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Sagging Ceiling Joists

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Ed,

Whatever you do, you will never remove all of the sag from the ceiling joists 
as wood creeps under long-term loading.  The most that you would get out of 
the ceiling joists would be about 1/2 the sag, then you would be trying to 
lift the entire roof.

Also, with a 1912 house, you undoubtedly have real plaster ceilings and if 
they are not cracked now, don't try to fix them or you will end up with 
cracked plaster. 

If all you are trying to do is to add insulation, I would suggest some light 
weight blown-in insulation that can cover the ceiling joists.  There also 
is some paper insulation that is constructed much like a pillow and uses 
the dead air space entrapped between the layers to provide insulation.  
Before that is done, you should probably tie the ceiling joists to the roof 
rafters to prevent additional sagging.  The roof rafters probably have collar 
ties at every other rafter and the rafter spacing is probably twice the 
spacing of the ceiling joists.  Trying to justify the construction by 
engineering analysis would probably lead you to believe that the house should 
not have stood one year, let alone 90.

Good luck,

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Ed Bosco wrote:

. > 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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