The roof is, quite literally, a shopping center's crowning glory.

Too often that critical part of the facility receives less attention than it should - occasionally while it's being constructed and frequently once it's in service.

Commercial property roofing specialists, including materials manufacturers, contractors, maintenance professionals and consultants, know that consistent care of a shopping center or mall's roof is critical to maximum life. The roof also provides protection from the dreaded enemy of all building owners, managers and tenants: water, not to mention its sidekicks wind and sun.

So it is something of a paradox that structures of centers or malls may be designed and constructed to last 50 to 70 years, while, according to one source, the likely lifespan of the original roof is one-half that timespan.

Shopping center roofs tend to lead hard lives. Like other roofs, they are exposed to elements that exact various tolls depending on geographic location, weather and atmospheric conditions. But unlike those of private warehouse complexes, shopping center roofs are subject to the changing needs of multiple tenants. They are also more likely to suffer damage from extensive foot traffic, as those tenants' vendors attend to rooftop-mounted HVAC units, satellite dishes, antennae, exhaust fans, security cameras, etc.

Power centers with big-box anchors tied to multiple-tenant strips pose expansion joint concerns. Centers or malls with atria, skylights, decorative roof accents, updated covered entrances, and food courts with elevated roofs also have expanded maintenance and leakage concerns.

Hospitals and manufacturing facilities may be tied for first place in having the greatest numbers of roof penetrations, but shopping centers run a strong second. Each penetration increases the chance of wind to loosen materials, allowing water to seep into a building.

Tenants: tough customers Eleven-year-old Hamilton Place in Chattanooga, Tenn., houses some 160 stores. Gary Reece, operations manager, says each tenant has from one to three HVAC units atop the mall, plus various exhaust fans for bathrooms and kitchens. The mall itself maintains 23 HVAC units, with three new ones on the way.

"We have as many as 30 HVAC companies working on our roof at one time or another," Reece says. "There is someone up there every day."

And that foot traffic, he says, is his biggest problem when it comes to maintaining the ballasted single-ply roof at Hamilton Place. If a maintenance person drops anything, even something as simple as an air conditioning panel, the drop-point could be the beginning of a leak - something Reece won't discover until the next rain.

"We require everyone who goes on the roof to read and sign our rules and regulations," says Reece. "Each company going onto the roof must have an insurance certificate worth $3 million. We even used to require a $500 damage deposit."

The problem is that it is unlikely that individuals who drop a tool or in some other way damage a roof will report the incident.

Reece says another problem is most people take the shortest route to the site of their equipment rather than staying on designated, protected walkways.

Among shopping center tenants, those involved in food preparation may be the most demanding when it comes to roof maintenance and longevity. Blame the national obsession with snacks ranging from french fries to elephant ears and egg rolls.

"Generally speaking, restaurants are the toughest of all on their roofs," says Scott Bieber, vice president of sales, Duro-Last Roofing Inc., Saginaw, Mich. "Their roofs are like elevated bathtubs where ponding water mixed with grease from the kitchen might stand indefinitely."

Many rooftops are hidden from public view by extended walls that serve as parapets, he says. These walls may keep rooftop fans and satellite dishes from the eyes of the public on the street below, but they also serve as the sides to the "bathtub" that Bieber describes, holding water and debris until they succumb to the forces of gravity and find ways into the building.

Most experts are roof-huggers Environmental activists are sometimes called tree-huggers. Professionals in the roofing industry who advocate treading lightly on roof surfaces and giving them regular care and maintenance - that includes the majority of them - are our roof-huggers. As if the plastics and gravel, adhesives and asphalt were animate, they describe a good roof as "healthy" and a bad one as "going sour."

While one roof-hugger referred to outside repair people as "those gorillas," all agreed that a building's operations manager or general manager should severely limit roof access. Anyone allowed on the roof must stick to designated walkways and treat the roof with the greatest respect, they say.

General Growth Properties Inc., the nation's second-largest regional mall owner and manager, is well aware of the need to inspect and maintain roofs. With mall interests in 38 states, the Chicago-based company must rely on inspections by third-party consultants who subsequently file written reports with General Growth.

