Like every other item in your home, drywall occasionally needs some TLC, especially when confronted with use and abuse. The good news is that it's not difficult to fix yourself. The materials are cheap, and even if you make a mistake, you can always sand down your errors and and start again, or call in a professional.
Contrary to popular belief, drywall is not structural in any way (there are a very few exceptions where drywall shear walls are used). Made of gypsum sandwiched between heavy paper, drywall became popular after World War II because it was easy to work with. Today,
99 percent of all homes use drywall.
Every home has some amount of drywall cracking, most of it from drying, shrinkage and minute flexing. This is especially prevalent in newer homes built with wetter wood.
Interior wall coverings can be a good barometer of what's going on with the house structurally. As a very general rule of thumb, if you have large separations or cracking in a random pattern - something other than 90-degree angles - then you likely have some notable building movement. Otherwise, you likely have normal imperfections.
Repair materials
The materials used to fill, seal and smooth drywall holes are called spackle, tape, drywall compound, taping mud and other names. They come in five basic flavors:
-- Paper or fiberglass tape, which comes on a roll similar to toilet paper, is used to join abutting pieces of drywall. Without the tape, cracking would occur at almost every seam. This material is imbedded in and covered with the differing drywall "muds."
-- Twenty-, 40- and 90-minute "hot mud" is a fast-setting material that is used for filling or anywhere a build-up coat is needed. It doesn't crack with thicker applications that would doom a conventional mud. It does not sand well, however. The catalyst in hot mud makes it less sensitive during setup to environmental conditions. Hot mud is the only type that should be used with the perforated, self-sticking fiberglass joint tape, as the catalyst will react chemically to bond it to the wall. Keep in mind that fiberglass tape has no fire rating for use in firewalls in garages. Hot mud will not come out of your clothing, whereas the others are water-based and wash out easily.
-- Straight "taping compound" has the most adhesive property and is used for initial setting of the paper tape over the joints. Taping compound tends to shrink after drying, which is one of the reasons subsequent coats of other materials are necessary to get the best final finish. Its job is simply to get the paper tape attached tightly to the paper face of the drywall.
-- Topping compound is used for finish coating, as it sands well and has little shrinkage - but also much less adhesive property.
-- All-purpose mud is the sport-utility vehicle of the drywall world: It has characteristics of the others, but will not perform as well in any given discipline.
Drywall mud comes premixed or in powder form. Jim Gore of Gore Enterprises, a drywall and general contractor in Snohomish, has this bit of advice for mixing large quantities of drywall mud: "Use a `stomper' (mixing tool) to mix the mud to a creamy consistency. I usually add one cup of water per four-gallon box of mud." To see how workable the mud is, "grab a knife full of mud and turn it sideways; if it falls completely off, it's too wet to be used."
Finally, sandpaper and sanding blocks are indispensable. Gore likes to use 150-grit sandpaper as his weapon of choice.
How to do repairs
Now that you understand your materials, let's look at the different methods you can use to patch holes of various sizes.
The easiest to fix is a dimple, pinhole or very small crack. Sometimes you can cover these with a few coats of paint. Any bigger, and you must break out the big guns - the tube of toothpaste, the caulking or spackle. Spread, squeeze, smear, sprinkle and paint - it's hard to mess up a job like this.
The most prevalent type of drywall glitch is the crack in a horizontal or vertical plane, many times in places where the building has shifted slightly due to drying or movement, or where shear points converge. These also can be caused by a minor earthquake.
Typically, these cracks are seen at cathedral-ceiling peaks, at inside wall corners and around doors and windows. Cracks caused by earthquake damage will have a wavy, back-and-forth appearance - the crack will start, stop and restart just off the plane of the first. (Earthquake damage is easiest to see in garages where the drywall has fewer coats of finish and tends to flex more.)
If the crack is very small, use a flexible material such as caulking, because if the stress point cracked once it may crack again. For larger cracks, use one of the drywall muds. Any crack larger than one-eighth of an inch wide should be repaired using drywall tape.
To fill the cracks, work the compound across the crack in all directions with a flexible putty knife. Use firm strokes to force the compound into the crack. The putty knife should bend with pressure as you draw it along the crack.
After drying, sand the area (apply another coat if shrinkage has occurred), texture to match, prime and paint.
Doorknobs very commonly get into pushing matches with drywall and always win. As with any patch, there needs to be something for the filler material to bind to. One method I'm fond of uses heavy-gauge window screen, lath, plywood, or whatever you have kicking around in the junk drawer.
