Home > Articles By Issue > Building Envelope & Exteriors > Article Jan. 2002

When Is A Roof More Than Just A Roof?: A Roof Should Be An Asset, Not A Liability

By Jill Aronson-Korot

The roof is too often neglected until a major problem arises. Once a problem is brought to the attention of the fm, it becomes just another item in the liabilities column of the company ledger. That liability could actually be an asset to the fm and to the surrounding community if it is treated as such.

Preventive Maintenance
According to a recent industry survey, preventive roof maintenance programs can extend roof life by 30% to 60%. Consequently, the first step toward making the roof an asset is preventive maintenance (PM).

John F. Miller, chairman of Tecta America, says, "That is significant to the bottom line for any property owner or manager. If a roof goes unmaintained, fms will pay the price not only for undergoing a major reroofing project earlier than needed, but also for enduring increased emergency calls, as well as the associated expenses and interruptions to their business."

According to Barry Tait of Golden, CO-based Tecta America Corp., age and exposure to the elements invariably cause deterioration and eventual failure of the roof. As a result, implementing a PM program to diagnose major roof problems before they occur is critical to extending roof life, protecting roof warranties, and reducing emergency repairs.

The first course of action, according to Frank Moore, manager of technical services at Cary, NC-based Honeywell Commercial Roofing, is to invite roofing professionals to inspect a facility's roof at least twice each year (once before winter and once before summer). In the event of a severe weather occurance (such as tornadoes, hail storms, blizzards, etc.), an additional professional roof inspection should be conducted. In-house personnel should conduct intermittent inspections to ensure the proper function and longevity of the system.

Bob Lyons, executive vice president of Indianapolis, IN-based New Millennium Roofing, Inc., says fms need to establish a business plan strategy for managing their roof portfolios. "A roof will either be an asset or a liability, depending upon the thoroughness of a company's roof management program (RMP)."

Roof Management Programs
Lyons recommends fms initiate an outline to begin the process of establishing a RMP. These are his suggestions:

• Identify all roofs and note current condition before attempting any repairs.
  
• Develop a database file of all roofs with condition surveys performed on each roof, along with a scale roof plan and photos of the in-place conditions.
  
• Establish a roof condition rating system to help rank and rate roof sections' individual needs when compared to the whole portfolio.
  
• Set roof priorities and budgets as either capital or expense budgets. These budgets should be tangible and realistic, and should be prepared by a knowledgeable party experienced in estimating roofing material and labor costs.
  
• Note that all buildings and roof sections may require different design considerations to match the system design to the roofing need (e.g.–high traffic vs. low traffic, heavy industrial environment vs. warehousing environment, high need for chemical exposure vs. no chemical exposure, etc.).
  
• Consider the different weather conditions that the roof will be exposed to over its lifetime, and select roof systems accordingly for maximum performance.
  
• Work with professional roofing services companies to evaluate all roofs, and develop a life cycle RMP for each one.

Moore says PM of a roof is comparable to the PM suggested for cars. Automotive manufacturers recommend oil changes every three months or 3,000 miles. If a car owner fails to perform regular, inexpensive maintenance, the manufacturer will not be sympathetic to a major malfunction caused by neglect. An $8,000 engine replacement could be avoided by simply performing a $20 oil change at regularly scheduled intervals.

Problems With Ponding
Ponded water (the precipitation that collects atop the enclosed space as a result of improper or ineffective channeling) is one of the greatest nemeses faced by roofing systems. The most effective tool fms have to protect their roofs and defeat ponding rainwater is a proper drainage system.

The first problem ponding water presents is the additional weight added to the roof. Moore states, "Drainage is crucial to any roof for reasons of structural integrity. One inch of water weighs five pounds per square foot of surface area. The weight alone could cause the roof to collapse, whether the water causes damage to the membrane or not."