"We look at life expectancies and warranties," says Brian Griffin, General Growth director of operations. "In some instances we may want an infrared scan, which indicates moisture under the membrane.

"Most roofs have at least some small leakage," he adds.

General Growth regulates pedestrian traffic on its roofs by keeping logs. Persons going out on a roof are required to sign in. Roof traffic is regulated, Griffin says, and users are advised to stay on designated walkways protected by rubber mats or other heavy duty materials.

"Each part of the country has its own problems - freezing and thawing in northern areas, heat elsewhere," says Griffin. "In Hawaii, roofs suffer from ultraviolet rays and from salt in the air."

Elements take their toll Even the most well-constructed and carefully installed roofs develop problems over time. Regular maintenance goes a long way toward keeping a roof healthy longer. Roof life and effectiveness are prolonged by clean drains, water-tight flashing, scuppers to relieve overworked drains following downpours and controlled numbers of perforations.

Alligatoring, oxidation, tar boils and cracked adhesives are significant signs of wear. Uneven or damaged ballast - weight-giving material atop single-ply roofing, such as river-washed stones or pavers - can produce stress, can leave other spots without weight and protection, and can puncture roofing membranes.

At Metrocenter in Phoenix, tenants are required to use the mall's own roofer for any final roof work. The landlord must approve all tenant plans affecting the roof, from the installation of satellite dishes to cell phone antennas, says Steve Conrad, Metrocenter operations manager.

Conrad says weather conditions in the valley where Phoenix lies can be harsh. "Storms are a different animal here," he says. "Rains may be heavy and the temperature could drop 20 degrees afterward."

The 25-year-old Metrocenter mall has a built-up roof that is being repaired/replaced in a rotation fashion, Conrad notes, by doing one section of it every year. "A healthy roof should last 20 to 25 to 30 years," Conrad adds.

In Arizona, where there are months of successive 100-plus-degree days, roof work frequently is done at night.

Dennis Smith, president of Law/Kingdon Inc., an architectural firm in Wichita, Kan., says his firm advises building owners through a suggested facilities management plan.

"We may not have been as good about that as we should have in the past," Smith admits. But now, he explains, "We will help owners set up a roof maintenance schedule, including a monthly checkup and a thorough annual inspection."

Smith also suggests having the roofing subcontractor walk the roof with the facility's maintenance people.

Future Construction Concerns Every developer faces contractor and budget decisions with each new venture. "How much to spend on roofing and the level of quality is a non-ending argument," says Michael Blanchette, vice president, Amtech Roofing Consultants Inc., Dallas, and current president of the Roof Consultants Institute. "An owner who doesn't anticipate having the building in five years won't want to put a lot of money into roofing," he says.

Choosing the right general contractor for a job is the key to its success, most agree. Multiple interviews, on-site inspections of existing work, reference checks, networking and having a sense of compatibility are at least as important as gathering bids.

The lowest bid, several roofing experts suggest, isn't always the best bid. Bids will typically be within 3 to 5 percent of one another. Very high and very low bids are suspect, they advise.

"Low bids may mean poorer installation practices," says a spokesman for Progressive Roofing in Phoenix. "Choose a contractor you feel comfortable with, and you'll be ahead."

Alfred Taylor, a retired shopping center appraiser living in Grosse Pointe Farms, Mich., agrees. "Poor construction is the primary cause of roofing problems," he says.

Architects may be a good source to suggest or specify certain roofing materials. "I prefer a four-ply, built-up roof system," says Craig Wasserman, architect with KA Inc. Architecture in Cleveland, Ohio. Often there are cost issues, he says. In a recent proposal, KA Inc. provided four roofing specs: single-ply and three alternatives.

An experienced building owner may have had problems with a certain type of roofing, yet is hesitant to deviate from the familiar, Wasserman adds.

"We've done shopping centers from Oregon to Maryland," he says. "Each one is different, depending on what owners are looking for in the way of roofing."

