Monday, March 7, 2011

How-To: Drywall Finishing (Part I)


Drywall is made with two beveled edges. When the beveled edges of two pieces of drywall come together, they form what is called a flat joint (it isn’t really flat; see Figure 6-1). Flat joints are the easiest of all joints to finish because the recess that is formed is about % inch. This leaves plenty of room to embed the tape, cover it with joint compound, and still end up with a flat wall. However, if a stud is out of line or the hangers made a mistake, it’s the finisher’s job to straighten it out.

Butt joints rarely are found perfectly flush (see Figure 6-1). One board usually will sit slightly higher than the other, creating a high side and a low side. Bad butt joints are the most difficult to cover. With no beveled edge to set tape into, the tape has to sit on top of the board, with joint compound layered over that. Thus, bad butt joints cannot be made completely flat no matter what you do, but you can camouflage it to look flat.

FIGURE 6-1 Butt joint and flat joint cross section

The corners are very seldom taped square even by people trained in this field. If the tape is rounded, it will need to be finished with thick mud to look square. Too much mud will later crack. I will explain later in taping.

To save money on wood, builders are using more metal for framing windows and doors. Metal requires a lot of joint compound and is frequently shallow. Special care should be taken when coating windows and doors because it looks cheap when they are not square.

The term bastard angle refers to any joint that does not form a 90 ° angle. They take special attention which will be explained during each phase of this book.

Before you even get your tools and materials unloaded, check the house to make sure all boards are nailed off tight and all metal is on. Check to see if the job can be completed. If any boards are hung improperly, you will have to make two or three extra trips back after you finish to fix it. This is what finishers call punch out, things to fix after the job is done. Punch out wastes time and money; my motto is “Knock out punch out.”

Once you decide to go ahead with the job, make sure you have enough tools and materials to finish. Put them in a central location that can be reached easily from all over the house. Use this location as a work area. Since someone will be working on the ceiling in this room, check this room first and arrange the tools on the floor directly under one board. This will make it easier for the person on stilts to reach the ceiling joints.

Then go through the rest of the house, checking it carefully. Pick a starting point and follow the wall all the way through the house. Anywhere the board is broken or cracked, pull it off and prefill it. It will never finish properly if it’s loose and moves at all. Remember, the house will be settling. Often, the drywall has been pried with something, and the edge is broken. Tear the paper off and prefill it. Check all butt joints. Bad butt joints should be prefilled. Receptacle boxes (the holes through which the wires are threaded) should be prefilled with joint compound along the edge that needs repairing. Make them strong enough to hold when the outlet cover goes on. Receptacle boxes are sometimes forced when they are covered with drywall. Maybe a wire doesn’t fit right under the drywall. Sometimes a hanger puts the drywall on and nails it tight. Then it cracks behind the board. The paper may the broken drywall and prefill it so it can be taped later on. Prefill any big cracks. (See Figures 6-2 through 6-4.)

FIGURE 6-2 The receptacle box shows a soft spot where the board has been broken underneath. The drywall immediately around it must be cut out and repaired. Hangers often break the corners

FIGURE 6-3 Loose drywall has been removed from the receptacle box. If the hole is too big and the joint compound falls behind the wall, place tape across the hole and push it in a little to act as a holder for the joint compound.

FIGURE 6-4 The receptacle box has been taped to act as a holder for the joint compound. If the joint compound still won't stay in place use more tape on top of it to hold it in.



When you tape, you should use a four-, five-, or six-inch knife, and you should
tape the room in an orderly and efficient manner.

Butts and Headers
Headers are the vertical joints over doors and windows. In a house, butts includes all vertical joints except the corners. These are all joints that are not made by factory (beveled) edges. These are all taped and coated like butt joints. When taping, always do butts and headers first, since they require the most joint compound and drying time.

Flat Joints
Flat joints are those that are made by factory (beveled) edges. These are taped

Angles are the corners. They should be taped third. Receptacle Boxes, Etc. Receptacle boxes, switch boxes, metal, pipes, and the like should be taped last. If you tape in this order, you will gain speed and efficiency. Also, your chances of forgetting something are minimized. Remember, you want to work as fast as you can but still do the job right. If you work too fast, you’ll do sloppy work, and it will slow you down during the following steps of the process. Any joint compound that goes on where it doesn’t belong will have to come off sooner or later. There are three ways to tape. The first is to do it by hand, the second is to use a banjo (which is much faster), and the third is to use the automatic taping tools. The third method is for the professional. I will explain hand taping and the banjo as I describe each kind of joint.

