How to Tape and Apply Joint Compound to Drywall
Taping and Applying Joint Compound to Drywall
For most home owners, there is no more dreaded job than finishing or applying tape and joint compound to drywall, but it doesn't have to be that way. With a little time and effort, the average homeowner who is reasonably handy around the home can successfully do the finish work prior to painting. Finishing drywall is an art that takes years to become a master at, so although you may never become that proficient, you can do a good job that you will be pleased with.
- Prep the wall.
- Apply at least three layers: tape with compound, a block coat, and a skim coat.
- Let the wall dry completely and sand before applying the next layer.
- Paint the wall.
Each of these steps is described in detail below, with photos and videos to guide you.
How long will it take?
Be prepared to spend time on this job. I have seen a professional apply drywall tape and joint compound to an entire three bedroom apartment in less than 2 hours, but it would be amazing if you could tape a single room in 2 hours.
In addition, tape is normally applied the first day; on the second and third days, you will apply joint compound again over all the joints and nails.
Tools and Supplies You'll Need for Applying Joint Compound
You will, of course, need joint compound and drywall tape.
What kind of joint compound do you need?
Joint compound comes in two "flavors"; hot mud and pre-mixed.
- Hot mud is primarily used for patching small areas, filling holes, and very quick work as it is plaster based and sets up quickly. Speed Set or Quick Set are trade names for this type of joint compound.
- Most work is done using normal pre-mixed joint compound, and for the most part an all purpose formulation is more than adequate. Both "taping" and "topping" formulations are available, but I do not recommend them for the homeowner as they are different to work with and have a different feel—stick to one formulation so that you can become more familiar with it.
What kind of tape do you need?
Drywall tape also comes in two styles; a fiberglass mesh with glue on one side and a paper tape with no glue. Both will do the job quite well, but the fiberglass mesh is a little easier to use. It is also considerably more expensive, so larger jobs usually use the paper type.
Tools for Drywall Work
Several tools are necessary to apply joint compound or tape to drywall. You will need...
- a 4" or 5" drywall knife
- an 8" - 12" knife
- a corner knife
- a hammer or screwgun (a cordless drill is perfect here)
- a drywall pan is well worth the cost; for the average homeowner a plastic one is much cheaper than stainless steel and works as well
- sandpaper will be used, in 100 or 150 grit, and a small sanding block is handy
- a razor knife or box cutter can be useful
- if your project is over finished flooring, some kind of floor covering is absolutely necessary; applying joint compound is messy and you will drop more than a little.
Prep the Wall First
It cannot emphasize enough that preparation is necessary before you begin to apply tape and joint compound. Your finished job will not only depend on this, but so will the amount of time and work needed as you proceed. Take a few minutes to check out the installation of the drywall, correcting minor problems as you discover them, and you will find that the job will be much faster and easier with better results.
- Check for protruding nails and/or screws. Nails and screws should be driven just slightly under the surface of the drywall, but not so much that they break the paper surface. Any protrusions will make a smooth surface impossible to achieve. Loose nails may be driven the proper depth but a twisted or deformed stud can still allow the drywall to move in and out as it does not actually contact the twisted stud. If this happens the nail will eventually "pop" through the joint compound so make sure the drywall is firmly attached to the studding behind it. A second nail is often placed about 2" from the first to firmly fasten the drywall.
- Drywall that has been crushed into an adjacent piece is not acceptable and must be either replaced (preferable) or at least the crushed protruding area trimmed off. Again, any protrusions will result in an unsatisfactory job.
- Gaps between pieces of drywall need to be filled if large. When applying joint compound, the compound will fill a small gap of perhaps 1/8" without trouble, but larger gaps will result in delayed shrinkage and a depression or cracking down the road. Apply a setting type of joint compound to fill gaps; large holes must be filled with additional drywall. Do not try to fill a two or three inch hole with joint compound of any type. Make sure the joint compound is not only set hard but dry before continuing.
- Walls should be reasonably clean before proceeding. Large amounts of dust, sawdust, or other materials will result in a lumpy wall and difficult application of joint compound. It is not necessary to vacuum or brush the entire wall, but heavy accumulations should be removed.
- As noted above, finished flooring needs to be covered; you absolutely will drip joint compound and while it is water soluble and not difficult to remove, you will probably drip a lot of it. Do not try to pick up and re-use such drippings as they will always contain foreign material that will show up on the finished wall. Just dispose of it.
Poor Drywall Installation
How to Apply the Tape and Joint Compound
After you've thoroughly prepped the wall, you're ready to start applying the tape and joint compound to your drywall.
