How To Finish Drywall With Joint Compound

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After I had put up the drywall in my basement refinishing project it was time for me to finish my walls with joint compound and tape and make them nice and smooth. I’ll be the first to admit that I wasn’t an expert in joint compound when I started this, and I’m certainly no professional now, but I have learned a few things as I’ve gone over my walls again and again.

First, it’s important to remember our final goal: to even out and smooth the walls out as much as possible before applying our first coat of primer and eventually paint. You’re going to do most of the smoothing with a substance called joint compound or vinyl spackling or drywall compound or just “mud” but it all refers to the same stuff: it’s a wet substance that’s spread on walls and dries hard, pretty much like plaster might.

This is not a difficult job, but it takes some patience and time. Finishing walls is definitely an art form more than a science. It’s a skill that you learn as you go along. When you work with joint compound you’re like the artist who uses clay to make pots, except you’re using joint compound to smooth walls. If you’re really uncertain about your abilities then you might want to call in a drywall professional.

Be cautious, though, of drywall professionals who offer a free “wall texturing” service unless you really want bumpy walls. If they offer “textured walls” then it often means a company can do a fairly messy job and cover any mistakes with “texture” which is just joint compound that’s been slapped on the wall and spread around in a pretty pattern.

It makes sense that if you’re going to smooth the walls out by applying joint compound then your walls not only have to be free of holes and dips and crevices, but also not have anything jutting out. Before you apply any joint compound or “mud” at all, look over your walls for anything sticking out like an errant nail or screw head. Those will have to removed or fixed before you finish your walls. You can run your hands over your walls feeling for anything poking out, but an easier way to do it is to turn on a bright flashlight and roll it over the wall. If there are any screw heads poking out they’ll cast a long shadow and you’ll see them quickly. You’ll also want to keep an eye out for any screws or nails that may be driven in so far that the paper on the drywall is ripped. I would suggest putting in another screw near those just to make sure your wall is secure.

Popped nails, messy screw holes and sloppy drywall finishing with joint compound are all ways you can sometimes find the wooden studs behind drywall, but in the ideal world your wall will be perfectly smooth and you won’t be able to see any evidence of construction work or materials.

Generally, you’re only going to apply the joint compound to two areas: over screw or nail indents and over seams in the drywall where two drywall sheet meet (this includes inside and outside corners and edges). You’re going to actually smooth over those spots with several different layers of drywall compound. Each layer will be a little thinner and a little wider, so you’ll essentially be “feathering” out your joint compound so that any hills and bumps are so gradual that they’ll be practically unnoticeable.

The tools you’ll need are pretty simple. You’ll need some sort of joint compound, some paper or mesh drywall tape, a mud tray and you’ll probably want a few different drywall knives or trowels. I used a little set of cheap plastic drywall blades or spatulas for covering my screw dimples, but for taping I used a wide metal drywall knife (these knives aren’t for cutting, they’re for spreading joint compound) and for the “inside” corners I also used a metal mud knife. You may also need a bucket of water and some sand paper or a rag or sponge for smoothing out your joint compound after it dries. A sharp razor or knife might be useful as well for cutting out any bubbles you may get in the tape.

Types of Joint Compound

There are now quite a few different choices when it comes to picking a joint compound, but unless you’re a professional you probably don’t have to worry too much about them all.

Dry or Premixed Joint Compound: There are dry mixes and premixed joint compounds. Dry mixes obviously require you to add your own water and mix according to instructions. Because I only have one room to do and because I know my limitations, I chose the premixed joint compound because I didn’t have the patience to worry about water ratios and mixing instructions. With the premixed compound you can just pop open the lid and get to work. If it’s too thick you can add a little water and mix it in a little bit. Most premixed joint compound comes in 1 or 5 gallon buckets and it’s relatively inexpensive.

Regular or Light Joint Compound: There’s also different weights of joint compound. Professionals seem to like the regular stuff because it is soft when it goes up and dries very hard. Regular drywall compound is a little more difficult for beginners to work with because it dries slowly and can actually drip and droop a little bit. The light drywall compound is much more stiff out of the bucket and is easier for beginners to use. It doesn’t dry quite as hard as the regular stuff, but in most cases that’s probably okay.

