During my 40 years in the trades, I’ve had a number of high-end drywall jobs that required dead-flat ceilings — no telltale bulges allowed where the ends of the drywall sheets abut one another. The method shown in the drawing is our solution to the problem I’ve inspected some jobs that we did 25 years ago using this method, and you still can’t see where the butt joints occur.
This drywall trick starts with a sheet of plywood. The plywood should be the same thickness as the drywall. First, trim an inch off the width of the sheet, then crosscut it into 10 equal strips. They will be 9-1/4 in. wide by 47 in. long. As shown in the drawing, we next staple strips of 1/16-in. thick poster board to the long edges of the plywood strip.
Before raising a drywall panel for installation, we screw one of the plywood strips to the end of the panel. The poster-board strip goes between the plywood and the drywall. As the drywall goes up, the butt ends are arranged to fall between the ceiling joists. When the adjacent drywall panel is screwed to the plywood strip, a shallow dip is created where the drywall bends over the poster board. This shallow dip creates a hollow for the tape.
We tape our joints in the usual manner, beginning with the butt joints. Once that joint compound has dried, we tape the long edges. Incidentally, a 20-in. long piece of 1-1/2-in. aluminum angle is a handy tool for leveling the finish coats of joint compound over the butt ends. Using this technique, we never had a joint show up on a punch list at the completion of a job.
Tim Hanson, Indianapolis, IN
Why is it necessary for the plywood to be the same thickness as the drywall?
I had to read it a couple of times to make sure I got it. He screws the 47" length of the piece of plywood along the back side of the end of a drywall sheet, leaving 4 5/8" (half of the 9 1/4" width) of the plywood strip exposed. The drywall screws are driven into the plywood near the edge of the drywall as if going into a ceiling joist (or stud). The plywood needs to be secured to one piece of drywall before going up in order to hold the plywood in position. This is so that once this first piece of drywall is screwed to the ceiling joists, the next piece of drywall can be butted up against the first piece of drywall and screwed to the exposed plywood in the same manner as the first piece of drywall. The strip of plywood is essentially taking the place of a ceiling joist. Hopefully this helps you to picture things a little better. I tried not to repeat details that were already covered in the third paragraph, so you might have to re-read that paragraph too. Best Regards.
Sounds like a good technique. However, your explanation is hurting. Hard to picture what you are talking about in the third paragraph. Try again?
For years I have used this too and it works great! I am surprised more don't use it.