According to Dan Fiala, senior consultant at Cedar Rapids, IA-based Alan Stevens Associates, Inc., the water poses a second serious problem: degradation. "Water, over a period of time, will, to some degree, degrade virtually all building materials, including the roof," says Fiala. "Therefore, it is very important to keep water from sitting on roofs for extended periods. One of the best ways to protect a roof and extend the longevity of a roof system is through proper roof drainage."

Fiala further states,"Ponding water will accelerate the degradation of a roof system, because it could cause the membrane itself to degrade or the seams to fail. Furthermore, [and consequently,] ponding water increases the risk of leaks, because the water remaining on the roof surface will continually enter through the damaged area until the pond is gone."

Unfortunately, asphalt roofs are particularly vulnerable to the effects of ponding. Collection and evaporation cycles accelerate the degradation of the asphalt, because the sun emits ultraviolet radiation, which chemically degrades asphalt through photo-oxidation. The end result is the migration of asphalt by-products to the surface of the roof membrane. These by-products then harden and are washed away, exposing a new surface layer to the photo-oxidation cycle.

In the summer, roof surface temperatures in ponded areas and dry areas can differ by as much as 60ûF, Fiala claims. This extreme temperature difference results in elongation and contraction of the roof membrane, which can create membrane wrinkles and reduce the tensile strength of roofing felts to less than 20% of their original strength. This combination of movement and reduced strength can increase the likelihood of membrane splitting and cracking.

Ponding water may also promote unexpected vegetative growth on the roof. The roots of these plants can penetrate the membrane and damage the roof structure. Water entering the facility around the penetrating roots may be slight at first, but once the plant dies or is removed, water entry will increase substantially.

Moore asserts prevention of unwanted plant growth should be part of the PM conducted by in-house staff. Debris collecting in areas of the roof can not be avoided, but since this is where seedlings will take root, these areas should be monitored and examined frequently. (For more about this phenomenon, read "Last Word" in the July 2001 issue of TFM.)

In colder climates, ice caused by ponding can be very damaging. In addition to the added weight that compromises the structural integrity of the roof, the ice can damage the membrane, too. The freeze/thaw cycle of the ice (melting in the sun during the day and refreezing at night) can rip seams, tear flashings, and erode membrane surfaces.

Benefits Of Drainage
Drainage is key to solving these problems. According to information provided by the Denver, CO-based Johns Manville Roofing Systems Group, water standing for more than 24 hours on roof areas is hazardous in the following ways:

• Possible seepage of moisture through the membrane into the roof system, as no multiple or single-ply membrane can be applied over a large area by practical roofing methods with absolute perfection.
  
• Damage to the roof from freeze/thaw cycles during winter months.
  
• Deformation of the deck structure.
  
• Relatively small amounts of moisture beneath the roof membrane reduce the thermal efficiency of both insulation and membrane through repetitive cycles of evaporation, condensation, freezing, and thawing.
  
• Ponding of water on roofs, in areas subject to winter freeze and thaw, can create further hazards. Ice formations move constantly with temperature changes. This movement can "scrub" the roof surface to such an extent that considerable damage to the membrane can result.
• Insufficient numbers of drains or inadequately sized drain leaders may restrict immediate run-off of surface water. In such cases, water may back up under the drain flanges or accumulate on the roof surface to a depth which exceeds the height of base flashings or other perimeter flashings. Overflow through wall scuppers should be considered in areas of excessively heavy rainfall or where delayed drainage is required. Internal drain systems, which provide drainage from the body of the roof, should be planned to ensure drains are located at low areas to facilitate water run-off. All roof decks should be sloped to the drains, or crickets installed to ensure proper drainage.

Johns Manville recommends the following guidelines to assure adequate drainage of roof surfaces:

• Provide maximum number and size drains practical for the roof area, and locate the drains at low areas in the roof system.
  
• Design raised edges and gravel stops by incorporating tapered edge strips at the perimeters when internal drains are employed.
  
• Install drains in sumps to assure drains are below the roof level, or taper the deck or roof insulation to eliminate ponded water at drain locations.
  
