I recently did some drywall patching and soon will have to drywall my entire
basement. From my little experience I have found that my results were not so
great. While I understand that practice is probably key to success I see
some problems that probably come from doing something wrong. I use
self-adhesive tape to seal joints. I apply 3-4 coats of joint compound each
time waiting at least one day to let the compound dry completely. I send
usually only after third coat. The first problem that I encounter is air
bubbles. after third and fourth coat and sending the surface turns flat but
with small holes I believe due to bubbles. How to eliminate them? Second
problem is that I don't understand how to make two sheets of drywall be flat
with joint when there is tape and several coats of joint compound over it?
It makes the joint bump a little. Also I realize I have to do a lot of
sending. much more then it should be? What's the secret to little sending?
And last question: what's the proper way to cut openings for switch boxes
and especially for recessed lights? Should I put the sheet, screw it and
then use utility knife or rotary tool to cut opening? Or I just measure and
cut the opening before putting the sheet?
There will always be a bump or ridge. The idea is to hide it by
"feathering" the joint compound out. The ridge will be about 1/8" high or
less, but it will taper from flat wall to 1/8" over a space of about 10",
and then taper back down for another 10", so it shouldn't be noticeable.
No more joint compound than you need. Flatter application of joint
compound. Using a scraper or taping knife to scrape off little ridges first
before sanding, so you don't sand those things down.
I think it's best to cut after putting up the drywall. If you have a rotary
tool, that works well. Make sure you're using a drywall bit with a "guide
tip" so it doesn't cut the electrical box. Also, do not screw the drywall
close to the box. Screw farther away first, then cut the opening, then
screw close to the box.
My technique is fairly simple, although perhaps a bit more work. I apply a
generous coating over the tape/hole/whatever, smoothing it carefully and
pressing firmly. I go over it with a damp sponge to further smooth it a
bit, then give it time to dry. Next day I sand. There will inevitably be
small pits here and there or perhaps a bit of edge showing that I don't
like, and so forth. In many cases there's nothing more to do -- I feather
the edges and all is well. If needed, I apply a second coat in the same
manner as the first, wait, and sand again the following day. With the
exception of a major repair, I've not had to do more than 2 coats (granted,
I'm not a contractor so my experience is limited to just what I've done in
my own home).
Drywall joings are recessed to account for the tape. When you fill and
sand, the goal is to smooth it over and feather the edges such that they do
not show up in the finished product. Even if YOU know it's there, it's not
terribly visible to the average joe.
Only use as much as is needed; press it firmly during application, smooth it
over and scrape off what's not needed; use a damp sponge to go over it
lightly, further smoothing it out. Those are my tricks at least.
The answer to this -- the way you feel most comfortable. When it comes to a
wall box, I'll mount my boxes, run a marker round the box (or chalk it) then
put the sheet up against it to get an outline. I'll cut the hole, mount the
sheet, then finish it up a bit. On the ceiling I also cut first after
measuring, then mount the drywall and clean. I also measure first for some
wall boxes as well.
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