First, open the joint compound and, if separated with liquid on top, mix it just enough to mix in any liquid. Do not discard the liquid; it is not simply water, but part of the joint compound. For taping the walls it should be used as received without any dilution as any water addition also dilutes the glue and bonding ability of the joint compound. It is preferable to mix lightly even if there is no separation; mixing changes the consistency somewhat and will make it easier to handle on a knife.
There are three types of joints to have tape and joint compound applied over them: flat, butt, and corner joints.
- Flat joints are those that have the wrapped, tapered edge of the drywall meeting another tapered edge.
- Butt joints are those that have cut edges of drywall meeting each other. (A tapered edge meeting a cut edge is unacceptable as it is not possible to finish it correctly).
- Corner joints are those that are in a corner, such as two walls meeting or the wall and ceiling.
- Flat joints are expected to be flat when finished as you will apply joint compound to fill in the taper in the drywall. Butt and corner joints will not be flat; a slight crown is inevitable as you apply joint compound over an already flat surface. Here, the goal is to cover the joint while maintaining the minimum crown effect.
Appearance will be greatly improved if the compound is spread over a wider area; the inevitable crown is not nearly as noticeable that way.
The Art of Applying the Joint Compound
There is an art to applying joint compound and now is the time to begin learning.
- When you begin to apply joint compound, load your knife with about 1/4 of what it could hold and, holding the knife nearly vertical to the wall move the knife across the wall.
- As you continue the stroke, slowly flatten the knife towards the wall, providing more joint compound to the wall.
- When smoothing joint compound already on the wall, keep the knife at around a 45 degree angle to the wall. The more vertical it is, the fewer air pockets will be produced and the smoother the surface, but also the more gouges you will produce with very small movements and changes in the knife. An intermediate approach at perhaps 45 degrees will work the best in the most circumstances.
If you have never tried to apply joint compound, a little practice with a piece of scrap drywall to learn how to handle the knife and how much pressure produces a layer of mud would be advantageous, but you can also learn while applying the drywall tape.
Use the Proper Size Knife
Tape, cover nails or screws
Final, Skim Coat
Applying the Tape
Taping: The First Layer
If using a fiberglass mesh tape, stick the tape to the drywall down the center of the joint, and apply joint compound over it with a four or five inch knife. This layer of joint compound should be pressed firmly onto the tape, but not so hard as to leave the tape exposed. The objective is to fill the holes in the mesh tape as much as possible while still covering the tape completely. Do not, however, cover the tape with a thick layer of joint compound; just the minimum to cover the tape. Small patches of tape that are still exposed will cover with succeeding coats. It can be difficult to cover both sides of a corner joint at one time as the knife tends to scrape off the material on one wall while smoothing the joint compound on the other wall. If necessary, this step can be done on separate days, doing one side on one day and the other on the next day after the first side as dried.
If using paper tape, apply a thin layer of joint compound to the wall (see picture for how much) and gently press the tape into it using only enough pressure so that it stays on the wall without holding it. The tape is slightly rougher on one side than the other and you must make sure the correct side is to the wall. The side to be applied to the wall is the outside of the roll, but can also be found by grasping the tape on each side and gently bending it. It will easily bend only one way, making a V of the tape; that V is to fit into a corner joint and will tell you which side is to lay on the wall. Once the tape is on the wall, it is pressed into the tape with the knife, once again with just enough pressure to firmly embed it into the applied joint compound but not so hard as to squeeze all the joint compound out from under the tape. There should still be a definite taper on the flat joints after this process; you have another two coats to apply before the surface is to be flat. Applied joint compound that has squeezed out from under the tape is scraped off using the same knife and can be reused unless it has picked up trash from the wall. Corner joints to be taped with paper tape must have both sides done at once, and a corner knife is a very useful tool to have for that purpose. It is set with the angle at a little over the normal 90 degree wall angle so that when pressure is applied it is still just slightly over 90 degrees; this produces a layer of applied joint compound that thins as it gets further from the center of the joint.
Normally at this time the nails or screws are covered. Apply a small amount of compound over the screw and, wiping at right angles to the application stroke, remove the excess. You should be left with a screw sized shallow hole filled with joint compound. Often times an entire row of screws are cover with one stroke, then the excess removed from each one individually or in one additional stroke. Carry a hammer or screwdriver and set any nails or screws that you can feel the knife go over.
Be very careful to remove all the excess, whether it be a small ridge in the applied joint compound or a little nubbin of compound left where it shouldn't be. If you don't get it now you will have to sand it out before the next application of joint compound or it will leave an uneven surface.
Applying the Tape and Joint CompoundClick thumbnail to view full-size
How Long Should You Wait Between Coats?
