Drywall textures are created using several different methods. The most common of these are spray-on finishes like knockdown, orange peel and popcorn. These are usually done on new construction by professional crews using special equipment. For instance, popcorn is applied with a hopper that stirs and mixes the finish as it is blown onto the wall or ceiling surface. Knockdown and orange peel are applied in basically the same way with professional grade machines that spray the finish onto large areas. In some cases as with knockdown, a joint knife is used to flatten the texturing material and create the finished effect.
A second type of drywall texture that can be done on a smaller scale is texturing paint. These include sand and stucco coatings commonly used on ceilings more than walls. The coating is applied using a brush and then manipulated to create a pattern in the finish. Another technique for applying a textured finish, that can be done on large or small areas, involves the use of joint compound to create a rough surface rather than the normally smooth finish associated with drywall.
Realistically there are only two texturing techniques possible on a small scale at home, paint textures and joint compound techniques including knockdown. Apply textured paints over a primer to ensure a good bond with no flashing in the finish coat. These coatings are not meant to go over bare surfaces and will pull away as you try to brush or roll them on.
Apply the coating using a brush to cover a small area at a time, then combed, rolled or brush the surface to create a design in the finish. These coating can also be applied using a specially made roller with nylon loops braided into the nap, as it rolls back and forth the loops pull the surface of the coating away to leave random peaks in the finish. It can be difficult to get textured paint to cover with this method, so brushing on and then rolling with the loops can be easier, though more steps are involved. In any case, these coatings will resist sticking and require a very full roller and repeated back and forth strokes to get good coverage. This can make doing an entire wall or ceiling difficult.
Drywall textures involving joint compound can be done using a number of different tools such as a trowel, a brush or a broom to create a design in the finish. The basic process is the same, apply a coat of joint compound over a surface and while it's wet, press a tool into the mud to leave a decorative finish. Ceilings are usually where you'll find a finish like this but walls may also be decorated with texturing.
One common joint compound texturing technique involves the use of a masonry trowel pressed flat against the surface and then pulled straight off to pull peaks in the mud, leaving a stippled appearance. The peaks can be small and delicate or they can be coarse and thick. The thickness of the mud coat will determine the size of the peaks.
A variation of the trowel method involves turning the tool while it is in contact with the surface. Turn the trowel 360° to leave circles in the finish or turn 180° to create arches in the finish. This can be done in an ordered pattern of straight lines or the design may be random across the surface.
Another way to do a finish like this involves the use of a nylon broom or brush to slap the wet mud. Use a broom with soft, floppy bristles that will yield when it comes in contact with the surface. Apply mud to the entire surface first and then go over it with the broom.
Also try a large, soft sponge like a sea sponge to create swirls and stippling, or a wallpaper brush with short, stiff nylon bristles to comb a texture into the wet mud. This can be done in straight lines or randomly with circles or arches.
When it comes to drywall textures there's a hugh number of finishes out there. Because these are applied using several different techniques and materials, with different tools, the resulting finishes can be hard to match when doing repairs and harder to blend at the edges. The best that can be done in most cases is to simulate the finish over the repair and live with an obvious border around the edges.
The hardest finishes to match seamlessly are popcorn and orange peel. Because these are specially made coatings, applied using specialized sprayers, they are virtually impossible to simulate exactly for an invisible repair. You can buy small amounts of these finishes in a spray can and use it to apply the finish over the repaired area. Work from the center out and spray lightly at the border to try and blend the new and old texture.
Knockdown, while originally applied with a sprayer, is easier to simulate and blend than popcorn and orange peel. Because knockdown texturing is just watered-down ready-mixed joint compound, spattered randomly across the wall, it is much easier to simulate with standard drywall tools.
Mix joint compound with water at about a 10 to 1 ratio to get a thin mud that pours but is not so runny that it slides right off a joint knife. Use a scrub brush with soft, short bristles and dip it into the wet mud. Hold the brush upside down and pull you thumb over the bristles quickly to splatter the surface with a random covering. Use a little mud to get small spatter and a thick load to get large spatter.
While the mud is wet, lightly drag a joint knife (about 6 inches or more) over the spatters to flatten them. You may want to practice this technique on a scrap of cardboard to match the existing finish before moving to the repair.
Use the same type of textured paint as the original finish. Recreate the finish on small wall repairs using a brush to apply a thick coat over the patch. Then hold a looped roller by hand and tap the surface of the paint to pull it up in peaks that match the existing finish, working from the center out. Wet the roller nap with paint first to avoid pulling too much off. If a 9 inch roller is too big to work on small repairs, cut the roller down to a size that will work.
To recreate an existing joint compound texture, first examine the finish and determine how it was created originally considering the methods described above. Use ready-mixed compound straight from the bucket and practice this method on a piece of scrap drywall or cardboard. Start with about ¼in. coat of mud and vary it as needed to get the right thickness for your finish.
When you're ready, move to the wall or ceiling. Make sure to apply the mud thick enough to saturated the surface. If there are dry spots on the wall, the mud will pull right back off when you try to apply the finish. If necessary, use a spray bottle to mist the surface with water first before applying the mud. Start from the center of the repair and work out to the surrounding finish. Try to blend the new and old finishes together around the perimeter using a light touch.
