Choosing the correct replacement for an aged roof – or identifying the best choice for a new building – is no easy task. The perfect roofing solution for one building may be the worst option for another just down the street. That’s because no two buildings are precisely alike, even if they closely resemble each other. So how do you choose a new roof, given all the choices in the marketplace? You can start by asking a series of questions, before you choose the roof, the roofing contractor or the manufacturer.
1. What is this building’s mission statement?
Before calls are made to roofing contractors or manufacturers, the first item to address is the company’s mission statement as it relates to the building.
Whether you are building new facilities or managing existing properties, you want to be confident that the roofing systems you select deliver the performance you expect. More often than not, the building itself dictates the appropriate roofing system specification.
You need to know as much about the building and its future as possible. Does the company plan to keep this building as part of its real estate assets for the next 10 to 20 years? Are there any plans to expand it in the near future, or to change its use? What are its current and future occupancy, insulation requirements, aesthetic priorities and even the maintenance schedules for rooftop equipment?
These and other mission statement issues will help shape answers to types of roofing to consider and how much of the capital budget is really needed for the job.
Start your questions with what is the building going to be used for. If it’s a spec building, maybe you only need a basic roof. But, if the facility has a special use, such as an airline reservation center with computers in it, then your considerations for roofing options are quite different.
For example, as more companies move toward operating 24 hours daily, seven days a week to satisfy global customers, the data center must never spring a rooftop leak. Water on computer systems generally spells disaster.
A special set of concerns arise for cooling-dominated climates. Does the roof contribute to air conditioning savings and address other key issues? Is it part of a total energy program? There is a growing concern about urban heat islands. Reflective, white roofs have become of interest in those areas for a few reasons. They keep the building cooler, reduce air conditioning costs and also minimize the heat-loading of the surrounding environment.
2. What physical and other elements influence the roofing system selection?
After identifying the goals and mission of a facility, it’s time to evaluate the building itself. You need to begin by looking at the building’s location and the attributes of its surrounding area. You need to examine building codes, weather trends, topography – even the direction the building faces.
The physical characteristics of the building are also crucial: size, shape, design, height and age.
You also need to look at the construction materials used to build the facility and the location of HVAC and fire protection equipment, particularly if either or both of these are partially or totally housed on the rooftop.
When it comes to roof replacement, you need to list the attributes of the roof area itself. It’s best to detail the roof’s size, shape, slope, deck construction, edge detailing, protrusions, rooftop access and existing roofing system. Along with this basic information, you need to find out why the original roof is no longer adequate.
3. What flexible-membrane roofing options are available?
SPRI, the association that represents sheet membrane and component suppliers to the commercial roofing industry, identifies three major categories of membranes: thermosets, thermoplastics and modified bitumens.
Thermoset membranes are made from rubber polymers. The most common is EPDM, often referred to as “rubber roofing.” These membranes are well suited to withstand the potentially damaging effects of sunlight and the common chemicals found on roofs. They are easily identified on the rooftop. Just look at the seams. Thermoset membranes require liquid or tape adhesives to form a watertight seal at the overlaps.
Thermoplastic membranes are based on plastic polymers. The most common is PVC, which is made flexible by adding plasticizers. Thermoplastic membranes have seams that are most commonly formed using heat welding. Most thermoplastic membranes are manufactured with a reinforcement layer, usually polyester or fiberglass to provide increased strength and dimensional stability.
Hypalon thermoplastic begins as a thermoplastic, but cures over time to become a thermoset. Like other thermoplastics, Hypalon materials are heat sealed at the seams.
Another thermoplastic hybrid is thermoplastic polyolefin (TPO), which combines the attributes of EPDM and PVC. TPO membranes do not cure after exposure to the elements and remain hot-air weldable throughout their service life. Most TPO membranes are reinforced with polyester, fiberglass or a combination of the two, but unreinforced TPO membranes are available.
Modified bitumen membranes incorporate the formulation and prefabrication advantages of flexible-membrane roofing with some of the traditional installation techniques used in built-up roofing. Modified bitumen sheets are factory-fabricated, composed of asphalt which is modified with a rubber or plastic polymer for increased flexibility, and combined with a reinforcement for added strength and stability.
4. Which type of membrane and attachment system are best for the building?
Many factors determine the best system for a particular building. For most buildings, there are a number of options and advantages that need to be weighed against the facility’s mission statement. The decision should not be made only on the basis of cost. Other important considerations for membranes are building height, wind exposure, anticipated roof traffic and aesthetics.
The attachment system also depends on the specific building’s characteristics. If the roof deck is able to withstand the weight, a ballasted roof may be the best option. But, if the slope of the roof is greater than 2 inches every foot, this system may not be appropriate. There are other limitations to ballasted systems, such as roof height, proximity to shorelines and other high wind zones, and the availability of ballast.
A steel or wood deck that easily accepts fasteners makes a good substrate for a mechanically fastened membrane. These systems can be designed to provide the necessary resistance to known wind forces and are not subject to slope limitations.
Another alternative is the fully adhered system, in which the membrane is attached to the prepared substrate using a specified adhesive. Depending on the membrane, the adhesive may be solvent- or water-based or asphalt. The finished surface of an adhered roof is smooth.