Work with joint compound straight out of the box, or as thick as possible. Never it down. The reason for this is that when the joint compound starts to dry, it doesn’t stick as well. It also leaves air pockets, which develop into blisters. Spread the joint compound along a joint. Place the tape on top and use the knife to smooth the tape, leaving the tape smoothed out on top of the joint compound.

The banjo is fairly inexpensive at about $85.00. If cared for properly, it will last indefinitely. This tool can be filled with joint compound with tape threaded through it. When you pull the tape out the end, it is already covered on one side with joint compound. This makes taping twice as fast.

Taping tools must be watched carefully when you’re first learning to use them. If you run low on joint compound and you’re not aware of it, you can have pieces of tape with no joint compound on them. This will leave blisters. So as the joint compound runs low, you will need to watch the joint compound-coated side of the tape as it comes out of the banjo.

Joint compound for the banjo should be diluted with water so it will pass through the tool more easily. However, if it’s too thin, it will drip on the floor as you tape, making quite a mess. Depending on the type of joint compound used, you will have to adjust the amount of water to thin it just right.

As a result of your earlier preparations, all bad butt joints should now be prefilled. Now go ahead and spread more joint compound right over joint compound that’s already there-even if it’s not dry. You want only the thinnest layer of joint compound between the high side of the joint and the tape, because you’re trying to make this as flush as possible. Make sure the tape is in contact with the joint compound, or it won’t stick. The low side should be as smooth as possible, with the tape sitting on the built-up joint compound. When smoothing excess joint compound from under the tape, hold the knife in a laid-down position. (See Figure 6-5.) Hold the knife with light pressure on the high side of the joint, floating over the built-up low side so you don’t pull any joint compound away from it. Don’t put too much pressure on the high side or you will take too much joint compound out from under the tape and cause a blister. By laying the knife down, you can control the amount of joint compound taken from under the tape. The more the knife is held out at an angle.

Lay the knife down so it doesn't take joint compound out from under the tape. Hold the knife up to pull off more joint compound.

FIGURE 6-5 Knife positioning

Bad butt joints must be prefilled before you use the banjo. The reason for this is that the banjo doesn’t lay down enough joint compound to build with. Be extra careful wiping them down: because butts create such an uneven surface, they blister easily. It’s easy to push out too much joint compound on the high spots. A knife will put even pressure on an uneven surface. Sometimes when the butt joint is bumpy and rough, it’s better just to run your hand over the tape and press the joint compound into all low areas.

Flush butt joints are rare, and they must be coated differently than bad butt possible. This will make it easier to achieve a flush finish. You will probably have a few blisters before you find out how close you can get the tape. You need to build joint compound up on both sides of the tape in order to make it appear flush. (See Figure 6-6.)

FIGURE 6-6 Taping butt joints

If they are hung and taped right, flat joints are the easiest part of drywall finishing. Flat joints are those made by the beveled edges of the board. (See Figure 6-7). Spread plenty of joint compound along the flat joints to secure the tape to the joint. When you roll out the tape, stretch it out, leaving no slack. Otherwise, you

will end up with wrinkles when you start wiping the tape down. A four-inch knife is the best tool for pressing the tape inside the recess. You can use a six-inch knife, but it needs to be limber and you have to apply quite a bit of pressure on it to push it in deep. If the tape sits above the recess, the joint must be built round instead of flat, so be careful. For a better finish, make the best use of those beveled edges.

When taping flat joints with the banjo, hold the banjo by the handle at the top. Pull a few feet of tape out, and place the end of the tape on the flat joint at a starting place. Then run your hand over the tape to stick it to the joint, keeping pressure on the tape while pulling the banjo along with the other hand. Hold the tape tight so it doesn’t slip. Repeat this all along the wall. When you reach the end of the wall and are ready to cut the tape, hold the cutting blade against the tape and twist.

The blade will cut easily if it is kept sharp. When taping with the banjo, you don’t have to worry about having too much joint compound in the recess, as the tape will at nicely into it. You can use a six-inch knife quite comfortably.

For taping angles or corners by hand, a four-inch knife is recommended because of the straighter edge on the side of the knife. Many finishers make their own knives for corners, cutting the sides of regular knives so they are straight. Because you turn your knife around to put joint compound on the wall, you might forget which corner of the knife to put the joint compound on. Put joint compound on the left corner of the knife to coat the right side of the angle, and on the right corner for the left side of the angle.

