Skylight Installation: Ideas on How to Coat Taping the Drywa
Hopefully you only have to do corners on this drywall job. If your skylight is larger or you had to piece things together, you'll have to do some tapered butt joints. For those instances, just use your small joint knife (about 4 inches wide) and put a 1/8" thick layer along the butt joint. This is the bed that the tape will rest on. Start on one end and press the tape into the bed. Hold that end with one hand and unroll the tape with the other. When you have the right length, lightly press the tape so that it sticks and then use your small knife to press it into the corner and tear it with the knife up against it firmly. This is much more difficult to explain than it is to do.
You should be able to press from the center outwards in both directions. This is to help prevent bubbles and crinkles, which are your enemy. Your knife should be able to press things in nice, and take away any extra mud. Don't cover the tape back up with more mud at this point, just make sure it is firmly pressed with no bubbles. If you put too much mud on top of the tape, it won't dry properly. Let it dry over night.
The next step depends on how well you did the first one. Most mudders, I would say, don't sand until the last coat. They are though, professionals and have been doing it a long time. If your mud has a lot of ridges, you'll have to lightly sand so that you knock those ridges down. I mean lightly sand. You do NOT want to sand through the mud or tape. You only want to knock the sharp ridges down. I'm reluctant to leave this subject alone because you might not realize the importance of it. For proper coverage, you need 3 coats. If you sand through the first coat, you now have zero coats. This applies to each additional coat. I typically only lightly sand the last coat. Using a wet sponge works for some folks too, more on that later. You can tell if you have ridges by getting out the next drywall knife, 8-10" wide. Don't press real hard, but run it across the joint. It shouldn't be scraping off all kinds of drywall. If it is hitting obstacles left and right, you probably need to sand.
When you're ready to apply the second coat, take your knife and get some compound on it. Start on one end and smoothly apply the compound towards the other end. Telling someone how to do this, on paper, is one thing. Doing it in real life is another. You don't want too much compound, it'll crack when it drys. You don't want too little, it won't cover. You should be able to run your knife down the joint with one fluid motion. Apply, wipe your knife in your tray to remove extra mud, wipe the joint with the clean knife, then move down and repeat.
You should be able to press from the center outwards in both directions. This is to help prevent bubbles and crinkles, which are your enemy. Your knife should be able to press things in nice, and take away any extra mud. Don't cover the tape back up with more mud at this point, just make sure it is firmly pressed with no bubbles. If you put too much mud on top of the tape, it won't dry properly. Let it dry over night.
Another Coat
The next step depends on how well you did the first one. Most mudders, I would say, don't sand until the last coat. They are though, professionals and have been doing it a long time. If your mud has a lot of ridges, you'll have to lightly sand so that you knock those ridges down. I mean lightly sand. You do NOT want to sand through the mud or tape. You only want to knock the sharp ridges down. I'm reluctant to leave this subject alone because you might not realize the importance of it. For proper coverage, you need 3 coats. If you sand through the first coat, you now have zero coats. This applies to each additional coat. I typically only lightly sand the last coat. Using a wet sponge works for some folks too, more on that later. You can tell if you have ridges by getting out the next drywall knife, 8-10" wide. Don't press real hard, but run it across the joint. It shouldn't be scraping off all kinds of drywall. If it is hitting obstacles left and right, you probably need to sand.
When you're ready to apply the second coat, take your knife and get some compound on it. Start on one end and smoothly apply the compound towards the other end. Telling someone how to do this, on paper, is one thing. Doing it in real life is another. You don't want too much compound, it'll crack when it drys. You don't want too little, it won't cover. You should be able to run your knife down the joint with one fluid motion. Apply, wipe your knife in your tray to remove extra mud, wipe the joint with the clean knife, then move down and repeat.
