In thinking of houses in light of both recent tornado activity in the Chicago area and reading the book The World Without Us, I was reminded of the importance of the roof for a building. Here is how author Alan Weisman puts it when discussing an abandoned home:

The resin in your cost-conscious choice of a woodchip roof, a waterproof goo of formaldehyde and phenol polymer, was also applied along the board’s exposed edges, but it fails anyway because moisture enters around the nails. Soon they’re rusting, and their grip begins to loosen. That presently leads not only to interior leaks, but to structural mayhem. Besides underlying the roofing, the wooden sheathing secures trusses to each other. The trusses – premanufactured braces held together with metal connection plates – are there to keep the roof from splaying. But when the sheathing goes, structural integrity goes with it.
As gravity increases tension on the trusses, the 1/4-inch pins securing their now-rusting connector plates pull free from the wet wood, which now sports a fuzzy coating of greenish mold. Beneath the mold, threadlike filaments called hyphae are secreting enzymes that break cellulose and lingin down into fungi food. The same thing is happening to the floors inside. When the heat went off, pipes burst if you lived where it freezes, and rain is blowing in where windows have cracked from bird collisions and the stress of sagging walls. Even where the glass is still intact, rain and snow mysteriously, inexorably work their way under sills. As the wood continues to rot, trusses start to collapse against each other. Eventually the walls lean to one side, and finally the roof falls in. That bard roof with the 18-by-18-inch hole was likely gone inside of 10 years. Your house’s lasts maybe 50 years; 100, tops. (19)
The roof helps connect all of the walls and hold the house together and it also serves to keep the elements out from above. Once a hole begins and air, sun, rain, snow, and creatures can get in through the roof, it is just a matter of time before it all starts falling apart. Without a functioning roof, a house may not last long.
Granted, the scenario above discusses when homes are abandoned, an unlikely outcome in many communities. At the same time, this provides a reminder of the need to stay vigilant about roofs. For many homeowners, this is not an easy task: it might be hard to view all of the roof from the ground or from inside the house, accessing the roof might be difficult, and not everyone regularly looks at the underside of the roof depending on the layout of the home and the access.
So when people complain about the build quality of homes or McMansions, I wonder how much they consider the roof. If a mass produced McMansion truly is inferior in quality, would the roof go first or the siding or the walls or the foundation or something else? All could be problematic for the longevity of a home but the roof in particular presents important problems.