Joint Compound Setting and Hardening Differences: Some joint compounds harden or “set” by drying, so exposure to dry air is what essentially turns them hard and drying time can be anywhere from 8 to 24 hours. There are also some professional quick setting joint compounds that harden with a chemical reaction instead of dry air. The advantage to these “hot mud” joint compounds is that the drying time can be a quick 20 minutes to 2 hours or so. That’s a lot faster than waiting 24 hours between coats, but that also means you have to work fast to make sure it doesn’t harden in your tray.

As a beginner, I chose to go with a 5 gallon bucket of the light premixed joint compound. Some professionals recommend using different types of joint compound for different parts of the job, but I’ve talked to some contractors who also just stick with the same stuff throughout. The light premixed joint compound I chose was good all-purpose compound, though there are topping and taping compounds offered as well. I wasn’t in a hurry, so I was able to give my walls 24 hours of drying time between coats pretty easily. I bought my 5 gallon bucket of drywall compound for about $14 and it was just enough to handle my entire 19′ x 14′ basement room. Different types of joint compound may cover different sized areas, so check the package before you buy.

Spackle vs Joint Compound

Joint compound is not really the same as “spackling paste”. The term “Spackle” is actually a trademarked name for spackling paste just as “Sheetrock” is a trademark name for a type of drywall. The term “spackle” has fallen into general usage. There are different grades of spackle from lightweight to heavier and some spackles even appear to be wet in the tub but turn white as they dry.

Spackle is more of a repair substance that should be used for filling in nail holes, small scrapes and even shallow gauges in walls that have already been finished and painted. Spackle is a drier and heavier compound and is not really meant to be spread and thinned as easily as joint compound. Spackle doesn’t shrink as much and should dry much faster than most air drying joint compounds. You can sand it and paint over just like joint compound, but spackle may not give you a very finished look when it’s applied over a wide area. So, spackle is for smaller jobs, joint compound is for larger jobs.

That being said, you can definitely use joint compound in a pinch to patch holes or scratches in walls if you don’t have spackle. Some basic sanding or sponging might still be needed after applying it and you may still need to go for two or more coats. I would generally not recommend using spackle to take the place of joint compound in bigger project.

Metal Drywall Knife vs Plastic Drywall Knife

A drywall “knife”is really the large spatula-type tool you’ll use to scoop out and spread on joint compound over joints, tapes and your screw holes.

Metal Drywall Knife: Most professionals will use a good metal drywall knife and you’ll want to as well. They’re going to obviously be more expensive than plastic drywall knives, but they’re almost much more rugged, they’re usually a little easier to hold and they can spread light or heavy joint compound equally as well. I used a 10-inch wide drywall knife for going over the joints between two pieces of drywall and I used a smaller metal blade for going over some of the screw holes and doing patch work. With metal drywall knives your cleanup after each joint compound application will be a little longer because you’ll want to clean the knive thoroughly with warm water and then dry them with a rag or paper towel.

Plastic Drywall Knife: You can get a little four pack of different sized plastic drywall knives for a buck or two and that’s about all they’re worth. Plastic is obviously much softer than metal and they won’t hold up for any more than an hour or so if that. Joint compound is hard, sandy material that simply rips up plastic. I use plastic drywall knives for little spackling jobs from time to time around the house or just for scooping the joint compound out of the bucket and into my tray. I usually treat them as disposable tools because they’re usually too chewed up to do much with them after one usage. They’e also not usually nearly as comfortable to hold in the hand as a good metal drywall knife.

