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taking out sag of ceiling (was no subject)

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I don't think this is a good idea. Lagging into the narrow face of the
2x required a very straight installation. You not only have the 4" of
the existing joist but another 3.5 or 5.5" of the second. I don't see
how you can jack the existing 2x4's by tightening the bolts. 3/8"
diameter is as big as you should go if you try this. You won't get much
strength since you only have 3" to embed into and the tip of the lag
isn't good for much.

What I would recommend is to jack the 2X4's at their low point from
underneath with shores and an adjustable base at the floor.

Then along side the 2x4's, double or triple up with another 2x or a
cold-formed stud for the entire span. Use nails (10d) for the 2x or
screws for the lt gage steel. Then remove the shores.

Another option is to install struts at the low point of the ceiling up
to the rafters. You'll need to make sure the rafters can take the
additional load.

-gerard
Santa Clara, CA

-----Original Message-----
From: ebosco(--nospam--at)vogeltayor.com [mailto:ebosco(--nospam--at)vogeltaylor.com] 
Sent: Friday, November 22, 2002 9:49 AM
To: seaint(--nospam--at)seaint.org
Subject: 

I am renovating my two story 1912 dutch colonial which is balloon
framed.
The ceiling joists on the second floor are 2x4 members (full 2x4
dimension)
which in some locations span as much as 15'.  The mid-span deflection of
these members is 1/2" in some locations and the small depth of the
members
gives me little room for adding insulation to the second floor ceiling.

In reviewing the alternatives for improving the situation it seems like
a
very stong beam is produced by stacking a second 2x4 or 2x6 on top of
the
existing joists. I would connect the two by lag bolting vertically
through
the top member into the bottom one.  A benefit of this plan is that I
could
use the bolts to raise the sagging members slowly over a period of
months to
reduce cracking of the plaster.

Has anyone ever seen this approach applied? Any recommendations for lag
bolt
frequency? Would it be necessary to add a vertical plywood plate (or
plates)
to the edge of the beam to help the two act as one?

This is a time when I wish my engineering experience covered more that
Mechanical, Electrical and Plumbing.

Thanks

Ed Bosco, PE


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