Photo courtesy of Green Roof Blocks, St. Louis
Photo courtesy of Green Roof Blocks, St. Louis
Photo courtesy of Green Roof Blocks, St. Louis
Photo courtesy of Green Roof Blocks, St. Louis
Like many in the roofing industry, I followed family members into the trade. I served most of my apprenticeship on a couple huge pitch tear-offs at a St. Louis brewery and an automobile plant. One day, after spending months scooping handfuls of stringy, chewing gum-grade adhesive from buckets and smearing it on a wall that seemed endless, my oldest brother asked me whether I wanted to fill in for a journeyman who was out that day.
I spent the next eight hours tagging a felt layer or, in layman's terms, chasing my brother with a push broom as he quickly walked backward pulling the felt layer. The green smoke from the coal tar pitch formed a cloud that shrouded me the entire day. My lips were burned; my taste buds seemed irreparably damaged; and in the coming days, I would completely shed all the skin from the top of my shirt collar to the base of my hairline. The experience convinced me there had to be a more pleasant way to earn $8.75 per hour.
So when the company owner came to the job site the following day and asked who wanted to learn how to install a new single-ply roof system using a torch, I jumped at the opportunity.
The material was thick and the rolls were heavy, but we soon became proficient installers of the new roofing technology. As demand for this type of roof system increased, so did demand for those of us with the skills to install it. It wouldn't be long before the single-ply revolution would forever change the face of the roofing industry.
Whether you agree with my father that we were better off with coal tar pitch or you embrace the modern roofing era, one thing is certain: Ours is not a static industry.
Some perceive vegetative green roofs (or what NRCA refers to as vegetative roof systems) as the next big wave of roofing innovation, and others are taking a wait-and-see approach; however, the market will undoubtedly create demand for this technology. This is not an unprecedented occurrence. Consider the market's swift move toward white reflective roofing. The roofing industry's response was reluctant acceptance, and reflective roof system installations have reached an unprecedented number. So what will happen when the tide shifts toward vegetative green roofs? Will our industry jump ahead of the empirical data to meet the demand of an ever-fickle market? You bet!
Will we make mistakes? Will there be some high-profile failures? The chances are pretty good. But the market will create the demand, and the roofing industry is uniquely qualified to undertake this new endeavor. To compete in this arena, every other trade must make the trip to the rooftop and contend with such things as unique safety issues and insurance requirements, which we already face on a regular basis.
Several years ago, I had the good fortune to attend the Green Roof Congress in Stuttgart, Germany, where I learned that initially there was somewhat of a struggle between roofing and landscaping contractors to control the vegetative green roof industry. However, the liability of roof leaks rests with the roofing contractor. Therefore, in Germany, primary contracts now are awarded to roofing contractors, and a project's landscaping portion is performed by a roofing contractor or subcontracted to a landscaping contractor. I foresee vegetative green roofing following the same path in the U.S.
Some obstacles
Those specifying roofing projects in the U.S. have become overly dependent on no-dollar-limit warranties, which is problematic for vegetative green roofing. A vegetative green roof is a living system susceptible to many elements that could kill the vegetation and call into effect a no-dollar-limit warranty. No plant provider will issue a warranty for a plant's survival in severe conditions. However, specifications requiring a single-source warranty seem to require such coverage.
Although there are some early players in the vegetative roofing arena who appear to be issuing warranties that extend from the roof deck to the foliage, honoring such warranties has yet to be challenged. It is likely plant failures that would call such warranties into question include contractor liability clauses that exceed those of typical roof system installations.
Also, when does a roofing contractor's liability begin? If all planting work is completed by June but the general contractor does not turn the building over to the owner until September, it is unclear when the one-year warranty for the plants would begin.
Additionally, the vegetative green roof concept has yet to unravel the complexities of building-code compliance. Although various efforts are under way to develop standards, lack of consensus about this new technology is slowing the pace at which regulations can be established. This topic also is addressed in "Code compliance for green roof systems," August 2007 issue, page 30.
So how can you navigate around the pitfalls to tap this new profit source while the roles and regulations still are being established?
Communication
A successful vegetative green roof installation's most critical element is the communication that takes place before signing the contract. I've known salespeople and estimators who avoided discussing such things as payment terms and contract exclusions for fear of killing a deal. However, a contract awarded from an uninformed building owner probably isn't a contract worth winning.
