Drywall joint compound comes in many different formulations, but none of them last forever. … The mud can dry out, become moldy or otherwise become unusable over time. The length of time that it lasts has a great deal to do with how it is stored.

Can you add water to dried out joint compound?

Dried joint compound cannot be rehydrated by mixing it with water. The binding agent in joint compound cannot be rehydrated. Even if mixed with water, the rehydrated joint compound won’t adhere to the wall properly.

How long does spackle last once opened?

Most wet compounds are rated for around nine months to a year so long as the compound is kept in the right conditions. Dry compounds have a similar shelf life of around a year so long as the proper storage methods are used.