It’s a pretty common scenario on the home improvement scene: You’ve removed some wallpaper or wainscoting, or you’ve relocated a door or a window, or maybe you’ve just repaired same drywall damage caused by one of life’s little mishaps. No matter the origin, you end up with some drywall that doesn’t have any texture on it. And now, you’re at a loss as to exactly how you’re going to get that flat, unadorned piece of drywall to blend in with the texture on the rest of the wall that’s surrounding it.
In truth, matching drywall texture is always a tricky process unless you’re experienced at it. Even the pros can have a tough time with it. You first have the issue of matching the existing texture for the main body of the patch, and then feathering the new texture out onto the old in ever-decreasing amounts so that the transition between new and old is seamless. It’s difficult to come up a perfect match, and the larger the area is and the more centered it is on the wall or ceiling, the more likely it is that you’re going to see it.
The other problem you’re likely to run into is what’s known as "flashing." After the patch is done and painted, the new texture will tend to absorb paint differently than the old texture, due to differences in previous paint, materials and other factors. The result can be a difference in sheen that also contributes to the patched area standing out from the rest of the wall, even if the texture matches. And the more sheen the new paint has — satin or semigloss as opposed to flat, for example — the worse the problem can be.
For all those reasons, especially if you’re not an experienced drywall texture matcher, your best bet is to simply start over with a fresh, flat wall. That doesn’t mean that you need to tear off all the drywall and replace it. It just means that you want to get rid of the old texture.
Tarp the floor in front of the wall with plastic sheeting. Don’t use canvas painter’s tarps, as the dust is hard to get back out of them. Wear a respirator to prevent breathing in the dust from the sanding and scraping operations, and always wear eye protection.
Sand or scrape the old texture on the wall to remove the majority of it. You don’t need to get rid of all of it — in fact, you want to be careful not to sand too deep and cut into the paper cover on the drywall. What you’re looking to do is knock down all of the high spots. Brush the wall down with a dry paintbrush or soft broom to get the bulk of the dust off it. Roll up the plastic sheeting to contain all the dust and dispose of the plastic, then put down new sheeting for the next operation.
The next step is to apply a light skim coat of drywall joint compound over the entire wall. You can use all-purpose compound for this, but topping compound will go on smoother and sand easier. For best results, thin the joint compound with a little water first to give it a smoother, creamier consistency that will allow it to trowel on easier. Use a 12-inch or larger drywall knife, and spread it onto the wall in broad strokes. The goal is to apply a thin, uniform coat over the entire wall, with as few ridges from the trowel as possible. Some ridges are going to be inevitable, and don’t worry about them — they’ll sand off later. But the fewer the better, since that’ll save you some sanding labor.
Allow the compound to dry completely. It will become lighter as it dries — how long it takes depends on temperature, humidity, and the thickness of the coat — but be sure that the entire wall is completely dry before proceeding. Next, sand the wall again lightly to remove any ridges, and then check your work. Use additional compound to fill in any low spots or flaws, allow the additional compound to dry, then lightly sand again. Thoroughly brush the wall down again, and you now have a smooth, uniform surface to work with, eliminating the need to try to match textures.
You’ll now want to seal the wall, using a drywall sealer or other primer. This will help to prevent uneven absorption of the paint. After the primer is dry, apply the texture of your choice to the entire wall. When the texture is dry, prime everything a second time, which will seal the texture itself. This step is especially important if you’re using satin or semigloss paint. If you’ll be painting the wall with a dark color, have your paint store tint the primer for you, which will give you a more uniform finish color. Finally, paint the wall.