How to Finish Drywall Butt Joints Like a Pro
No matter how hard you try to avoid them, you’re inevitably going to encounter a butt joint or two during your drywall installation. In a perfect world, drywall would create zero joints. In the real world this is unavoidable because whenever a contractor or other drywall installer cuts a drywall panel, which is often a necessity, the cut edge is of course un-tapered. As any experienced contractor will tell you, trying to hide the inevitable mounds butt joints produce is one of the most frustrating aspects of the job.
In this guide, we’ll show you how to finish your butt joints in a way that will make them nearly unnoticeable to the naked eye—just like a pro.
What is a drywall butt joint?
A joint is formed when two pieces of drywall are placed next to each other and secured together using drywall tape and joint compound. Drywall joints are an unfortunate fact of life for DIY’ers using 4’ by 8’ drywall sheets. When it comes to drywall installation, there are two main types of seams or joints: tapered joints (often called flat joints) and butt joints.
A tapered joint is formed when the longer sides of drywall (typically 8 ft. or 12 ft. in length) are brought together. If you take a look at a drywall panel, you’ll notice these edges are machined down in thickness which creates a recessed area when two similar edges are brought together. If the sheet is ½” thick, these reduced edges will be about ¼” thick. This allows for tape and compound to be applied while still maintaining a smooth, flat surface.
A butt joint, on the other hand, is when two short sides of drywall (typically 4 ft. in length) are joined together. Unlike the longer sides, these ends are not tapered and are the same thickness as the rest of the drywall sheet. For example, if a sheet is ½” thick, the edges will also be ½” thick. If these two ½” edges meet, this is a butt joint. Because of this, it is rather difficult to finish them with tape and compound without producing a noticeable bump.
What tools and materials you’ll need to get started
Before you begin, make sure you have the following tools and materials on hand:
- Paper joint tape
- Joint compound (also known as mud)
- A 6-inch joint knife
- A 10-inch joint knife
- A sander or sandpaper (or both)
Without further ado, here are five simple steps for finishing your drywall butt joints like a pro.
Step 1: Make sure all fasteners are countersunk
Before you begin, make sure that all screw or nail heads within 12 inches of the butt joint are recessed at least ⅛” below the drywall surface. If a fastener head is flush or sticking out even a little, it will be harder to create your gradual compound slope.
Pro Tip: You will end up using far more drywall compound than is necessary if you skip this step.
Step 2: Use paper tape to cover the joint
For tapered joints, you’d typically want to use a stronger fiberglass-mesh tape. Some even advise doing so with butt joints, however, for butt joints, this thicker tape will often result in bulges and unwanted texture pop out. Instead, opt for paper joint tape in these cases. See Below.
Step 3: Apply a thin first coat of compound
Using your 6” joint knife, cover the entire length of the tape with a very thin, even layer of drywall mud. Press hard enough to ensure there are no bubbles or gaps under the tape while always being careful not to tear the tape or damage the drywall. Allow the compound to dry fully overnight.
Step 4: Feather out a second coat
Use the 10" joint knife to apply another thin coat of compound to both sides of the joint, making 6” swipes to both sides of the joint's centerline, feathering the outside edges as you go. The goal is to get the mud from the second coat to overlap the mud from the first coat. Use the blade of the joint knife to smooth and blend the mud with the drywall, creating a slight, gradual mound. Again, let the compound dry completely overnight.
Step 5: Sand smooth if necessary
Once the second coat has dried, sand it to smooth the surface and remove any excess mud. Feather the edges of the mud into the wall, being extra careful not to dig into the drywall paper with the sander. Once it’s to your liking, clear the dust from the walls with a damp cloth before moving on to priming and painting. Just remember, with the careful application of compound and sanding, any butt joint can be made to disappear.
Pro Tip: When you begin sanding, you should start with 120-grit sandpaper so as not to leave visible scratches in your joint compound or drywall.
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Al’s Taping Tools has been providing contractors with the most extensive selection of professional-quality tools, parts, and accessories since 1985. Our experts are here to help you find easy ways to save time and money on your next project. Shop our products today to give yourself an advantage on any job site. Feel free to get in contact anytime!