Working With Concrete

Whether it is new construction of retrofit; there is always a way to install window washing, suspended maintenance, and fall protection equipment.  While equipment can be installed on structural steel or even wood structure, the easiest structure to work with is reinforced concrete.  It is the most cost effective and does not typically require access to the underside or localized reinforcing.  It also has a number of other benefits such as improved insulation and sound barrier qualities.

The best part in the new construction phase is that we do not have to send anyone to the site for installation (which obviously saves everyone money, time, and other resources).  We simply send the equipment (usually a “roof anchor”) to the site (with our shop drawings) and the roof anchors are cast into the concrete.  There are three types of “cast in” anchors:

  • single stud,
  • four stud, and
  • fully embedded.

Single Stud Roof Anchor

A single stud roof anchor is the most physically difficult to place (for casting in) as there is only have one bolt to balance the anchor.

single stud

Four Stud Roof Anchor

A four stud roof anchor is much easier to place when casting in.  As you can imagine, there are more studs (or bolts) from which to stand the anchor on.  These extra studs are required by engineering (specifically for taller anchors).

four stud

Fully Embedded Roof Anchor

A fully embedded roof anchor is actually the easiest to cast in because of its flat bottom.  Also, it is the most cost effective because it is all pier (instead of having stud(s) on the bottom).

fully embedded

What If Pours Are Missed?

In the unfortunate event that a pour is missed by the roof anchor manufacturer and anchors have to be retrofitted, it is not the end of the world!  

Adhesive Roof Anchor

An adhesive roof anchor is glued into place with an epoxy.  This type of anchor does require load testing once every five years though (which is an extra service).

adhesive

Bolt Through Roof Anchor

A bolt through roof anchor is another solution for a roof anchor that has to be retrofitted.  This type of anchor does require access to the underside of the concrete though and it leaves components (base plate, bolt, nut) exposed.

bolt through

 

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Roof Anchor Design Principles

The selection of proper roof anchors is critical and requires an in depth knowledge of fall window washing, suspended maintenance, and fall protection codes and rigging methods.  Also, recognizing that each building is different, most architects, developers, and general contractors find the selection of a professional roof anchor company a daunting task.

Lifelines

A standard lifeline is 5/8 inch (1.59 centimeters) in diameter and has a breaking strength of 5,000 pounds (2,267.96 kilograms).  However, tying off to an anchor using a knot in a rope can reduce its strength by 50% (or more) to the cutting action of the lifeline or lanyard.

Therefore, good design must ensure that the anchor eye is greater in diameter than the rope itself.  The proper anchor eye for a possible knot connection is 3/4 inch (or 1.9 centimeters).  This design principle will ensure that the anchor eye will not cut, damage, or weaken the rope.

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Flate Plate Anchors

Special caution should be noted when considering a flat thin plate anchor.  These anchor designs are intended to be used with a snap hook or D-ring connection.  However, if a knot is tied to these anchors the rope is more likely to sever and fail.

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D-Rings and Snap Hooks

D-rings and snap hooks are designed with minimum tensile strength of 5,000 pounds (2,267.96 kilograms).  D-rings and snap hooks shall be proof-tested to a minimum tensile load of 3,600 pounds (1,632.93 kilograms) without cracking, breaking, or suffering permanent deformation.

Other problematic compatibility issues include the use of non-locking snap hooks or D-rings that are sized incorrectly and are not compatible with the anchor diameter and/or inside dimension of the anchor.  These incompatible dimensions, relative to the snap hook, will cause the connected object to depress the snap hook keeper and release unintentionally.

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Forged Eye Bolts

Eye bolts are rated along the axis of the bolt and its strength is greatly reduced if the force is applied at an angle to this axis in the direction of shear.

Generally roll out can occur using small eyebolts of 1/2 inch (1.27 centimeters) and 5/8 inch (1.59 centimeters) diameter.  These eyebolts are also too rigid so when put to a fall arrest test they will damage the securement stud and cannot be designed with redundancy.  They are too small and should not be used as part of a fall arrest system.

Also, it should be stated that forged eyebolts, non-shoulder, and shoulder eye bolts are not designed and approved by the manufacturer as a life safety product.  These anchors are designed for vertical loading not angle loading.   Also, recognizing that forged eye bolts are rigid, the securement bolt is almost always damaged under a test load or cyclical normal use conditions.

A hook must be compatible when the diameter of anchor to which the snap hook is attached is greater than the inside length of the snap hook when measured from the bottom (hinged end) of the keeper to the inside curved top of the snap hook.  Thus, no matter how the D-ring is positioned or moved (rolls) with the snap hook attached, the D-ring cannot touch the outside of the keeper, thus depressing it open.

