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Next kind of damage. We're going to talk about a bit of flooding action. Now, I'm not talking about your whole house is floating down the street kind of flood. I'm talking about situations where, let's say, you have a basement with a finished drywall and you get a sewer backup or heavy rain and the system's overwhelmed in the city and so it all kind of works its way back into your home. Those are never pleasant, but they do happen. And so, for argument's sake, we're going to go with about a 6-inch water line in your home.
The water that gets into here in a lot of cases is not going to be rainwater. It's going to be mixed with sewage. But the idea is that when sewer water gets backed up from the rain, it mixes and so it's got bacteria in it. And so all these baseboards get removed and thrown in the garbage. Same with your door casings. Same with your door jambs, and should be same with your doors. Now, if you had water damage that didn't touch the bottom of the door, you'll know because if it did, it'll have a watermark stain on it. That's the easiest way to tell, but for our purpose, we're going to assume we're dealing with about six or seven inches of water.
Now, generally, what happens is the system can be overwhelmed for like an hour or two, and then the water goes right back down the drain once it catches up. Wet drywall can dry out. But the bacteria issue is what I'm talking about. Once it has proliferated and is inside that wall cavity, behind it is now soaking wet. The bacteria has an environment to grow, it's going to get stinky, and it's most likely going to go to mold as well.
So what we do is the wet test. You just take your screwdriver and go, and it should pop through really, really easy. Your 10-year-old should be able to grab a screwdriver and punch through a wet wall. You go like this, and you go a little more solid here. What happens is for a couple of hours the water is sitting here, but it's soaking up. The moisture content at this point might be around 90% and it'll go to 80, 70, 60. You'll have a water stain on your drywall, but even above the stain the moisture content is still too high to save. So you punch away until you get some resistance. Now you've got nice drywall, and that's what you want to save.
We know a full 48-inch sheet is way up here, so we're going to go down to where the drywall is nice and tough. You set the tip in and pull it around the height of your doorknob, which is a really good guide. You pull it twice and let every stud guide you as you go across. Now you're cut clean through, so you can take your hammer. There's a hole, and we bounce and vibrate until the drywall pops off the screws. It's a lot easier when it's wet, trust me. That drywall goes in the garbage. The only thing left is to remove all the screws. The point of this is to get that wet material out so it can dry.
If you call your insurance company, they'll come over, cut all that out for you if you have coverage, and treat the wood to kill the bacteria. But you have an option to do it yourself with a solution of bleach and water. You can get a small spray jug and spray down your wood. Go about three or four days before you rebuild, and give it a week. Make sure the basement smells good. If it smells stinky, you still have bacteria that needs to be treated, because it will grow over time.
The tools for repairing your drywall are simple. Grab a square, which as a homeowner is your best friend. You can use a tape measure or eyeball it. Pull out your knife and score the paper. Before you install your sheet, you can grab the old tape, give it a yank, and find out where the tape joint is. You can see it developing there. Pull this and hopefully it brings the tape with it as well.
Now we have to get rid of all the screws. Good news: drywall screws have really low shear strength, so you can hit them off with a hammer or pull them out with a drill. Don't save them. Get a new box. They'll go rusty if exposed to too much water, and a rusty screw will translate that stain through your mud work.
Depending on your situation, results will vary. Not everybody has a 4-foot sheet that fits perfectly from the floor to the replacement point. Sometimes you measure 4 and a half feet, or sorry, 4 and a half inches, because it's okay to have a gap at the bottom. Measure two lengths, snap a chalk line, and cut on that line. Don't worry about where the natural joint is. Come back with a full sheet, and once you know it will fit, get it out of the way a little.
Mark your studs by throwing a new screw on every stud. This drywall probably doesn't need to be reattached, but maybe it does because of all this activity. Most people put the first drywall screw within the first inch, so go to two inches and you're almost guaranteed not to hit anything. Next, grab your marker and mark on your floor, probably concrete since most floods are in basements. If you had a water event from a bad shower leak and you're doing the same kind of replacement, mark right on the subfloor. If you have carpet or something similar and you're upstairs, put down a couple rows of tape and then mark your stud locations. This is going to be really key, because when you go back to install your drywall, you can identify where the studs are on the top and bottom by those little black marks and little screws.
Now we've got our pedal underneath the drywall. We put a little weight on it and lift the drywall to close the gap. Go straight underneath the other screws, set the right depth, and carry the whole sheet. This is 1/2-inch drywall, which is ultra light.
The easiest way for a homeowner to do this is to buy premixed all-purpose compound. If you're restoring from a flood, it's a major event and you'll have a bunch of taping to do. You don't have to worry about quick-set compound, because you aren't going to be in that much of a hurry, unless you're really handy and want to get two coats in your entire basement in the same day, which is a lot to ask of most folks. Take the compound out for paper tape and work the mud up a little to soften it. Fill like this. The tape comes off the roll with a crease line down the middle, which self-creases for inside and outside corners. You want that crease toward the back. If you lose track of where your joint is, use your knife and it will click when it finds the middle. Set it, run it all the way over, and adjust until it's perfect.
The best way is to hold one end of the tape and flatten it out, adding a little pressure. Take off the excess. I like to apply moisture to the face of the tape, then come back with your big towel and fill the gap. That's your first coat. For screws, use the side of your knife. The bottom gets covered by baseboard, and the ones near the top will be covered by casing, so you don't have to fill those, just the other ones. Run the mud off the side of your knife.
If you use regular mud, you need three coats, which is fine since you're here anyway. If you use hot mud, remember that hot mud doesn't shrink, so you can get away with just one coat of hot mud followed by one coat of finish. For this joint we're doing a nice fill coat and finish coat. Hold the knife on the edge so you're holding the mud and pushing it up as you go across. Snow-plow down with a little pressure on the top edge until it's feathered in nicely, then go the other way, feathering toward the middle.