During the past several years, building security for residences and businesses has become an expanding topic. Consumers are demanding improved protection from potential intruders and extreme weather conditions. Door manufacturers are responding by focusing on the locking hardware for their products. While many hardware systems inspire the confidence consumers seek, few non-electrical security products change opinions as dramatically as multiple locking door hardware (MLDH) systems.
What is MLDH?
By definition, MLDH is any system featuring multiple locking point interactions (between door and frame) at various perimeter locations. Despite a recent re-emergence in the United States, MLDH has remained popular in Europe throughout the years. The term re-emergence applies to the U.S. market because many current MLDH systems resemble the old, surface-mounted cremone and slide-bolt systems used on American-made doors during the 1800s. It seems likely that these early locks were either spawned from European designs or brought over directly.
At some point, U.S. consumers changed their attitude toward such locks and abandoned further use and development. MLDH virtually was unchanged and unpromoted in the United States for more than 100 years. Single-point latches and deadbolts became the more common hardwareoffering simpler and more cost-effective choices. Concurrently in Europe, however, existing MLDH designs continued to be enhanced and improved. Perpetual development is a clear and defining factor between modern MLDH as a European versus American product.
In Europe, a breakthrough in MLDH design was achieved when the first centrally-operated systems were introduced about 30 years ago. Centrally-operated systems meant all points of the system would be engaged and disengaged with one lever action. The entire system could be locked with a cylinder. Prior to this development, MLDH was a collection of individually-operated hardware pieces that together comprised the system. Now, all locking points are a complete system.
The modern MLDH system was born.
Centrally-operated MLDH systems were introduced initially to improve the water, air and wind tightness of wood doors. Success was accomplished easily even with the most basic designsnumerous roller pins along the vertical edge. But it was the introduction and rise of uPVC doors that gave MLDH technology its greatest push. Doors made of uPVC materials are not as rigid as wood doors and are susceptible to flexing under wind loads and pressure changes. Over time, the doors warp. With protection from weather, and now door flatness to consider, MLDH designs began featuring locking points at the top and bottom to complement those already along the vertical edge. These top and bottom locking points helped maintain door stability by keeping the corners and horizontal edges tight and flat against the jamb stop. Also, the addition of top and bottom locking points added a level of security that manufacturers eventually would use to promote MLDH to global markets.
Security was not a major concern in Europe and MLDH designs were not influenced by the need for high security. Therefore, most MLDH did not incorporate deadbolts. Some current European models still do not. As crime rates increased, security became a serious consideration in the MLDH used for entry doors. Simultaneously, two MLDH concepts evolvedpatio doors and security doors. Patio door hardware continued to be manufactured with rolling pin locking pointsvarying and increasing the perimeter locations. Security door hardware for main entry doors, however, began featuring deadbolts with a minimum of three locking points. The popularity of MLDH spread across Europe and Asia. Interestingly, each market and door application began identifying its own specific needs. MLDH designs became different as each manufacturer created unique features and designed models to provide specific benefits.
Coming to America
No more than 15 years ago, modern MLDH systems made their first appearance in the United States. Mass-produced, wood patio double doors were the first American-made products introduced with centrally-operated MLDH. Despite weather-resistance, door stability, intrusion security and convenience benefits beyond the capabilities of manually operated, individual locks, MLDH did not gain immediate acceptance with U.S. consumers. Many viewed MLDH as an expensive, complex and unproven substitute for hardware that was familiar and dependable. But door manufacturers (mass producers and custom) realized MLDH could improve their product marketability for both patio and entry doors significantly. Consumers concluded that an investment in a high-quality door should be protected with the most advanced, secure locking hardware available. A sweeping move to MLDH on doors was inevitable.
As MLDH became popular in the United States, manufacturers began developing more doors with MLDH as standard equipment. As use increased, European manufacturers redesigned MLDH systems with added features.
These enhancements included:
Introduction of new bolt configurations (e.g., hook bolts, horn bolts, flipper bolts, etc.);
Deadbolts with more throw distance (3/4- to 1-inch);
90 degree key/thumbturn lock functions instead of the 180 degree-plus previously required with standard profile cylinders; and
Custom-powder-coated and plated faceplate finishes to meet aesthetic desires.
Within the past ten years, several U.S. door manufacturers had developed relationships with Europes established MLDH manufacturers through distributors transplanted into the United States. MLDH businesses grew slowly but steadily as new construction and remodeling surges brought increased door sales. As a result, U.S. door manufacturers sought more unique and convenient features from the MLDH being used on their doors.
