On Feb 13, 12:07 pm, RicodJour wrote:
On Feb 13, 9:07 am, Jeff B wrote:
In the middle of my kitchen reno and while working in my attic, I
discovered that 1 or 2 full sheets of drywall in my living room are
sagging badly. Apparently the construction adhesive used 30 yrs ago
simply dried up and lost its hold. Since they used nails not screws
in the 1970s to attach the drywall to the rafters, there wasn't much
to keep it up. At the lowest spot, the gap between the drywall and
rafter was about 3/4"!! From inside the attic, I could slide 1/2 my
hand into the gap! I figured the whole thing would collapse from its
own weight any minute. I raced to HD and propped it up with a bunch
of 2x4s. My living room looks like a circus tent.
Getting it supported was step 1. I now need to figure out step
2...repair. Replacing all of that ceiling drywall is NOT the
preferred option. My attic has about 18" of loose, powdery, blown-in
insulation. Moving that stuff around is a nasty job. I don't believe
the drywall is cracked anywhere. It simply sagged as a full sheet (or
2 sheets). I'm hoping that getting it flush to the rafters with the
2x4s and then using LOTS of drywall screws will keep it up there for
another 20 years. With the loose insulation, getting adhesive in the
gap before screwing up will be difficult if not impossible.
Anyone have experience dealing with this problem?
You are in a tough situation. You have several factors adding up to a
practical impossibility.
Newer drywall panels intended for ceiling use are more sag resistant -
the stuff made 30 years ago is more prone to sagging without any
additional load being placed upon it.
You do have a load - that 18" of blown insulation can easily exceed
the sag resistant drywall rating of 1.3 PSF. Blown insulation can
vary a great deal, but 1 to 2 PCF is not unusual. The conversion does
not work in your favor.
USG specifies ceiling screws to be on 12" centers, and that's with the
newer sag resistant stuff. The older spec was screws on 8" centers.
Again, that's based on a 1.3 PSF maximum surplus loading.
The insulation that has worked its way between the drywall and the
ceiling framing isn't going anywhere without help. Buildings,
particularly wood framed buildings, move with changes in temperature
and humidity and with loads applied from above, such as your crawling
around in the attic. If you screw the panel back up as best you can
and there's a gap, more insulation will squeeze its way into the gap
as the building moves. This will be slow to happen, but it will
happen and it will create a fair amount of force and the screw heads
will start to pull through the face paper.
I see zero chance of a long term solution if you don't remove the
insulation from the area in which you are working. You could start at
one end, push the loose insulation to the far end, vacuum out the
crevice under the joist, and then jack up that area and screw the
board up tight. Then you'd have to move the insulation back into the
area you worked and start on the adjacent section.
In your situation you will definitely want the screws more closely
spaced - say 8" centers. Adhesive or expanding foam would help seal
the drywall/joist gap and keep more insulation from working its way
between the two. I would also consider filling the joist bay with
loose fill insulation, then stapling Tyvek on top of the joists so
it's fairly taught, then putting the rest of the loose insulation on
top of the Tyvek. That would be one way, off the top of my head, of
keeping the insulation and taking some of the load off of the drywall
ceiling.
Another option - and it's really easy for me to spend your money for
you - is to remove all of the loose fill insulation and use spray foam
over the entire drywall ceiling. If you put six or more inches in
place in place it would bond to the back of the drywall ceiling and to
the joists and make the whole system more of a diaphragm/beam.
Basically, this is the situation: rock you hard place. Sorry.
R
Jeff-
Per Rico's comments.......getting the drywall snug back up against
with joists with that isulation is going to be very difficult (read:
nearly impossible).
If you really want the ceiling to be flat you've got to get that
insulation out of the way....even a few stray clumps, chunks, bit will
locally prevent the drywall from seating properly & as you drive
screws (or ideally as you gently jack it into place) the insulation
will compress & the drywall will bulge or crack.
Vacuuming all out is doable & you can save it in large trash bags
which you could hang from the roof rafters (if you have enough room)
Ideally getting all of the insulation off the drywall is the way to go
but if the material handling logistics is too difficult maybe doing
1/2 of the room at a time could work.
Are you going to try & save the joint work?
If so, ideally you need to jack the ceiling up evenly over the entire
area, You fashion a could several "strong back frames" to distribute
the jacking force to the ceiling. Something like the lift points of
a drywall lift. This would minimize the number of jacks you
needed.....the load per sheet isn't huge but each sheets needs several
jacking points. But this would be a lot of work.
Your situation is difficult because of the loose fill insulation & the
fact the entire ceiling has sagged.
Jacking up the entire ceiling (or even "strips) is a lot of work but
incrementally screwing screws in sounds tedious.
Jeff... I think MIke D's comments about starting from the edge &
working a "strip" of drywall along a rafter makes sense. I believe
his concept is to use the screws to slowly draw the drywall back up
against the joists and avoid the jacking setup entirely. If his
concept works it would be much less effort than jacking the entire
ceiling.
If you try to use screws only (no jacking) space them relatively far
apart so you have fewer jacking screws to incrementally screw.
When the sheet or ceiling is completely flat, go back a drive
intermediate screws home in one shot.
In my town per code, 1/2 drywall ceilings get 1 5/8" screws at 6" o/
c.
Which seem rather long and rather close together.
What ever spacing you choose, consider making the jacking screw
pattern an even multiple of the final screw spacing and an even
divisor of the sheet size.
If you had a helper or two you could do the work with a lot less "up &
down the ladder".
Or, if you're up to it....drywall stilts
let us know how it all works out
cheers
Bob