The Inside (Corners) Story
Taping inside corners. It’s no fun, it takes too long and it is the worst part of the taping job. I would rather tape a ceiling with 10 butted seams than tape those inside corners.
Over the 20 years I’ve been taping, I have tried a few different techniques and have gotten excellent results with each method. Unfortunately, each seemed too slow and required too much sanding. It wasn’t until recently that I discovered a method that has me looking forward to taping those inside corners.
I’ll go through and explain all the methods I’ve tried, then tell you about my favorite method and the excellent results I’ve been getting.
Paper tape and the first layer of compoundAnybody who has ever taped drywall knows about the pre-creased paper tape. It is strong, easy to tear to length, easy to crease and inexpensive. It’s usually about 2 inches wide and comes in 250- or 500-foot rolls. Sometimes I will purchase a brand of tape that is a little thicker, but I find it difficult to crease and more easily wrinkled.
Generally, the paper tape is embedded in a layer of joint compound and then covered with one or two thin coats of joint compound. (One is usually enough but sometimes two is necessary, although industry recommendations call for only one coat over inside corners.) Once dry, it is sanded smooth, resulting in a perfectly smooth and straight 90-degree inside corner. It sure sounds simple and it really is quite simple. However, getting it straight and smooth, in what I would consider a timely manner, is the more difficult part.
A method of applying the embedding layer of compound that I have used for years is as follows:
1. Apply the compound undiluted from the bucket with a 4- or 5-inch taping knife.
2. Apply the compound 1/8-inch or less thick to each edge of the corner.
3. Make sure the entire inside corner is covered with compound (no dry areas or unfilled gaps). This method ensures a good layer of compound and makes it easy to fill any gaps. However, it is slow and tough on the hands if done day after day.
Another method that works very well for applying the embedding layer of compound is as follows:
1. Apply the compound with a 4-inch corner mud roller. (See photo 1)
2. Thin down the compound slightly, being careful not to get it too thin; this would result in too many dry spots.
3. Roll the compound into the corner, leaving a good even layer of compound on both edges at the same time.
4. Pre-fill larger gaps with compound.
I like this method because it is quite a bit faster than the taping knife and it reduces stress on the hands and arms.
Embedding the tapeOnce the mud is applied, the tape needs to be embedded. Here’s how:
1. Fold the tape along its crease with one hand and lightly press it into the corner every 12 inches or so with the other hand, keeping the tape pulled tight as you go. (See photo 2)
2. Embed the tape into the compound with a 4- or 5-inch taping knife, working one edge at a time.
3. Firmly press the tape into the corner, forcing out a good deal of compound.
4. Avoid wrinkles, uneven or bumpy edges.
5. Go over each edge again, if necessary, to smooth.
If I am taping an inside corner on a wall, I get better results embedding the tape from top to bottom. If I am taping a longer inside corner along a ceiling, I embed the tape working from the center toward the ends. It may be necessary to use light pressure with the knife when embedding the ends of a piece of tape, then make a few more passes with increased pressure. This will help prevent pulling the tape loose.
The angle trowel or a double-edged knife, I believe, was originally used for interior corner finishing of veneer plaster jobs, but I have seen it used to embed the tape. It does a pretty good job with a couple of firmly pressed passes. The outer edges usually need to be feathered out with a regular taping knife.
A lot of tapers are using mechanical taping tools, myself included. The automatic taper is great for putting the mud and tape into the corner. It is embedded in the following manner:
1. Embed the tape with the corner roller once the mud and tape are in place. This flattens the tape nicely and pushes out the excess mud along the edges. (See photo 3)
2. Glide the corner finisher along the tape, smoothing and feathering out the compound as it goes. (See photo 4)
3. Make a couple of passes with the corner finisher if necessary.
I really like the roller and finisher method because I get the tape embedded and first-coated during the process, which puts me one step ahead of the game. (Note: The roller and finisher does not get tight into corner intersections, so a little work with a 4-inch taping knife is necessary to clean up this area.)
Finish coatsTaping knives or double-edged trowels provide similar results. The tape is embedded in the compound and the edges are clean and feathered out, but there isn’t any compound over the tape itself. For years I would apply a thin layer of compound to both sides of the corner with a 4- or 5-inch taping knife for my second coat, filling and feathering out the compound while trying not to mess up the other edge. Once this layer of joint compound was dry, I would do the same thing again using a 5- or 6-inch taping knife, being careful to fill areas not filled before. This method works great and, when dry, requires very little sanding. The drawback is that it takes quite a bit of skill and time to get the desired results.
So I tried another method that entails coating only one side of each corner at a time. Here’s how I do it:
1. Apply enough compound with a 5- or 6-inch knife to conceal the tape and allow for some sanding. There is only one layer of compound applied over the tape, so get it as smooth and bubble free as possible.
2. Try to keep the abutting edge of the corner as free of compound as possible.
3. At corner intersections, apply the compound to alternating sides to help minimize interfering with wet compound.
4. Once dry, lightly sand or gently scrape with a taping knife, any compound that was left on the edges, then apply compound to these other edges.
This method is faster than the double coating of each side edge method and it achieves excellent results. However, it does require more touch-up and sanding than I like doing.
Double edgeAnother method of smoothing the compound over the tape is trowel, as follows:
1. Apply the compound to each edge to use the double-edged approximately 3 to 4 inches wide and enough to cover the tape completely.
2. Press the corner trowel into the corner and pull it along, leaving a clean center as the excess mud is forced to the outside edges and feathered out. This works great if the exact right amount of compound is applied to the right width.
3. Apply the compound with a knife approximately 1 1/2 inches narrower than the corner trowel. If the edges are not tapered out properly, use a regular taping knife to complete this task. If finished properly with a corner trowel, the inside edge should be clean and require little sanding.
4. Touch up at intersections with a knife, if necessary.
As I explained before, during the process of embedding the tape and smoothing the compound when using the mechanical tools (the roller and corner finisher), one is left with a corner that is essentially already second coated. In most instances, all that is needed is one more coat with the corner finisher. I use the same 3-inch-wide corner finisher for this coat. A mud box is attached to the finisher, which holds a good quantity of thinned compound.
Pressure against the back of the box forces compound into the finisher head. As it is glided along the corner, a thin layer of compound is left along each edge of the corner. The inside edge is smooth and the edges are feathered out nicely. For best results, I like to lightly brush over these corners with a pole sander before applying this finish coat. This removes any small chunks or ridges left during the first coat and it helps ensure a smooth finish. Very little sanding is needed once the finish coat is dry. Using the mechanical taping tools, especially the corner roller and corner finisher, is my favorite way of taping those inside corners.