Built-up vs. single-ply A built-up roof membrane is a continuous, semi-flexible, multi-ply roof membrane. It consists of plies or layers of saturated or coated felts, fabrics or mats with alternate layers applied in between. Built-up roofs generally are surfaced with mineral aggregate and bitumen, a liquid-applied coating, or a granule-surfaced cap sheet, according to a definition from the National Roofing Contractors Association in Rosemont, Ill. Built-ups are constructed on-site, and they may weigh 4 to 6 pounds per sq. ft.

Single-ply roofing refers to a roofing system in which the principal covering is a single layer of flexible membrane, often of thermoset, thermoplastic or polymer-modified bituminous compounds. This system may be ballasted - weighted and protected by river-washed (smooth) stones, pavers or concrete material.

Single-ply has been around since the early 1970s, says Tom Gallivan, marketing manager for Stevens Roofing in Holyoke, Mass. It began to take hold in the market around the end of that decade.

"With single-ply, the cost goes into the material," Gallivan says. "With built-up, the cost is in the labor."

Lightweight, resistant and relatively easy to install, single-ply roofing now accounts for about 50percent of the roofing market, and Gallivan says he sees that market share increasing.

With an eye toward the new millennium, Stevens offers heat-weldable roofing membranes that are available in white. White roofing, Gallivan says, is the wave of the future. By reflecting heat, it significantly reduces a building's energy load.

Single-ply proponents insist this type of roofing system is faster to install, allowing shopping center owners to open their doors - and tenants' cash registers - more quickly. Installation isn't as messy as built-up roofing, they say. The same goes for repair and re-roofing projects.

Duro-Last vice president Scott Bieber says his company takes roofing a step further by pre-assembling roofing panels up to 2,500 sq. ft. in size. This way, says the roofing expert, the maker has greater control over quality, particularly detail areas involving flashing and counter-flashing.

"The three areas of concern in roofing are perimeters, interfaces and penetrations," Bieber says. "We will custom-manufacture flashings for new air conditioning units if they are added to a building."

Second opinions can be key An owner or contractor should not hesitate to call an outside roofing consultant if there is some concern about the quality of a new roof, says Roofing Consultants Institute past-president Robb Smith.

"Poor design and/or poor installation can cause a roof to go sour quickly," Smith says. His company helped avert a disaster in Mississippi a couple of years ago on a unique structure with complex roofing.

"We saw abuse by various trades, and the details were substandard," he says. As is often the case, the building user was anxious to open for business, and, says Smith, the roofing materials manufacturer was ready to issue a warranty.

"Roofing accounts for 5 to 10 percent of total building cost and 60 to 80 percent of litigation," Smith warns. Hire a good contractor and a good consultant, he adds.

"Think of a roof as an insurance policy," adds Ridge Ross, of Westcor Partnership, in Phoenix. "It provides the protection you need."

Recent changes in the roofing industry are translating into cost savings for building owners, and at the same time, benefiting the environment. One example is the industry use of white and light-colored roofing systems to achieve significant energy savings.

A new material known as thermoplastic polyolefin (TPO), an environmentally friendly, single-ply roofing membrane, is presenting itself as a leader in the move toward light-colored or white roofing systems, and TPO is well on its way to becoming officially recognized and mandated within industry standards.

Why the industry urgency to move toward the use of materials such as TPO? Because white roof membranes help reduce both energy requirements and costs for cooling - a reason that sits well with building owners as well. And according to Patrick Downey, CSI, RRC, president of Atlanta's Merik Inc., a roof consulting firm that specializes in energy efficiency, "White and light roof studies throughout the Sunbelt have demonstrated that the savings in hot/warm weather cooling costs more than offset the slight increase in cold/cool weather heating costs."

In contrast, the dark, heat-absorbing roofing of days gone by is associated with a condition known as the "urban heat island" effect and is also linked with hazardous ozone levels. Both of these conditions, coupled with a reduction in natural shading, contribute to a considerable increase in metropolitan area temperatures and, hence, higher energy bills.