Applying Joint Compound

No matter where you’re applying joint compound and smoothing out your walls, the steps will follow this basic pattern:

1. Apply drywall compound.

2. Allow time, usually 24 hours, for the joint compound to dry.

3. Sand or sponge down excess joint compound, essentially “feathering” out and tapering off the layer of joint compound you put on around the edges

4. Repeat the first three steps for another thinner and wider coat of joint compound.

Generally, you’ll end up going over your walls 2 or 3 times like this until most of the areas where you applied your joint compound is wide and smooth and your walls are universally flat. If you’re a beginner you probably won’t get everything perfect on the first, second or third try. You can give yourself another pass or two or you can begin to slightly lower your standards and plan to put up picture frames and furniture around the parts of the walls that aren’t perfectly smooth :-)

Sand or Sponge Your Joint Compound

Sanding Joint Compound: If you sand you’ll want to use 80 to 120 grit sandpaper and it’s usually easier to make a little sanding block by just wrapping a piece of sandpaper around a piece of wood and stapling it in place. If you sand you’ll also want to do a couple of things including making sure you wear goggles and a mask, making sure you have plenty of air and definitely covering anything in the room (or any other rooms nearby) that you don’t want to be covered with a fine white dust. Sanding your drywall is a messy, messy process and sanding only takes joint compound off.

Sponging Joint Compound: I prefer going over my joing compound with a damp rag or sponge, though this takes a little more finesse. A damp sponge sort of softens hard joint compound and while it does wipe off excess, it also allows you push and move it around a little bit. You can actually fill in little gaps and holes this way, without putting on another layer of drywall compound. This damp sponge method is messy, but you don’t have to worry about dust, you just have to worry about dripping water and getting wet joint compound on everything. You may go through a couple of sponges at any one time (joint compound is hard on sponges) so you may find that a few old (but initially clean and lint-free) rags work better. I’ve used old t-shirts to wipe down joint compound.

There’s also a third option which combines the first two. Some companies are now producing a wet or dry drywall sanding sponge and they get fairly good reviews. They look neat, they’re reusable and they’re fairly cheap, so I might try one of these the next time I have some drywall to finish.

How To Apply Joint Compound Over Screw or Nail Holes

You’ve checked your wall for things sticking out, you’ve got your joint compound and you’re ready to go. If you’re never used joint compound before then I strongly suggest you start with the screw or nail holes or dimples in your wall first. That will give you a feel for the weight and smoothness of the joint compound and how it spreads.

For covering holes you don’t need a big drywall knife. I used a plastic knife that was just 3 inches across. Here’s how you’re going to apply joint compound to those screw holes:

1. Scoop out a little glob of drywall compound and wipe it over the screw hole. This puts the joint compound on the wall.

2. Now take your knife and hold the blade tight against the wall and sweep over the hole from a different direction. You’re basically scraping the wall (and over the hole) with the full flat edge of the blade. This will remove some of the excess joint compound.

3. Repeat this swiping motion a third time, removing even more excess joint compound. The end goal is to fill the screw hole and leave no more than a tissue-paper thin layer of joint compound around the hole.

I like to move from right to left to apply the joint compound and fill in the hole and then move from top to bottom and then left to right to “clean off” all the excess around the hole. When you’re finished you’ll have a solid white filled in screw hole that should be fairly flat. You should also have a very thin layer of white joint compound a few inches in every direction around the screw hole, and that’s fine.

You now repeat this for the other 40 million screw holes! At least, it will feel like that when you’re done.

The idea is to fill in the screw or nail dimples, but not leave much else drywall compound on the wall. This is just the first coat because after 24 hours or so this joint compound will dry and shrink just a little bit, but that shrinkage will mean that most of the screw holes will actually still have a tiny sunken dimple on them.

After you’ve put on your first coat you can run over your walls lightly with sandpaper or a damp sponge or rag to smooth out any ridges you may have left from excess joint compound. Don’t worry about things being perfect at this point because they won’t be. If you’re using traditional joint compound then you’ll probably want to give your walls 12 to 24 hours to dry before moing on to your first sanding or sponging.

Taping Drywall Joints

You’ve covered your screw or nail dimples, now it’s time to go over all the joints you have between two pieces of drywall. You don’t want to just put joint compound in those joints and let them go because over time the drywall may slightly shift or the wall will bend and the joint compound will end up cracking. To avoid this cracking you’ll want to a paper or mesh tape over the joint. You’re essentially going to make a “tape sandwich” with joint compound put into the joint, a layer of tape placed over it, and another thin layer of joint compound over that.

