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how to cross existing footing with new footing diytequila 11-20-2006
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Posted by diytequila on November 20, 2006, 12:24 am
Hello, any advice on this is much appreciated...thanks in advance.

Plans for an addition to my home, include crossing an existing stem
wall concrete footing with a new footing near one corner of the
existing structure. I suppose this is to "tie" the new structure with
the old as well as provide a stronger footing support for the new
second story which is over this part of the addition. My question is,
does the new footing simply butt up to the old footing on either side,
or do I need to remove or channel the old footing to allow the new
footing to cross? I hope that is clear to understand.
Other parts of the footing plans call for underpinning the old
footings, and also there are several areas where large pads of concrete
will be underpinning the new footings as well.
I think this footing design is a bit "over" engineered, but maybe its
because there are no steel beams used on this 2nd story addition.

-diytequila


Posted by Alan on November 20, 2006, 2:33 am
This doesn't sound like over engineering to me. I'm a bit confused by
your problem, but the need to underpin an existing foundation can be
considerable if the addition is two stories high. Also, one serious
problem to consider is the need to tie the foundations together such
that cracks don't appear in the drywall later as the new vs old
foundations settle. I have that problem on an addition added years ago
to my house. Both foundations are quite adequate, but we have a
seasonally recurring drywall crack, inspite of fact that no crack
appears in the exterior stucco. The expansive adobe soils on our area
expand as they dry during summer. In a current project, I had to add
three 3' cubed concrete and rebar footings for posts to very large
support beams over a garage space. Originally, the new garage roof
with room in truss design created by the truss company put a very heavy
calculated "point load" on parts of the existing footing, according to
the engineer at the planning department who said was it too much for my
existing foundation that otherwise quite large as it met code for
convention second story construction. So, I had to hire an engineer to
develop a plan that spread the load out. So, the result was cutting
the garage floor, digging big holes, and then filling them with rebar
and concrete. It was a hassle, and the engineer seemed to take
forever, but I don't want cracks in the foundation or uneven settling
that could put the garage door frames out of square--a common problem
with old houses in our neighborhood. I also want solid seismic
stability since we live in California.

diytequila wrote:
> Hello, any advice on this is much appreciated...thanks in advance.
>
> Plans for an addition to my home, include crossing an existing stem
> wall concrete footing with a new footing near one corner of the
> existing structure. I suppose this is to "tie" the new structure with
> the old as well as provide a stronger footing support for the new
> second story which is over this part of the addition. My question is,
> does the new footing simply butt up to the old footing on either side,
> or do I need to remove or channel the old footing to allow the new
> footing to cross? I hope that is clear to understand.
> Other parts of the footing plans call for underpinning the old
> footings, and also there are several areas where large pads of concrete
> will be underpinning the new footings as well.
> I think this footing design is a bit "over" engineered, but maybe its
> because there are no steel beams used on this 2nd story addition.
>
> -diytequila


Posted by Michael Bulatovich on November 20, 2006, 9:21 am

> Hello, any advice on this is much appreciated...thanks in advance.
>
> Plans for an addition to my home, include crossing an existing stem
> wall concrete footing with a new footing near one corner of the
> existing structure. I suppose this is to "tie" the new structure with
> the old as well as provide a stronger footing support for the new
> second story which is over this part of the addition. My question is,
> does the new footing simply butt up to the old footing on either side,
> or do I need to remove or channel the old footing to allow the new
> footing to cross? I hope that is clear to understand.
> Other parts of the footing plans call for underpinning the old
> footings, and also there are several areas where large pads of concrete
> will be underpinning the new footings as well.
> I think this footing design is a bit "over" engineered, but maybe its
> because there are no steel beams used on this 2nd story addition.

Why not ask the designer for clarification?
--


MichaelB
www.michaelbulatovich.ca



Posted by Bob Morrison on November 20, 2006, 10:30 am
In a previous post Michael Bulatovich wrote...
> Why not ask the designer for clarification?
>

Exactly my response.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

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