Joint Compound: Everything You Need To Know

Joint compound

Have you installed new drywall or do you need to patch some holes in your wall? Are you looking to spruce up your walls before you put up new wallpaper or paint?

If so, joint compound is what you’ll need next to level out the surface of your wall or ceiling and give it a smooth, finished look.

In this article, I’ll discuss what joint compound is, what it is used for, what it’s made of and other relevant information.

What is joint compound and what is it used for?

Joint compound, which is also known as drywall mud or simply mud, is a type of material that is used to fill in the joints between pieces of drywall, fill in any holes, and create a smooth surface before painting or wallpapering.

Joint compound is a thick paste that dries to a hard, sandable finish. Once dried, joint compound can be painted over or covered with wallpaper.

Joint compound is available in both pre-mixed and powder form. The powder form must be mixed with water before use.

Once dried, it can be sanded smooth with sandpaper, orbital sanders and drywall sanders. Joint compound is an essential material when renovating, remodeling, and for any drywall project or repair.

What are the ingredients in joint compound?

Most of the powdered compound is made up of limestone which is about 60%. The rest is made up of mica, attapulgite, starch and crystalline silica.

Ready-mixed is made up of limestone, talc, attapulgite,mica, perlite, quartz (sand) and kaolin 

Is joint compound toxic?

Ready-mixed joint compound is safer to handle compared to powdered joint compound. When sanding you should use a respirator to avoid inhaling the dust which can be irritating and cause coughing.

Powdered joint compound, on the other hand, is carconigenic (Category 1A) and may cause cancer when inhaled. It may also cause damage to organs (Lungs) through prolonged or repeated exposure. 

It’s important to wear a mask when mixing and using powdered joint compound to avoid inhaling the dust.

What are the different types of joint compound available on the market today?

all purpose mud
Ready-mixed joint compound Photo: USG.com

Joint compound can be purchased either in powder form or as a pre-mixed paste. The powder form of joint compound must be mixed with water before use, whereas the pre-mixed joint compound is ready to be used straight from the container.

Joint compound is available in different makes, ranging from lightweight to all-purpose joint compounds, taping, topping and tapeless joint compounds.

The type of joint compound you’ll need will depend on the project you’re working on.

Taping joint compound typically performs as the highest shrinking, strongest bonding, and hardest sanding and is used for embedding tape.

Topping compounds are usually the lowest-shrinking, easiest to apply and sand, and are used in second and third coats. Taping and topping mud is designed for use with each other to give the highest quality finish.

All-purpose can be used for both taping and topping coats, it is also good for skim coating.

Lightweight all-purpose joint compound has the same performance, but is lighter in weight, shrinks less, and sands easier than a conventional weight all-purpose.

Hot mud

easy sand
Powdered joint compound Photo: USG.com

Joint compound in powder form which is mixed with water is usually called hot mud. It gets its name from the heat it produces from the chemical process when mixed with water.

Hot mud is a setting type of joint compound, meaning that it hardens through a chemical process rather than drying through evaporation like ready-mixed joint compounds.

The main advantage of hot mud is that it dries fast and doesn’t shrink much. Filling holes is best done with hot mud and not pre-mixed joint compound which would shrink a lot and crack.

It’s also the joint compound of choice for professional drywallers as it dries fast so two coats of mud can be applied in a day, and it’s stronger than a pre-mixed joint compound.

However, hot mud is more difficult to work with and can be messier than pre-mixed.

Mesh tape should be used with hot mud and not pre-mixed drywall mud.

Tapeless joint compound

This type comes as fibers you add to hot mud such as Easy Sand. Tape In Mud is a fiber reinforcement solution for tapeless drywall finishing.

Instead of applying tapes to the joints, you mix fibers in the taping mud and apply the fiber-reinforced mud to the joints directly. 

The fibers cross-link to each other and form a 3D structural mat like Fibafuse Paperless Drywall Tape in the mud.

It gives the mud enough tensile strength and flexibility to resist cracks caused by building shifting, moisture and temperature changes, or poor workmanship. And the joints are much stronger than finished with paper tape and taping mud.

By skipping the taping process you can save up to 40% of the labor time and it’s easy to use for beginners and DIYers. 

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What do I need to apply joint compound?

The tools needed for applying joint compound are:

  • Joint/Taping Knives
  • Mud pan or Hawk For holding the mud
  • Putty knife For smaller holes

If you plan to use powder joint compound, you’ll also need:

  • A bucket
  • A drill with a mixer attachment

The drill is used to mix the joint compound and water together until it’s smooth with no lumps.

You can also mix joint compound by hand using the putty knife when you don’t need a lot but it can be harder to get a smooth consistency without lumps.

If you’re planning on doing a lot of taping then you could rent or get a taping bazooka. It takes some practice but it will speed up your work and won’t be as strenuous and tedious as doing it manually.

Another type of automatic drywall tool is the Banjo. It works in a similar way as the taping bazooka, although you will have to refill it with joint compound manually as with the bazooka you refill it with a pump.

joint compound tools
Tools for applying joint compound

Can I use joint compound to fill hole on drywall?

When filling larger holes you should use the setting type joint compound, such as Easy Sand, since it will dry faster and it won’t shrink as much as the drying type.

Drying type joint compound such as pre-mixed joint compound works fine for smaller holes, although you might need to spackle twice.

Is joint compound waterproof?

Pre-mixed joint compound isn’t waterproof so you’ll need to seal it with appropriate paint.

There are moisture and mold resistant joint compounds of the setting type.

Should I prime before applying joint compound?

Priming before joint compound isn’t necessary but it can help joint compound to adhere better if the substrate is very porous. Always make sure that the surface is dust-free before applying joint compound.

Can you mud joints without tape?

You can spackle your joints with the tapeless joint compound which has fibers mixed in it to reinforce the joint. Be sure to follow the manufacturer’s instructions.

If you use a thick lining paper over your walls then taping won’t be necessary. Otherwise using tape is the best way to go to be sure that no cracks appear later.

Conclusion

It can be confusing when you’re in the store looking at joint compound because there are so many different types.

An all-purpose joint compound should be enough for both taping and finishing but use the setting type for larger holes.

Joint compound is a versatile product that every homeowner should have on hand. It can be used for many different repair and construction projects around the house.

With a little joint compound and some elbow grease, you can tackle just about any drywall repair project. So don’t be afraid to get started on your next home improvement.

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6 responses to “Joint Compound: Everything You Need To Know”

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