How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

What is the average life expectancy of a house?

Saturday, July 28, 2018

How long does a home last? 

Because all of the components of a site-built residence can be repaired or replaced, there is no average lifespan for a house. It can last indefinitely if maintenance and replacement are done as needed.   But each component of a house has its own life expectancy that is reasonably well-defined. Plumbing pipe, for example, lasts anywhere from 40 to 80 years depending on the type of pipe used. Stucco is good for about 60 years, an air conditioning system’s estimated life is 15 to 20 years, and brick can still be in good shape for up to 100 years or more. 

   As a house ages, and especially after the first 20 years, a well-maintained home might have brand-new exterior paint and a 5-year old air conditioning system, but need a new roof right away. When evaluating the purchase of an older home, the age of the house itself is not as relevant as the age and condition of each of its major components.

   The average age of the housing stock in the United States has been increasing steadily over past few decades and, according to recent data from HUD’s American Housing Survey (AHS), the median age of an owner-occupied home has jumped upward from 23 years old in 1985 to 35 years old in 2011. Also, two out of five American houses are now more than 45 years old.

  So, with such a large part of the housing market being older homes, it’s especially important to be able to gauge a house’s overall condition based on the age and condition of its components. Your home inspector can help you do this as part of the inspection report, and the age of the component should be given more weight in your analysis than it’s condition in most cases.

   Probably the best way to explain this is to use a comparison to buying a used car—which, incidentally, is also a product that has an average lifespan. Most people know that a 1998 Buick, even if in wonderful condition, does not have as many miles left in it as a 2011 Buick that’s just in good condition. In the same way, if the home you are considering buying has a 20-year old central air conditioning system, and you know that the average lifespan is 14 to 18 years, even if looks good and is performing fine when examined, you should expect to have to replace it soon.

   Condominium association managers develop spreadsheets for large properties with the age of each of the building components, estimated time until required replacement, and projected cost of replacement. This enables them to do regular set-asides for things like a new roof, parking lot repaving or pool refinishing. You can do the same thing in a more casual manner for a home you are considering purchasing, comparing the age and condition of key components between your house choices and coming up with an estimate of repair and replacement expenses for at least the first few years of ownership. 

   Furnaces sometimes die before their time and, occasionally, a roof lasts much longer than anyone expected. So it is a calculation with a margin of error, but still valuable in comparing different house purchase options and projecting future expenses. As an example, let’s say you are buying a 18-year old home that has not had any major component replacements. That means you have a water heater that is 4 years past the end of an average lifespan of about 14 years, an air conditioner that is 2 years past an average lifespan of 16 years, and a roof that is at or near an average lifespan, depending of type of roof covering. While one or two of these items could have a surprisingly long life, it is very likely that within the first two years of ownership one of them will require replacement—and it’s a good idea for that to become part of your evaluation of the property.


   So, if it is possible for a house to last for a hundred years and longer, why do some homes have an early demise? The main reason is functional obsolescence. Between 50 to 70 years old, if no major upgrades have been done, the plumbing and electrical systems need replacement, the doors and windows are deteriorated, the kitchen is battered, and the floor plan and interior details are outdated. A major renovation is necessary to keep the house going forward in time and sometimes no one steps up to take on the project.

    Eventually, houses of an older era become retro-popular and a wave of renovation sweeps through a neighborhood, especially the ones well-located to urban shopping and nightlife. But right now, for example, 1970s era homes with diagonal siding, sunken bathtubs, and exotic rooflines have not caught the imagination of a younger generation of homeowners. Most of them feel more odd than interesting to current sensibilities.

   While many of these homes will find a buyer willing to make a big investment in improvements in the coming years, others will simply become cheap living quarters that eventually cross the line of no return—where the investment necessary to make them acceptable to an owner-occupant is not warranted—and it’s downhill as a rental property from there. 

   If a home becomes abandoned and remains unoccupied for any time longer than a few months, deterioration accelerates. Roof leaks grow mold and wood rot below them. Insect colonies and rodents move in and, while the walls of a concrete block house remain intact years after abandonment, the walls of a wood frame home, along with the wooden roof structure atop all homes progresses towards structural failure.

   For a fascinating, if somewhat depressing, description of the process of slow destruction of an abandoned home, we suggest reading The World Without Us, by Alan Weisman (St. Martins Press, 2007). It’s actually about a larger view of what the earth will be like after the extinction of the human species, based on current scientific knowledge, and includes detailed timeline sequences. 

   At the other end of the spectrum, in a neighborhood with dramatically improving property values the real estate maxim of “highest and best use” for a property may dictate tearing it down to build a new and larger home with more modern amenities. Many of the landmark home designs by architects of an earlier era now exist only as photographs because of the economic impetus to build a more extravagant home on coveted real estate.

    See our blog post How accurate are the average life expectancy ratings of home components? Are they actually useful? to learn more about life expectancy ratings. Also, see our blog post What is the average lifespan of the parts of a house?

  To learn more strategies for getting the best possible home inspection, here’s a few of our other blog posts:

How can I make sure I don't get screwed on my home inspection? 

How thorough is a home inspector required to be when inspecting a house?

Should I trust the Seller's Property Disclosure Statement?

Can I do my own home inspection?

How can homebuyers protect themselves against buying a house over a sinkhole? 

The seller gave me a report from a previous home inspection. Should I use it or get my own inspector? 

    To read about issues related to homes of particular type or one built in a specific decade, visit one of these blog posts:

What are the common problems to look for when buying a 1940s house?

What are the common problems to look for when buying a 1950s house?

What are the common problems to look for when buying a 1960s house?

• What are the common problems to look for when buying a 1970s house?

What are the common problems to look for when buying a 1980s house?

What are the common problems to look for when buying a 1990s house?

What problems should I look for when buying a country house or rural property? 

What problems should I look for when buying a house that has been moved?

What problems should I look for when buying a house that has been vacant or abandoned?

What are the most common problems with older mobile homes?

What do I need to know about a condo inspection?

What are the "Aging In Place" features to look for when buying a retirement home?

   Visit our HOME INSPECTION page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

NOTE: These life expectancies are based on data provided by InterNACHI, NAHB, FannieMae, and our own professional experience. Because of the numerous variables that can affect a lifespan, they should be used as rough guidelines only, and not relied upon as a warranty or guarantee of future performance.

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