"Jim Mc Namara" wrote in message
. com...
How far is the span of the existing joists, Andy? Not the o.c. dimensions
but rather how long are the joists? If all you do is add additional
joists, they will require the same support as the existing ones. If
they're
not supported over a long span (and keep in mind I'm not a structural
engineer) all you will do is weight down the areas between the existing
supporting ones when you screw down the floor to them.

Ok, here's the revised scoop. I hate going down in that crawlspace, but my
hazy memory clearly needed the boost. Maybe I have my terminology all wrong
and the "joists" I've been referring to are more properly "beams" (as in
pier and beam, which sounds like what I have in the crawlspace).

The joists are not sistered 2x boards as I stated earlier; they are solid
4x8s. They sit atop either 4x4 or 4x6 solid posts (it's a mystery why some
are 4x4 and some are 4x6 - there didn't seem to be an obvious pattern to
me). These posts are distributed 4 feet o.c. in one direction and 6 feet
o.c. in the other. The joists run on top of the posts in the "long" (6 foot
spacing) direction, and they are butted together on on top of the posts with
a 4 foot long 2x6 nailed to them to keep them together. I now realize after
coming back up that I forgot to measure how long the sections of joist were
between butts - but I would wager they span at least two of the posts (and
would hence be at least 6 feet.

Andy