Danger Overhead: Ensuring future access for the façade

by Elaina Adams | May 1, 2012 10:38 am

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By Karol L. Kazmierczak, CSI, CDT, AIA, ASHRAE, NCARB, LEED AP, and Jerzy Tuscher, M.Sc.
It is safe to suggest there are many architects and building owners who do not like the ‘industrial look’ associated with the means of façade access. However, once a beautiful building is occupied, there must be a way for others to maintain, repair, and inspect the claddings and façades well above the ground. Early inclusion in a design may minimize the esthetic impact.

This article deals with systems like building maintenance units (BMUs)—essentially, roof cranes—that provide a permanent means of façade access; this is not about the temporary ‘general conditions’ of a new construction site. The distinction is important because some architects might dismissively wonder whether this is all simply the general contractor’s task, confusing the hoists and scaffoldings of a newly erected building with house cranes and gantries of a building in operation.

Some facility owners, meanwhile, may question the need for BMUs because they feel the systems will be used infrequently or out-of-house contractors will be hired. However, pushing the provision of access on contractors results in either more expensive maintenance or cutting corners in safety. Considering future work to be done by building inspectors, window-washers, and maintenance specialists is very much part of the design professional’s responsibility.

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Expensive examples
How many designers does it take to change a light bulb? A few years back, an overhead lamp at one of the train stations along a New Jersey Transit line needed to be replaced. This seemingly simple task became more complex than any bad punch line—it required use of two cranes; one lifted another through a hole cut in a roof at the expense of tens of thousands of dollars. The architect explained the particular building façade’s access was sacrificed on the altar of a subjectively perceived beauty: a desired dramatic visual effect of a skylight, void of any unsightly obstructions.

Not too long ago, this author was involved in an investigation of 13 irreparably damaged glass panes in two adjacent, brand-new residential apartments. Glass replacement was estimated at $650,000. At that price, one might wonder whether the glass was covered with a layer of a precious metal to justify the elevated cost. (Technically, it was—but this is the case for any regular, off-the-shelf, low-emissivity [low-e] glass.) Indeed, the material accounted for only seven per cent of the total cost. The high price tag was due to the need to have a 36.6-m (120-ft) hydraulic truck crane in spite of the addition of a BMU installed on the roof (Figure 1).

Using a truck crane required negotiations with the city to close a busy street for traffic (twice—due to the curing duration of a structural silicone sealant). The expensive house crane not only had insufficient reach, but also indirectly contributed to the glass damage problem. The BMU’s weight was not initially calculated into the building structure. To carry the loads after the top floor was already closed, the roof slab needed to be remedially strengthened by welding thick steel plates underneath. To make matters worse, the weld splatter generated by the heavy construction operations irreparably damaged glass throughout the top floor. This is how costly a lack of design co-ordination and planning of façade access can turn out to be.

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Façade access safety
On many buildings this author inspects, even the most elementary tie-off anchors are frequently missing—in other words, there is no reliable spot to secure one’s fall-arrest system. (This is why I bring my own concrete drill, while window-washing contractors drag concrete or water-filled tanks instead.) How does this happen, given the inherent liability attached to such an omission? In one particular case, the architect did not initially design the anchors, therefore they were not included in the budget. When I spoke to the owner, the building was already in the construction phase and over budget—the addition of tie-offs would require strengthening of the structural steel to take the 2270-kg (5000-lb) reaction at each davit’s location. The building is in operation now, without any fall-arrest protection.

Of course, it is not solely façade inspectors who rely on these safety measures. Frequent window-washing is required under most glass warranties (Figure 2). The well-being of individuals performing work at elevation is the owner’s and/or building manager’s responsibility. An out-of-house crew is subject to the same rules of gravity as the in-house employee and deserves the same safety measures. Design professionals should educate the owner about safety regulations and propose workable solutions to fit the budget.

Designing a new high-rise building
The need for façade-access systems must be explained to building owners early in the design process to ensure room is left for reasonable budgeting. Theoretically, an owner of a high-rise building may retrofit the façade or roof to allow access after the completion, but there are many factors rendering this solution uneconomical and impractical, compared to the integrated design. The aforementioned strengthening of the structure to achieve the required structural performance of anchor points, interruptions and penetrations of roofing, and unsightly modifications of cladding are among them.

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The primary access system must be doubled by a personal fall-arrest system. However, in addition to people, repair work requires transportation of tools and materials. This complicates matters due to limited weight capacities. For example, a single pane of glass may weigh as much as 680 kg (1500 lb) on the average building. Therefore, a façade may require a tertiary hoisting system to lift the materials in addition to the access and fall-arrest systems.

