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RE: Inverted Key vs Starter Wall

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I have used both. We use to use the inverted key method, but I definitely prefer the curb method since I think it is more foolproof. I would insist that if he wants to use the inverted key that he set up a demo to show he can do it correctly before I would approve that method. It is difficult to do properly! You might ask him how he plans to fix it when it leaks.
 
Jim K.
-----Original Message-----
From: Mark Urback, P.E. [mailto:murback(--nospam--at)ehrainc.com]
Sent: Friday, March 31, 2006 11:30 AM
To: seaint(--nospam--at)seaint.org
Subject: Inverted Key vs Starter Wall

Our standard detail for a wastewater tank wall is to provide a starter wall on the slab with a key and PVC waterstop in the joint.  The contractor has proposed an inverted key using 1x4 form attached to the inside of the vertical rebar with a PVC waterstop at the top of the key.  My concern with this method is that the base of the key is at the slab/wall interface.  If the key were to crack at the slab (where the bottom of the joint is located), there would be a potential water path because the water stop would be above the crack.  Has anyone used the inverted key and have there been any problems?

 

Thank you,

 

Mark L. Urback, PE

Assistant Manager

Public Infrastructure Services

Edminster, Hinshaw, Russ and Associates

10555 Westoffice Drive

Houston, Texas  77042

713-784-4500 ofc

713-784-4577 fax

713-202-1579 cell