Horizontal Wall Cracks

Just recently my husband and I noticed a horizontal crack about half-way through the walls of our home. Almost every wall in the house has the same crack in it. There are a few exceptions,.. but it is definitely there throughout most of the house. The house was built in 1967 and I am assuming that it is drywall. We are on a concrete foundation in the Mojave Desert of California. No basement. We have lived in the home for about 6 years and it just appeared recently. We have been pondering the possible causes and have come up with,.. 1) we recently installed a Swamp Cooler (evaporative cooler)to cut our electric bill from the A/C unit. Possibly the added moisture in the air caused the crack? Or, 2) The Army base nearby doing desert warfare training sometimes uses explosives and we have a lot of loud "booms". It is a hairline crack. Any ideas?? And what about repairs?
Thanks, Laurie
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Just recently moved from Arizona and had similar problem. Caused by water pipe leaking under concrete slab. In your case I would be suspicious that you are allowing the evap cooler to drain too near the slab. If you have "expansive soil" which is a type of clay like in Arizona, it will swell up when water is added. A little fibreglass drywall tape and drywall compound and a fresh coat of paint will hide the cracks.
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snipped-for-privacy@earthlink.net (LJMRDAEF) wrote in message

I'd check doors and windows for changes in ease of opening. That might give an idea of the extent of changes. If door and window frames haven't shifted, the problem is limited to drywall.
If the frames have shifted, it's time to look at slab movement (see expansive clay suggestion).
" horizontal crack about

TB
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Do you have 8 foot ceilings or 9 foot? If the crack is 4 or 4.5' off the floor, then it looks like a sloppy drywall joint job, which is annoying but relatively speaking not much of a problem (of course it will take time and money to fix and repaint.)
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<< Almost every wall in the house has the same crack in it. >>
How far away is the nearest geological faultline? Just curious...
Joe
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