Waterproofing and drainage
Whether preservation, restoration, rehabilitation, or renovation, all plaza projects need to consider water management. Water is the single largest source of plaza deterioration and premature failure—without appropriate provision for water protection and drainage, even the most visually arresting of plazas becomes a source of ongoing problems.
Adequate pitch to drains is necessary for the integrity and longevity of a plaza. Without sufficient slope, water will pond, causing staining, deterioration, safety concerns, and maintenance issues. Depending on the climate, porous paving materials without adequate drainage can retain water and undergo freeze-thaw damage, including heaving, cracking, and displacement. Installation of bi-level drains and appropriate substrate slope facilitate removal of water at the plaza level, as well as at the surface of the waterproofing membrane.
There are many different waterproofing systems, including loose-laid and self-adhered membrane assemblies. Self-adhered systems, which are bonded to the structure below, include cold-applied membrane waterproofing, urethane systems, and hot-applied membrane systems. Loose-laid waterproofing offers the advantage of ease of installation and is forgiving of surface preparation deficiencies; however, a properly installed, fully adhered system prevents moisture from traveling beneath the membrane. Provided the membrane is applied at the minimum thickness recommended by the manufacturer, hot-applied systems may be preferable for continuous plaza waterproofing, due to their resiliency.
For large plaza areas, expansion joints are necessary to absorb expansion and contraction of paving materials and prevent cracking. The design professional should position these flexible joints at the high point on the plaza deck. A watertight connection keeps moisture intrusion from causing building component deterioration and leaks into occupied spaces.
Fixed site features, such as planters or fountains, present additional challenges to drainage and waterproofing. These features may make the drainage pattern more complex; double-checking slope and proper detailing of the system can prevent problems with safety and maintenance.
Anticipating maintenance needs
When redesigning an existing plaza, maintenance demands should be considered as part of the design process, rather than as an afterthought. With advance planning, owners and facility managers can streamline plaza upkeep and reduce the time and expense of future repairs.
In northern climates, snow removal can be a major challenge. Labor, equipment, and materials like de-icing chemicals and sand represent a significant expense. Installing a snow-melt system as part of a plaza rehabilitation project can decrease the effort of snow and ice management over the life of the plaza.
Planting beds add to the plaza aesthetic, but they require thought and care. Selection of plantings should consider the plaza climate, location, and orientation if plants are to thrive. It is also important to consider the cost and labor involved to trim and maintain plants, and to supplement beds with annual flowers, as desired. Each fall, irrigation systems must be winterized and inspected.
Periodically, lighting fixtures will need attention and light bulbs will need to be replaced, so fixtures should be accessible to maintenance personnel. The plaza paving must be able to accommodate aerial lifts if required to service lighting. As days get shorter, timer systems must be monitored to ensure lighting is on and adequate for safety.
Whether plant matter, litter, or accumulated sand and salt, debris inevitably collects in certain locations and needs to be removed. Drains must be routinely cleaned and inspected, and displaced and damaged pavers should be reset or replaced as needed.
A maintenance plan can help keep all these tasks in order. This includes a master list of items for staff that should be done daily, weekly, monthly, seasonally, and annually. For a restored or renovated plaza, the design professional can tailor a maintenance program to meet the demands of specific features, fixtures, and landscape elements.
| SKATEBOARD DETERRENCE |
 Skateboard use on plaza fixtures, including benches and pavers, causes damage and poses safety concerns. Fortunately, there are products and design elements that can be incorporated into the plaza to discourage unwelcome skateboarding activity. Wide joints in the paving system, along with rough pavement sets, deter skateboarders by creating ruts in the surface. Rather than long, smooth edges, it is best to opt for faceted sitting walls, or install edge-applied brackets and obstructions to eliminate clear runs. The configuration of plaza elements may also be arranged to remove potential locations for jumps. Remedial measures for existing plazas need to be undertaken with consideration for aesthetics, as well as compliance with building code and with the Americans with Disabilities Act (ADA). For instance, protruding knobs or blocks installed on handrails may be dangerous to those using the stairs, as loose handbag straps can become entangled in the projecting elements. Before taking action to stop skateboard use, check with a design professional or local building official for guidance. With proactive measures, the broken concrete, skid marks, and crumbling masonry that are the hallmarks of skateboard activity can become a thing of the past, without any compromising of safety or appearance. |
