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Re: Porch Concrete Cracking

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A cause of settlement and cracking of front porches (which we see all too
frequently) is that the builder excavates for the basement/foundation, and
doesn't compact the backfill.  (Or even worse, "water compacts" the backfill
before the floor diaphragm is in place.)

Conrad Guymon, P.E.


----- Original Message -----
From: "Gerard Madden" <GMadden(--nospam--at)mplusl.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, May 30, 2001 6:12 PM
Subject: Porch Concrete Cracking


A buddy of mine bought his house about a year ago and is complaining that
the concrete porch at his front door is cracking. The house was brand new
when he moved into it and apparently others in the subdivision have had the
builder rip up their driveways and sidewalks and have them re-done.

Anyway, he asked me what I thought and if I could right him a letter. I said
hell no to the letter, at least not with my stamp on it (I don't enjoy
getting into pissing contests), but I did say I write him something up
letting him know of the possible reasons for the cracks.

The porch is a 4" step up cast monolithically with a 4-5" slab on-grade
driveway/sidewalk. The porch is a semi-circle in plan. The crack is along
the circumference of the semi-circle at the base of the step about 1 inch
outside of the curve in plan (side walk level- not on the porch). When the
crack reaches the end of the semi-circle, it goes out 45 degrees until it
hits the side of his house.

I suspect they used welded-wire fabric for the reinforcing and did not
provide a curved bar along the circumference of the porch step which
initiated the cracking.

Other reasons I was going to list as possible causes are inadequate
frequency of weakened plane joists, lack of greasing dowels at construction
joints, soil movements, & lack of minimum reinforcing.

If anyone can hazard a guess to the likely cause based on my description or
come up with additional reasons, I'd appreciate it. I told him that
structurally, it is likely nothing to worry about, but the guy did spend 850
grand on a house and he has cracks right at the entrance to the home. Plus,
with the poor reputation of the builder, he is hoping something can get done
to fix it.

Oh yeah, you Texans, that 850k equates to a 4 bedroom, 3000 sq.ft house in
lovely San Ramon, CA. Now you are really jealous aren't you. (grin)

Thanks in advance,
-gerard
San Francisco, CA


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