Most wall surfaces in new construction are made from drywall—thin panels consisting of mineral gypsum sandwiched between paper faces. Drywall is a very easy material to install, and most of the challenge lies in finishing it—covering the seams between panels with paper or fiberglass tape, then finishing the seams and the screw or nail holes with drywall taping compound to hide them.
The process is often known in the building trades as taping and mudding. Finishing drywall is not a hard process for experienced drywallers, but for DIYers can be tricky to get it right. Part of the taping and mudding process includes sanding the dried compound (mud) to smooth the edges, For skilled professionals, sanding is minimal, but DIYers may find that sanding is surprisingly complicated and messy. The secret is in applying just the right amount of wet mud.
When the process is done correctly, the wall surface will be perfectly smooth, the joints will be invisible to the naked eye, and the finished drywall surface is ready for paint or a textured finish. But taping and mudding can be a frustrating job, so it's important to understand the process well.
Before You Begin
Drywall tape is available in two types: paper and fiberglass mesh. As a general rule, either paper or fiberglass tape will work for straight seams, but inside corners are best covered with paper tape. For corners, there are also corner bead products available, which have paper flanges attached to a metal bead. There are inside corner beads that are mudded into interior corners, as well as outside corner beads that are applied to outside corners.
Joint compound is available in premixed and powdered forms. The premixed all-purpose compound is the best choice for most DIY jobs, though pros may opt for different formulations for different applications.
- Taping compound is the mud used for the main application of tape to the seams and corners, and for the second coat. It is designed to fill in the major gaps.
- Topping compound is used for the third finish layer of mud, a skim coat over the seams, and fastener holes. It is designed to create the final smooth coat, but it won't adhere the tape to the drywall panels in the same way that taping compound does.
- All-purpose compound is a general-purpose mud that serves all purposes. For most DIYers, this is the only mud you really need.
- Lightweight compound is another all-purpose mud, designed to dry faster. Many pros avoid lightweight compound, believing it has inferior adhesion when compared to the other types.
Whether using powdered drywall compound or a premixed product, give the mud a thorough stirring before using it.
DIYers often have trouble applying just enough mud when taping, and over-application makes it necessary to do a considerable amount of sanding to get the joints perfectly smooth. The sanding dust, while not toxic, can irritate lungs and eyes, so it's important to wear a dust mask and eye protection while sanding. Better yet is to hone your skills so you apply just the right amount of mud reducing the amount of sanding necessary.
Watch Now: How to Properly Finish Drywall
Equipment / Tools
- Drywall taping knives (6-inch, 10-inch, 12-inch)
- Taping compound tray
- Screwgun or hammer (as needed)
- Dust mask
- Eye protection
- Drywall sanding block
- All-purpose taping compound
- Fiberglass or paper drywall tape
- Drywall sandpaper
- Dry cloths
Prepare the Surface
Make sure that all nail or screw heads are driven down below the paper surface of the wallboard. Ideally, the paper surface of the drywall should not be broken (if so, it lessens the holding power of the fastener), but should be recessed just slightly below the surface of the drywall panel. Before mudding, drag a taping knife over the surface to detect fasteners that might not be fully recessed, and if you find any, tighten the screws up or drive the nails just enough to remove the obstacle.
If there are any spots with torn paper on the drywall cut them off with a razor or other sharp tool. These will be obstructions to smooth taping and mudding.
Apply the First Mud Coat (Paper Tape)
If you are using paper tape, it must be embedded in a layer of compound, and thus the process takes slightly longer than with fiberglass tape. Many pros, however, feel that paper tape creates a joint that is less likely to crack and show through after painting.
Begin by cutting a length of paper tape to the exact length of the joint. Next, scoop some mud into a compound tray. With a six-inch taping knife, apply a smooth, thin layer of mud over the joint.
Immediately press the paper tape into the mud, centered over the joint. Hold the tape in place with one hand while pulling the taping knife over the tape (work from the middle of the joint toward the ends). Apply just enough pressure to squeeze a little compound out from under the tape.
Immediately apply another thin layer of compound to cover the tape and fill the joint. There should be a very thin layer of compound over the tape at this point, but you will still clearly see the tape through the mud. The edges of drywall panels are slightly recessed as they are manufactured, allowing the paper tape to lay just slightly below the outer surface as it is applied. It will be subsequent layers of mud applied with a wide wallboard knife that raises out the joints so they are perfectly flush with the surrounding panel areas.