To facilitate the move toward mandating white roofing, components of regulations such as the ASHRAE 90.1 Energy Efficient Standards indicate that white roof membranes can now be used in place of additional insulation to reduce cooling energy consumption in some instances. Similarly, in the state of Georgia, precedent-setting white roofing legislation known as the Georgia White Roof Amendment was passed to enforce the same standards. On a nationalscale, the U.S. Department of Energy and the Environmental Protection Agency are now funding efforts to encourage the use of white roofing.

While the white TPO material can help save on building cooling costs, this benefit is just one of the many environmentally sound attributes of the single-ply roofing membrane. From initial raw materials manufacturing to disposal at the end of the system's useful life, TPO offers product features that pose less of an adverse impact on the general environment than other popular single-ply roofing materials.

Following is a quick look at why TPO is an environmentally sound, front-row leader in the move toward white and light-colored roofing:

* TPO's raw materials are created in sealed reactors without production of hazardous by-products.

* TPO's manufacturing process ensures that scraps or reject materials are immediately recycled into the product stream.

* TPO is hot-air welded; therefore, no smoke or strong fumes are produced during application.

* Unlike PVC, TPO contains no migratory plasticizers that leak into the air and/or storm-water runoff.

In addition to its environmental desirability, TPO provides the weatherability of an EPDM and the superior seam strength of PVC - translating into savings in maintenance and repair. The result: more green all the way around.

Explanations are courtesy of the National Roofing Contractors Association and Duro-Last Roofing Inc., Saginaw, Mich.

Alligatoring: the cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks similar to an alligator's hide; the cracks may or may not extend through the surfacing bitumen.

Ballast: an anchoring material, such as aggregate, or precast concrete pavers, which employ the force of gravity to hold (or assist in holding) single-ply roof membranes in place.

Base flashing: plies or strips of roof membrane material used to close off and/or seal a roof at the roof-to-vertical intersections, such as at a roof-to-wall juncture.

Bitumen: a class of amorphous, black or dark-colored cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, soluble in carbon disulfide, and found in petroleum asphalt, coal tars and pitches, wood tars and asphalt.

Blister: an enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between impermeable layers of felt or membrane, or between the membrane and substrate. Built-up roof membrane: a continuous, semi-flexible, multi-ply roof membrane, consisting of plies or layers of saturated felts, coated felts, fabrics or mats, between which alternate layers of bitumen are applied. Generally, built-up roof membranes are surfaced with mineral aggregate and bitumen, a liquid-applied coating or a granule-surfaced cap sheet.

Camber: a slight convex curve of a surface, such as in a prestressed concrete deck.

Cant strip: a beveled or triangular-shaped strip of wood, wood fiber, perlite or other material designed to serve as a gradual transitional plane between the horizontal surface of a roof deck or rigid insulation and a vertical surface.

Deck: the structural surface to which the roofing or waterproofing system (including insulation) is applied. The deck must be capable of supporting the design dead and live loads, including the weight of the roof systems and the additional live loads required by the governing building codes.

Expansion joint: a structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.

Flashing: the system used to seal membrane edges at walls, expansion joints, drains, gravel stops and other places where the membrane is interrupted or terminated. Base flashing covers the edge of the membrane. Cap flashing or counterflashing shields the upper edges of the base flashing.

Roof assembly: an assembly of interacting roof components (includes the roof deck, vapor retarder - if present, insulation and roof covering).

Saddle: a small structure that helps channel surface water to drains, frequently located in a valley, and often constructed like a small hip roof or like a pyramid with a diamond-shaped base (also called a "cricket").

Scupper: a point of drainage, usually a rectangular opening in the wall around a roof. If it is a primary drain, it handles overflow - water not going through regular roof drains either because of volume or blocked drains.

Single-ply roofing: a roofing system in which the principal roof covering is a single layer of flexible membrane, often of thermoset, thermoplastic, or polymer-modified bituminous compounds.

Sump: an intentional depression around a drain.

Thermal shock: the stress-producing phenomenon resulting from sudden temperature changes in a roof membrane when, for example, a rain shower follows brilliant sunshine.

Walk pads: pads that provide extra thickness to protect designated walkways on roofs.