Figure 3 depicts a façade accessibility analysis of portable lifts and boatswain chairs. The typically overlooked areas of concern are interior yards and perimeter security berms, along with intervening roofs and sloped glazing below walls and overhangs, which restrict access of portable equipment (Figure 4).

A good rule is to have a roof hoist for transporting materials on and off the roof, and rolling gantries under and over all elevated sloped glazing. Unless specifically engineered as a floor, sloped glazing is not a walking surface. Items requiring frequent maintenance (i.e. gutters, drains, and all waterproofing or roofing subjected to prolonged water contact) should have adequate access.

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A worker must be provided with a fall-restraint system when approaching a distance 2 m (6 ft) from a fall hazard—a term that includes skylights and sloped glazing. A façade should be served by a system of roof davits spaced no more than 3.7 m (12 ft) apart to allow support of powered platforms and lifelines, and located so the ropes should not turn more than 75 degrees from the façade plane.

A façade stabilization system should be provided on buildings higher than 39.6 m (130 ft) to restrain lateral movement of the equipment, even though a high-rise may be successfully served by a road crane. A simple one would consist of window-washing pins spaced 15 m (50 ft) apart; a sophisticated system includes a tie-in guide rail (i.e. mullion track).

This author once inspected a 213-m (700-ft) high-rise façade from a corner swing stage, when a sudden gust of wind swirled the platform 180 degrees, hitting and damaging a perpendicular curtain wall of the inspected building. The power cables, motor ropes, and lifelines twisted and tied together. This accident would not have happened if the façade stabilization system was used.

All equipment and anchorage are typically specified as delegated design items, but they need to be properly co-ordinated with the remainder of the design, most notably with a structure and a water-resistant layer of roofing. This author typically advises architects in the design stage to draw a roof plan and co-ordinate all the necessary components likely to be present. These include:

• roofing slopes;
• drains;
• scuppers;
• control joints;
• movement joints;
• hatches;
• mechanical equipment with supports;
• ducts;
• parapets;
• electrical trays and equipment;
• antennas;
• lightning protection rods and lines;
• low-voltage systems;
• rails;
• ladders;
• fall-arrest systems; and
• storage zones for heavy equipment.

Safety issues aside, lack of co-ordinated design may produce a mess on a roof—the very portion of the building shielding it from elements.

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Making choices
From a designer’s perspective, façade access can be roughly classified as proactive and reactive. The latter includes all portable equipment, such as:

• aerial platforms;
• truck cranes;
• parapet hooks;
• counterweighted outriggers;
• ladders;
• boatswain’s chairs;
• supported scaffolds; and
• powered platforms.

It is assumed they can be rented out and brought to the site by a service contractor.

Proactive measures include all permanent anchorage and equipment and can be further divided into standard and dedicated systems. Myriad manufacturers provide standard systems at differing levels of utility, ranging from simple loop davits and guards to house cranes. The dedicated systems are custom-engineered to respond to a challenge created by a specific building—gantries, for instance, are almost always created for safe access to a specific bridge or a skylight (Figure 5). Vertical gantries are a very effective means of wall access, coupled with recently-in-fashion architectural accent bands that can be engineered to serve as horizontal rails.

The need for access anchors and tie-offs typically arises unless all façades are accessible by portable off-the-street equipment and the roofs are free from any fall hazard (e.g. fully surrounded by tall parapet walls). The choice of equipment and anchorage is up to the owner, as it is mainly a financial dilemma of weighing the initial cost versus the long-term one over the building lifecycle. Smaller buildings inaccessible from any driveway (as is often the case with courtyards and monumental lobbies) may also require dedicated provisions for access.

There are boom lifts and truck cranes that can reach above 39.6 m (130 ft) at a high rental cost. The interior façades can be frequently accessed by aerial platforms, providing the doors, elevators, and corridors on the way have sufficient size and capacity to allow for transportation. For situations where permanent equipment is the only means of access to the façade (e.g. buildings taller than 91 m [300 ft]), an architect should provide a design solution co-ordinated with structural, electrical, and façade engineering.

These dedicated, permanent solutions are characterized by a higher initial cost and hard-to-calculate return on investment (ROI). Every project is different. Most glass manufacturers require frequent washing of window glass—about every three months—to keep the glazing free from corrosive residues. As-needed repairs may turn out to be required more often than initially expected. The duration of work may extend beyond initial expectations. This author has heard the George Washington Bridge connecting New York and New Jersey needs to be repainted only every two years—but since the repainting process takes two years, the suspended gantry underneath the bridge is operated on an ongoing basis.

