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Re: Two conditions in residential construction

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A couple of thoughts.

1.    Is it an isolated rock, or is it bedrock?  Is the rock competent
enough and large enough to act as a footing?  If so, it may work.  Is there
someone you could call that has a knowledge of local conditions and can give
you some guidance?

BTW, the 'it's just a single family home' thing doesn't sit very well with
me.  This is the most expensive purchase most families will make.  They
deserve something that won't cost them money later because of poor design or
shoddy workmanship.

2.    A diagonal strap instead of a wood shear wall?  Who are they kidding,
and whose pocket is the money going into?  You are correct about the
connection being the weakest link in this design.  My understanding is that
diagonal strapping is to keep walls plumb during construction, not to
provide lateral resistance to wind and seismic forces.  Even the gypsum
sheating will most likely provide better resistance than this strap.  Here
in seismic zone 3, that substitution wouldn't be permitted by any
knowledgeable (or even half-knowledgeable) building official.

I don't think you're being too conservative, just realistic.

Conrad Guymon, P.E.
----- Original Message -----
From: "Albert Meyer" <Ameyer(--nospam--at)martinaia.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, December 06, 2001 11:33 AM
Subject: Two conditions in residential construction


> I have a few questions regarding some conditions that occasionally come up
> in residential construction that we deal with, and I thought I'd solicit
> some opinions on two of them that have come up recently.
>
> 1) A contactor building a single family home encountered "rock" when
> excavating for a basement foundation, and where we had specified an
> unreinforced 36"x36"x14" concrete footing, a footing with a 10" depth was
> placed.  The wants to know if this is OK.  There is no soils report, as is
> typical for this type of job, and neither he or I know what type of rock
is
> on site.  Many take the attitude that "Oh it's only a single family home,
> it's fine", but what would you do?
>
> Would you say: Hire a geotech to ascertain the allowable soil value,
> use this value to determine what minimum footing size is required and
check
> to see that the footing works for both bending and punching shear?
>
> Or: Remove the existing footing and excavate to the required depth
> and replace the footing?
>
> 2) A contractor has elected to not provide the required shear wall
sheathing
> on some interior unit separation walls of a multi-family dwelling, and has
> instead installed diagonal straps on the walls.  No special nailing or
> attachment at the ends of the straps has been done nor was specified by
the
> "other" engineer they hired to provide them with an alternate detail.  It
is
> my feeling that diagonal straps on wood frame shear walls are not a
> practical solution since even though you can specify a strap that works
for
> the tension load you generally can not provide the attachment required at
> the end of the strap unless you provide a large solid sawn post (not
> typically available in this area) or a Parallam post and or solid blocking
> appropriately fastened into the corners of the shear panel.
>
> Am I being too conservative the issues here?
> Does any one else do diagonal strapping on wood shear walls and if so,
how?
> Any and all opinions are gratefully appreciated!
>
> Albert J. Meyer, Jr., P.E.
> Martin-Espenlaub Engineering
> (215) 665-8570 Tel
> (215) 561-5064 Fax
> ameyer(--nospam--at)martinaia.com
>
>
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