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Why 5,000 pounds?

The design rule is that 5,000 pounds (2,267.96 kilograms) fracture or pull out is sufficient to accept all tie-back and life line loads that are likely to be subjected to the anchor using conventional equipment on a roof top.

The anchor eye, base, or base plate should accept this energy and load not the securement studs to support a worker in the event of a fall.  The codes state that the 5,000 pounds (2,267.96 kilograms) based on the weight of a worker being 250 pounds (113.4 kilograms), experiencing a force of gravity multipled by 10 times a safety factor of 2.

250 x 10= 2,500 x 2= 5,000 pounds

While the energy absorbing lanyards hold in excess of 5,000 pounds (2,267.96 kilograms) when fully absorbed, most limit the load during the fall to under 1,250 pounds (566.99 kilograms).

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Working At Heights

Everyone is responsible for preventing falls when working at heights.  The building owner/property manager/owner’s representative, the self-employed contractor, any subcontractor and the worker are all responsible for safety considerations when on a roof.

The concern for health and safety on a roof becomes critical as soon as someone steps foot on a roof (and not just when they “get close” to the edge).  All aspects of working safely at heights should be considered.  The general rule is that fall protection is required: 

  • In Canada, where any section of the parapet wall is less than 36 inches (and someone is subject to a 10 foot fall)
  • In the USA, where any section of the parapet wall is less than 42 inches (and someone is subject to a 4 foot fall)

Preventing falls from heights is a priority for the Department of Labour (DOL) and Ministry of Labour (MOL).  Each expects contractors and employers with staff working at heights to actively manage any significant hazard.

Controlling the Hazard 

In order to stay safe when working at heights you must ensure effective controls are in place to prevent people from being harmed.

To select the most effective controls, you must consider the following steps: 

  • Eliminate the chances of a fall by doing as much of the preparation work as possible before work begins.  Normally this is done by doing a fall hazard roof assessment.  The assessment report will review all aspects of safe access and egress for all work activities that may take place on the roof.  The intent is to isolate the worker from the risk of a fall by using guard rails, scaffolds and roof edge protection as means of prevention.  In some situations a combination of controls will be required to ensure safe work.
  • Edge protection is imperative.  Edge protection should be used as a means of isolating workers from a fall.  This includes guard rails, horizontal life lines, localized tieback and lifeline anchors, access ladders and catwalks.  Edge protection should be provided on all the exposed edges of a roof, including the perimeter of buildings, skylights or other fragile roof materials and for any openings in the roof.  This also applies to openings and edges of floor areas.
  • Where there is the risk of workers falling through openings in a roof, the openings should be identified and guarded. 

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Check List for Working Safely on a Roof 

  • Are workers trained or supervised to work on a roof, near the roof edge or over the edge using suspended equipment safely?
  • Has a full hazard assessment been completed before work starts?
  • Is there safe access to all roof areas?
  • Has the contractor provided a work plan to safely access the building edge or facade?
  • Have the roof and fall arrest system been inspected, reviewed and tested if needed?
  • Have all the access restrictions been identified and understood by the contractors?
  • Are workers protected from falling off roof edges and do they have a rescue plan?
  • Are workers protected from falling from incomplete roofs?
  • Are workers protected from falling through skylights and penetrations or other brittle roofing?
  • Are people below the work protected from the dangers of falling materials?
  • Do roof workers have appropriate footwear to prevent them from slipping?
  • Are the weather conditions suitable for working on a roof?
  • Have lower electrical hazards and vehicle traffic hazards been identified?  

Other Possible Considerations

  • Eliminate the hazard of a fall from a roof.
  • Work from the ground.
  • Work from inside where there is no possibility of a fall.
  • Prefabricate components at ground level or prior to installation.
  • Remove complete fixtures to ground level or shop for maintenance (e.g. air conditioning units).
  • Pre-paint fixtures/roof prior to installation.
  • When isolating the hazard of a fall from a roof you can consider some addition temporary protections.
  • Scaffolding and mobile scaffolds/step platforms/working in an elevating work platform.

It is the law so doing nothing to address safety when working at heights is not an option!

worker

Davit Systems

I often hear people referring to window washing systems as davit systems.  While this certainly is true it is not the only way to complete window washing (see The Roof Anchor and Roof Anchors Explained for more).  So what exactly are davits, davit arms, davit bases, and davit systems then?

