"Markem" wrote in message
...
On Tue, 10 Aug 2010 01:50:27 -0400, Bill wrote:

Having put up most of my drywall, I have left a few gaps that are too
big (for instance, next to my plastic electrical boxes). At least one of
these gaps is at least 3/8" wide (and 4" long). My current plan is to
"glue in" a small block of drywall using my heavier joint compound, and
then build that up--allowing it to dry in between layers.

Is this approach likely to be successful (w/tape?)?

Thank you for your thoughts.

The dry 90 minute compound, 3/8 caulking backer and glass mesh tape.
That is what I would do, hope that helps.

Nobody has said how to put the final finish on it. For the O.P.:

If you go with 90 minute stuff, you can put it on without tape, but build it
up thick enough to taper out over the original sheet rock, or it will
shurely crack out. If you don't use tape or fiberglass, it may crack,
anyway. If your technique on the 90 min. stuff, you may need to use regular
joint compound to put a final sandable finish over it. Note, if you didn't
know, the 90 min. stuff is nearly impossible to sand, at all, so get it
right, or another technique is to let it get almost completly dry, and use
the drywall blade laying down like a chisel to take off the high spots. If
you want to go that route, put extra on, but don't fall asleep at the wheel.
That stuff kicks off fast, and goes from unworkable soft to unworkable hard,
pretty quickly.

You can use 90 minute stuff with paper or fiberglass tape over the goo over
the hole. That is my personal preference, using paper tape with regular
compound over the top. It is more work, but no risk of cracking later.
Worth it to me. It is easier to get it smooth and not risk getting the
texture of the fiberglass showing though the top with using the paper tape.

If you are good and good and fast, you can use 90 minute stuff to plug the
hole, put on a thin layer over that to embed a paper tape big enough to
cover, then put a layer of 90 min. over the paper with some extra thickness
to take off to get a smooth final finish. Just do not leave extra on while
smoothing to the final finish, because you will not be happy with yourself
as you are trying to sand that extra 90 minute stuff back off.

Hope that helps, and is not so basic as to be insulting. It is the teacher
in me trying to be complete and not knowing your skill levels.
--
Jim in NC