You pull out a two-year-old bucket of joint compound to finish some freshly hung drywall. But when you open the container, the compound has a horrible smell.

Does drywall mud go bad? The short answer is yes. 

Drywall mud does go bad. Many factors affect its shelf life, including the way it’s stored, whether or not it’s mold-resistant, and the specific type or brand.

Signs of drywall mud being past its expiration include dryness, mold, and an unpleasant smell.

Here’s what else you should know.

What Is The Shelf Life For Drywall Mud?

The shelf life for premixed drywall mud is up to 9 months after opening – although if not kept airtight, it can go bad even sooner. The recommended shelf life for powdered joint compounds is around 12 months.

These estimates vary depending on the manufacturer. So, if you have a bucket of drywall mud that you previously opened, check the back of the package or manufacturer websites for specific advice.

The good news, though, is that if you’ve stored your joint compound in an airtight container in a room with stable temperatures, it might last far beyond the manufacturer’s recommended shelf life.

If you’re trying to determine whether or not your drywall mud is still okay to use, look for discoloration, signs of mold, dryness, or a foul smell. 

If you notice any of these signs, toss out that two-year-old bucket of drywall and head to the home improvement store to buy some new. You don’t want to ruin any DIY projects with expired joint compound.

What Does Bad Drywall Mud Smell Like?

All drywall mud has a smell to it. Most would describe the scent as being a light chalky scent that’s relatively pleasant.  

Which is why when you open a tub of joint compound and have to plug your nose, you know it has gone bad.

This foul smell is the result of the drywall mud decomposing. It happens when the drywall joint compound hasn’t been stored properly or is well beyond its expiration date.

Most people describe this smell as being similar to roadkill or rotten eggs.

Bottom line: If your drywall mud has a foul odor, don’t use it.

Can You Use Moldy Drywall Mud?

Determining whether moldy drywall is usable depends on how much mold is present and how old the drywall mud is.

Since premixed gypsum drywall mud is damp, once opened and exposed to air, it can grow mold. So, if you’ve recently bought a pail of joint compound, used it, and then put it away, there may be a few mold spots on the top.

In this instance, it’s probably okay to scrape off and throw away the moldy spots. 

On the other hand, if your drywall compound is full of mold or past its expiration, you need to throw it all away. Even though the mold spores would probably die when the drywall mud hardened, you don’t want to take that chance.

You’re better off using a fresh batch of drywall mud or ready mix joint compound to go over the taping and joints on your sheetrock.

Fortunately, you can avoid mold developing in future packages of drywall compound or spackle by keeping it in an airtight container after opening. You could also purchase mold-resistant drywall mud if mold is a common problem for you.

Conclusion

If you’re wondering whether your drywall mud is still good to use, look for signs of black mold, dryness, discoloration, or a foul smell. If you notice any of these, chances are your drywall mud is past its expiration.

In the future, extend the life of your compound by storing it in an airtight container in a room with stable temps. Alternatively, buy only what you need for a project so that there’s no leftover joint compound to store.