One of the aggravating parts about installing drywall is cutting holes around electrical boxes, switches and outlets.
You need to take care when measuring, marking and cutting or the box will not fit right. Accuracy is a must or the electrical box will interfere with the drywall and your sheet will get damaged. Most electrical codes call for a maximum gap around the electrical box of only 1/8 inch, so you can’t cheat by cutting an extra large hole, either.
It is possible to fill gaps with joint compound and tape over them, but make sure to keep the fill flush with the drywall or the cover plate won’t fit. One trick that will buy you a little wiggle room is to cut the hole slightly angled (as opposed to holding the say blade perpendicular to the drywall surface) such that the back of the hole on the surface facing the electrical box will be slightly larger. That makes fitting the panel over the electrical box a little easier.
Measure and Mark
To ensure precision measurement, hole the tape measure level for horizontal marks and plumb for vertical marks. Positioning the measuring tape at even a small angle will make for inaccurate measurements and will give you problems.
Place your drywall panel where it will be after installation and mark off with a pencil the side edge and bottom or top edge, closest to the electrical box. Measure carefully from these marks to the side and bottom edges of the box, then mark off lines on your drywall panel to match.
Find out the dimensions of the electrical box, either by measurement, or from the manufacturer’s spec sheet, and mark off the other edges of the box. If you have a straightedge and a drafter’s triangle, you can these these to good use at this point to draw the box cutout. Remember, precision is key. Double check your measurements before doing any cutting.
Were your measurements verified as ok? Good, the sheet of drywall can now be cut, using a keyhole saw. Only cut three sides of the box with the saw. Score the last side of the cutout with a utility knife, then break the flap free with a blow from the other end of the knife. This way you’re not as likely to mar the hole’s edges.
Fasten the sheet in place with as few drywall screws as possible to hold it in place against the wall. Carefully press the panel flat around the electrical box cutout. You can use a utility knife to open up the hole a little if it’s a tight fir, but remember the 1/8 inch gap requirement. Once you’ve gotten the box fitted in it’s cutout hole, you can attach the remainder of the screws for the drywall.