Roofing Design: Process considerations for smoother installations

by Katie Daniel | February 2, 2017 10:30 am

All photos courtesy RSS Roofing Services and Solutions

by Ted Kinsella
From a design standpoint, there are many different criteria, situations, and owner temperaments capable of affecting the outcome of a roofing installation. Roofing contractors have unique insight into the real-world factors design professionals should consider in order to make the installation as smooth and hassle-free as possible for everyone involved.

There are multiple ways to approach a new or renovated roofing installation, many of which are determined by parties other than the designer. For example, the owner could be familiar with roofing systems and have specific requirements that need to be met during the new installation. On the other hand, some owners rely on contractors or designers to make recommendations that will best fit their needs. Regardless, it is vital for the designer to interface with the owner and contractor throughout the entire process to avoid confusion or miscommunication.

Overview of roofing process
Prior to installing a new roof, a roofing contractor will first meet with the client and perform an inspection to assess the condition of the roof, documenting any problems or issues that need to be resolved. At this point, a contractor will determine what roofing systems the client has used in the past and whether that system meets the needs of an upcoming project. The owner could also recommend a specific assembly, perhaps the same system previously used on the roof.

After this decision is made, the roof designer or engineer needs to be open to discussions with the contractor. It is helpful for the designer to have previous roofing experience so she or he can make recommendations from a design or engineering standpoint the roofing contractor may not have considered.

To make the bidding process as smooth as possible, designers should only request a bid for one type of system, rather than multiple options. This method avoids confusion and lets the owner evaluate the bidders by the same criteria.

Finally, the designer and roofing contractor must work together to overcome any specific issues arising during the installation process. There are many variables and situations that must be considered beforehand to ensure a smooth, problem-free installation and a high-performance final product.

Working with the building owner
Owners of buildings in need of new or repaired roofs are faced with an overwhelming amount of choices. Terms such as adhered, mechanically attached, ballasted, two-ply, single-ply, and membrane thickness may be outside their comfort zone, while there are also considerations for appearance, weather resistance, and maintenance.

The roof designer or engineer must be prepared to guide the owner through this process to ensure all options are considered and the owner is comfortable with their new or repaired roof. Resolving these issues early in the process is very important to ensuring a smooth installation process.

Working with the roofing contractor
When the specific roofing contractor involved with the project is determined, the designer or engineer should ask about examples of the contractor’s work or previous customer testimonials to get an accurate description of the company’s quality of work and past installations. Another important question for the contractor involves production capabilities and the ability to increase production to meet deadlines if needed. The deadline must be coordinated to present a realistic timeline to the building owner.

This author believes that, prior to the installation process, the most important job of the designer is clearly communicating the roof installation specifications to the contractor while answering any questions or concerns. These specifications
will be the central focus of the contractor during the roofing installation, and must be thoroughly reviewed for quality and accuracy before the installation begins. Submittals including materials used for project and shop drawings that show design and detail information will assist contractor/designer communications. Warranty information from the contractor and manufacturer should also be included to address terms and length of coverage.

Walkpad installation around cooling tower.

Variables to consider
As previously stated, roofing projects face a wide range of variables that can affect the final product, particularly during the installation phase. The following paragraphs offer an overview of individual variables designers and engineers should closely consider to ensure a smooth roofing installation on upcoming projects.

Building usage
A primary consideration during the design phase is the intended use of the building. The interior can be crucial in determining the roof system to eventually be applied to the exterior of the building. For example, based on the needs of the facility, the choice of assembly can vary widely between schools, office buildings, hospitals, manufacturing facilities, and warehouses. Considering the end user’s needs during the design phase will help avoid time-consuming issues during the installation process.

Roofing materials play an important role in our environment. Light-colored roofs reduce heat load on buildings, and dark-colored roofs increase heat load. Highly reflective materials return ultraviolet (UV) rays back into the atmosphere, raising overall temperatures as they bounce off the ozone layer. Roof designs incorporating vegetation reduce water runoff into municipal sewer systems, cool the environment, increase roof longevity, reduce energy use, and even calm the soul.

Another variable to consider is whether a particular R-value requirement needs to be met when installing the roof. This measure of thermal resistance represents the ratio of the temperature difference across an insulator and the heat flux through it. The necessary R-value speaks to the energy efficiency of the building; it must be taken into account when planning the roof installation.

Another factor to take into consideration is the possible return on investment (ROI) of installing photovoltaic (PV) panels. The technology offers considerable benefits in terms of energy reduction and cost savings on electricity, but the transition does not always make sense from a financial standpoint, depending of the nature of the building.

Membrane wall flashing being adhered to wall.

System specifications
Several different types of roofing systems can be selected, depending on the needs of the building. Mechanically attached roofs are some of the most common—with this system, the building has a metal deck, then a layer of insulation, and then the roof. In this scenario, the membrane roll is screwed down and successive rolls are added piece by piece. A waterproof seal is then created by welding the membranes together, creating a flat, waterproof surface.

