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Re: Wall loading to exist. slab

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Walls which carries more than 100 plf are considered "Bearing Walls" by code definition. And bearing walls require footing by code requirement. 
4" thick slab on grade does not quality as footing. By the way, you are not too clear whether the 780 plf is shear or vertical load. At either case you  should have a footing because you can not embed anchor bolts and holdown anchors of shear walls in the slab.
J. K. Hosseinzadeh, S.E.
Jamkar Engineering                                                                                         
Newport Beach, CA 92660         
 ----- Original Message -----
Sent: Thursday, March 16, 2006 4:34 PM
Subject: Re: Wall loading to exist. slab

        I've seen this done a lot.  Usually it works well but sometimes it does not.
        When it does not work well the reason is usually related to movement (usually settlement) of the slab.  Poor compaction or a swelling clay would make it a no no!
        If the owner wants to gamble (and it's pretty much a willing gamble, I think) it should be clearly established that it's his savings if it works and his loss, (not yours) if it does not.
H. Daryl Richardson
----- Original Message -----
From: Joe Grill
To: seaint
Sent: Thursday, March 16, 2006 11:29 AM
Subject: Wall loading to exist. slab

I am working on a small remodel.  There is a wall that has been shown as a partition wall that I would like to use as a shear wall.  The wall is supported on an existing 4? thick slab.  If the wall carries 780 plf I really don?t think that cutting the slab and adding a footing is required.  If I assume a 45 deg. distribution through the slab and add the thick of the wall (3.5?) the resulting soil pressure is only 810 psf almost half of the 1500 psf that is being used on the project.  The exist. slab is in very good condition.  Is there a reason why this just can?t be done?


Joe Grill


Joseph R. Grill, P.E. (Structural)

Shephard - Wesnitzer, Inc.

Civil Engineering and Surveying

P.O. Box 3924

Sedona, AZ  86340

PHONE (928) 282-1061

FAX (928) 282-2058