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RE: Two conditions - Differential Settlement

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Differential settlement can be an interesting issue.  I stayed a night at a friend's house in PA recently (a rental, thankfully); the house was probably 70 - 80 years old.  Half the house sat on bedrock, which sloped/dropped down over the footprint of the house such that the other half sat on a 3 or 4 foot thick layer of soil.  The soil had settled a few inches while the bedrock had not settled at all.  Making matters worse, the house was supported on series of small posts under the walls, set on small concrete or rock footings, spaced every 3 or 4 feet.  In some places it appeared that one post might be on rock while the next one, only a few feet away, was on soil and had settled, creating some very abrupt jogs in the walls.  The floors in the house are extremely uneven, and the door frames were noticably crooked in a few places.  The top of one door had been cut at an angle to accomodate the deformed door jam, leaving it a couple inches taller at the hinges than at the outside edge.  It was fairly comical, really, although I doubt it was amusing in the years following the house's construction when things no doubt were going badly and expensively wrong.  It was a very interesting case study in placing parts of a house on different materials with radically different settlement properties.  Something to think about. 
 
Paul Crocker, P.E.
-----Original Message-----
From: Jnapd(--nospam--at)aol.com [mailto:Jnapd(--nospam--at)aol.com]
Sent: Thursday, December 06, 2001 1:56 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Two conditions in residential construction

As far as the rock you encounter....
You  will probably have differential settlments at varios areas around the house.
Slab cracks and possible vertical offsets at the cracks.
Yes to soils report.

Joe Venuti

Johnson & Nielsen Associates
Palm Springs,  CA