New revolutions in the MLDH designs were stagnant as European manufacturers absorbed the request made by U.S. consumers. Manufacturers had to consider global concerns as well, since MLDH was still extensively used outside of the United States. But, once introduced, the changes represented remarkable advancements that offered new levels of security and convenience. Despite these significant improvements, most of these features were not available to markets outside of North America. The needs and applications of MLDH differed regionally (i.e., North America, South America, Europe, Africa, etc.). These new MLDH systems were completely different from any previous versions and had gained identity as an American product. Some examples of these Americanized upgrades were:
Deadbolt located above the operating levers. Previously, the levers were located above the deadbolt;
Nightlatch type (aka semi-automatic) functions allowing deadbolts to be engaged merely by turning the key or thumbturn. Previously, all locking points (including deadbolts) were engaged by the lifting lever;
Spring-loaded shoot bolts that allow systems to be locked even if the shoots are not fully engaged. Previously, shoot bolts had to be fully engaged for the system to be locked; and
The refinement of automatic locking systems that instantly and automatically engage the locking points when the door makes contact with the frame. Previous attempts at automatic MLDH proved difficult to install, adjust and service, with a generally unreliable service life.
Building Ordinances and the Need for MLDH
Increases in new construction and remodeling projects were not the only factors contributing to the rise of MLDH in the United States. Special building ordinances and ratings, namely the California Model Building Security Ordinance (CMBSO) and hurricane codes in Dade County, FL, were also influential.
The CMBSO began as a local construction ordinance in Orange County, CA. A crime prevention task force, in conjunction with Orange County police, initiated and furthered development. The ordinance was intended to improve the forced entry prevention capabilities of exterior door and windows by establishing standard requirements.
Compliance to CMBSO was (and is) the responsibility of the project architect and door manufacturer. One method used to meet such requirements incorporates hardware systems with multiple locks on doors. Since multiple locking points afford additional security, this method increased the likelihood that a manufacturers product would meet the minimum requirements for compliance.
CMBSO is a local ordinance that has gained broad exposure. Although it is not related to Californias building codes, it is estimated that approximately 85 percent of localities in California comply. Whether all doors meeting the compliance requirements used MLDH is unknown. Certainly, though, MLDH has gained increased exposure as a result.
Yet another example of a building ordinance that has contributed to the increased popularity of MLDH has been the hurricane approval rating of Dade County. Developed to establish guidelines for doors and windows that must withstand hurricane conditions, Dade County had worked closely with the American Architectural Manufacturers Association (AAMA) to create compliance testing and approval standards. Manufacturers seeking an approval rating for doors are required to submit a complete product for laboratory testing.
A complete door product consists of the sash and frame with locking
hardware installed. The most extensive and rigorous hurricane testing consists of several
qualification areas for structural integrity including air/water infiltration, cycles,
forced entry and missile impact. Each product that complies with Dade County compliance
must be tested and approved separatelyeven if there are only slight differences.
MLDH systems have been used on doors that have achieved Dade Countys approval rating. This is not to imply that only MLDH will allow a door to pass such testing, but it seems that MLDH increases the probability. This is obvious when considering the missile impact test that requires the launch of a projectile to contact a closed door at various locations. Successful passage of the test requires the door to remain closed during impact and prevail completely functional. With the top and bottom corners opposite the hinge side among the locations directly impacted, locking points at the corners may improve performance. Door manufacturers understandably are reluctant to share designs that have successfully passed the Dade County testing. Nevertheless, as more manufactures seek to gain Dade County approval ratings for their products, more MLDH systems will be contemplated and used.
Undoubtedly, the popularity and needs of CMBSO and Dade County approval system will affect MLDH in the future. So will the newer, upgraded lock varieties, as more appealing options are available. As more architects and millwork shops design custom doors, more MLDH will be specified to maintain the stability and security. Additionally, as more manufacturers incorporate MLDH into their products, more end-use consumers will be enlightened to the benefits and features.
In the United States, MLDH systems will probably never out-sell the standard latches and deadbolts; yet growth in this area is expected to continue. Presently, not everyone is familiar with MLDH. Perhaps this is part of the reason MLDH had not attained the same level of prevalence as in Europe and other regions. Soon, though, every American will at least recognize hardware with multiple locking points. Once that happens, we can begin to ask, Whats your point?
John Imbriale is customer service supervisor for G-U Hardware, based in Newport News, VA. This article was reprinted with permission from Doors and Hardware magazine, published by the Door and Hardware Institute, 14150 Newbrook Dr., Suite 200, Chantilly, VA 20151; 703/222-2010; www.dhi.com
© Copyright 1999 Key Communications, Inc. All rights reserved. No reproduction of any type without expressed written permission.