For those concerned with building aesthetics, colored membranes can make an attractive contribution to the building’s appearance.
5. Does all roofing material delivered to the job site bear the UL label?
If not, specify that it must. This is the only way you can guarantee that the roofing materials installed on your roof are the same materials tested by Underwriter’s Laboratories. Additionally, be sure that the roof assembly you buy or specify, which includes the insulation, is UL-classified and -labeled. Using an insulation other than what was tested with the roofing membrane may void the UL classification. If the UL Building Materials Directory does not list the roofing system you are sold, insist on verification of the classification in the form of a photocopy of the UL’s letter of approval.
Make sure that the product you are getting is the actual product that was tested. You don’t want something that is similar but not equal. Look for the label at the job site and make sure all components of the system were tested together. You want the membrane tested with the insulation that you are using on your building.
6. Does the system require a wind uplift rating?
Wind uplift damage can be extensive and expensive. Accepted as an industry standard, American Society of Civil Engineers Standard 7-95, “Minimum Design Loads for Buildings and Other Structures,” can be used to determine the wind zone of the building. Wind uplift testing, such as that performed at Factory Mutual or Underwriters Laboratories, can be used to determine that the selected roof system meets or exceeds the local wind uplift requirements.
7. How much does the completed system add to the dead load weight of the roof structure?
In choosing any reroofing option, the facility executive should be aware of the load-bearing capacity of the roof deck to make sure the right flexible-membrane option is chosen. In new construction, savings in structural steel can often be achieved by installing one of the lighter flexible-membrane systems.
A ballasted thermoplastic or EPDM roof may require in excess of 1,000 pounds per 100 square feet, while a mechanically attached or fully adhered thermoset or thermoplastic membrane weighs 33 pounds per 100 square feet. A lighter system often allows you to reroof directly over your existing roof, while the heavier ones may require you to tear off the old roof and begin anew. But weight is only one consideration in the selection of a roof membrane and attachment system. A ballasted roof may be the best choice for a given facility. Facility executives must assure that all relevant considerations, including weight, are taken into account in the decision-making process.
8. What are the expertise and financial strengths of the roofing contractor you are considering?
Roofing contractors need to be chosen with great care. The introduction of new roofing materials and application techniques within the past 10 years has led to many changes. A professional roofing contractor should be familiar with different types of roofing systems, to help you make the best decision for your facility, based on your budget.
Ask the contractor if his or her company is a member of a local, state, regional or national industry association. Contractors involved in professional associations generally are better informed on the latest developments and issues of their industry.
Insist the contractor supply you with copies of insurance certificates that verify workers’ compensation and general liability coverages. Check that those coverages are in effect for the duration of your roofing job. If the contractor is not properly insured, your company, as the property owner, may be liable for accidents occurring on the property. Also check your state’s licensing requirements and find out if the contractor is bonded by a surety company.
The installation of different roofing systems varies considerably. Education and training are the most important elements in the installation of roofing systems. Make sure the roofing contractor you choose has had detailed and ongoing training on the system being installed.
One rule of thumb is to find out if the contractor has installed at least 100,000 square feet of the system you want in the past 18 months. Also, make sure the contractor is approved by the manufacturer to install that specific system.
The quality of workmanship is crucial to good roof performance. The National Roofing Contractors Association offers a professional roofing selection guide. In addition, many manufacturers have approved contractor programs with specific qualifications that roofers must complete before approval.
9. What is warranted and by whom?
There are two basic categories of roofing warranties. The contractor’s warranty typically covers workmanship. The manufacturer’s warranty covers at least the materials, though many cover additional items. Even if the manufacturer’s warranty is broad, it will not completely protect you if the roof is improperly installed.
Carefully read and understand any roofing warranty offered and watch for provisions that would void it. For example, it’s nearly impossible to avoid all ponded water. Ponded water can be caused by a clogged roof drain or deflection of the roof deck in between the support columns. Proper roof maintenance can help assure that the warranty remains valid. Be aware of warranty language that voids the guarantee.
Most professional roofing contractors will offer periodic maintenance inspections throughout the year. These inspections help ensure your project complies with the standards specified in the warranty. A typical maintenance program consists of a detailed visual examination of the roof system, flashing, insulation and related components to identify any potential trouble areas.
More important than the warranty, however, is getting the right flexible-membrane roof on your building in the first place. If the roof is correctly designed and installed to meet your facility’s needs, building codes and geographical considerations, and the warranty covers those needs, you probably will be enjoying the benefits of a flexible-membrane roof many years after the original warranty expires.
10. After the roof is installed, what after service and educational programs are available for the facilities management team?
Seminars offered by roofing industry associations like SPRI and manufacturers can be invaluable ways for the building’s roofing team to expand their understanding of commercial roofing system types, installation processes and maintenance considerations. Specific courses are available to help building owners and facilities managers learn more about various roofing systems, materials and components; insulation and accessory products; elements of roof design; contractor selection; warranties and maintenance considerations.
Julian Arhire is a Manager with DtiCorp.com – DtiCorp.com carries more than 35,000 HVAC products, including industrial, commercial and residential parts and equipment from Honeywell, Johnson Contols, Robertshaw, Jandy, Grundfos, Armstrong and more.
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