Buying a home is one of the most rewarding, yet potentially costly, life experiences. Construction takes months, sometimes years, and despite the existence of building codes and municipal oversight, mistakes happen. Due to the concealed nature of construction (e.g. important construction elements get closed up by siding, cladding, and drywall), mistakes are hidden and unidentified until the consequences of those mistakes begin to manifest. Water intrusion is the hallmark of construction defects and is almost always an indicator that construction deficiencies exist. Unfortunately, by the time the water manifests itself inside the house, the builder and/or seller are long gone, leaving the homeowner with the expense of performing investigations and subsequent repairs.
So what should a prospective homebuyer look for when evaluating homes to purchase? First, an understanding of basic home construction is necessary. The name of the game is simple: manage water. The intent behind every home design is water management and drainage. Thus, regardless of whether a house is clad with stucco, stone, brick, or vinyl siding, all those systems have to be installed in such a way as to protect the home from the elements and manage any water that gets behind the cladding system. While visual observations from the exterior will not reveal whether necessary drainage provisions exist behind the cladding (i.e. building paper, flashings, and moisture barriers); certain drainage provisions are nevertheless observable. For instance, once water gets behind the cladding it needs to be able to drain back out through small holes at the base of the cladding. Therefore, you should be able to observe spaces or holes around the areas where the cladding terminates at the base of the home.
Additionally, proper slope is extremely important for adequately managing water and preventing water intrusion. Balconies, decks, exterior window sills, decorative trim, and any other protruding surface that has the potential to hold water must be sloped away from the structure to direct water away from the house. Otherwise, water is directed towards the building and will find a way inside.
Any signs of cracking, buckling, bending, or sprawling of any piece of the exterior cladding should be investigated further. While home inspectors are licensed and trained, they are not professional engineers and do not always recognize the existence or potential for construction defects. If you are serious about purchasing a home, hire a professional engineer to perform a visual inspection and draft a report. It will be money well spent and may save you from buying a home that will require expensive repairs soon after you move in.