Clean up the hole's rough edges and cut the screen in a rectangle that is longer and narrower than the hole. For a three-inch round hole, cut a strip of screen two inches by six inches. Put a screw, or reversed nail, in the center of the screen so you can hold onto the screen as you push it through the hole and center it.
Drive countersunk screws on either side of the hole through the drywall into the screen; this will hold the screen to the back of the drywall. Using a 6-inch taping knife, run compound or hot mud over the screen. Go watch "Gilligan's Island" if it's hot mud; come back tomorrow if using the other types.
Sand the high areas and repeat with a lighter mud to get a good finish. Sand again, texture, prime and paint.
Sometimes these doorknob patches will crack and separate at their edges as no tape was used with much fill. To be sure of a better, more permanent patch, you could use tape around the perimeter. Set the tape in the compound on the first coat, let it dry and come over the top of the tape on successive coats to blend it into the wall.
To set tape in mud initially, center it over the joint and press it into the first layer of compound firmly. Hold the putty knife at a 45-degree angle. Press just hard enough to squeeze out some of the compound from under the tape, but be sure you leave enough compound for a good bond.
There are other methods for filling doorknob holes, some very inventive. Commercial self-sticking "plates" and fix-it kits are available and require less filling and taping. Other methods involve cradling a piece of drywall behind the patch with drywall mud and tape, or my personal favorite, the "hat trick" (which works well for somewhat larger holes, as well). All these methods do not involve fill a half-inch deep (as with the screen method), lessening the chance of cracking.
To properly perform the hat trick, you must trace the hole you wish to fill onto the back of a scrap of drywall. Take a ruler and draw out beyond and around the tracing mark an inch and a half or so. Take your handy dandy drywall saw and cut out around the larger circumference. Next, use a utility knife to score down through the gypsum almost to the paper on the front of the drywall, taking care not to cut it. Snap the gypsum off around the perimeter, leaving facing paper wings on all four sides - a hat, if you will.
Place your newly created masterpiece over the hole and mud the backside of the wings to the area beyond the perimeter of the hole. Scouring the paint and actually digging out the drywall on the wall a bit beyond the hole itself will help you patch more easily. The wings will serve as the tape to eliminate cracking again.
Larger drywall holes require different methods. The only way I have run across that consistently brings good results is to cut out the drywall from stud to stud and replace.
Use a drywall saw to cut a straight line horizontally across from one stud to the next (usually 14 1/2 inches away). Next, cut vertically along the studs to the desired upper or lower termination point, taking care not to cut a hole through the other side of the wall or nick plumbing or wiring - if you feel any resistance, STOP. Make a nice, neat rectangle. Nail a two-by-four alongside the existing studs - you'll nail your patch to this wood.
If you don't have a two-by-four and feel confident with a utility knife, you may cut a narrow section of the adjoining piece of drywall away, revealing the stud underneath. Watch for nails and screws in the stud. It is necessary to refasten the existing edge when splitting the joint on a stud.
When finishing, allow the tape to dry over the seams for at least 24 hours and then apply the next coat, extending it beyond the edge of the tape. Feather the edges of the compound to get a seamless look. After the second coat has dried, use a 10-inch finishing blade to apply the finish mud. Feather this coat out about two inches beyond the edge of the last.
Finishing tips
Making your repair's texture match the texture of your wall can be a bit tricky and takes some trial and error. Take a couple of cans of aerosol texture and practice with the differing spray heads on a piece of drywall or plywood. Some textures are light, some heavy, and some are meant to be smoothed flat with a trowel after application.
Sometimes a bit of creativity and differing methods and materials are required to match a texture. Thinking outside the box is necessary at times. Aerosol texture is inappropriate when large areas are to be done. You can rent and buy backpack-mounted texture guns, or hire a professional with a truck- or trailer-mounted rig for assured results.
Once your repair's texture matches its surroundings, use paint primer on the repair, which will give the compound, the tape, the drywall and the painted wall a uniform surface for paint to adhere. Without primer, an otherwise good patching job may "flash," or have a different sheen or texture from the surrounding wall.
Nails will sometimes pop through the surface of drywall. To fix these, resink the nail into the drywall. Then drive a new screw into the stud next to and over the top of the nailhead to hold the nail and drywall tightly to the framing. Finish with compound over both fastener heads. When dry, you can sand, texture and prime.
Don't be afraid to add extra coats if necessary to get the desired finish in any patching situation. You always can sand it down and start over again.
Take your time with drywall. Nothing is magical about it, but it is not conducive to sloppy, hurried work. Most importantly, don't let kids ride skateboards in the house. However, if they do, fix the holes right away before any permanent mental scarring occurs. |
