How To Drywall Inside and Outside Corners | Wallboard Trim & Tool

How to Drywall Corners

How to Drywall Corners: a Complete Guide

Lots of people, whether professionals or do-it-yourselfers, love drywall because not only does it offer a great final product, it’s low cost and relatively simple to work with. Still, don’t confuse “simple” with “easy.” After all, they’re drywall pros for a reason: it takes practice and a sure hand to get the best results. Without a doubt, the toughest aspect of drywall work to get perfect is finishing – and that goes double for corners, since you have to seamlessly blend not only multiple sheets of drywall, but multiple surfaces together. It can be tricky at first but it’s the key to beautiful results. In this guide, we’ll take a look at everything you need to know to get great results on both inside and outside corners.

Planning and Practice

Like any DIY project or construction job, planning is key. Make sure you’ve got all the tools and materials you need before you start – there’s nothing more frustrating than getting part of the way through the job and then finding you don’t have enough supplies or that you’re missing an important tool. Consider preparing materials in advance as well – for instance, you can cut tape to length before you start, saving you crucial seconds while the mud is drying. The other fundamental component of any finishing job is practice. You probably won’t nail it the very first time you try, so before you tackle difficult finishing tasks like inside corners, you should practice mudding and taping somewhere easier – like a standard tapered joint – before moving on. Even better is to practice somewhere that the results won’t be easily visible, such as inside a closet or utility room. This will ensure that the joints that count, like high-visibility joints and corners in heavily trafficked rooms, will look their best.

How to Drywall Outside Corners?

While finishing corners of any type is trickier than doing flat joints, outside corners are the easier of the two types, thanks to corner bead. If you’re not familiar with it, corner beads are pre-finished corners in either metal or vinyl that can be applied to the outside corner to finish it almost instantly. Some companies even make decorative beads that can be used to create molding, rounded corners, and other effects in an instant while simultaneously taking the hassle out of finishing. Let’s take a look at how to do it:

If your corner isn’t hung correctly, there’s no way to get a good result, even with corner bead.

Using pre-mixed compound, apply a thin coat of compound on either side of the outside corner, around 2- 3 inches wide on each side. Use a 6-inch knife to spread the compound down the wall, apply

Put your bead (already cut to length) over the adhesive layer and make sure it’s flush with the ceiling. Once it’s in place, run your hand or fingers along the entire length, with a slight, even pressure to ensure a good bond. Double check that the bead is on straight, then wipe down the edges, holding the knife at 45° to blend the edges

Once the bead is mounted, you’ll need to apply several coats of joint compound over the bead. These coats should cover the bead entirely and proceed smoothly onto the wall. This is what makes the corner look seamless and smooth. Be sure to scrape away any excess compound so that it doesn’t leave bumps (it’s easier to smooth the compound now than sand it later). Do your first cover coat with a 6-inch knife, the second coat with a 10- inch knife, and the third coat with a 12-inch knife. Make sure to allow the compound to harden completely between coats, and sand it lightly with a fine-grit sandpaper (100-150 grit will work well) after each coat dries.

That’s it! Outside corners are pretty simple, even if they take a bit of practice.

How to Drywall Inside Corners?

As mentioned above, inside corners are a bit more complicated than outside corners, so do them second. Finishing the outside corners first will give you some extra practice with your knives and materials before you tackle the more difficult inside corners. Don’t worry, though – inside corners are still well within reach even for an amateur craftsperson. Here’s what you need to do:

Finishing inside corners can take several days while you wait for mud to dry. Not only that, but each step requires precision, so don’t rush. Take your time and make sure that each step is done as cleanly as possible.

Inside corners can be done by hand with a standard drywall knife, but if you’re doing more than a few feet of inside corner (and you almost certainly are unless it’s a patch job), a corner trowel is a great buy that will drastically improve your results. This special corner tool finishes both sides of the corner at once, eliminating the scratches and scuffs that you can easily put on one surface while working on the other and ensuring even pressure on both sides of the joint. You may also want to give some thought to what type of tape you’ll be using: standard or metal-backed. You’ve probably already got standard tape from your flat joints, but metal-backed gives you a rigid line and can help guide your knife while you apply mud, making it easier to keep your corners straight.

Once you’ve assembled your tools and materials, you can get started. It’s a good idea to tape all the flat joints first, since having that done gives you more stability when doing the difficult corners. The corner tape will overlap the tape from the flat joints.

Put a generous coating of joint compound on both sides of the corner in question, roughly 1/8” thick.

Take your tape (already cut to length and folded along the center crease from step 2) and apply it to the inside corner, smoothing by hand from the center towards the ends with a gentle pressure to eliminate air bubbles and ensure a good bond. Finally, mud the tape in with a knife coated with a small amount of mud. Start at one end (the top if the corner runs vertically) and drag the knife towards the other end, applying a light coating of mud. Do the same thing from the other side and repeat if necessary to create a smooth result. Consider using a corner knife for this step to save time and minimize errors. 

That’s all you can do the first day. Wait for everything to dry and come back tomorrow to do finishing coats.

Apply mud on one side of each corner so that there’s no overlap. Don’t use the corner knife, just a regular taping knife. Keep the handle of the knife parallel to the other wall to ensure that the compound from piling up (if you’re doing the right side of the vertical corner, for instance, keep the knife handle parallel to the left side wall forming the joint).

Let the first finishing coat dry before doing the second. You should have only done one side of each corner at this point.

On the third day, repeat the process from the first finishing coat on the other side. If you did the right side of the vertical corner in the first finishing coat, now you’ll do the left side.

Final Thoughts

In general, but especially with inside corners, be sure to apply your first coats of mud very precisely. They will form a guide for the knife in subsequent steps, so doing a precise job at the beginning will help you achieve good results in the steps that follow. You can save yourself a lot of time sanding and correcting other errors later by taking care early on. And that’s it – everything you need to know to start finishing corners on your own. Following these steps carefully will ensure that outside corners will be a straightforward project and inside corners, though they take some practice, will quickly become an approachable challenge for any motivated DIY-er.

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