Davit Arm Assemblies

Davit arms are commonly used to rig over non-structural parapets, decorative cornices, and glass balcony guardrails.  These arms act as the primary suspension points usually for swingstages, but are also used for supporting single man cages and bosun’s chairs.  Comprised of a mast (the vertical piece) and boom (the horizontal piece), davit arms are secured to the structure using bases.  These bases vary to suit the roof or wall construction.

Davit Arm

The main distinction in davit systems is whether or not the system is designed to be ground rigged or roof rigged.  In a ground rigged scenario, each successive “drop” is done by picking up the platform from ground level, raising it to roof level, then back to the ground level.  At ground level the platform is then moved to the next “drop” location.

In a roof rigged scenario, the mast on the davit arm is tall enough to allow it to pick the platform up from ground level, and hoist it onto the roof.  The stage is then relocated on the roof level to align with each “drop” location.

stage on roof

 

Quick Facts

  • Davit arms are typically portable and are relocated to new bases for every drop. 
  • They can be broken down into segments for ease of carrying. 
  • Mast and boom size vary depending on building requirements.
  • At times, arms that are very large or are required in difficult to access areas, are recommended or necessary to be permanently left in place for facade access.  Also referred to as, “dedicated arms”.

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stage repelling

Basics of Fall Protection

Our industry is most commonly associated with window washing systems and suspended maintenance systems.  Because of this, fall protection (specifically on low-rise buildings) is often overlooked. 

Fall Arrest vs. Fall Restraint

“Fall protection” is actually a term that encompasses the method of either “fall arrest” or “fall restraint”.

Fall arrest prevents a person from reaching the ground (once a fall occurs).  An example of fall arrest is a worker tripping over the edge of a building but then being suspended midair (by a lanyard tied to a cable system) and not reaching the ground.

Fall restraint prevents a worker from even reaching a fall.  An example of fall restraint is a worker not being able to reach the edge of a building because a guard rail is located in the way.

guard2

Preventing Falls

Data shows that falls are the most common accident in the construction industry and that 75% of the falls occur at elevations of less than 3 stories.

A fall protection system can include:

  • Cable systems
  • Fixed ladders
  • Guard rails
  • Localized anchors

IMG0038a

When designing a fall protection system one must concerned itself with:

Function

 
What type of work is being completed while the system is in use?

Is it…

  • Washing the windows from a ladder

or fixing/replacing/servicing…

  • Antennas
  • Cooling tower
  • Drains
  • Equipment located on the façade of the building (from a ladder on the ground)
  • Lights
  • Mechanical units
  • Pipes
  • Roofing
  • Satellites
  • Surveillance cameras

Frequency


How often will this work occur?

If it is expected, routine, scheduled maintenance then the most user friendly system (to encourage its use) should be implemented.

If it is unexpected, non-routine, unscheduled maintenance then the most basic and cost effective system should be implemented.

Users


Who is using the system?

A worker who is trained and supervised may not require as much equipment as someone who is unfamiliar with fall protection.

IMG0086 

Falls can effectively be prevented with adequate safety equipment, proper training, and a suitable fall protection system.

The bottom-line is; fall protection equipment is needed:

  • In Canada, where any section of the parapet wall is less than 36 inches (and someone is subject to a 10 foot fall)
  • In the USA, where any section of the parapet wall is less than 42 inches (and someone is subject to a 4 foot fall)

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The Roof Anchor

There are many different types of equipment that are installed for window washing, suspended maintenance, and fall protection.  They can include (but are not limited to):

  • roof anchors,
  • wall anchors,
  • soffit anchors,
  • davits,
  • rigging sleeves,
  • horizontal trolley’s,
  • monorail,
  • gantry’s and
  • roof cars.

With all the customized equipment out there – nine times out of ten it is a simple roof anchor that gets the job done!

Different companies (around the globe) use different styles of roof anchors that are each unique in their own way.  A vertical steel pier anchor is the most common and are all pretty much the same.  It is usually the actual tie-off (or anchorage point) that varies.  Some companies utilize a swivel head U-bar that actually points horizontal (perpendicular) to the pier and can swivel while others have fixed “U-bars” or “eyelets”.  These point vertical such as in the picture shown below.  The material’s used from pier, U-bar, and hardware can vary in material from galvanized to stainless steel (depending on the project specifications) although stainless steel piers are not used very often due to cost.

Weld To Structure Roof Anchor

These (steel pier) anchors can be installed to accommodate three different styles of systems: window washing, suspended maintenance, and fall protection.