Adhered roofs are different in that they are glued directly to the insulation below them. This method can be more expensive and quite challenging, as large amounts of glue need to be applied at specific times and temperatures. These adhered roofs generally only make sense in very specific climates.

Ballasted roof systems can also be an attractive option due to their quick installation times. They also have one of the lowest life cycle costs of any roof system commonly used in the market. In a ballasted roof system, stones or pavers hold the roofing components in place. Through this process, nearly all the adhesives and fasteners required by other systems are eliminated. This can greatly reduce the cost of the roof.

There is also the question of access—what difficulties are there in getting to the job, and how can they be overcome? For example, powerlines may act as an obstruction or building occupants may need to be taken into consideration. Often, particularly potent odors can emanate from a roofing install, presenting a potential issue for multi-family residential projects, hospitals, and schools.

Roofing crew tearing up concrete, existing roof material, and ballasted ethylene propylene diene monomer (EPDM) membrane from a commercial roof.

The most important element to consider when determining the schedule of a roof install is the expectations of the customer. It is important to set realistic expectations on the front end of the discussions in order to avoid miscommunication and confusion during the installation.

It is critical to set a realistic deadline that works for both the installer and the customer. If uncontrollable factors arise during the process, it is important to keep the lines of communication open with the customer. Setting specific work schedules and meeting agreed-upon deadlines is crucial to a smooth installation.

Special considerations
Other special considerations may need to be worked out and understood before the project begins. For example, if the building for which the roof installation is scheduled has dock doors, it is important to remember they allow wind to enter the building, creating a positive pressure underneath the roof deck. A specific fastening pattern design is required to ensure the roof maintains attachment when the doors are open.

Case study
Located in St. Louis, Missouri, the Washington University School of Medicine is consistently ranked among the top 10 medical schools in the country. The school’s faculty physicians see patients at Barnes-Jewish Hospital and St. Louis Children’s Hospital.

The medical campus was founded in 1891, since expanding to cover nearly 17 city blocks (approximately 66 ha [164 acres]). It is home to several buildings housing laboratories for research, including the Clinical Sciences Research Building, which was constructed in the mid-1980s. In the late 1990s, the school had outgrown the original research building and needed to expand. The faculty and staff decided to expand the facilities and build the North Tower Addition. The addition currently includes laboratory space where scientists in anesthesiology, immunobiology, and cardiovascular research carry out their work.

In order to ensure the faculty’s continued operation in the laboratories and research facilities, the cooling tower roof on the North Tower Addition needed to be fixed. RSS Roofing Services & Solutions was hired to complete the reroofing process. During the renovation, approximately 372 m2 (4000 sf) of concrete pavers, roof membrane, and saturated tapered insulation were removed to expose the structure’s concrete deck. As many of these roof items would be reused, the contractor was responsible for field-verifying reusable components and properly disposing of damaged ones.

After removing the existing roofing materials, new tapered insulation (80-mil) and polyvinyl chloride (PVC) white membrane were installed, along with the existing concrete pavers. After the workers reinstalled the concrete pavers, there was still an issue involving water pooling on the roof in various areas. To fix this issue, a new roof drain was installed. The workers noticed an important stumbling block when first assessing how the job on the North Tower Addition would be completed—getting the materials to the roof would prove to be a challenge because access to the 12th-floor cooling tower was limited. Therefore, all material was brought in carts through the loading dock, up an elevator, and through a penthouse door.

Dealing with waste materials is always an issue when handling a roofing job of any size. Workers needed to ensure all waste materials were transported out of the building in large wheeled bins—similar to the way they had originally taken the materials to the roof.

The roofing system, which carries a 20-year warranty, is performing well and protecting the research facility. The roof and sheet metal labor hours totaled 1643 and included working Monday through Saturday. Thanks to the dedication of the five-man team, the project was completed on budget and within one month.

Many of the approaches to a new or renovated roofing installation are determined by parties other than the designer. Commercial roofing contractors have significant and exclusive understanding of the varying factors design professionals should consider for a seamless installation, which can affect the project’s outcome. These considerations include building usage, climate, efficiency, system specifications, access, and scheduling.

It is critical roofing contractors, designers, and other project team members collaborate with the building owner throughout the entire process to successfully and smoothly install a long-lasting roofing system.

Ted Kinsella is a senior project manager for RSS Roofing Services and Solutions, a design-build roofing contractor covering projects of all sizes for the commercial, industrial, and institutional markets. He has more than three decades of roofing industry experience. A member of both the International Facilities Management Association (IFMA) and the St. Louis Council of Construction Consumers (SLCCC), Kinsella is a past member of the American Subcontractor Association (ASA).He can be reached at[5].

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