Removing an existing textured finish may or may not be possible, depending on the material used to create it. In addition, if it's been painted it will complicate the job further. Joint compound finishes can sometimes be removed using the spray and scrape method described below. In other cases it may be possible to scrape the finish off with a joint knife, for instance, if the mud was applied over a primed or painted surface it may pop off with minimal effort.
Test this possibility by using a thin putty knife to chip an opening in the surface and see if the blade will slip under and pop the finish off. If it begins to come free, use a wider blade to remove larger sheets. Usually, if the putty knife test works to begin peeling the finish, it's a good bet it will all come off this way. If the finish becomes difficult to remove in places use a chisel blade joint knife and hammer to force it off. A razor-blade scraper may also improve results. These may cause minor damage to the surface but that can be easily repaired with a little joint compound.
If a joint compound texture was applied over bare drywall, it will not usually come off easily and a putty knife will not work to remove it. In these cases, the finish can be chipped, sanded and then skim coated. This is a very dusty and difficult way to remove a textured finish and most people choose either to live with what they have or install a new drywall ceiling over it instead.
If you choose to chip and sand, use a chisel blade joint knife to remove the bulk of the texture first and then use a belt or rotary sander to smooth it out as much as possible and minimize the need to fill in with mud. Remove sanding dust with a shopvac and wipe the surface with a damp rag or sponge. Prime with a flat latex paint to ensure a good bond with the new coating and then skim coated with several applications of joint compound. Expect to do 5 or more coats, sanding in between to build up a smooth finished ceiling.
Popcorn texture can sometimes be removed using a wet scraping method. Before proceeding, check to see if your popcorn ceiling contains asbestos. This may be true if it was apply before 1980, at which time asbestos was banned as a building material. If your ceiling contains asbestos you are prohibited in the US from hiring anyone other than a certified asbestos abatement contractor to do the job for you. This doesn't necessarily mean you can't do it yourself. You are allowed, but you must use caution if you choose the diy approach and check your local regulation for the laws concerning asbestos removal in your area.
Have your popcorn tested by a lab to see if it contains asbestos, if it does, follow the guidelines and procedures at this link for help with removing popcorn asbestos yourself. You will have to block off the room involved and cover every square inch of wall and floor space with thick plastic to contain the asbestos. Wet scraping is the only accepted procedure for asbestos removal. If you are not able to wet the popcorn because it has been painted, you will not be able to remove it because any release of the asbestos by dry scraping is prohibited by government regulations.
If your ceiling doesn't contain asbestos you can simply spray it with a soapy water solution and scrape off the resulting goo. First remove as much furniture, etc. as possible from the room and cover all floors and other vulnerable surfaces with plastic drop cloths. Use a compression sprayer and warm to hot, soapy water to soak the popcorn. Add the water to the sprayer first and then squirt in about a tablespoon of dishwashing liquid. Close the sprayer and shake it up a little to mix in the soap.
Work on a small, manageable area at a time spraying repeatedly with the water to soak the finish. When it's good and wet, use a joint knife to scrape the popcorn off and deposit it into a plastic bag. It may be difficult to get the goo off the blade so try using a second joint knife to scrape it off the first and into a bucket or other receptacle.
When it has all been removed from one section wipe the surface with a clean, wet rag or sponge. Rinse the rag frequently to remove all the remaining residue while it's still wet, before moving on to a new section.
If you want to paint a whole textured wall or ceiling you can, with a little care and preparation. First get a quality roller with a long nap of ¾ inch or more. Thin your paint slightly to make it easier to push into all the nooks and crannies of the finish. If the texturing is subtle, you may not have to thin at all, if it's very thick however, you will want to thin the paint a bit and maybe do two coats to get good coverage.
Cut in and then roll pressing lightly with the roller to avoid breaking peaks in the mud or pulling the material off as much as possible. Go over the same space repeatedly with the roller, or use the brush to try and fill all the little crevices in the finish. You will most likely miss some spots, watch for this and touch up the missed spots with a brush or use the roller at an angle to press paint into the gaps.
If you're painting a popcorn ceiling, expect a good amount of it to come off in the wet roller. Allow the roller to fill with the particles as you roll and they will redistribute over the ceiling as you work. This works well to create a shell of paint that will contain the popcorn when it has dried. This is an advantage when your popcorn ceiling material contains asbestos because the coating will help contain any dust.
The loose bits will also get in the roller tray, just allow this to happen and fill the roller as usual. Keeping it well loaded as you work will minimize the particles that come off on the roller. When you're done painting the ceiling and you need the remainder to be free of debris, pass it through a strainer or old nylon pantyhose to clean it up.
If you have the original paint you're all set, if not, see this link for help matching existing colors. Touch up on small repair patches using a soft brush to gently apply the paint, watch for missed spots in creases and at the edges. Let the paint dry and go back to catch any missed spots or do an entire second coat over the whole repair if you can still see the patching compound.