Residential buildings are constantly under attack—not by barbarians or marauding bandits, but by a force far more subtle and  insidious. The most tenacious enemy of a residential building is not fire or  structural collapse—though a building obviously should be protected from such catastrophes. It’s water. Left unchecked, simple moisture can quietly infiltrate your building  envelope and wreak havoc throughout.  

 Water damage usually doesn’t have the same dramatic and immediate impact that a fire has on a building, but  the damage caused by water infiltration can be problematic for years, even long  after the initial leak has been resolved. Mildew and mold are common problems  associated with water infiltration in a building, and are not only gross to  look at and tough to eradicate but may also pose health threats to residents.  Over time, water seepage can also erode a building’s components, compromising their structure and necessitating expensive repairs,  according to Henry Cercone, president of Cercone Exterior Restoration in  Manhattan and the Bronx.  

 Because of these potentially devastating effects, co-op and condo boards,  managers and staff members should have a general understanding of the makeup,  maintenance and repair of their building’s waterproofing systems. While a building’s superintendent or property manager should be the first line of defense against  leaks, broken pipes and so forth, board members and residents do play a role in  protecting their building from the ravages of water. Watchful eyes now can save  many thousands, or even millions of dollars, in repair costs later.  

 Keeping Dry

 Every residential building has mechanisms that prevent water from seeping into  the  

 structure but even when these systems are in top condition, they don’t make the building truly waterproof. Rather, they help to make the building  resistant to water infiltration. The degree to which the systems keep the  building dry depends upon how well they were installed, and how they are  maintained.  

 “If you want to begin to waterproof the outside of a building and do it properly,  No. 1, you have to have a specifier who understands what it takes to waterproof  a wall,” says Jerry Yates, president of Yates Restoration in the Bronx. “No. 2, you need the correct materials and No. 3, you need the proper applicator.  And if you do all of those things you can have a building that will stay water  resistant for a good number of years, but nothing is permanent. Even with the  best materials, specifications and contractor, eventually, even the best built  structures can leak. You can in the short term, if things are done properly,  keep water out of the building. Or at least if it gets into the building,  control its flow so it doesn't interfere with the building's occupants.”  

 The roof of a building is the most important linchpin of a building’s waterproofing system, according to Cercone. “The integrity of the building performing in such a way that the building is  tight and water-free will start at rooftop conditions such as sealed roofing  membrane, sealed penetrations and coping covers,” he says. The drainage system for the roof—be it the downspouts on small buildings or the larger, internal roof drainage  pipe known as a “leader” that is found in larger buildings—is also vital in keeping a building dry. Because the leader and downspouts take  water off of a roof when it rains or snows, even a small blockage of that  drainage system can back things up and quickly cause water damage to the  building.  

 Most roofs in the city of the flat roof variety—are made up of several different types of material layered together—like the different levels of a person's skin. Those materials usually include a  substructure of steel under a concrete deck, topped with a "vapor barrier" like  tarred paper. Over that goes a layer of insulation several inches thick, which  is in turn topped by a waterproof membrane—and a decorative decking material, in some cases.  

 The waterproof membrane functions much like the skin's epidermis, serving as the  first—though by no means impenetrable—line of defense against the outside environment. Unlike our skin, however, roofs  can only be expected to last between 10 and 25 years. Residents of buildings  with rooftop gardens should be especially thorough with rooftop maintenance to  avoid water infiltration. Andrew Wist, president of Standard Waterproofing Co.  in the Bronx, emphasizes the importance of cleaning roof drains at least twice  a year.  

 “We do a lot of rooftop gardens,” Wist says. “We come in the spring and check the entire roof for them, especially with the  green roofs because there's a lot of dirt and debris. We have to make sure the  drains are flowing because if a drain gets stuffed up it's basically a  disaster. It becomes a flood in the building.”  

 Flashing on the roof, caulking around windows and doors, and mortar joints in a  brick or stone facade also are integral parts of a building’s weather defense system. Keeping an eye on these various components to ensure  they are properly functioning is critical.  

