Drywall Finish Coat Tips

This small section of wall has just about every drywall finish challenge in it: flat and tapered seams, inside and outside corners and an archway! Photo credit: Tim Carter

Drywall Finish Coat

DEAR TIM: Money is tight and I have to tackle a drywall project. I've never done it before and from what I see on the cable home improvement shows it looks simple. I've also watched quite a few videos on YouTube, including all of your videos.
My wife thinks I'm delusional. I don't want to provide her with years of teasing fodder, so please share all your magic drywall finish coat tips with me. Help me Tim, you're my only hope. Shawn C., Austin, TX

DEAR SHAWN: What's interesting is that when I watch the home improvement shows on TV, I walk out of the room shaking my head. Most of them are unrealistic. They don't really tell you the truth about how hard and complex most jobs are.

What's more, they rarely talk about the required hand-eye coordination that's required for many tasks. You'd be surprised how much of it you need just to hammer a nail into wood without bending the nail or denting the wood. You need even more to master the technique of floating a 10-inch broadknife over a flat seam in drywall!

You've put a lot of pressure on me, so let's get started. Hanging the drywall is a very important aspect of finishing it. If the hang job is poor, you'll fight it all the way as you finish it.

In a perfect world, all tapered seams on the long edges of the drywall will meet with no gaps. This is very important on ceilings. When you do have flat seams that meet that aren't tapered, you want those tight too, but you can get by with a 1/8-inch gap. Large gaps present big problems when you go to tape the drywall.

The screws and fasteners need to be recessed so they have enough of the joint compound covering them. Drywall screws are usually recessed no more than 1/16th-inch. If you drive them deeper, then there's a risk of tearing the paper around the head of the screw. If the drywall panels are loose, the finish will fail over time.

Metal cornerbead needs to be installed so it's tight and that it doesn't flex when you float a finish knife over it. Nails need to be opposite one another spaced no more than 16 inches apart. Use a finishing knife as you nail it to ensure there's a gap on both sides of the bead so the joint compound covers all the metal.

Now it's time to tape! I'm not a huge fan of the mesh tape. It's probably a personal preference. Paper tape works great if you have the drywall joint compound the consistency of warm cake icing and you make sure that you always leave 1/16th-inch of compound between the tape and the drywall. Remember, the joint compound is simply glue and magic dust, so if you don't have enough between the tape and drywall, you'll get blisters when you apply the second coat of compound.

If you get a new 5-inch taping knife, use a metal file and round off the corners of the knife just a little bit. If you don't, you'll be tearing the tape when you work inside corners. You may need to do the same rounding, just a small amount, on the larger 10 and 12-inch broadknives you'll use to apply your second and third coats on the large flat seams and cornerbead.

You need to finish one side of inside corners first before you go to the other side. The compound needs to completely dry or you'll make marks in the uncured compound. Professionals alternate which side of an inside corner they work to speed a job up.

If you're in a typical room and facing a wall, you may start with second coating an inside corner along the ceiling. That means the wall to your left and right you'll then second coat the wall side of the inside corner. The wall behind you, you'll second coat the ceiling part of that corner. You do this all at the same time. The next day you'll then go back and second coat the other side of each of the corners.

The key to finishing is proper consistency of the compound. From the factory, the compound is always a little too stiff. Just add a small amount of water and stir until it's just like warm cake icing. As you work with the mud applying it to the drywall and then scraping off excess to put back in your work pan, water will be extracted from the mud by the paper. You'll have to add a very small amount of water to the mud as you work, unless you work very fast.

Flat seams are the bane of most beginners. The rookie almost always applies too much compound making a mess. You apply the compound with a 10-inch knife and have about 4 inches of compound extend each side of the center of seams. Applying pressure to the knife so the blade gets in a little bit of a twist, you make sure the compound is completely scraped away from the far edges away from the center of the seam, but that there's just a small amount of compound that's higher than the drywall surface at the center of the seam.

You'll end up with an ugly tiny ridge doing this, but after the compound dries, you can sand this off easily making the seam flat. The key is to get good as fast as possible so that you don't leave too much compound which then creates a hump in the wall.

Sanding is key. I suggest sanding drywall at night with a light flooding the wall at a low angle. You'll see all imperfections when you shine a light nearly parallel to the wall. Work diligently so you keep your wife happy!

This popular column was featured in the March 31, 2015 AsktheBuilder Newsletter.

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