Drywall is available in standard 4-foot widths. The length of the drywall sheets can vary from 4 feet to 12 feet. Most do-it-yourselfers would find any length over 8 feet awkward to handle, but the longer sheets give a smoother finished appearance on long walls because there are fewer joints to finish.
First, it is often best to span at least two studs in a repair. I also recommend staggering the joints; that is, one sheet would span two studs and the other would span three studs.
You will need the following tools and materials to do this repair job:
1. drywall panels
2. drywall joint compound
3. drywall screws or nails
4. joint tape
5. 4-inch and 6-inch drywall knives
6. hammer or drill/driver (depending on whether you use nails or screws)
7. a utility knife
8. a metal straight-edge
9. A sheet of plastic to use as a drop-cloth might be a good investment. The plastic can be placed on the floor or in the bathtub to catch most of the mess from the old drywall.
Now you’re ready to begin the actual repair.
You may need to remove a section of baseboard before starting. Then you can begin to tear the old stuff out. First you’ll need to remove the old drywall panels. To do this, locate the studs and use your straightedge to mark a centerline on the stud where you want the drywall patch to begin. Next, use the metal straightedge and utility knife to score and then cut through the old drywall panels. Don’t apply too much pressure when making the first cut; a shallow cut gives you better control of the knife. Once a guide cut has been made, subsequent cuts can be made with more pressure.
Locate any joints where pieces of drywall which you do not need to replace adjoin the damaged one. Score through the seam with your utility knife to separate the damaged piece from the others.
Now it’s time to remove the old drywall. Make sure that you pull out all the old nails or screws before you begin replacing the panels. There is not much you can do that will keep the old drywall from breaking up into small pieces when it’s removed. This is only a minor inconvenience because of the mess.
Measure the width of the section that you’re replacing and mark a panel for cutting. I like to use a chalk line for marking. If you have a steady hand and can follow the line you won’t need to use the straightedge to guide your knife. Score the top covering and then snap the panel back away from the cut as you would snap a stick over your knee. Now with the two sections folded back, lightly use your knife to cut the back covering of the panel by running the blade up the crease.
The section you’ve cut from the larger drywall sheet should exactly fit the hole left when you removed the damaged piece of drywall.
Put the bottom sheet in place first and screw or nail it to the studs about every 8 to 10 inches along each stud. Repeat this procedure for the top panel. The fasteners should be depressed into the surface of the panel. If you’re using nails, the hammer head should dimple the surface over the nail; if you’re using screws, they should be screwed down to just below the surface. These slight indentations make it easier to get a smooth finish when you apply the drywall compound.
You are now ready to cover the heads of the fasteners with compound. Use the smaller drywall knife and load about 2 tablespoons of drywall compound on the end. Pull the knife across the indentation over the nail or screw, filling in the depression. Let this application dry overnight, then sand lightly and make a second application.
If you find there was no metal outside corner, you may want to consider installing one before finishing your repairs. Unlike the metal cones that used to be used for plastering, metal corners for drywall are put in after the sheetrock panels are installed. After a corner is installed, apply drywall compound over it with the wide drywall knife as you did with the fastener heads. (This process is called “floating.”) The corners will need to be sanded and compound reapplied at least once.
If you have joints between panels, this is how you tape them: Load your knife and fill the joint with compound. Cut a piece of drywall tape to the length you need and moisten it. Place it over the joint, then use your knife to push it into the compound. Reload the knife (the larger of the two mentioned above) and pull compound over the tape. This joint will need to dry overnight just like the patches over the nails or screws. Sand the seam lightly and then reapply compound to smooth it further. The compound has a tendency to shrink slightly. This is why a second application is needed. After a second period of drying, everything should be sanded lightly to make sure it is smooth. Visually check the surface from an angle to see if there are any spots that need more compound and repeat the process if necessary.
You can apply compound to your fastener heads, corner and joints at the same time, then sand all the compounded areas together.
This has been a short course in drywall repair and finishing. I hope it is enough for you to feel comfortable in doing your own repairs.