• Equip drain outlets with proper strainers to prevent debris from clogging carry-off pipes. Strainers must be maintained to prevent blocking.
• Provide scuppers secured to wood nailers and flashed into the roofing system when interior drains are not used.
  
• Follow the recommendations of local plumbing and building codes for number and size of drains and carry-off pipes.
  
• Drains should be located in every area of the roof, preferably not more than 75' apart, with no leader or carry-off pipe less than 3" in diameter. It is recommended that two drains minimum be installed on any roof area as a safety factor; if one should cease to function, the second drain will be available to prevent excessive build-up of water. Roof areas surrounded by parapets must have through-wall scuppers to allow for overflow in the event drains become blocked.

Fiala concludes, "Whether proactive (with proper roof design during original installation) or reactive (by adding drains, pumps, or an additional surfacing to an already ponding roof), any approach to getting water off of the roof will be beneficial in the long run."

Membrane Selection
According to Moore, any manufacturer will say that no one roofing membrane or system is right for all projects. "One size does not fit all." Fms need to have enough information to make the right call.

"Institutional facilities, for example, tend to be built for the long haul," says Moore. "These are the buildings that are supposed to be around forever, so their engineers design for the longevity. Retail facilities, on the other hand, tend to look for less risk and smaller initial investment." All of this information should be considered in roofing membrane system selection.

According to David Harrison, senior vice president of Wayne, NJ-based GAF Materials Corp., types of roofing systems can be categorized into levels of cost and performance.

EPDM is a popular choice because it is cheap, easy to install, and can be covered with gravel in areas where traffic on the roof is a concern. EPDM membranes are glued to the roof deck, and they are usually black and non-reflective. When maintenance personnel walk on this system, the gravel can cut into the membrane, but it then masks the holes. Damage isn't seen until it is too late.

The next level up includes thermoplastic polyolefin (TPO) and polyvinyl chloride (PVC) single-ply membranes. Both TPO and PVC are heat welded, so there is a reduced chance of having leaks occur in seam areas. Vinyl is usually light colored (grey, white, or tan), so it is reflective and energy efficient. The surface is very strong and virtually puncture resistant. These systems do not require gravel as a buffer, so if there was a hole, it could be seen before too much damage ensued. They also hold up to weather and pollution better than the EPDM.

Level three moves away from the single ply membrane into the realm of built up roofing (BUR) systems. These are multi-layered systems (usually three or four layers in total), so they are redundant. Should the top layer be scratched, knicked, punctured, weathered, etc., there is another layer beneath it that prevents damage to the roof deck below. Should that layer be compromised, there is another layer beneath that, and so on. This gives better protection against high-traffic or extreme weather conditions.

Level four is comprised of modified bitumous systems. Bitumen is the generic term that refers to all types of asphaltic or tar-based membranes that are hot- or cold-applied. Bitumen is usually modified by reinforcing it with glass to increase its weatherability and durability.

Harrison says the best way to increase performance and protection would be a composite system. A combination of a built-up roof covered by a reflective and protective fleece-backed TPO would give all of the benefits of the best systems: a weather-resistant, waterproof, durable, low-maintenance, energy efficient, high-performance system.

Some of the factors involved in the selection of a roofing membrane extend beyond the individual physical structure being covered. The environment and the community can also be affected by the decision.

According to Allen Blakey, director of public affairs for the Arlington, VA-based Vinyl Institute, reflective surfaces on tops of buildings can play a critical role in cutting the amount of energy consumed within them.

Blakey asserts temperatures are significantly lower in geographical areas with more vegetation and light-colored, reflective surfaces than in urban "heat islands" caused by acres of dark, asphalt parking lots and black roofs. "In fact," says Blakey, "scientists have found that the air in urban heat islands can be as much as 6ûF to 8ûF warmer than in surrounding areas."

California offers cash rebates to companies that replace dark roofs reflecting less than 30% of sunlight with non-metallic "cool roofs" that reflect at least 65%. The incentives, offered through the California Energy Commission (CEC) Cool Roofing Retrofit Program, apply to low-slope roofs on non-residential buildings that are mechanically cooled in the summer.