IMG0036Z

Window Washing

Window washers can utilize anchor points to suspend themselves adjacent to the building facade to perform window washing operations.  This is commonly done on a bosun’s chair but can also be performed on swing stages as well.

Suspended Maintenance

Companies performing facade maintenance such as brick restoration, window caulking, or balcony repair can utilize anchor points to suspend the platform (swing stage) that they work from.

Fall Protection

Workers can utilize either individual, localized anchor points or a horizontal lifeline cable system to prevent them from falling (travel restraint) or save them from hitting the ground (fall arrest) in the event they do fall.

A2-DET~1

Often the simplest approach is the best one and window washing, suspended maintenance, and fall protection systems are no exception.

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Working Near Electrical Hazards

If you are washing windows in a downtown metropolis city, you will certainly be working close to live power lines.  Whether it is working from a:

  • Bosun’s chair
  • Ladder
  • Temporary platform
  • Scaffold

working near hydro lines can be dangerous!  Unfortunately, some property managers and maintenance workers do not fully understand the risk that these lines present.

Making the Area Safe

In Ontario for instance, the Occupational Health and Safety Act states that it is the constructor’s responsibility to assess hazards and ensure that everyone on the work site adheres to the safe limits of approach for live lines (this is not the responsibility of the hydro company).  A constructor may be a building owner, general contractor, property manager/owners representative (amongst others).  

If the hazard assessment and the safe limits are not conducted or adhered to then the work site could be shut down.  If an injury did occur one or all of the constructor’s could be held liable.

If you are working near lines, you must do one of two things:

  1. call the hydro company for more information about having the power lines de-energized (power temporarily cut off) or relocated/removed.
  2. call the hydro company to have the lines covered.  This option is beneficial as it makes the lines much more visible than they usually would to alert (remind) the workers of the danger.  Please be aware that while covered lines draw attention to the lines; they do not provide any protection when contacted.  These covers must also be removed, tested and replaced every six months.

There is a fee for the above mentioned services though.  Cost estimates and installation schedules can be obtained by contacting the hydro company ahead of time.  Although, the work may be performed by a contractor if authorized by the hydro company.  Check your local listing for the hydro company in your area.

All Electrical Lines Are Hazardous

It must be noted that contact with any line (even a residential secondary line) can cause serious injury or death.  That is why it is important that proper precautions are taken to protect workers.

In Ontario, it is required that all workers and “tools ladders, scaffolding and other equipment that are capable of conducting electricity” keep a minimum distance of three metres (ten feet) from high voltage lines between 750 V and 75 kV (the full listing is shown below).

Table 

All lines must be treated as high voltage until the voltage has been identified by the hydro company.

The property manager/owners representative must evaluate the work site well in advance.  Then before the work starts they should review the work site with their general contractor (and their workers) and point out the location of all lines near or within the building.

Daily Inspection

If you have covers installed (option 2. mentioned above) you must inspect them each day prior to work commencing.  You should look for:

  •  Fallen covers
  •  Loose covers
  •  Gaps in the covers

If you notice any exposed equipment or lines then call the hydro company immediately and they will make the necessary repairs.  Only the hydro company or one of their authorized contractors may install or repair covers and only their covers may be used on lines.

Bottom Line

If you come across any power line:

  • Stay back three metres (ten feet)
  • Contact your local hydro company
  • Have the lines de-energized or covered
  • Stay alert daily

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Customized Rigging Sleeve

Pro-Bel was recently faced with the problem of installing a rigging sleeve on an existing building where we had no access to the ceiling below the roof.

The interior atrium of the building could not be cleaned (or maintained) because there was no lift/platform that would reach the height required (and there was no other access point to install any other equipment).  The biggest problem though was that there was no access inside the ceiling and between the drywall and the roof there was a ten foot gap (which again complicated things even more).

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What we did was add a large twelve foot extension bit to a drill and then (once we opened up the roof beside an I-beam) lowered the extended drill ten feet and drilled through the drywall below (to create a circular hole).  

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Once that was completed we installed the pier of the rigging sleeve by wrapping its base plate around the I-beam and then offsetting the pier. 

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Once the pier was installed we lowered a cable through it and the drywall hole and eventually all of the way to the ground floor.  Once the cable was hung from the roof to the ground we were able to thread the cable through a PVC tube insert.  The insert had a cap on the bottom which would give it a nice looking finish with the ceiling.  We had to find a way to attach the cable to the insert prior to lifting it to the ceiling though so we secured an anchor to the end of the cable. 

130620115848_0009 
 

We then began to hoist the insert (along with the cap and anchor) up to the ceiling. 

