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Fwd: Re: Monlithic or Two Pour Slab on Grade

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Here in Simi Valley in 1994 (Northridge EQ), many homes actually
separated at the cold joint and the slab slid off the footings.   Repair
costs were of course very high. In Canyon Country and areas of San
Fernando Valley, many foundation anchor bolts failed by breaking out the
edge of the concrete slab.  Most of these appeared to have also been
two-pour slabs-on-grade, with a cold joint.  Again high repair costs. 
My recommendation is either to insist on monolithic, or provide both
edge dowels, bent into the slab and a continuous bar at the edges, tied
to the dowels. These will provide some confinement for the AB's.  Assume
a cold joint separation and design dowels and anchors accordingly.  For
highly loaded anchor bolts, consider a "hairpin bar" around each AB.

Russ Nester
On Wed, 5 Mar 1997 08:59:06 -0800 "Dennis S. Wish PE" <wish(--nospam--at)>
>I need some quick advise on this topic. I designed a custom home with 
>monolithically poured slab on grade. The contractor wants to do the 
>slab as
>a two pour because he feels that it is easier to set and locate his
>holddowns and anchor bolts. 
>I remember some posts regarding problems with two pour slabs and the
>potential for sliding during heavy seismic activity.
>Is a two pour slab still considered a viable construction method. The
>structure is a one story custom home in the Palm Springs area.
>Dennis Wish PE
>PS: I understand about the necessity to assure that my anchor bolts 
>holddowns are properly embedded into the continuous footing of the 

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Date: Thu, 6 Mar 1997 00:28:59 PST
Subject: Re: Monlithic or Two Pour Slab on Grade
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