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Important long-term consideration is the downtime of crews performing the work. It is not uncommon for a building to have only two dedicated davit arms that must be relocated by hand, requiring several people to lift. Every time a scaffold finishes a drop, the crew needs to move the arms and reels of cable from one socket to another, as opposed to having two spare davit arms simultaneously installed on the next drop. Quick and constant façade access would reduce both schedule and budget uncertainty due to the weather.

In other instances, the nearest electrical outlet may be too far away for the powered scaffold, which typically needs a three-phase 230-V supply. A dedicated, splash-proof outlet and water bib should be available at strategic locations, serving roofs and façades.

Another important consideration is ease of use. A worker who needs to detach and tie his or her lanyard repeatedly is not only left without protection while doing so, but is also less productive than a worker able to rely on a building’s monorail system, moving a trolley along the rail (Figure 6).

Among the dedicated solutions, the most economical solution is a single BMU. These units require a contiguous, dedicated perimeter of roof or parapet wall close enough to at least one spot near the podium in such a way that it is possible to park the platform with some access to and from a public road (so an average size truck may be loaded and unloaded in front).

Building shapes, sizes, and locations
The obstructions are typically of architectural character. In the past, many designers of high-rises loved fragmented roofs—a low-slope area here, a steep slope there, and a terrace over the way. Today, the current fashion can eliminate roofs, as a curtain wall slopes back into a glazed assembly instead, creating a similar challenge.

The courtyards among the podiums can also be glazed, creating impenetrable and inaccessible zones usually marked by wildlife nests and thick deposits of dirt and debris due to the difficult access for maintenance. The ultimate result is an expensive BMU may serve only a fragment of a building, and an owner (or insurance company) would still need to spend $5000 daily for rental of a hydraulic crane.

Another caveat is the shape of the building façade plan. Deep pockets and narrow recessions in a façade can not only make swinging platforms access impractical or impossible, but also render them out of human reach. This situation may result in construction defects and deferred maintenance.

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Additionally, a frequent picture is a service contractor installing a portable rig in front of a perfectly good in-house access system. Possible reasons include a house rig may be too challenging to work with—it may require, for example, temporary dismantling of façade finishes and relocation by a crew of several labourers (Figure 7). A BMU often requires a skilled and certified operator who would either need to be permanently employed or temporarily hired by the owner or a contractor. A rig like this requires annual inspection and maintenance, which might have been postponed by the owner.

Hazards may be created by the very fall-arrest systems intended to prevent them. For example, there are davits located at the edge of a roof that require a worker to approach them to install a façade fall arrest system, but do not allow for an earlier personal fall-arrest tie-in. They should be protected by a secondary means of fall arrest, which would allow for their approach.

Falls are not only dangerous on high-rises. A few years ago, this author was inspecting more than 40 roofs of a community of low-rise, multi-family, residential buildings in Miami. A 7.6-m (25-ft), extended, portable ladder was the only means of access, there was no lifeline or davits—nothing to protect a worker from a free fall. While walking on one of the roofs, a flat portion of its deck began to collapse. On a close-up investigation, the deck turned out to be rotten.

Low-rise buildings often avoid the scrutiny reserved for taller buildings and are typically void of any safeguards expected in high-rise construction. This often makes them the most dangerous. After all, it does not make much of a difference to fall 7 or 70 m—the result is usually the same.

Conclusion
Façade access, along with the requisite safety systems, is among the items most often overlooked by designers. However, the need for access becomes acutely obvious in the early construction phase; the necessary addition of window-washing equipment comes as a late and unwelcome surprise and plays havoc with design, budget, and construction schedule. Understanding the various BMU and fall-arrest systems is critical for both architects and specifiers.

Karol Kazmierczak, CSI, CDT, AIA, ASHRAE, NCARB, LEED AP, is the senior building science architect and president at Building Enclosure Consulting LLC. The current leader of the Building Enclosure Council (BEC) Miami, he has 16 years of experience in envelope design, engineering, consulting, and inspection. Kazmierczak can be contacted via e-mail at info@b-e-c.info.

Jerzy Tuscher, M.Sc., is the president of Biuro Techniczne Tuscher. He has 34 years of architectural façade engineering experience. Tuscher can be reached at george@b-e-c.us.

Source URL: https://www.constructioncanada.net/danger-overhead-ensuring-future-access-for-the-facade/

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