As I visit various people and examine their homes, I am surprised by how many don't realize that their home has a finite life.  Like people, houses only last so long.  At some point in time, someone will make a decision to tear down the house you live in today.  How long will your house last, and what determines it's life?

A house an be compared to a person in its lifetime.  There are common factors that determine how long it lasts:

1.  How well it is built - like your heredity.  If you are lucky to be born with a strong heart and so on, you will live longer.  If your house is well built, it will last longer.

2.  How well is it treated - like you, if the house is abused during its life, it will not last too long.  If you smoke, drink excessively, do drugs, and eat too much, your life is going to be rather short.  If a house is allowed to get infested with termites, the roof is allowed to leak, and the gutters not maintained, a lot of structural damage will happen over time.

3.  What happens to it.  If you get hit by a car, it can end your life suddenly.  Likewise, if your house gets hit by a tornado, or a tree falls on it, that could be it no matter how well it was built or how well it was maintained.

In general though, it is my observation that house will last 50 to 60 years.  At that point the wood is losing strength, the floors are sagging, and the different bits of abuse and poor maintenance are adding up.  Furthermore, houses are built in styles to match the way people live.  A 50 year old house probably isn't generally suitable for what people want today.  The space layout is totally different and doesn't work with how we live in our current culture.  So, in many cases we see the older homes become "tear downs" if the neighborhood is desirable.  

Here is what I've seen for lifespan for different components of the house:

1.  Foundations:  If the foundation is on good soil  and drainage is maintained, the foundation has an almost indefinite lifespan.  When archaeologists dig up old villages, they find the foundations pretty much in the same condition as when the buildings were built hundreds to thousands of years ago.

2.  Wood framing - If termites get to wood, that's it.  However, if you keep the termites away, the wood framing loses strength in about 50 years as it dries out.  Floors start to sag and creak.  By 100 years, you need to do major reinforcement, so I give this part of the house a 75 to 100 year life span.  However, many of the houses around Atlanta built in the 70's and 80's don't have moisture barriers behind the veneer.  In these houses, the wood framing is already beyond hope due to rot.

3.  Brick veneer -  brick can last a long time.  I had the fortune of seeing the Roman Coliseum a couple of years ago, and it is made from brick.  I was amazed.  It's lasted 2000 years for the most part, which is good considering it made it through barbarian invasions, the Dark Ages, scavengers, and two World Wars.  However, you won't be so fortunate.  In older houses the mortar was mixed by hand, and homebuilders weren't any better back then in spite of the belief that "they don't make things like they used to".  In older homes the brick mortar is failing, and you can figure on about a 60 to 75 year lifespan for many brick veneers.  The mortar is still in good shape at the Coliseum, which says a lot about the Romans.

4.  Heating and Air Conditioning Systems - you will be lucky to get 10 to 15 years out of your system.  I know older homes have ancient furnaces and so on, but they require a lot of repair work, and will cost you more in lost energy due to their inefficiency than if you replaced them.  The mechanical parts just wear out.

5.  Electric - other than the old knob and tube electric, the lifespan is theoretically indefinite.  You have minimal corrosion worries, and there are no moving parts. You can have rodent damage, and damage from DIY projects, but that's it. However, power needs change over time.  Houses built in the 50's rarely had air conditioning, and you didn't have 3 or 4 TV's and computers either.  So, older electrical systems always need an upgrade.  Figure 30 to 40 years.

6.  Plumbing - in older homes you don't have mixing faucets.  The seats of the valves wear out.  Leaks develop in the joints.  Stuff builds up in the pipes.  Toilets in houses built in the 50's are at child height and don't work too well for us older fatter people of today.  Your plumbing fixtures have a 15 to 20 year lifespan.  The pipes can last 75 to 100 years from what I've seen.  The PVC pipes we use now may have an indefinite life depending on how they were put in.

7.  Concrete - while I was in Rome, I had the good fortune to visit the Pantheon.  It has concrete dome that is in amazing shape. No cracks, no cold joints, and no spalling after 2000 years.  I would love to know how the Romans mixed concrete so good, and managed to pour such a structure using pretty much hand tools.  You will not be so lucky.  Exterior concrete has a lifespan of 20 to 40 years.  If you have a concrete driveway, you probably will have to replace it at 30 years of age. 

The Pantheon, that dome is concrete poured over 2000 years ago - your concrete driveway will NOT look this good 2000 years from now. The Romans didn't build it, which is your loss.

 The problem is the quality control of residential concrete.  It's never cured correctly, there is almost never the proper additives placed in it, and the contractors never pay attention to batch-to-placement time.  Further, if the mix is a bit stiff, the contractors just add some water to it.  The result is a concrete driveway, patio, or basement slab that cracks up after a few years.  The Romans avoided this problem by feeding people to lions in the Coliseum if they didn't do the work right, today we don't have that leverage.  

8. Roofs:  Your roof shingles will last 10 to 15 years.  I know you can buy "20 year" shingles, but the warranties are for the material only, and are pro-rated.  So, when your roof needs replacement in 15 years, if you kept receipts, you might get a few hundred dollars off replacing it.  If you let your roof leak, the water damage will affect your wood structure, your finishes, and your heating and ac equipment, hastening the end of your house.  Don't let that happen.

9.  Windows:  The glazing dries out, the frames shrink, moisture gets in the insulated panes.  The lifespan of your windows is about 20 to 30 years.  You can find old houses with the original windows, but they are drafty, and the windows don't open and close like they should.

That is a fairly good summary of what I've seen in examining about 2000 houses.  When you buy a house, you need to take the life of the different parts under consideration, because you might be buying into an expensive proposition that you haven't budgeted for.  Also, you have build in your budget the different things you have to do to maintain and repair the house you have.