Adding a sheet of new drywall next to a sheet of existing drywall may create a stark contrast initially, but with the right techniques, you can blend the two pieces seamlessly together. You may have to add a new sheet of drywall to a room if the drywall gets damaged by water or cracked by accident. Removing the old sheet tidily can be challenging, but once it's gone, you're ready to blend in the new sheet.
Set the new piece of drywall in the gap between the two pieces of old drywall. When purchasing a new piece of drywall to install, make sure it is of the same width as the existing pieces. Using the same width of drywall is integral to blending the new and old sheets together seamlessly.
Attach the new piece of drywall to the studs with drywall screws and a screwdriver or a drill with a screwdriver bit. Tighten the drywall into position so that its sides are flush with the other sheets. Over-tightening or under-tightening may result in the drywall not being flush.
Apply drywall mud with a putty knife to the screw holes and along the length of the seam between the new and old drywall.
Rip appropriately sized pieces of drywall tape and place them along the seam between the sheets, then use the putty knife to apply drywall mud over the tape. As you apply the second coat of drywall mud, be mindful of the relationship between the two pieces of drywall. The mud should make a smooth transition between both sheets.
Allow the drywall mud to dry for several hours; the length of drying time is dependent on the humidity in the room and the thickness of the mud when you applied it. When the mud is dry, use sandpaper and a sanding block to sand the excess mud off the wall. As you sand, run your hand between the two sheets of drywall; there should be no apparent gap or bump.
Prime the wall and paint it the same color as the existing panels of drywall to help blend the new sheet with the old sheets. Once you have the new sheet primed and painted, you should not be able to tell that it is any different from the other drywall.