While these incentives save money up front, the most significant savings come in reduced energy consumption over years of use. According to the CEC, cool roofs reduce peak electricity demand, reduce cooling energy use, improve building comfort, reduce the heat island effect, and even reduce air pollution.

Additional studies by the Florida Solar Energy Center and the U.S. Environmental Protection Agency (EPA) confirm that reflective roofs made of PVC or other single-ply materials can reduce air conditioning costs by as much as 50%. And cooling demand in the peak hours can be cut by 10% to 15%, reducing demand on the grid.

It has been noted, however, that the energy savings provided by reflective vinyl roofing varies with the building type, level of roof insulation, ventilation rate between roof and ceiling, size and efficiency of HVAC system, and roof solar reflectance.

"Green Roofing"
Making a roof green actually means covering it with vegetation. In contrast to the negative effects of unwanted vegetation sprouting from ponded areas of the roof, green roofs do have significant benefits. Green roofs improve the energy efficiency of buildings, enhance the look of urban rooftops, and promote healthier air in such areas.

Bill Woodring, director of contractor field services at GAF Materials, recommends green roofs only be applied in new construction or in reconstruction, not in retrofit applications. The project should start with a deck that is structurally sound and strong enough to handle the additional weight (generally, concrete decks are recommended).

The second layer to be applied is the waterproofing layer (usually a TPO or asphaltic roof membrane would suffice). Woodring cautions fms to be certain that the membrane they select has been designed or treated for green roof applications. If it is not, it could be sensitive to chemicals (fertilizers, pesticides, etc.), which could result in the need for the entire garden–trees, shrubs, grass, everything–to be ripped up for repairs to be made and/or the membrane to be replaced.

The next layer to be applied to the roof is the drainage barrier that covers the entire surface of the roof. This not only promotes drainage (much the same as putting gravel in the bottom of a flower pot) at both the soil level and the the waterproofing membrane level, but it also prevents tree roots (should there be any trees on the green roof) from penetrating the roof system. This layer also works as a filter for the drainage system, allowing water to pass through without allowing soil to be lost or debris to clog drains.

Moore says plants, grasses, and flowers are less dangerous than trees and shrubs, because the roots are less destructive and easier to control.

Moore says a roof barrier is the first thing fms should ask about. This product will ensure that nothing penetrates or damages the roofing membrane. It is recommended that fms contact a professional landscaper to determine what foliage should be selected for the project to achieve the best results. (For more on this subject, see "Creating A Corporate Garden" in the September 2001 issue of TFM.)

The greatest disadvantages to having a green roof are costs and maintenance. Fms with a green roof need to have landscaping crews on the payroll in addition to the regular maintenance staff. The only other disadvantage to this concept is that it cannot be retrofitted. An existing facility would need to reconstruct an entire roof deck, not just the membrane–a costly undertaking.

Snow removal is a problem with green roofs. Woodring recommends that the snow not be removed, as some of the soil, vegetation, seed, etc. would be lost in the process. Instead, make certain that the roof structure can handle the added weight, and make sure that the drains are functioning properly.

Woodring cautions fms to be certain to involve the expertise of an architect or engineer who has previous experience with green roofs. This might not be a simple task, as the technique–widely used in Europe–is relatively new to American markets.

What's On Your Roof?
Much the same way an fm has many secondary and tertiary functions, the facility and its roof also serve multiple purposes. Based upon the media chosen to cover it, a roof can provide more than shelter. It can alleviate environmental concerns like heat and smog, it can reduce the amount of energy consumed within the facility it covers, and it can provide its occupants with a place to "get away from it all."

Fms should not think of the roof as something to worry about or something to neglect until it needs to be dealt with. Instead, the roof could be an fm's greatest ally in the war against waste: mitigating wasted space, wasted energy, and wasted money.

–Jill Lori Aronson, TFM New Products Editor (jaronson@groupc.com).