If you've ever watched a pro finish drywall, you probably thought to yourself, "I can do that." And probably the first time you tried it -- and the tape didn't stick, and the joint compound had lumps and the ridges wouldn't ever go away -- you thought, "I can't do that."

Actually, you probably can do it. Once you know what pitfalls to avoid and have gotten in a little practice, you should be able to finish a lot of drywall with only a little sanding.

Sanding is the key. It's labor-intensive, time-consuming, messy and bor-rrring. The less you have to do, the better you can rate your technique.

Don't start out thinking you'll find shortcuts. Shortcuts are exactly what create a bad drywall job. Set your mind to the painstaking process of following every step completely and thoroughly, and you'll be rewarded with a wall that is virtually indistinguishable from plaster.

There are three stages to a finishing job (four counting cleanup). Ideally you will complete one before going on to the next. In reality, you may be on Stage 1 in one spot and Stage 3 somewhere else. If you start getting confused, pencil a note on the wall.

Stage 1, the base coat:

1. Open the compound and mix it up with a drywall mixer or a clean strong stick. You want the compound you apply to be as smooth as possible. Scoop up a couple of cupfuls on the knife and put it on the hawk (a flat metal or wooden plate with a handle in the bottom) or in the joint compound pan. Make sure there aren't any lumps. You may want to add a few drops of water and mix it up thoroughly, to get a creamier consistency.

2. Use a 4-inch drywall knife to spread a thin layer of compound over the seam. (If the drywall has been hung properly, most of the seams will join two beveled edges, so there is a slight depression. Some butt joints are unavoidable, and they're harder to finish because you are starting out with a flat surface. The first layer of compound should be as wide as the knife with no gaps or bare spaces, and somewhere between 1/16 and 1/8 inch thick.

Measure off the paper drywall tape. You can cut it with a knife or scissors, but the standard way is to tear it against the edge of the knife. (Make sure the knife is clean and use a hard, flat surface underneath.) If it's a long seam, you may want to do it in two or three pieces, overlapping the tape just slightly where it joins. On a vertical joint work from the top down; on a horizontal one, determine whether you're more comfortable starting at one end or starting in the middle and working out in both directions.

Embed the tape in the compound by pressing it with the blade. Try to use long, smooth strokes. The point is to avoid any bubbles or creases. It may take a couple of hard passes to get the tape thoroughly embedded. Force the compound to ooze out from under the edges of the tape and press out any bubbles. Bubbles tend to travel ahead of the knife. If a bubble seems too big to simply press out, stop, hold the tape with the blade, and lift it from the end back to the bubble, then re-embed it.

On inside corners, fold the tape along the groove, apply a thin layer of compound to each side of the corner, then embed the tape, working on one side at a time. On outside corners, apply a metal corner bead, nailed extensively on both sides to get it flat and tight to the surface. If the corner bead isn't flat enough, you'll have problems later. Apply joint compound to each side with the 4-inch knife; scrape off excess. (Don't worry if the edge is a little rough. That's one place you invariably have to sand.)

3. Once the tape is embedded, scrape off the excess compound with the 4-inch knife so the joint is smooth and the tape is showing. This step is important -- if you don't remove the excess, you will have to sand it later.

4. Let the embedded tape dry thoroughly. It usually takes at least 12 hours. (It will take longer if humidity is high.) Don't rush it. Don't touch it until it's dry. If you were careful when you scraped off the excess, you won't have to sand at this point. (If you do have to sand some spots, avoid sanding the tape. It will fuzz up the surface and make it harder to cover.

Stage 2, the block coat:

1. The goal of this coat is to cover the tape or corner bead. On the corner bead, use a 6-inch drywall knife to apply a second, thin coat of compound. Don't apply too much; you'd just have to sand it off later. On the joints, use the 6-inch knife to fill the bevel and just cover the tape. Hold the knife at an angle of about 30 degrees from the surface on the compound side. Use long smooth strokes and try to make the compound surface as flat as possible -- not concave or mounded.

It's hard for an amateur to do both sides of an inside corner at the same time, unless you become adept at using a corner knife. We prefer to finish one side at a time. It takes longer in hours, but it may be shorter in terms of actual labor.

