Drywall mud (also known as joint compound) consists of organic compounds and contains a lot of moisture. That makes it the perfect food for mold. So can you still use drywall mud with mold in it?
It may be tempting to scrape out the moldy bits using a knife or other tool. However, doing so is still a health hazard. You’re better off buying a new product rather than using drywall mud with mold. Read on to learn about the shelf life for different types of drywall mud, how mold forms, and how to prevent it from happening.
Types of Drywall Mud and Shelf Life
Hardware and home improvement stores carry a wide variety of drywall mud, and the large variety may seem overwhelming. Depending on the mixture and ingredients, different types may have a different shelf life.
“Hot Mud”
You’ll find that quick Setting drywall mud, sometimes called “hot mud,” is in powder form and is typically in a plastic container lined with bags. Combining it with water creates a chemical reaction that hardens it. After it becomes hard, you cannot reuse this type of drywall mud.
Don’t confuse the hardening time with the amount of usable time. The hot mud package usually lists a time that refers to how long it takes to harden after adding water, such as 45 minutes.
The time the drywall mud will take for setting is typically lesser than the time it takes to harden.
Additionally, hot mud may take several hours to dry, despite hardening in up to 45 minutes.
Many people use quick setting mud as a base to provide a more efficient resistance to cracking. However, the more common use for quick setting mud is for patches and small areas that you need to dry in 24 hours. It’s a quick solution for emergencies such as covering up a large hole or smoothing out crushed corners.
A common belief is that, unlike the premixed variety, quick-setting drywall mud doesn’t have a shelf life. This isn’t true. You should use up your quick-setting drywall mud within a year.
Pre-mixed Drywall Mud
Premixed drywall mud is the most common type, and you can find it in larger containers. As the name suggests, premixed drywall mud is thinned out with water and ready to use.
There are three subcategories of premixed drywall mud: all-purpose joint compound, lightweight all-purpose drywall compound, and topping compound.
All-Purpose Joint Compound
You can use all-purpose joint compound for most applications. The mixture contains bonding agents that strengthen drywall tape and provide long-lasting protection. All-purpose joint compound is more difficult to sand, however, so you should avoid using it as a finishing coat.
Lightweight All-purpose Joint Compound
Lightweight drywall mud may contain less binding agents than the traditional all-purpose type, which could explain its lighter consistency. That said, the lightness means it is easier to sand. Because of its thinner consistency, it’s great for first and second coats.
Topping Compound
Topping compound is typically used for textured application as well as a top coat for seams and corner beads. It is much whiter in color than other types of drywall mud and has a much more limited use. In particular, you should avoid using it for taping joints.
So what’s the shelf life for premixed drywall mud? While the exact expiration date may vary by manufacturer, premixed drywall lasts between 9 and 12 months.
How Does Mold Form in Your Drywall Mud?
Mold spores are generally everywhere you look. However, to grow and thrive, mold needs a moist environment and organic matter to feed off. As mentioned earlier, both of these are present in drywall mud.
Another component that must be present for mold growth is oxygen. As long as your drywall mud is sealed properly and stored in an appropriate environment, you should be able to store it safely up to its expiration date.
Is it possible to store your drywall mud past its expiration date? Technically, yes. You may get lucky and find that your drywall mud is perfect after a few years.
Once you open it, however, you will invite spores to grow inside by allowing contact with oxygen. That means you should use the product after opening it instead of trying to store it again. Introducing mold into your home is dangerous and can lead to many kinds of health issues.
How to Prevent Mold From Forming
For optimum storage, you should check the conditions in the room you place your drywall mud and ensure the container is sealed correctly. Here are some things to keep in mind:
- Water-based drywall mud mixes should be stored in temperatures between 55 and 95 degrees Fahrenheit
- Avoid putting your premixed drywall mud in rooms with freezing temperatures during the winter
- Avoid humidity when possible
- Make sure your drywall mud container is airtight. Lock the lid into place every time.
- Store dry mixes in bags or buckets that are protected form the elements
FAQs
Here are some common questions to take into consideration regarding drywall mud and mold.
Can I use drywall mud with mold?
You should avoid introducing mold into your home at all costs, as it can create both obvious and not-so-obvious health problems. Breathing in mold is associated with several serious health conditions and respiratory illnesses. Therefore, you should resist the temptation to use drywall mud with mold.
Can joint compound go bad?
Drywall mud has an expiration date, whether it is the powder form or the wet, premixed kind. Generally, both types have a shelf life of 9 months to a year.
How long should joint compound sit?
You should let drywall mud dry for 24 hours between each coat. Keep in mind that it may take longer if you live in a warm or humid climate.
Summary
Whether you’re an avid DIY-er or you’re planning a one-time home improvement project, knowing the type of drywall mud to use and how to maintain it are essential. Understanding proper storage conditions and shelf life will help prevent any mold spores from ruining your future projects.
