On Mon, 11 Jan 2010 19:57:51 -0800 (PST), Limp Arbor
wrote:

My house was built in the 1970s when apparently there was a huge
shortage of either lumber or smarts.

2x8 joists, 12" O.C.,14' span
1x3 X bracing in the center of the span
1/2" plywood subfloor nailed with spiral nails - no glue
Oak hardwoord floors nailed perpindicular to the joists - the flooring
is short with most pieces less than 3'
Easy access from below in full basement

Floor bounces noticeably from normal walking, knick knacks rattle,
etc,

I tried on the other side of the beam with 16" O.C. 2x8 joists solid
blocking with little success.

I've seen 3 suggestions and want to know if anyone has tried them and
what the result was

1 Metal X bracing installed on either side of the current bracing
(splitting the difference between the center and the ends of the
joists)

2 Sistering the joists with glued & screwed plywood on both sides
(All plumbing & electric are either below the joists or parallel
to them)


3 Installing a plywood 'ceiling' in the basement glued & screwed to
the bottom of each joist.
(I guess the idea here is to make the whole joist sytem a giant
torsion box)

The best option I could think of would be for you could sister the
existing 2x8 joists with a 2x10 joist screwed and glued to the
original. A 2x10 on 16" centers is good for a 14'-6" span. You
wouldn't have to go the full span with the 2x10's just make sure you
do at least the middle 2/3 of the span. You would loose a couple
inches of headroom but you would get the strength you need.

If you had access from the top by removing the subfloor (I'm not sure
how deep you're getting into this) you could go the full distance by
just notching each end of the 2x10 to the height of the 2x8 and
dropping the 2x10's in. Piece of cake! Hehe. On television it could
be done in less than an hour...

Gordon Shumway

Our Constitution needs to be used less as a shield
for the guilty and more as a sword for the victim.