130620115848_0007  
 

The insert eventually entered the pier and then screws were inserted into the side of each to secure it into place. 

130620115848_0006 
 

The rigging sleeve was then finished (like any other rigging sleeve) with a cap on top of the pier and the roofing around it was patched to a watertight condition. 

130620115848_0008 
 

This is the first time that we have ever completed an installation under these circumstances and it was an enormous success.  There really is a solution to every problem! 

Always A Solution

Working With A Standing Seam Roof

We are often asked to provide our equipment on buildings with a standing seam roof.  In the past this request would make even our most knowledgeable designers cringe but alas we have engineered a solution.

What is a Standing Seam Roof?

A standing seam roof consists of a series of sheet metal panels that are connected “above” the panels (creating a “standing seam”) in a manner that does not penetrate them.

These are some examples of connections:

Various Types

Pro-Bel is an official distributor of S-5!® clamps (as seen in the picture below) which connect the panels by tightening the seams together.  You can learn more about this product from their website (http://www.s-5.com/home/index.cfm) and by following them on Twitter @S5_TheRightWay.

S-5!® Clamps

Structural Requirements

The big obstacle with our equipment being on a standing seam roof is that the panels will not support the applied load/force that our equipment is engineered to accept.

CAN/CSA-Z271, Section 6.3.2  – “Strength Requirement” asks that all “anchoring systems shall be designed to resist a force” of five thousand (5,000) pounds.  This load/force is indirectly applied to the structure of the roof as well which is where the problem arises.

The Ridge Cap Flashing

Usually with a sloped roof there is a gap at the peak of it between the panels.  This is usually covered by a ridge cap flashing which actually does penetrate the flashing and panel (in a strategic way).  As seen in the picture below, Z bar connection penetrates the flashing and connects it to the panel.  As long as the penetration is “above” and “away” from the envelope (the area inside the flashing) there is no concern for water damage.  If the Z bar is installed incorrectly (as shown on the right side of the picture below) then water could potentially enter the envelope and travel toward the unprotected roof material and structure.

Ridge cap flashing

The flashing will run along the peak of a sloped roof with a large amount of connections (nails or screws) running along each side of it like so:

Ridge cap flashing 1

ridge cap flashing 2

Our Solution

Our Engineers agreed that the connections make the flashing the strongest component of a standing seam roof and thus the ideal location to install a piece of our equipment to.

What we did was design a large galvanized rectangular plate with ninety degree angle pieces welded to it (the plate).  Our standard stainless steel U-bar is centred on the plate and the angles would be screwed into the flashing (standing seam where the Z bar would be) instead of penetrating the envelope or panel.

Anchor Details

We hope to build upon this application as this solution will revolutionize fall protection systems on a standing seam roof.

IMG_0307

Working With Hollow Core Precast

Every type of roof structure presents its own unique challenges in new construction for companies who supply and install permanent equipment on them.  With structural steel its reinforcing, with concrete it can be missing a pour.  Hollow core precast can be looked at as one of the most challenging roof construction types for the installation of window washing, suspended maintenance and fall protection systems.

The main issue with precast lies with the fact that there usually is no drop ceiling underneath.  It is quite often stucco and even plaster which means bolting through the structure would require leaving a backplate exposed to view at the underside of the precast.  Not only is this not aesthetically pleasing, it also presents a potential danger to the workers who use the roof anchors as the base securement of the anchors is exposed and could potentially be tampered with.  This provides us with two options: cracking open the cores and grouting the anchor in or having the precast manufacturer embed plates.

Grouting A Roof Anchor Into Hollow Core Precast

This option requires two cores to be broken open and embed plates at bottom of the bolts to be cast in with rebar and grouting.  This prevents from having to bolt through the structure but is very labour intensive and thus costly.  Ideally in new construction the roof anchor company would supply only this anchor and leave it up to the general contractor to break open the cores and grout the anchor in.  Grouting in hollow core is quite common.

Having The Precast Manufacturer Embed A Plate

This option although the most cost effective when you cannot bolt through, is unfortunately very impractical and rarely used.  An embed plate is sent to the precast manufacturer along with an engineered stamped layout showing the location of the roof anchors on the roof plan.  The precast manufacturer then embeds this plate in to the hollow core structure at the appropriate locations.  The roof anchor manufacturer goes to the site afterwards and welds the pier and U-bar in place.  The problem with this approach is that the precast manufacturer will usually not want to take responsibility for casting the embeds in.

At the end of the day bolting through is the best way to go but when you cannot here are a few options for you to consider.