"djay" wrote in message news:gkvCj.4$CO3.1@trnddc04...

"John Grabowski" wrote in message
...

"djay" wrote in message
news:m%nCj.8985$HA3.8232@trnddc02...
I'm installing a Panasonic bathroom exhaust fan - approx fan box size is
12 X 12 inches and it's replacing a POS nutone NOISE maker that has an
opening about 8 X 10. Panasonic has an approx 1" lip on the underside
that would normally screw right to ceiling joists for new construction
(would need to add a 2X4 to make the 12" span instead of the normal 16".
Anyway, I'm in a quandary as to how to correctly install this fan.



It came with "joist spanners" that seem flimsy and possibly difficult to
install. Alternatively it has mounting screw holes in the lip. I want
to just cut out the old fan and expand the hole (I have been up in the
attic and inspected. the existing joist/electrical etc before doing so).
One side of the existing fan is already attached to a ceiling joist.
I'd still use this point as a starting point and expand the drywall hole
away from that existing joist accordingly to fit the new Panisonic box.
My goal is to just cut the hole, install an new spanner joist to snug up
to the other side of the box (would cross between the headers of the two
existing walls) and just use some longer pan head wood screws to screw
up through the "lip" with mounting holes right through the existing
drywall ceiling and into the old existing joist and the newly install
joist.

So in my example above after the new hole is cut into the drywall fit
the larger fan, and new joist installed (parallel to the existing joist
but for the other side of the fan hole). I'd push the new fan up
through this hole until the mounting lip rested on the ceiling. I'd put
screws in through this lip, up into the drywall and into the joist
above. Then of course seal in the fan from above and replace the 3"
exhaust duct with 4". Does that sound doable? I guess normally this
lip would be between the ceiling drywall and joist but I can't see a
downside to installing it directly onto the existing drywall.



That's usually how I do it, but without adding any additional wood
bracing. On the side of the fan housing that will be against the existing
joist I drill a screw hole about three quarters up near each corner. I
use them to screw the fan housing to the side of the joist. I also screw
that bottom lip in from underneath. That gets the housing up solid
enough to where you almost don't need the spanning brace, but I use it
anyway.

The joist spanners that came with the Panasonic fan are quite solid. You
will only need to install one. I usually attach the U bracket loosely on
the side that does not have the duct connector. That makes it easier to
slide the joist spanner in while up in the attic. You can snug up the
screws after the spanner is in place.

When cutting the hole in the ceiling, make a notch for the U bracket.
Also on the side that the duct connector will attach the hole must be
almost the full size of the lip so that the duct connector can seat
properly. The finish trim is big enough to cover the larger opening.

Don't forget to use the thumb screw to secure the duct connector to the
housing. There is a little hole near the internal electrical plug that
it goes into.

I recommend that you use knee pads and a dust mask.

That's good advice and is pretty much exactly what I was going to do. I
like the idea of using the screws through the side of the housing... I
may do that if installing the extra wood brace becomes.... "challenging"


As the other poster mentioned, I put the plastic fan cover in place and it
looks like it will snug up to the ceiling without a gap. Has that been
your experience too?


I've never had a problem with the plastic trim. It is a little deep to
accommodate the screws that you install from underneath. Make sure that the
extra wood brace does not interfere with the duct connector.