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Old 02-13-2010, 07:09 AM
Location: Tampa FL
5 posts, read 26,440 times
Reputation: 13


After about the first 18 months or so that a home has been built, there is no such thing as "normal settlement" - whatever settling a home is going to do, it'll have done it within about a year and a half of having been built. If cracking or "normal settlement" occurs after the first 18 mts, something else is likely causing it. That something else may or may not be sinkhole activity, but it would be incorrect to simply ignore they symptoms of cracking, etc. It's like having a mole on my skin - chances are it isn't cancerous, but darn it, I'd be stupid to not have my Dr. look at it next time I get a checkup.

Most people incorrectly believe a sinkhole is an actual "hole" that opens up or is likely to open up. While a surface hole or surface depression certainly is a sign of sinkhole activity, most sinkhole activity occurs below ground with few visible, noticeable changes to the surface landscape. And Florida homeowners insurance doesn't cover sinkholes - it covers "sinkhole activity" which impacts a structure (such as a home). If a sinkhole opened up in an empty field, there'd be no insurance for it. On the other hand, sinkhole activity which causes a home to shift (known as "differential settlement") can cause serious structural damage, weaken the home, cause all sorts of other problems, and cause a dramatic decrease in property value - BUT it won't necessarily cause the home to collapse.

Sinkhole activity occurs when rainwater, which is acidic, interacts with the alkline limestone which is under all of Florida. The acidic rainwater causes the limestone to very very slowly dissolve - over hundreds of thousands of years. As the limestone slowly crumbles and dissolves, gravity pulls the soils above the limestone downward into the voids. An easy way to picture it is to think of an hour glass - the hole at the bottom of the hour glass is very tiny. But as sand moves slowly through the hour glass hole, it causes shifting and changes to the surface of the sand - at first slight dips, depressions, waves, etc. Sinkhole activity kinda acts the same way - it's impact at surface level may only be slight at first (inches, or even fractions of inches a year) which may not be easily visible to the naked eye.

These surface changes are not a big deal in an open field. But when it happens under homes, problems can arise - most Florida homes are built using a "slab on grade" foundation. Slab on grade foundations rest the entire weight of the foundation and home on the soil directly beneth the concrete slab. So long as there is dense soil below the slab to support the weight of the slab, this type of foundation works great and is very cost effective (e.g. cheap). However, when sinkhole activity causes part of the soil beneath the slab to drop away (again, even fractions of an inch), differential stress and strain is placed on the slab in a way the home was never built to handle.

As a result, signs of distress begin to occur - such as cracking on the exterior/interior, cracks that look like "stair steps" going up and down, windows and doors that stick or crack in the corners, strange popping noises, higher than usual water and electric bills, or leaky pools and plumbing problems. These are all signs of movement of the home, which can cause serious problems.

John Byrne
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Old 02-13-2010, 10:36 AM
Location: Tampa
1,317 posts, read 1,861,404 times
Reputation: 508
if the whole town of brandon sank into the earth, nobody would miss it.
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