Spreading joint compound on the first side of the angle is easy. When spreading the second side, though, be careful not to let the side of the knife scrape the joint compound off the first side. Otherwise, you will have a blister where there’s no joint compound. When spreading joint compound on the second side, hold the knife down flat, tilting it sideways away from the adjacent wall. This way, only the corner of the knife will be working in the center. (See Figure 6-8).

Wiping down corner tape can also create problems. Use a four-inch knife because the side of the knife is straighter and helps prevent pushing the tape back into any cracks. Holding the knife out straight from the wall helps make the corner square. If a corner is rounded, it has to be built up thick with joint compound to make it

FIGURE 6-8 Spreading joint compound on angles

To fold the tape for angles, you can thread it through a tape creaser tool, or you can simply pull it through your hand, as shown in Figure 6-9.

Hold the banjo by the side handle (there should be a cloth handle through which you can slide your hand). Pull out some tape and push it into the corner, running your fingers down the center to stick the tape well into the corner. As you do so, keep the tape pulled out tight, maintaining pressure on it. Continue pressing into the center. Pull the tape out another few feet and repeat the procedure. When you get to the floor, twist the blade to cut the tape. The tape should always be left an inch or so from the floor. You never know what kind of trim will go around the base, so tape down as low as you can. Push the tape in tight the rest of the way


FIGURE 6-9 To fold the tape for angles, thread it through a tape creaser tool, or simply pull it through your hand in this fashion: Hold your hand around the tape as shown. Close your thumb and pull the tape through your hand, taking care not to cut your hand.

Where different angles join (such as ceiling corners), be sure to get the tape all the way into the corners. Otherwise, you will leave a hole that will be visible from across the room. Merely pushing joint compound into the corner without taping it won’t work because the joint compound will fall out of the hole. (See Figure 6-10).

A bastard angle is any angle that is other than 90°. It usually has a big crack

FIGURE 6-10 Taping ceiling angles

bad inside angles should already have been prefilled with joint compound when you prepared the job for taping. If it is a fairly straight angle, it can be taped in the usual way. If it has a deep side, prefill and flat tape it, and then apply an angle piece of tape. Take care to avoid pushing the tape into the deep crack. If the angle is crooked and has big pieces broken or cut out of it, you should use flex bead on it.

To use flex bead, measure and cut the strip to the necessary length with tin snips. Crease it by folding it in the middle, keeping it as straight as possible. Spread on a lot of joint compound, place your creased flex bead in position, and wipe it down.

Flex bead on an outside bastard corner is applied in the same way as it is on an inside corner, except that you must pinch the edge and check for straightness. Flex bead twists very easily, and if it isn’t straight, it will adversely effect the appearance of the job. Flex bead also needs to be pinched out just enough to allow the joint compound to coat the angle and clear the tape. (See Figure 6-11.)

You might need to use metal corner bead. Corner bead comes only in a 90° angle. Here’s how to bend it to the angle you need: Lay the corner bead on the floor, take a piece of one-inch pipe conduit about a foot long. place this inside the

Pinch the center so it can be lightly coated with plaster over the flex bead.

FIGURE 6-11 Flex bead

can use this metal on inside or outside bastard angles and corners. A flexible plastic corner bead is now available. You may find this easier to use.

Receptacle boxes are difficult to get exact each time and they are frequently missed by the hanger. If missed by more than a quarter inch, they should be taped, you don’t know which outlet covers will be used, it’s better to just go ahead and tape them. If you have to come back later and fix the job, it will cost you. Any broken board should have been repaired already. If the prefilled hole is three inches in diameter or bigger, it must be reinforced. A good-sized hole can be made as strong as the rest of the wall if it is done right. If a hole is bigger than about five inches across, it will need a hot patch.

When taping these holes, overlap the tape, making sure the back of the tape is coated with joint compound even over the hole. Tape at least three inches past the hole on each side to secure it well. Overlap the pieces of tape by at least half of the tape’s width. When this is dry, you should be able to press the middle in just a little. When filled with joint compound and coated, it will be strong. If the hole is deep, it may need to be taped again to reinforce the joint compound. If you retape do it in the opposite direction for extra strength. (See Figure 6-12.)

The hot patch is a method used to fill and smooth holes in the drywall up to about a foot square. For ceilings, though, this method can be used only for small holes because of the weight of the drywall used for the hot patch. On the walls, any hole bigger than a foot should be cut back to the stud. Then the drywall should be nailed or screwed into place.

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