- Each coat must be allowed to dry completely before succeeding coats may be applied.
- Room temperature is good for this and individual coats should dry in about a day, but colder temperatures or high humidity can increase the time to as much as a month in very unusual circumstances.
- Incomplete drying can cause delayed shrinkage; pre-mixed joint compound will shrink as it dries and if a second coat is put over a layer of compound that is still damp under the surface that first coat will shrink later, causing the second coat to shrink or crack.
Apply the Second, Block Coat of Joint Compound
- Before applying the second coat of joint compound, make a quick look-over of your tape coat and repair or sand away any protrusions from the surface.
- It is common, though not recommended, to thin the joint compound slightly (one pint of water per 5 gallons of joint compound) for the second and third coats. It is easier to pull under the knife and makes fewer air pockets, but also falls off both the knife and wall easier. For a beginner doing only a room or so, the recommendation is that it not be thinned.
- The object of the second, or block, coat is to remove any imperfections (there will be many) in the tape coat and to extend the width of the applied joint compound. The three types of joints are treated somewhat differently, although all with the eight or ten inch knife.
- The flat joint will need one pass with the knife to apply the joint compound followed by one or two more to smooth the compound, remove air pockets, clean up the edges, etc. You will be left with a joint around 10 inches wide.
- The butt joint will need two passes to apply the joint compound. As the center of the joint is already crowned slightly from the tape you must apply joint compound to each side of the crown, to about six or eight inches out on each side. Each side will then need one or two more passes to smooth it, followed by a pass or two down the center to remove the ridge that has been left there.
- Corner joints are best done over two days for the beginner. It is very difficult to apply joint compound to one side of the corner and then the other side without disturbing the first side, although the corner knife may be used again for the block coat.
- In all cases, the block coat is applied quite thin - 1/16" is too heavy and will probably need sanding, especially on butt joints. The block coat needs to be done as neatly as possible - you are approaching the finished product. Any imperfection at all will show up in the final, skim, coat; it is not uncommon to lightly sand the block coat after it is dried to make a superior job. This is also the time to apply joint compound a second time to the nails and screws, using the same method you did for the first coat.
As textured ceilings and walls have become more and more common the block coat has often become the final coat, needing only sanding, texturing and paint for a complete project. It results in cost savings for the professional and usually has a smaller crown on the butt joints. If you decide to take this route, however, be aware that it becomes even more imperative that a very good block coat be applied with an absolute minimum of imperfections, and this is difficult for most homeowners. A skim coat is recommended even when anything but the heaviest texture is to be used.
Apply the Third, Skim Coat of Joint Compound
After drying the block coat, you are ready to apply the final, skim, coat of joint compound. This is the last chance you will have to produce a perfect job, so make the best of it and check carefully for any imperfections in the block coat.
- Remove all protrusions and any trash that has made its way into your work. A light sanding is recommended, but may not be necessary depending on the quality of what you have accomplished so far.
- The skim coat should be at least eighteen inches wide over both flat and butt joints, and at least a foot each way on the corners. This time, each type of joint will get a full knife width on each side with a final pass again in the center to remove the inevitable ridge. Take a great deal of care to produce a flawless surface, without ridges, air pockets, or grooves from trash in the mud or on the knife. You will sand this coat when finished, but it will pay large dividends to take extra time during the application to produce as flawless a surface as possible.
- The skim coat is quite thin, just enough to cover what is there and make a minimum depth coat further out. This does not mean that you will see drywall through a wafer thin coat of joint compound; there must be something there or you may as well not do it at all!
- The skim coat process is again the time for a final coat on nails and screws. One last time use the same procedure as you have already used twice and cover nails and screws.
- After the skim coat has dried it will need sanding, either with sandpaper or a damp sponge. Sandpaper makes a much bigger mess with dust everywhere, but wet sponging is more difficult to get a good job with. Most people prefer sandpaper, around 100-150 grit. Either way, try not to scuff the paper on the drywall - roughened paper will flash through paint and show up in splotches on the finished surface. A little paint and your home improvement project is complete. Not as hard as you thought!
A final thought about sanding: I once had a neighbor that begged some joint compound from me (I was the quality supervisor at a joint compound manufacturing plant for 22 years) to finish his basement, but did not ask for advice or help. He ended up sanding off nearly an inch of joint compound, using a belt sander to do it, and nearly destroying the drywall underneath. His whole house was a fog of dust for a week. Don't make that mistake. Yes you will sand it, but only minimally. Make each coat as near to a finished product as possible, given what you are trying to accomplish with that coat. You may get tired of working on it, but you will be happy you did in the long run.
Skimming a block coat
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
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© 2010 Dan Harmon