fall restraint system and reduce the number of anchors. So, in order for a worker to safely work on this part, they’ll need to be tied off to anchors at 6’ off-center for the entire thing. This is common when we have things like bay windows or balconies on the sides of buildings that prevent us from properly arrest the fall due to the lack of space.

So, in that case, first, we’re going to measure the distance and go up a size. We’ll go up to 42’ and then center it on the part of the roof that sticks out… add one anchor right here… and we’ll need to make sure that the distance between these two anchors is 6 feet or less. As you can see, the distance is currently over 7’, so that’s obviously a no-go. So I’ll just move the top anchor closer to ensure it’s within the 6’ safe range, and then just realign and space out the top anchors as well to make sure that everything is in line.

So from here, I’m just going to make a line of anchors here in a single line, 6 feet apart each. Now, I’m going to select them all and Distribute Equally Vertically, which will then place them with 6 feet apart for each in a nice row of anchors.

Now, we could terminate here and not have that extra anchor, but as you can see, the equipment on the roof could get in the way of the cabling. So, instead we’ll bring this last anchor up a bit. So now, I’ll measure 7 feet from the roof edge, and then we’re going to create another line of anchors starting from this corner. But, we’re gonna be smart about it – to avoid being closer than the 7 feet, we’re going to instead start by placing an anchor on the other side, like that. Then we’ll make additional anchors, select them, select distribute horizontally… and there we go.

Okay, now that we’re done with that part, we’re going to go back to the snow screen wall. So we’re going to copy one of these anchors and see if it fits in the 30’ limit… no, it doesn’t, but what we can do is just place a wall anchor here, and move this anchor here so it fits within the 30’. The benefit of a wall anchor over a roof anchor is not only that it’s cheaper than a roof anchor, but it also helps cut down on the roof penetration. The fewer amount of times you have to install an anchor to cut down on the roof penetration and waterproofing/etc, the better. So tying off to additional equipment whenever possible also helps keep those costs down and roof structure integrity up.

So now we’re just going to go to almost the end position and roughly measure about 7 feet, then we’ll use that same square trick from before to make sure the anchor is perfectly aligned. Now, this is a long length of roof so we’re going to do the same thing again as before – 7 feet from the edge to place an anchor, select the anchors, and distribute them evenly along the roof edges.

Fall protection is essential for keeping rooftop workers safe and any design needs to be reviewed by a professional to ensure the design is optimal with no risks in place. If you aren’t in the fall protection industry, give me a call or email. I’ll review your building and I can set up a consultation with a lead designer if you’d like. My contact information is in the bio below.

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