I personally like the paper joint tape much better than the mesh tape because the paper tape is smooth and thin and relatively easy to work with. I’ve found the mesh tape to be slightly thicker (and therefore more difficult to cover on the wall) and harder to put up because it isn’t as rigid as paper. The paper joint tape usually does not have any sort of adhesive on it, so it’s really just a roll of paper. The mesh joint tape does sometimes have adhesive on the back and I’ve found that to be a little more difficult to use at times.

Taping your joints is pretty straight forward. First, cut a piece of paper joint tape the length of the joint you want to cover.

Then, you’ll fill the full length of the joint with wet joint compound. You don’t want to put too much in, but you do want to fill in the gap and have some extra on the wall.

This is an optional step, but I’ve found that it does help: quickly dip your joint tape in a bucket of clean water (or even use a spray bottle to wet one side). Wipe off the excess water (you want it damp but not dripping) and then cover the joint with the tape. The paper tape will stick to the wet joint compound much better if it has some moisture on it.

Use your hands and smooth out the tape, pressing out any bubbles and making sure it lays straight. You can do this any way you want, but basically you want to make sure the tape is straight and smooth.

Take your 10 inch or widest joint compound knife (it should be wider than the tape and preferably wider than the slight slopes on the edges of the drywall) and evenly press it against the tape as you move down or across the joint. This will smooth out the tape more, push out excess joint compound and help the tape stick even better. After the tape is on pretty well I’ll usually take a little joint compound on my knife and go over the joint again, spreading a thin layer of compound on it.

Now you just smooth the whole joint as much as you can. I usually move perpendicular to the joint in wide swipes and then sometimes move back over the whole joint. You essentially want to make a wide, gradual “speed bump” of joint compound with the peak at the center of the tape and each side tapering out to each piece of drywall it’s sitting over.

If your tape wasn’t wet enough or if you squeeze out too much joint compound you may find that the tape sort of “pops” up and away from the wall, forming an ugly drywall tape bubble. You’ll want to remove these drywall tape bubbles before you move on to priming or painting.

Inside corners are not that much different, except you’re going to end up folding the tape before putting in into the corner. Once the tape is placed and pressed down with my hand I like to use a corner trowel to go over it, pushing the joint compound out and pressing the tape further into the corner. It’s a good way to “neaten” up an inside corner.

For outside corners you can use a piece of tape, but because outside corners often get bumped and usually undergo a lot of wear and rubbing you’re much better off using a plastic or metal corner joint piece instead of tape. The basics are the same: you put up some joint compound, lay the plastic or metal corner joint molding over it and press down and cover with more joint compound.

Covering screw and nail holes is usually pretty easy, but covering the joints of a wall takes a little more skill, practice and patience.

You’re probably not going to get your walls perfect the first time you try this. You can easily get caught in an endless loop of rolling a flashlight over your walls, applying and spreading out some joint compound to fix the errors and then sanding or sponging the walls down to make them smooth. Once everything dries you might look it over and decide it needs more work. And then more work. And then even more work.

I would say this: limit yourself to four or five application and smoothing cycles for just about any single area or wall. Then apply a thin coat of primer and let it dry for a few days. Take a day off if you can and don’t do anything on your walls. Give yourself some “space” away from the project.

Then go back and look at your walls in every day light from different angles. Don’t go over your walls again with a flashlight looking for tiny errors. You’ll probably be amazed at how smooth and generally consistent your walls look in regular light with a thin coat of primer. If you find flaws you can still use your joint compound to fill in holes or smooth out bumps. You can even sand out little flaws as long as your primer is fairly thin. Thick coats of primer might make this a little more difficult but not impossible.

I don’t always use paint primer (I didn’t use it when I painted my house), but when you’re dealing with new drywall it really is a pretty good idea. Once your walls are primed and painted you can move on to finishing your room with base and crown molding. It adds a decorative element and it hides any little gaps and flaws at the edges of your walls.

That’s about it! If you take your time and have some patience you really can get a good sense of accomplishment and save a lot of money by finishing your own drywall.

Tags: diy, drywall, paint

This entry was posted on September 24, 2009 at 5:54 am and is filed under Basement Remodeling, Interior Projects. You can follow any responses to this entry through the RSS 2.0 feed.