Apply the First Mud Coat (Fiberglass Tape)
Fiberglass-mesh tape is self-adhesive and can be applied directly to the drywall seams without first applying a layer of mud.
Cut a length of tape to the exact length of the joint, and press it over the joint, making sure there are no bumps or ripples. Use a six-inch taping knife to apply a layer of compound thick enough to fill and cover the mesh surface, but again you will still be able to see the fiberglass fibers at this point.
Smooth the surface and feather the edges as best as you can by pressing it down with a drywall knife.
Finish Inside Corners
Following the process you used for either paper or fiberglass tape, finish the inside corners where walls meet. For paper tape or corner bead, first apply a thin layer of mud compound, then apply a folded strip of paper tape or corner bead, then cover the paper with a thin coat of mud. There are special corner drywall knives made for this purpose, but you can also apply compound and cover the tape using a standard 6-inch wallboard knife.
Fiberglass tape can simply be folded into a long angled strip, then pressed into the corner to adhere it to the walls. Some care is necessary to ensure to crisp, sharp corners.
For finishing inside corners, consider using prefabricated corner bead. DIYers often find this to be an easier method of finishing inside corners. Corner bead consists of narrow paper flanges attached to an L-shaped metal bead. It can be cut to length with tin snips, then simply pressed into a corner that has been coated with taping compound. When covered over with another coat of taping compound, the corner will be perfectly smooth.
Finish Outside Corners and Screw/Nail Heads
For outside corners that have already been covered with metal bead, applying tape is not necessary—just apply the mud over each face of the corner, using a drywall knife.
With the joints and corners all taped and mudded, apply a small amount of compound over each nail or screw head and smooth the surface.
Let the compound dry overnight, or longer if necessary. Clean the tools and put the lid back on the bucket of mud.
Sand, Then Apply the Fill Coat
Lightly sand the dried compound to remove any ridges and bumps. (Wear a dust mask and eye protection while sanding.) Some professionals omit sanding entirely, simply using a wallboard knife to knock down raised areas of the dried compound. DIYers, though, are more likely to need a light sanding before applying the fill coat.
It is best to use a hand sanding block; do not use a power sander on drywall. A special drywall sanding block can be mounted with fine-grit drywall sandpaper, and it accepts a threaded pole to allow you to easily sand high up on walls without a ladder.
After sanding, wipe down the wallboard with a clean cloth to remove sanding dust, then use a 10- or 12-inch knife to spread another layer of compound over the joints, feathering the edges. With this application from a wide knife, the joint areas will now be raised up nearly flush with the faces of the wallboard panels, and the tape should now be hidden under the compound.
Once dry, give the surface another light sanding. Take care not to expose the tape. Over-sanding is a common DIY mistake.
Drying time for taping compound will vary, depending mostly on humidity levels. You will know that the compound is dry when it all lightens to a uniform, white appearance. With heavy coats, this can require overnight drying, but with light coats in arid weather conditions, drying may take just an hour or so.
Apply the Finish Coat
If you’ve taken care when applying and sanding the first coats, the finish coat should require only a very light final application of mud to create a smooth surface. Use the widest drywall knife trowel you have to apply this coat. This knife should be at least 12 inches wide; pros may use even wider drywall knives.
Some pros add a little water to the mud before the final coat (but never more than the equivalent of one pint of water to a five-gallon bucket of mud). If you do this, make sure to mix the water in thoroughly.
This very light finish coat will likely be dry within an hour or two.
Finish-Sand the Wall
Let the finish coat of compound dry thoroughly, then lightly sand the dried compound. Avoid the temptation to over-sand, as it is easy to sand down into the tape. If the finish doesn't quite meet the smoothness test, don’t be afraid to apply another thin layer of mud.
Your drywall surface is now ready to accept paint, wallpaper, or a texturizing treatment. Wipe the surfaces clean of dust before painting or texturizing the wall or ceiling surfaces.
A "wet sander" is a textured sponge designed to smooth wallboard joints without dry sanding. Wet sanders are popular among DIYers, since they eliminate sanding dust. But with wet sanders, it can be quite hard to get perfectly smooth seams without waves and without dissolving and removing too much of the dried mud. Most people get better results by dry sanding, which is relatively easy once you learn the technique of proper mud application.