How to resolve uneven meeting of new and existing drywall pieces

Question

While installing a new piece of drywall into a painted wall with existing drywall of the same thickness, parts of the new drywall seem to sit or sink back further into the wall even with pressure evenly distributed on the new piece. I imagine this since the new piece is not pressed up against a stud.

What is the best way to resolve this gap?

At the base, the drywall pieces do not have this problem since they are both against a board.

What is the best way to approach in this scenario to end up with a smooth wall, is there some method to shim behind the drywall to get a more flush fit? Or does it make more sense to just install as is and apply joint compound until level?

Answer 1

First of all you want to make sure that you fully support the drywall from within the wall. If the drywall patch runs out to the studs this is best done by widening out the studs with scrap pieces of 2x4 screwed into the studs. You need to make sure that the support surfaces are even with the existing studs so the drywall will be even when you put it in place. If the patch is smaller and doesn't abut the studs I will often take scrap pieces of 1x2 that are somewhat longer than the patch. Place the 1x in the wall with the ends overlapping the back of the existing drywall and support it in place while you screw in a couple of dry wall screws through the drywall into the 1x to hold it firmly in place. You'll probably need at least two of these to give the patch good support.
Then attach the drywall patch to the supporting cross pieces. The surface should be fairly level - within 1/16. Then finish with tape and joint compound.

Answer 2

Cut a few furring strips 4" longer than the opening. Place them behind the opening and screw them in place through the existing drywall on each side of the opening. Now place the new piece of drywall in the opening against the furring strips and use drywall screws to fasten it to the furring strips. you should now have a smooth surface to mud, tape and paint.