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Re: Cracked cmu basement wall

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Thanks Harold.

I told the owner the same thing yesterday about it being that old and
comparing it to some older churches in the area and how they don't have to
be brought up to code because a crack appears after 80 years. I asked and
he said he needs a statement that the wall is structurally sound so that it
can be sold in the future. I wasn't trying to bring it up to code, but for
me to give an OK for the future of that wall I would like for it to have
some rebar in it. The strongbacks are a good idea also.

I first also thought settlement caused the diagonal crack but the wall is
pushed out of plane about 1/8" at most at the interface of the top side of
the diagonal and the bottom. The top part of the wall above the diagonal is
sticking out.

The owner said the roots were pushing on the wall *at the diagonal crack
location* about 2.5 blocks down from the top of the wall. This is at about
the same elevation as the long horizontal crack where it intersects the
diagonal crack.

The owner states all cracks have definitely formed in the past year or two.
If there was settlement at the corner, I would expect the diagonal crack to
be running in the opposite direction. If it is settlement, I think the wall
would have had to settle toward the middle away from the corner. I think
the long horizontal crack at 2.5 blocks down is flexural from the roots
pushing on the wall. I didn't see a connection from the joists to the top
of the wall at the interior.

Will H

On Thu, Oct 18, 2012 at 12:27 PM, Harold Sprague 
<spraguehope(--nospam--at)hotmail.com>wrote:

> Will,
> Codes change all of the time.  And unreinforced masonry basement walls
> crack.  We can't rehabilitate structures every time there is a change 
> those of us sitting in some hotel conference room.  You could not build 
> the cathedrals of Europe by modern standards, but they work through 
> various mechanisms (another topic).  That is unless there is an 
> earthquake like happens in Italy from time to time.
> 
> Go to the NCMA Tek Notes to look for standards for basement walls, but 
> you will have to go back to old residential codes to determine the 
> standard of care employed at the time of construction.
> 
> I take a different approach.  A crack as you indicated in the photos does
> not look like a flexural crack.  It appears to be more of a settlement
> crack because it is diagonal.  Clays settle in time.  It is just what 
> they do.  A CMU wall on top of a strip footing will settle and will crack 
> unless there is significant steel and bond beams to control the cracks. 
> Most residential codes do not require that volume of reinforcing steel 
> even in modern residential codes.
> 

Truncated 3535 characters in the previous message to save energy.

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