Building owners, general contractors and architects must receive as much information about a project as possible from contractors. Whether through the text in a proposal, the submittal process or the sales meeting, clearly articulated details about each facet of the project will allow all involved parties to form realistic expectations regarding the contract's execution.
Following are some particulars that should be discussed thoroughly before signing a vegetative green roof contract:
Planning
Although planning is a critical component of any roofing project, the addition of vegetative green roofing components means there will be more materials to order, deliver and convey to the rooftop.
Much of the planning is typical of any roofing project: staggering truckloads of material to minimize standing charges, for example, or scheduling a crane to allow for setup before starting work. Regional and seasonal availability of some vegetative green roof components makes the planning process more complex. Plant materials can require a six- to eight-week lead time and have sunlight and hydration requirements before, during and after being planted. Additionally, drainage layers and root barriers may not be locally available and may need to be ordered in advance to allow time for shipping.
Drafting a flow chart showing the sequence of each phase of the project can help your project team stay organized. Sharing the flow chart with suppliers, freight companies, general contractors, other trades and building owners will help them identify their roles in the process, as well as possible conflicts. When the inevitable snafu arises, the flow chart will allow you to more easily make changes and understand those changes' effects on the rest of the process.
During the planning process, you should meet with the local code enforcement official. Until the roofing industry establishes clear requirements for designers and roofing contractors to meet when designing and installing vegetative green roofs, local building departments reign supreme in terms of code compliance.
Gather all the information you have, including construction documents, product literature, samples and your flow chart, and make an appointment to review the project with the official who will be accepting the design and completed work.
You'll find some city building departments will be familiar with vegetative green roofing construction and may even have an established set of guidelines and procedures. For others, planting rooftops with vegetation may be a completely new concept, in which case your meeting may become as much about educating the code official as it is about code compliance—so be prepared to provide articles and Web site links to help with this process. The Chicago Department of Environment's Green Roof and Cool Roof Grants Program Web site, egov.cityofchicago.org, is a good resource.
Also, be mindful that the approval process varies for different cities and building departments.
Execution
Any roofing professional can attest to the reality that exhaustive planning quickly can be thwarted by poor plan execution.
The most frustrating experience for project managers is dealing with forces beyond their control. As a roofing contractor, I can control when my employees arrive. I have less control when working with suppliers and subcontractors, and problems can arise.
A fundamental problem when dealing with late deliveries from suppliers and freight companies is the costs their tardiness can inflict. For example, consider the costs when a delivery from a supplier charging $375 is an hour late and you are paying $225 per hour for a crane and $550 per hour for an eight-person crew.
Although I have no absolute solution for these predicaments, I can share some strategies. When working with suppliers and freight companies, I typically attach my project flow chart to the bill of lading and follow up with a telephone call to be certain each party understands its place in the order of events and the costs associated with failure to perform as promised. I also try to have a contingency plan, such as keeping a small amount of material or vegetative green roofing accessories on hand that would allow my crew to get started if the delivery driver or crane arrive late.
Managing a roofing project means balancing material installation with material flow. For most roofing projects, this is accomplished through strategic material stocking to allow for consumption of stockpiles without double handling of materials.
Vegetative green roof growth media often are too heavy to be stockpiled on a roof. Additionally, vegetative green roof components such as root barriers and drainage layers often are loose-laid and then ballasted by the growth media. Therefore, these materials should flow through the job site much like they would in a ballasted single-ply roofing project. Growth media packaged in large 2-yard sacks can be stocked on the ground and hoisted to the rooftop as the growth medium is gradually applied.
Growth media delivered to a job site in dump truck loads should be scheduled to arrive in staggered deliveries based on the time it takes to get the truck load conveyed to the rooftop and installed. The same equipment and procedures the roofing industry uses to convey and distribute gravel ballast can be used to convey and distribute vegetative green roof growth media.
Because all vegetative green roof components are installed over a finished roof or waterproofing system, care must be taken to protect these surfaces. Although plywood pathways are a popular means of providing protection from foot and equipment traffic, the plywood's corners easily can damage a roof surface. Drain core composite materials typically come in 4-foot-wide rolls that easily can be rolled out to protect roof surfaces and then rolled back up at the end of the day. These materials are much lighter and easier to use than plywood and pose no threat of damage to roof surfaces. Similar to ballasted single-ply roof installation, traffic pathways should be relocated frequently to minimize compression of the roof insulation, which can occur when the same pathway is traveled repeatedly.
