The National Association of Home Builders (NAHB) in partnership with Bank of America Home Equity recently completed a study that should be of interest to home owners and home buyers, especially those that are buying or living in homes that have been around for a while.

The Study of Life Expectancy of Housing Components is the result of a telephone survey conducted by NAHB of manufacturers, trade associations, researchers, and others to gather information about how long various components of a house should be expected to last.

Expectations are, of course, only that. They are not hard and fast guarantees of durability or the absence of same. Maintenance is a big factor in determining how long something is going to last and changing technology, styles, or other consumer preferences can impact how long consumers are willing to keep a component if they feel it is outmoded or can afford to replace it.

According to the 2005 U.S. Census Bureau Housing Survey, there are 124.3 million homes in the U.S. housing inventory with a median age of 32 years. About one-third of the homes were built in 1960 or earlier, 10 percent were built in the decade of the 1960's, 20 percent in the 1970s, 13 percent in the 1990's and 13 percent in the first five years of the new century.

Approximately 11.6 million of the total houses are vacant and another 4 million are used seasonally. While two-thirds of units are single family residences and 8 percent are in two-to-four-family buildings.

About 18 percent of the occupied housing is in the Northeast, 23 percent is in the Midwest, 37 percent in the South, and 21 percent is located in the West.

Data from the survey is reported several ways. Some components are given a range of years (aluminum windows are expected to last between 15 and 20 years while wooden windows should last upwards of 30 years.) Others are said to be good for a lifetime or for 100 plus years. There was no explanation for the difference between the latter two descriptors but perhaps the selection was left up to the respondents.

The executive summary is a quick read with a lot of information on life expectancy but the back-up tables are more comprehensive with a few explanatory comments or suggestions for maintenance The survey covers an impressive number of building parts; structural components (engineered lumber, masonry, brick veneers, footings, foundations, and framing;) appliances, cabinets, doors made of a number of materials; heating, ventilation, and air conditioning components; insulation; roofing; even components related to the site and to landscaping such as sprinklers, driveways, tennis courts, and swimming pools.

The authors of the survey are careful to disclaim the study findings as being more than general guidance and that is good advice. Dishwashers, for example, are expected to last about 9 years which means that the 44 year old Kitchen Aid in my kitchen is, as I suspected, continuing to run solely out of spite. Vinyl floors are supposed to last 50 years which begs the question of what they must look like even half-way into their expected life span. Still, most of the information is relevant and helpful, especially where figures are given for different types of the same component ("natural wood floorings have a life expectance of 100+ years while marble, slate, and granite can fail earlier due to lack of maintenance.")

While logic may suggest that the older sub-sample of homes mentioned above would have had many original components replaced that is probably not true where those components continue to function. Therefore, someone looking at a house built in 1975 is probably looking at a lot of 32 year-old parts so this study can be a useful source of information to guide purchases and remodeling decisions. NAHB may not keep this on its website for long so it would be well to print it off and keep it for future reference. The entire report is contained in a 19 page PDF file and is available at