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Re: roto-hammers, masonry & city of LA

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I worked on a seismic upgrade of a wood framed, concrete shear wall building
that was later turned into a dance club. The Owner of the adjacent URM
building protested the nightclub on the basis that the dance music caused
vibrations that were weakening his URM building. The URM owner hired both a
structural and acoustic engineer.  Regards,
Jeff Smith
-----Original Message-----
From: wish <wish(--nospam--at)>
To: seaoc(--nospam--at) <seaoc(--nospam--at)>
Date: Monday, January 12, 1998 3:59 PM
Subject: Re: roto-hammers, masonry & city of LA

>Roto-hammers (Impact tools) are expressly forbidden in URM work. The
>should be obvious. Impact tools can damage and loosen surrounding mortar
>capacity and weaken the walls. The code is very specific about the use of
>Impact tools in Unreinforced Masonry. The conventional methods us simple
>rotary drills with carbide or diamond bits to drill holes.
>I have gone as far as to prevent the use of a jackhammer anywhere near a
>wall for fear that it will weaken the bond between the mortar and the
>Dennis Wish PE
>-----Original Message-----
>From: Century West Engineering Corp. <cwec(--nospam--at)>
>To: seaoc(--nospam--at) <seaoc(--nospam--at)>
>Date: Monday, January 12, 1998 11:02 AM
>Subject: roto-hammers, masonry & city of LA

>>we are planning on using a 'helifix' anchor system
>>to retrofit a masonry building. The installation of these anchors
>>requires the use of a pre-drilled hole in the mansory.
>>During conversation with the anchor manufacturer, he stated
>>that the City of LA does not allow the use of impact or
>>roto-hammers on masonry retrofits. -This seems a bit restrictive.
>>Has anyone heard of this? - if so, could you explain why?
>>thanks in advance,
>>Tim Terich
>>Century West Engineering Corp.
>>825 NE Multnomah, Suite 425
>>Portland, OR 97232
>>v(503) 231-6078 f(503) 231-6482