I'd like to put the additional joists in to fix two problems:

1) Some sagging - not severe
2) A load bearing wall in the original construction was placed
parallel to, but between the span of two joists. The wall is supported
by the subflooring now. This is where the double joist will go.

The more I read (thank you for the comments, everyone!) the more I see
this is nothing I need a contractor for.

There is an easy way to get 12' joists into the basement. The
foundation end and the center beam end have clearance for the new
joists, just like for the existing joists.

I plan to use screw jacks to relieve the stress on the nearby joists,
while the new ones are going in.

My initial concern - and reason for seeking a contractor - was how to
slide the joists into their end points. I suspected that a notch is
the only way. I could see how the screwposts can be used to get
additional clearance in the span, but the endpoints are fixed in
height.

Just so I am understanding this correctly: The "notch" should be the
removal of about 1/8" of the joist height, along about 3" of its
length, from both ends. If correct, then the only q. that remains is:
top of the joist, or bottom? Both ways seem possible, but shimming
would be required if the joist is notched on the bottom (the ends that
sit on the beam get the shims). I am not crazy about that idea and
plan on attempting guiding the joist in with the top ends (crown side)
notched for clearance.

The other area where a notch might go is on the leading top edge, in
the direction of the joist roll, if that's what ends up needing to
happen to get the joist in.

Am I on the right track?

On 25 Mar 2004 21:37:46 GMT, (Chris Lewis)
wrote:

According to Giznawz :
"Chris Lewis" wrote in message
...

If you can't (both ends boxed), you have to resort cutting the joist
shorter (one wall width plus span length, plus a diagonal fudge factor),
which means that the ends of the joists aren't fully bedded into the wall.
Which isn't optimal. Sistering to an existing beam is fine, however - a
little less end support makes no difference if you're just trying to
stiffen
it up.

This is a good point. What is it that we are trying to beef up here, the
shear strength at the bearing ends of the joists, or the bending strength
(read deflection) at the mid span of the joists under new larger loads than
in the original design?

I'm pretty sure that the OP is doing this to eliminate sag problems,
_not_ to improve overall load bearing. This is a "cosmetic" thing, not
a structural thing.

If he's doing it for "shake" problems (stepping on the floor causes the
fridge to bang off the wall and the glassware to rattle), it's bridging
he needs, not more joists.

If we feel comfortable with the shear and bearing
strength of the original joists under the new conditions, and are only
concerned about bending strength, then there is really no need to bear the
sisters on the supports - assuming of course that the sister joists project
far enough into the low bending stress zones at the ends of the joists and
they can be fastened properly to the original joists to share the load in
bending.

Right,

... if he's sistering joists in for sag problems, the ends don't have to
bear on the supports at all...

Just needs proper "overlap nailing" patterns (see building code/engineering
tables on sistering/splicing/multiple board joists), and have the new joist
ends reasonably close to the old joist ends. Though, it'd be smart to
put bridging in to prevent any tendency for the final assembly to
"roll".

If it's purely for sag, I'd stick a post jack in the center of the existing
joist to get it into (or slightly above) line. Then sister in a second
joist, crown edge _up_, with the proper nailing pattern. The new joists would
end just at the wall face.

Put in a "box bridge" at either end.

Then lower the jack.

As always, it is best to have a professional look at the existing
conditions and evaluate the situation for safety... but this could be a
cost saving measure if found to be a safe alternative. One word of caution,
however... If you are not planning to have an engineer evaluate your
situation, disregard my comments and do what must be done to bear the
sisters on the supports.

OP? _Why_ are you installing these extra joists anyway?
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.