Patching a Large Hole in Drywall

An operation of correcting a large hole (more than a foot wide) in a section of drywall takes special tools in addition drywall compound, tape and broad knives. And performing a single large patch should be approached somewhat differently than patching multiple large drywall holes.

For cuts and cleanouts - expose the new opening for bracing at 2 studs or beams if possible (removing the cutout to halfway on the beams). Use the guide of a T-square or straight edge markings and make the cut with a drywall router if possible. Be sure to remove any weakness or loss of wallboard integrity due to hole impact. Give the gypsum edges a quick hit with a rasp in order to clean any bumpy lines (the larger the piece, the more you will need to do this).

Drywall screw backing around the cutout perimeter using wood strips or even plywood. Have plastic sheeting placed beneath areas of work and vacuum for dust as you sand, since the dust can float off to unsuspected areas.

For the finish cuts on the wall side: with the new drywall you intend to replace with, transfer the dimension of the new patch by marking with this template that will be either square or rectangular in shape. Following this, cut with a drywall saw, a drywall router (quick but can set off a lot of dust) or a sharp utility knife.

Positioning the patch: double check the measurements of the new replacement with that of the wall to make sure it will form a comfortable fit before going further. Rasping adjustments as needed.

For patches of large hole sections at or near the floor-level - station a prybar atop the slab, or elevated with wood strips to lever into position the new large replacement. Note that the baseboard may need removing - the new wall section should meet up with the same concealed wall level at the lowest edge, for casing support. A word on drywall storage: store the larger pieces of drywall flat on a level surface to prevent warping. Gypsum does bow easily, and must remain straight for patching.

For replacement at ceiling level a panel lift/hoist can typically extend the piece reaching about 11 foot on the horizontal. Some models can be operated by a single person.

Fasten with screws, both on the new and existing drywall sections. Knife on the mixed mud and apply paper tape, or apply adhesive mesh and mudd the seam.

For larger patch mudding: increasingly broad knives become important the greater the size of the patch or, at times, age of the structure (speaking of wall contours, due to settling, or crooked framing). An exterior door replacement that becomes plugged with a new drywall section that must be matched with the surrounding interior drywall surface, would best be made undetectable as a patch by floating the mud off with 10" or 12" broad knife over spans of dips, rises and traverses. And as a rule, the larger the patch, the more passes that should be taken with the compound.

Following sanding, seal with drywall primer for surfaces to be painted with oil paints and/or higher gloss and for areas exposed to moisture.