 While it may seem tough to keep a building free of unwanted rainwater or melting  snow, the task is not so onerous if people keep on top of it. Part of that  regular care should be routine check-ups. His company’s workers inspect client buildings twice a year, in the spring and the fall,  says Wist, and customers are given a report on the condition of the building  after each inspection. “If you take care of the building, you don’t have problems,” Wist says.  

 Don’t Get Soaked

 Water making its way into a building leaves telltale signs for those who are  able to spot them. Aside from obvious water stains on walls and ceiling leaks,  Yates advises residents to watch for bubbling and streaking of wall paint.  Signs of water infiltration might also be evident from outside of the building.  “From the exterior, signs of water can be discoloration of the building  materials, presence of moss or vegetation, peeling paint and cracked finishes  and ceiling joints,” Cercone says. Also be on the lookout for rust, which can quickly destroy  property or create damage that will cost a lot to repair. Rust stains can bleed  through concrete or other masonry building exteriors, showing that metal inside  or attached to the masonry is rusting and, hence, weaker and less structurally  sound than it should be.  

 In addition to creating the need for repairs, water leaking into a building can  make the structure an uncomfortable place in which to live. No resident wants  to have to leave a cooking pot out to catch water dripping through a ceiling,  or deal with incessantly recurring mold. Such conditions can make residents  consider filing lawsuits against the board or others involved in managing the  building. And increased maintenance fees resulting from poor maintenance of a  building and subsequent necessary repairs also might lead some residents to  sue.  

 Water leaking into a building can not only divide residents, it also can  literally divide the building itself. Leaks, if left unrepaired long enough,  can weaken a building’s structure. “If water has been infiltrating a building for a long period of time and people  aren't aware of it, you might start to see the walls start to buckle,” Yates says. “When rust forms on steel it expands. In some cases where it's been a prolonged  period of time and nobody has done any maintenance, you might have to replace  the whole entire structural membrane. That's where rust is really a problem.  Rust inside a building is insidious—it's not obvious—and when it becomes obvious you have a problem.”  

 Repairing such damage can be so costly that it might take years to do the work,  and many years more to pay for it. The water problem often starts with a small  leak or fissure, and gets worse from there.  

 Local Law 11 requires residential structures greater than six stories in height  to undergo a total exterior facade building inspection every five years. An  engineer and contractor will be hired to inspect the outer surface, and the  engineer will write and submit to the board of directors a report on the  building’s physical condition. If repairs are needed, the board might direct the engineer  to write specifications for the work. Then the work will be put out to bid, and  the board will review bids and pick a contractor for the job. If the roof of a  flat-roofed building needs to be replaced, a contractor will likely use a  liquid membrane that is rolled out and cures over time to create a watertight  seal.  

 Costs & Disruptions

 The cost of a major waterproofing project varies, depending upon the size of the  building and the amount of work that needs to be done. The price of a major  waterproofing project for a mid-sized building in Manhattan could start  anywhere between $100,000 and $300,000, but the cost could range up to $2  million, Wist says.  

 How much time such a large project will take to complete depends not only upon  the size and complexity of the job, says Wist, but also on the abilities of the  contractor. “We just finished a job that was an eight-month project on a 40-story residential  building. That was about $900,000. We used 24 men every day,” he says, but other jobs might take more or less time, depending on various  factors.  

 Because so many residential buildings—especially older ones—have masonry walls, some waterproofing work can be quite disruptive to residents’ daily lives. Wall waterproofing jobs, or work on parapets, can be annoying. “Wall repair work is more complicated because there's engineering and steel work  involved with the brickwork. You have to open up the facade, hang scaffolds,  put a sidewalk bridge in front of the building,” Wist says.  

 Experts say above all, the most important aspect of any waterproofing job is  hiring a contractor who has the proper qualifications and resources to complete  the work correctly and efficiently. “Investigate the contractor—go look at his shop to see if he's a real contractor and not just a middleman,” Wist advises. “The real important thing in this day and age is insurance. A lot of contractors  don't have the right insurance because insurance is very, very costly. These  guys have defective insurance. Get references from the contractor. Use a  contractor who owns his own equipment—not a general contractor—you want a waterproofing contractor.”      

 Jonathan Barnes is a freelance writer and a frequent contributor to The  Cooperator and other publications. Editorial Assistant Enjolie Esteve  contributed to this article.