Patios, Plaza Decks & Balconies . . . a Case of Mistaken Identity?
Today, more and more commercial properties such as apartments, hotels, condomiums, and office buildings are being designed with custom features such as balconies, plaza decks and patios. Often, these features are constructed over useable space and thus must also be considered rooftops. Frequently, the construction details and installation of balconies, plaza decks and patios are not scrutinized as closely as those in a roofing assembly, yet they still require properly designed waterproofing/roofing systems to prevent the infiltration of water into the building.
Because we don’t remember to treat patios and the like as the rooftops they are, we often misuse and abuse them. On rooftops, maintenance personnel are encouraged to restrict access to reduce unnecessary foot traffic and potential damage to the roof system. Roofing assemblies are also designed to shed water and thus eliminate ponding. Yet with balconies, plaza decks and patios there is a great deal of pedestrian traffic because tenants and guests entertain on them. Elaborate, decorative planters and the like are also often placed on these areas, complete with sprinkler systems. These things seem harmless, but in actuality, planters, sprinkler systems and even foot traffic are the kinds of things we avoid putting on a roof system since there is occupied space below.
Plaza areas, patios, balconies and the like often have the waterproofing material submerged below the walking surface. The walking surface generally consists of tile, concrete topping, concrete pavers or some other barrier over the waterproofing membrane itself. Sometimes these designs have some form of drainage such as internal drains and/or through-wall scuppers. Other times the design simply allows the water to flow off the edge of the balcony. It seems that designers often fail to remember that these areas are essentially rooftops and thus forget the fundamental elements of roofing such as drainage and long-term waterproofing. Aesthetics often overrule functionality and typically the critical function, long-term waterproofing, is overlooked. In many cases drainage is completely neglected, which leads to premature deck or balcony failure.
Another serious challenge related to pedestrian plaza decks is that they are most often accessed by way of doors with thresholds and will typically have wall systems directly above them. The transition between the vertical wall systems and the horizontal waterproofing system must be designed in a manner so as to prevent the entrance of water into the structure. Thus, every construction detail above the roofline (horizontal plane which is waterproofed below the wall) must be designed to be watertight. Control joints, window/door mullions, thresholds and so forth all must be integrated into the waterproofing assembly to provide flow away from this transition.
One of the most disregarded details is the door and/or window pan, which is typically custom fabricated to fit beneath the door and/or window system. Water damage that results from the lack of these critical details can be unbelievably costly. In the absence of a pan, water accumulates within the deck and begins to damage the substrate below until complete structural failure occurs. The pan resists the backflow and blown-in rain while also providing a catch for any water accumulated above this detail, which gravity forces toward the vertical to horizontal transition.
Even when the door pans have been properly provided, they are sometimes mechanically anchored to the base of the door and/or window system, thus setting up this well thought out detail for failure. This is rather common. Though a property manager or building engineer should not consider this type of detail to be complicated, it is very often overlooked and not addressed properly during the new construction phase. These and similar waterproofing details are usually only discovered once a failure has occurred, thus requiring a leak investigation of the plaza deck.
More specific detailing and coordination of work would go a long way toward preventing these types of water infiltration problems. Property managers clearly bear the burden of maintaining these types of plaza decks and balconies in a watertight condition. When problems arise it is critical to get to the source of water entry in order to design a long-term, yet cost effective, repair. Trapped water or moisture will cause extensive damage to areas that are not normally considered a roof. These areas should be considered what they actually are: rooftops. Truth is, they’re quite challenging rooftops.
About the author:
Paul Beavers is the president and manager of Systems Building Envelope Consultants, Ltd., which provides roof and wall evaluations, draft and issue specifications and installation monitoring on a nationwide basis. His expertise is frequently called upon as an expert witness in litigation as well as for destructive testing and evaluating failed roof and wall assemblies.