Gardens in the sky

Think of yourself as the NASA space agency. Your mission: To send up a team of complex living organisms-in this case, plants-into permanent orbit in space. Your rewards: An oasis of beauty high above a concrete jungle and an appreciative clientele with an available budget. Perhaps you think this analogy is a little far flung. Nevertheless, after reading a bit more, you're likely to agree that the effort a successful rooftop garden requires is considerable. It involves many more factors than normally encountered "on earth." And even the smallest misstep can have serious and costly consequences.

The bonus to the complexities involved in rooftop gardening is that you'll have little competition. Clients in urban areas are not exposed to the vast network of landscape services that have, for the most part, saturated suburban areas. While it is likely that your existing suburban clients may be bombarded with dozens of fliers in the spring each year touting competing services, this situation rarely happens in the urban environment. In fact, many urban clients would have a hard time finding a landscape provider except, perhaps, in the Yellow Pages. You'll rarely be able to drive by an urban site and see such landscape crews in action, and rarely do building owners have a "neighbor" to ask for a reference. Even more rare is the familiar sight of a landscape truck in the driveway next door.

Another advantage to rooftop gardens is that, because they are isolated sites, you don't have to worry about conformity to the neighborhood as you might with a suburban installation. Each site can be as unique as you or the client wishes. Plus, the urban client is often a newcomer to the landscape process, whether he or she is an individual owner of a penthouse, a building manager who has been assigned a property with rooftop space or a co-op board that manages a common roof area. This lack of experience meansthese individuals often may find they have limited understanding of what they wa nt and even for what to ask. Rarely will the client think ahead about irrigation, lighting and maintenance aspects of a garden. You, then, must show your client that you understand all of these issues, as well as all of the other technical aspects of the rooftop garden.

A new world of details Working on the roof of a building means working in, around, on and with a building. You need to take great care in considering each and every aspect in developing your plan, your estimate and its execution. For example: *Building rules and regulations. These rules and regulations may be clearly enumerated, such as in some co-op/condo by-laws, which deal with almost every conceivable condition, including weight limitations, size of planters, distance from parapet walls, distance from drains, overall planter height, overall height with plantings, spacer size, etc. * Building access. What hours will you have access to the building? Most buildings have general rules, such as days and hours permitted for working. Some "white glove" complexes may restrict hours specifically to 10 a.m. to 4 p.m. during weekdays. Further restrictions may limit noise, etc. * Insurance concerns. What type of insurance do you have? Building owners/manager may require you to show separate insurance certificates naming the building owners, managing agents, clients, etc., as additionally insured parties. Such insurance requirements often have relatively high limits of liability. * City regulations. On the opposite end of the spectrum is the individual building owner who has no rules with which to contend. Even so, don't forget that, in most cases, city rules and regulations apply, and you should be well- familiar with them. For example, consider: Are you installing decking that will raise the roof surface several inches higher and render the parapet walls or railings unsafe? Do codes limit or restrict the use of wood or other combustible materials on the roof? Manufacturers of playground surfaces have begun to develop rubberized tiles that are suitable for rooftop gardens and meet many fire codes.

Logistics of materials handling You have many physical and logistical aspects to consider to ensure the success of a rooftop-gardening project. I can't stress enough how critically you must think about even the most basic project. Consider: * How will you protect easily damaged interior spaces through which you must pass with materials? * What is the size of the elevator you must use? Do you need to reserve it in advance? * What are the size openings of the smallest doors through which you must pass? * What are the most-restrictive turns? * Do you need to use stairs?

You have few options if your plants, planters or hardscapes won't fit through a five-story or higher building. Meet with the building superintendent early on to determine how you can work together and solve any anticipated problems in advance.

In some cases, you can best access materials onto the roof through the use of a crane. Doing so, however, may require special permitting from city agencies. And while a crane can move heavy and bulky materials up to roofs, once up top, you still need manual labor and ingenuity to move and lift large planters and plants into place. A word of caution to those taking to the skies for the first time: Working on roofs high above pedestrians and traffic presents a special safety issue. Any item not properly secured can, with a gust of wind, become a deadly airborne object. Make sure everyone on your crew is aware of this potential hazard.