Until it is time for the planting work, plants must be stored in sunlight and watered according to their specific hydration requirements. Selection of the propagation method requires striking a balance between the owner's aesthetic requirements, each method's limitations and the project's budget constraints.
Most vegetative green roofs use prerooted young plants called plugs, which are delivered in plastic trays or cells and transferred into the growth medium one at a time. Typical spacing of plugs eight inches apart and staggered will achieve vegetative coverage in one or two years.
Vegetative green roofs also can be planted by broadcasting small pieces of plant material called cuttings, which have a much shorter shelf life than plugs and may need to be kept refrigerated depending on the time of year. Using cuttings to plant a vegetative green roof is most effective in cooler temperatures; cuttings can become increasingly difficult to keep hydrated as temperatures increase.
There also are several prevegetated mat-based products available that are placed over growth media in a manner similar to rolling out sod. These products provide a mature plant canopy at installation and can root into growth media in as little as two weeks.
Finally, modular roof products can simplify and reduce some material handling for a vegetative green roof installation. The roof modules allow easy access to the roof surface and allow the plants to mature off-site. Modules grown off-site can present a more mature level of vegetation at installation rather than maturing on the roof.
Maintenance
For many years, roofing contractors have been encouraging building owners—with limited success—to invest in maintenance to extend their roof systems' service lives. This can be an even more difficult sale regarding a vegetative green roof because of the amount of false information that has been produced in various media outlets. A quick Google™ search, for example, turns up many articles, blogs and videos touting vegetative green roofs as being maintenance-free and never needing water.
In plain terms: There is no such thing as a drought-proof plant. All plants require food and water to survive. Vegetative green roofs are designed to minimize these necessary inputs, of course, but to allow a client to enter into a vegetative green roof endeavor with the expectation that he or she will never need to provide maintenance only sets the client up to be unhappy and the roofing contractor to be liable.
So what are a vegetative green roof's maintenance requirements? Although these can vary somewhat based on the plants used and project location, there are some basic guidelines.
A newly planted vegetative green roof requires some time to establish the plant roots. During this establishment period, the hydration requirements are higher than for mature vegetative roof plants. Newly planted plugs require water about every three days for the first six to eight weeks. Newly applied cuttings require water as often as several times per day until rooted into the growth media.
Once the plants are established, hydration requirements can vary among planting schemes. A scheme made of sedums and succulents can survive up to a month without rainfall. Native species and grasses can require rain more often. With either plant scheme, when rainfall does not provide an adequate level of hydration, it is up to the owner to do so.
Supplemental irrigation can be provided by simple means such as a garden hose or lawn sprinkler or by sophisticated automatic irrigation systems. It is not important how water is delivered to the plants, only that the building owner realizes before purchasing the roof system that there may be occasions when supplemental irrigation must be provided.
In addition to hydration requirements, fertilizers are necessary for establishing vegetative green roof plants. Be sure to select a slow release granular fertilizer so the vegetative green roof does not contaminate storm water exiting the rooftop. Commercially available fertilizers with minimum release durations of 12 months applied in early spring will provide the plants' nutrients for an entire year. Fertilizing vegetative green roof plants for the first three to five years will allow the plants to establish root systems and foliage necessary to become self-sustaining.
Finally, weeds can and will grow in vegetative green roofs. However, because most vegetative green roofs have soil depths shallower than weeds typically find hospitable, many weeds will die when the weather turns hot and dry. Weeds that survive the summer months must be removed from the roof in the fall.
Remember to be careful when using herbicides and pesticides; when used on a shallow vegetative green roof, they can enter roof drains and downspouts in high concentrations.
As the plants mature and cover the growth medium's surface, reducing the fertile surface exposed to weed germination, weeds become less of a maintenance issue. Remove weeds regularly to prevent them from becoming a huge chore.
The bottom line
So what's the bottom line for vegetative green roofs? Do they present a business opportunity? Absolutely. Are there issues that will need to be handled? Undoubtedly. But if the roofing industry doesn't assume leadership in the vegetative green roofing movement, some less-qualified groups of people will step up to fill the void.
By now we've all heard the list of benefits vegetative green roofs hold for the environment. However, for vegetative green roofs to meaningfully affect environmental issues, a significant portion of our built environment needs to be adorned with vegetation. Roofing contractors are uniquely positioned to help make this possible.
Kelly Luckett, LEED AP, is president of Green Roof Blocks, St. Louis.
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