If you're new to DIY, you might wonder if priming is required before applying joint compound. We have researched the topic, and here's what we found out.
No, you do not need to prime before applying the joint compound. This is because, unlike paint, a joint compound has glue (vinyl alcohol polymer) as one of its ingredients. This alone is sufficient to hold the compound on the surface together.
There are two major kinds of joint compounds, and your choice of a joint compound depends on your project. While you may not be familiar with these two types, don’t worry: we're here to help!
Types Of Joint Compounds: Pros And Cons
Joint compounds come in two major types depending on their application. In this section, we'll focus on how and when each type is applied and the pros and cons of each.
1. Premixed Joint Compound
A premixed joint compound contains all the ingredients needed for the job: limestone, mica, clay, glue (polymer), starch, and silica.
If you're not in a hurry and don't mind room for errors, this is probably the best option.
A premixed joint compound is water-soluble. You can easily reactivate the compound when needed by wetting it with water.
So, if you want to smooth out any joint lines or ridges or have an excess compound that needs to be removed, you can do this by wetting the surface and kneading and scraping it a bit.
This makes a premixed joint compound perfect for first-time DIYers who are just getting started with drywall projects and are most likely prone to making mistakes.
You can easily sand it down if you have a rough finish after it dries. This is because the clay content in the compound makes it more susceptible and less resistant to abrasion.
Premix Joint Compound And Water Ratio
A premixed joint compound is an easy way to start a project, but it can be challenging to mix the right amount of water as it depends on your climate.
If you live in a cold climate, you'll need to add more water than in a hot and humid environment. Always check the label for the recommended water content and use this as a guideline.
Takes Overnight To Dry
A premixed joint compound is ideally aired dry overnight. If you're in a hurry and want a quick job done, you'd be better off with the setting-type joint compound, which we will discuss next.
Not Recommended For Moisture-Prone Areas
A water-soluble joint compound is not recommended if you use it in your bathroom or anywhere that is likely to get damp. It will not hold up against moisture.
2. Setting-Type Joint Compound
A setting-type joint compound works the same way as a premixed joint compound. However, a couple of key features set the setting-type joint compound apart, which we will discuss below.
Sets Very Quickly
One of the remarkable features of a setting-type joint compound is that it sets very quickly.
If you're racing against time and want the job done without compromising the quality of your final finish, you should be able to get away with using a setting-type joint compound.
In addition, setting-type joint compounds come with time-release hardening properties, allowing you to choose the period of time you want the joint compound to set.
There's a 20-minute, 45-minute, or an hour and 30-minute setting option, depending on your goal.
Setting-type joint compounds also have better resistance to water and moisture than premixed joint compounds. This means you can use this type of joint compound in any environment where moisture is a concern.
Not Easily Sandable
Setting-type joint compound is the type that dries into a hard finish, so you can expect it to be a bit harder to sand.
Here's a quick video explaining the differences between the two, including plaster:
How To Apply Joint Compound
Choosing what joint compound to use can be tricky, so knowing the differences between a ready-mixed joint compound and a ready-to-use joint compound is essential.
A ready-mix is a premix of everything you need except the right amount of water. You'll receive mud, literally. This means you must add some water to reduce its thickness and make it workable.
On the other hand, you can apply a ready-to-use joint compound right off the bat without any additional preparation.
Here's how you apply a joint compound:
1. Prep The Joint Compound
Add water to achieve the desired thickness and consistency. Use a drywall mud beater or mixer to mix the joint compound thoroughly.
The goal is to create a smooth paste that will adhere to the wall, ceiling, or any surface you want to use without issues and make it easy to feather and smooth out.
Feathering is smoothing the edges by angling the putty knife slightly as you spread the compound. You do this to ensure a straight and even finish.
2. Clean The Drywall
It is important to clean the drywall first before applying the joint compound because any dust and grease will affect the surface of the wall and cause the joint compound to be uneven and not adhere properly.
Also, it will look messy if it is applied poorly.
To ensure a clean surface, you can sand it down and wipe the fine dust with a damp sponge. Finish it off with a dry cloth.
3. Check For Surface Imperfections
Check for gaps and holes, start working from there, and apply drywall tape when necessary. Make sure these imperfections are filled with the compound.
Once done, you can spread and apply the compound to the unaffected areas.
It is highly recommended that you use mesh-type drywall tape when working on gaps and holes. Paper drywall tapes are great for taping corners and for general purposes.
However, they tend to curl and buckle when applied to gaps.
4. Apply The Joint Compound
Use a putty knife to spread the joint compound over the surface, ensuring it is even.
Start at the top and work toward the bottom or from side to side. It's best to work in small sections rather than do the whole thing once. Use a smooth linear motion when smoothing.
Avoid using too much force because it will force the joint compound to squeeze out of the edges. You only apply pressure when working on a surface with drywall tape to ensure it adheres tightly.
For corners, you can use the same technique as the straight edges, working from one corner to the next. Smooth out any bumps or lumps in the joint compound.
Continue this process until you finish coating. Make sure the joint compound is thick enough to provide a good surface.
5. Remove The Excess Joint Compound
If you have too much joint compound left, use a putty knife to scrape off the excess. You should be able to apply joint compound with ease with the right tools.
6. Let It Dry
After the joint compound has been applied and smoothed, please wait for it to dry and allow it to cure, usually for 24 hours at least.
However, the waiting period may depend on the type of joint compound that you are using, so you have to pay attention to the manufacturer's recommendation.
How Thick Should I Apply Joint Compound Between Drywall Tape?
Generally speaking, you should do better with a thickness of 1/8 of an inch. An application thicker than this will result in cracking. The 1/8-inch thickness will give you a seamless appearance.
You can also see the joint compound level better, allowing you to create a nice finish.
Is Primer Required Before Painting Joint Compound?
The general rule of thumb is to always give the surface a coat of primer before painting it. The primer allows the paint to adhere better and makes it harder to chip off.
However, if you're on a tight budget, skipping this step is okay, especially if you'll only be dealing with minor repairs.
Since there's no paint on the joint compound, the paint should stick to the surface with no issues. It helps the paint to adhere well if you sand the surface.
How Long Should I Wait For Joint Compound To Be Ready For Painting?
You should allow the compound to dry completely before painting. We highly recommend waiting at least 24 hours after application for the joint compound to dry completely before painting.
This will create a perfect bond between the new surface and the existing finish.
How Many Coats Of Joint Compound Should I Do?
There is no exact amount of joint compound that you need, but it all depends on the size of your joint and how deep you want to apply the joint compound. The general practice is one coat for seams and three coats after taping.
However, don't allow this rule to limit you. Apply the amount of joint compound you think you need according to the situation.
To Wrap Up
You will achieve the desired result if you apply the right amount of joint compound and wait the necessary time for it to dry. Priming only applies when prepping a surface for painting.
Applying joint compound or drywall mud is an entirely different process than painting, and a primer doesn't substantially improve the quality of your joint compound adhesion.
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