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Elevators

Elevators make modern buildings possible. They have also been known to instill all kinds of fears and fantasies, from free falling to getting trapped, inducing claustrophobia and sparking 30-second trysts. We have no data on this latter aspect, but there is much data to support that the first two instances are extremely rare.

The modern elevator is largely a self-contained system, with few of its operating components visible to the casual observer. What then should the average building owner know and understand about elevators to ensure their smooth and long-lasting operation? And what should he or she expect from a typical building inspection?

Types of Elevators

There are two primary types of elevators. Hydraulic elevators were introduced in the 1920s and make up 80% of the elevators in use today. They are typically used in low-rise buildings like multi-family, parking garages and small office buildings. They are generally limited to a 70-foot rise and travel at about 100-150 feet per minute.

Traction elevators were introduced just a little earlier – the 1910s. Geared versions are intended to serve buildings up to 15 stories and travel at 350-500 feet per minute. Gearless elevators are designed for 15-60 floors and travel much faster, at speeds up to 2,400 feet per minute.

New technologies, like permanent magnet machines, are being introduced, but today most of the market consists of either hydraulic or traction elevators.

Controls

Originally, elevators were controlled by switches, relays and solenoids. The electro-mechanical devices responded to input from inside and outside the cab. In recent years, controls have become electronic, which makes them generally more reliable, and they also can be programmed. Programming is intended to reduce passenger wait time and improve overall efficiency.

Preliminary Criteria

When performing a Property Condition Assessment (PCA) for a buyer or lender, the review of elevator systems is generally quite simplified:

  • Does the elevator arrive in a decent amount of time?
  • Is travel time swift?
  • Does the elevator level itself smoothly?
  • Is the travel smooth?
  • Is the cab clean and free of defects?
  • Is the pit (below) and/or equipment room (above) clean and free of hydraulic leaks?

The engineer may also look at the rails that guide the cab, especially in humid climates, because they may rust. He or she may check to see that appropriate safety equipment is present and that inspections are up-to-date.

Design Criteria

Since elevators are observed in place, there is little that can be done to change overall design specifications if they were incorrect to begin with. According to elevator consultants Lerch Bates, some of the more standard design criteria for commercial buildings include the following:

  • Handling capacity should be between 12% and 14% of all tenants.
  • There should be one elevator per 50,000 gross square feet.
  • There should be one elevator for every 2-3 floors served.
  • There should be one elevator for every 250-300 people.
  • Waiting time is a key measure. Generally speaking, it should not exceed 20 seconds.

Unfortunately, in some types of buildings (office, hotel), certain times of day create unusual challenges. That may result in designers incorporating additional elevators and, more recently, more intelligent controls. Other building types (e.g., residential, hospital) have their own requirements.

Long-Term Maintenance Requirements

Elevators are generally long-lived components within most facilities. However, they do require replacement of components over time, and that can be expensive. Many of these components have an estimated useful life (EUL) of 20-25 years according to such industry guides as Marshall and Swift. Key components include:

  • Car structure and cab interior finishes
  • Door operating equipment
  • Controls
  • Rails
  • Hoist equipment
  • Cables/ropes

We have often observed that elevators and related equipment last more than the estimated 20-25 years. However, safety, modernization and, in commercial space, competition all argue for a planned upgrade in that time frame. Cosmetic upgrades may cost as little as $10,000, whereas a major upgrade may cost in excess of $300,000.

Maintenance Contracts

Most elevator manufacturers offer maintenance contracts. These contracts cover the normal servicing of the elevator and related equipment. They often also cover emergency service. Many contracts also include the cost of replacing major components. Although these contracts can be quite expensive, they ensure that upgrades are undertaken when they should be. Be sure to read and evaluate your maintenance contract very carefully so that you fully understand what is covered and what is not.

Accessibility

Elevators, almost by definition, are an important element in making modern buildings accessible. However, something often overlooked is that elevators have their own accessibility criteria. Much of the configuration of an elevator from cab size to control locations to audible signals is driven by ADA requirements. The doors and interior space should meet requirements for entry and circulation. There must be handrails. There must be audible indicators alerting occupants to where the elevator is and the direction it is going. Keypads should include Braille instructions.

Upgrading

Although elevators may remain functional for a long time, there are a number of reasons that upgrades may be required beyond just exceeding their EUL. Control upgrades may be required to meet fire codes. Current codes require that controls be coupled to the building fire alarm system and return to the first floor in an emergency. There are also ADA requirements as discussed above as well as security issues such as emergency phones with dedicated lines. The good news is that often these upgrades provide a valuable source of deductions when a cost segregation study (CSS) is performed. For additional information about these studies, please contact your local Criterium office.

As noted at the beginning, despite rare human phobias and an occasional media report, the modern elevator is extremely safe. According to an article by Nick Paumgarten (The New Yorker, April 21, 2008), an average of only 26 people die in or on elevators each year in the U.S. (the majority of whom were working on them at the time) despite a statistic from Otis Elevator that their products “carry the equivalent of the world’s population every five days.”

Volume 20, Number 2

May 2009

Copyright © 2009

The Engineering Advisor is intended to enhance your knowledge of technical issues relating to buildings.  For additional information on any subject, please feel free to call us.  Our commitment is to provide you with timely, accurate information.