Keep the joint compound smooth and free of lumps. After a while you will be able to judge exactly how much compound to scoop up and how to keep it evenly mounded along the knife. Don't try to scoop up too much at one time; less is better.

2. Let the compound dry thoroughly -- again, it could take 12 hours or more.

3. After the compound is dry, check for ridges or lumps; if there are any, sand them out with special 100-grit drywall sandpaper. Use a light hand with the sander -- don't sand right through the lTC compound to the tape or metal. If there are craters (places where the knife skipped, leaving a shallow depression) or grooves, ignore them; the finish coat should take care of such flaws.

Stage 3, the finish coat:

1. Load joint compound on a 12-inch drywall knife. The compound should cover the whole knife. Apply with the compound side of the knife at an angle of about 30 degrees to the wall.

Work from corners out to the middle of the wall. Every time you stop a stroke and pick up the knife, the consistency of the compound means a line of it will pull out with the knife edge. You can sand out ridges left by picking up the knife, but it's easier to do if they're in the middle of the wall and not in the corners.

2. Feather the edges. To do this, press the blade of the knife against the wet edge of compound. Hold the knife out at an angle so you're using only about the last two inches of the blade and the outside tip is about an inch beyond edge of the compound. Move the blade smoothly down the joint. It's a little hard to describe, but basically you will be beveling the edges of the wet compound. (If you just kept stroking the knife down flat, you would simply keep spreading the compound, and the finally the edge of the knife would leave a ridge in it. When you tried to smooth out that ridge, you'd leave another in the middle . . . and so on.)

3. For the final pass on the wet compound, run the 12-inch knife in a long sweeping stroke straight along the joint. That should smooth every thing and blend in the bevels.

4. Let the compound dry thoroughly, then do any finish sanding. If you've gotten really good, there shouldn't be much to sand. Joint compound dust is one of the most insidious substances known to man; it will go everywhere. Wear a dust mask and eye protection. Be careful using a fan in the room; exhausting the dusty air is fine, but you don't want to simply keep the particles moving. If you don't want the dust to get into an adjoining space, use tape and plastic to seal that space -- don't forget registers. If you have a duct system that circulates air, you may want to turn it off to keep it from circulating the dust.

Some people smooth the dry finish coat with wet rags. It works well if there's a place that needs a lot of smoothing, and it can create perfectly feathered edges. However, there are some problems. You have to be careful not to wipe off so much compound you get the tape wet; if that happens, you'll have to start all over on that joint. Also, the compound will pick up any texture from the material. It's hard to hold the fabric flat enough to avoid getting patterns in the compound. (If the patterns aren't too pronounced, you may be able to get them out with a very light sanding.) The other thing to avoid is getting the bare paper covering of the drywall wet, which will ruin it.

5. Clean up thoroughly. Dust the walls down with a feather duster or dust mop, then sweep, vacuum, and wet mop. You may have to repeat this whole procedure a couple of times, but it will be worth it if you minimize the amount of dust that escapes. Before you paint the walls, wipe them down once more with a dry rag.

Laid out in black and white, this all sounds difficult and tedious. It's not that bad. As you go along, you'll develop a rhythm and you'll be able to move along fairly quickly. It helps to have the biggest, baddest boom box you can afford blasting out your favorite music. Go ahead and sing along. We do.

Next: When walls just need repairs.

Drywall finishing tips

*Take care of the compound. Stir it thoroughly before using and remove lumps. Don't let a crust of hardened compound build up around the sides of the bucket -- keep scraping it out. If a crust builds up on the surface, scoop it out and throw it away.

Don't put hardened compound from the hawk or compound pan back in the bucket. Throw it away.

Keep the lid on while you're working to keep out dust and debris. When you're finished for the day, clean up the bucket and seal it tightly.

*Keep tools clean. Scrape them off after each pass over compound.

When you're through for the day, scrape tools thoroughly and let them dry. Before using, sand them down to remove any residue.

Don't use the knives for anything else, like scraping paint or opening cans. If you get a nick or bent edge, it will leave marks in the compound.

Mr. Johnson is construction manager for Neighborhood Housing Services of Baltimore. Ms. Menzie is Home Editor of The Sun.

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