In many ways, a building is like the human body: If you want it to function properly over the long haul, you have to take care of it with clean fuel, regular maintenance, and the occasional visit to a specialist. And like a body's vital organs, a building's systems are integrated and reliant upon each other to function properly, so it's important to know the basics of how the various systems operate. It also means being able to recognize potential problems early so that they don't develop into something major.
Few parts of a residential building are as important as the roof - it helps maintain the temperature in the building no matter what the thermometer reading says, protects its contents from the ravages of leaks and water damage, and literally keeps the rain off residents' heads. A neglected roof is a liability - it hemorrhages money in the form of constant stopgap repair work, damage to property, and even legal action brought by angry shareholders.
Even with conscientious care and maintenance, however, roofs can be tricky things. As one contractor puts it, "There are two types of flat roofs: the ones that leak, and the ones that will leak." The reasons for this are manifold; unlike pitched roofs, flat roofs - like the vast majority of those found in New York City - are subject to the weight of snow in the winter, big puddles of standing water after rainy weather, direct sunlight nearly every day, damage from residents walking on them, construction debris, and a host of other potential threats.
"Roofs can be punctured or disrupted fairly easily, says R. Neal Eisenberg, preservation and restoration consultant to Garden State Commercial Services, with offices in Manhattan and Bayonne, New Jersey. "Some roof materials can be disrupted by the weight of a footprint."
Most roofs in the city 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.