Finally, study the parking situation at ground level. In highly congested urban areas, you may need to arrive at the site during off-hours to make sure you can find parking and unload.

Get "on top" of roof concerns The rooftop garden requires you to deal with a new set of design issues. The most important consideration before proceeding is protecting the roof on which the garden will sit. Make sure the building owner's architect or engineer carefully inspects the roof. (It's their job, not your's.) Ensure that they have made all roof repairs and that they are adequately waterproofed and insulated before you proceed with your installation.

Because all roofs at some point require inspection and maintenance, make sure your rooftop installation is moveable. Place all planters on synthetic spacers to ensure drainage and reduce the risk of roots growing through planter bottoms and into the roof surface. Avoid bolting planters together through the inner lower walls or running irrigation pipes through the planters. Anchorage of any plants or structures must not penetrate the roofing's waterproof membrane.

Weight is another major issue in rooftop installations. You must know the maximum load-bearing capacity of the roof. Weight and weight distribution takes on special importance, and you should consult an engineer so you won't exceed these loads. In addition, you also must factor in weights with snowloads and people. Keep planters, water and heavy features near load-bearing walls when working with restrictive weight limits. When needed, use a weight-distribution system that spreads out heavy weights over the roof surface.

Environmental factors Environmental factors pose additional problems for the successful rooftop garden. * Planter choices. Choose planter sizes and shapes that will support the plantings in their mature size. For example, avoid vase-shaped or tapered planters with tall trees or shrubs, which will easily blow over in gusty winds. * Soil selection. Soils in planters atop roofs freeze at a faster rate than soils in the ground at the same air temperature. Use insulation board along the interior planter walls to help reduce this. * Irrigation. Irrigation systems are a must on rooftop gardens. Rooftop planters require considerably more water than similar in-ground plantings where subsurface water is normally available. In addition, soils used in rooftop gardens are light and fast-draining, and the plantings are exposed to harsh wind and sun extremes. Finally, soil volume and surface area is greatly restricted in containers. Irrigation problems may also arise because access to rooftop gardens may be limited on weekends when commercial buildings are closed or when owners go on vacation. Hand-watering is too labor-intensive to be practical. Therefore, for most rooftop gardens, you must install low-volume drip systems using emitters or pressure-compensating tubing. Today's professional, battery-operated controllers and valves allow easy control without access to electricity.

More weighty concerns To keep within weight limitations, you must look at every possible combination of materials: * Soils. Standard topsoil-when wet-can actually be heavier than concrete. Lightweight soil mixes are available, however. Look for local suppliers who can supply lightweight mixes in bulk quantities. * Planters. Fiberglass planters are quickly gaining popularity for rooftop installations. They are durable, movable, lightweight and come in an unlimited array of sizes, shapes, finishes and colors. * Drainage. You can use lightweight drainage mats to replace heavy gravel and in situations where planter depth is greater than you need for plant growth. Install Styrofoam insulation board to further reduce weight and mass of the planting medium.

Tender, loving care While rooftop-garden hardscapes require the same basic maintenance found in gardens on the ground, rooftop-garden plantings do require special care. You must apply more frequent feedings to replenish the nutrients in the soil, as well as periodically top up the soil mix to maintain its original level. You also must frequently inspect rooftop-garden areas to keep them clean of leaves and debris, which can clog drains.

To break into this market, you must position yourself in front of the prospective client base. They will be the building-management companies in your area for commercial projects; penthouse and townhouse owners for residential projects; and landscape architects with whom you may already have contact. You also may want to exhibit at a local garden show to display installation suitable for a rooftop garden.

The mission of installing and maintaining rooftop gardens is a challenging one. But it can also be a rewarding one. Just remember to beware of the obstacles and carefully plan your solutions.

Don Sussman is president of Town & Gardens Ltd. (New York, N.Y.), which has won six national awards for rooftop-garden design, including three grand awards from the Associated Landscape Contractors of America.

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