Mudding drywall

When you start mudding drywall, you’re in the first step of the finishing phase. It’s time to open up, mix, apply and smooth on joint compound–the stuff that fills cracks and hides your drywall seams.




As you probably already know, mudding drywall goes beyond just throwing on some joint compound. You’re going on a little journey of sorts; you have a few stages to complete over a few days to get your walls looking completely smooth.

The different legs of your trip consist of various layers, or coats (explained just below). You’ll use this coat layering process mostly for mudding drywall seams as well as for mudding drywall fasteners. Also included here is how to fix potential problems when working with drywall mud.

Mudding Coats

It’s common practice to use three total coats for anything you’re mudding on your walls and ceilings. This is actually the norm for good reason. You get great results. You want the best results, right?

Think about mudding drywall coats like filling the valley between your sheetrock panels. As each of your layers dries, it will shrink slightly; so in a sense, you’re building on top of the previous surface you’ve created with your drywall mud.

Here are the three coats explained:

First Coat: Rough coat or “taping coat”
For seams, the first coat is really all about laying down a foundation or bed for your paper tape to stick to and then smoothing down the tape For mesh tape, you’ll be applying your first coat on top of the tape to embed it.

For fasteners (nail/screw heads), this first coat is just a thin coat only to cover the head and dimple depression. Wait an entire day for this coat to dry.

Second Coat: Filler coat
The next coat is where most of the joint compound is applied. Since the tape in the first coat is there to add strength to the joint, the filler applied here is to fill the majority of the depression created by seams (tapered). Use an all-purpose, topping, or setting-type compound.

You’ll notice your walls look really good after this coat! But even so, you don’t have to worry about being perfectly smooth on this coat.

Note, that you don’t want to see any air bubbles along your seam as you complete this coat. Also, ensure you knock down any ridges or chunks before you get going on this second coat. Wait an entire day for this coat to dry.

Third Coat: Finish coat
This last coat is the finesse coat. What you’re after here is fixing any small imperfections left over from the first two coats. This is where the smoothness of your walls becomes complete as you fan out your joint compound into nothing, about 8″ to 10″ on either side of the seam.

The third coat will probably be your easiest coat, and is the one where you use the least amount of filler. This layer of mudding drywall is also the most rewarding, because it’s your last! You can actually step back and admire the smooth seams of your walls. Wait an entire day for this coat to dry.

Mudding Drywall: Knives

As you mud drywall in three coats of joint compound, you’ll want a different size knife for each. Get a 6″ knife for the first coat, an 8″ one for the second, and a 10″ or 12″ one for the final coat.

Mudding Large Gaps and Openings

If you’ve found some larger gaps (over 1/4″), you’ll want to roughly fill those in before doing your first coat as normal.

Using a 4″ knife (larger is fine too), apply compound into these large crevices until the filler is flush with the surface of the panels. The idea here is that after this filler dries, it will have shrunk down to about the depth of a normal tapered drywall edge.

Mudding Drywall Seams

We know that with drywall, there will only be two types of seams to hide. Tapered and butted (the short edge or cut edge of a panel).

For tapered seams, you will just fill the pre-existing depression that’s there. It’s there on purpose, so you end up with a level surface after you add your three coats of mud, plus tape.

Butt joints don’t have this taper to work with, so you have to create the illusion that the seam is flat (no small hill) while mudding drywall. This is accomplished by feathering out the mud farther than you would for your tapered seams.

Tips for applying first coat:

Paper tape: For seams, apply a thin layer of joint compound along the seam, using a 5″ or 6″ taping knife. Leave about a 1/16″ layer for the tape to lay into.

Next pull a strip of tape and stretch tightly along the seam centering the seam line itself. Press lightly with the pads of a couple fingers to get it to stay. Then, embed the tape lightly by pulling your knife along the seam, getting rid of wrinkles and bubbles.

Mesh tape: Lay down your tape first, centered over the seam. Ensure it is affixed solidly all along the seam. Put a small amount of joint compound on your knife and press it evenly down the seam.

In general, use setting-type compound if possible, since it is actually stronger and shrinks/cracks less when drying.

Mudding Drywall Fastener Heads

When you cover screw/nail heads and other indentations that might be present on your panels, follow the same three-coat process for mudding drywall outlined above. Sure, it might appear that you can make one simple pass over the heads and simples, but remember this: the filler you apply there will shrink down a little when it dries. You’ll want to do your subsequent coats so you don’t end up with little dimples across your walls!

Tips for applying:

  • Use a 5″ or 6″ knife.
  • Apply in long, vertical strips. Think rows of fastener heads instead of single ones. Vertical lines applied in one sweeping pass will speed up your time in covering the many screws/nails you’ve placed on your walls and ceilings.

Fixing Mudding Problems

When you’re all done with your three coats, you should do one final inspection. While you don’t want to find anything wrong with your (or others!) work, you’re bound to find some spots that require some touching up.

Here are some common things you may find:

Problem The Fix
Scrape marks or pits Add an additional thin coat (can lightly sand)
Cracked top coat Add an additional thin coat, can also re-tape and
re-coat
Coat feathering not even *Check where it’s uneven, and fill with thin coat
– Concave Seams Repeat filler and finish coats
– Crowned Seams Lightly sand along center, add final layer with wide
knife
Tape has bubbled Cut out area with utility knife and retape as normal

*To check how level your seams are, try this: Hold a 12″ taping knife or T-Square perpendicular to the seam. If it rocks back and forth, you can see where to add filler to better fan out edge. Don’t worry if this happens; mudding drywall takes practice!

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