Q: The shower in our ‘new to us’ home got moldy quickly in the corners and low on the tile walls. Do we need to tear out our shower and rebuild it?
A: Probably not. Mold like a moist environment and showers get wet with daily use. First, I would focus on air circulation. You want the shower to dry-out between uses. If you have glass doors, or a curtain, leave them open when done. Ensure the exhaust fans is running during showers, and for a while after. If you don’t have an exhaust fan, or the one you have doesn’t seem capable, consider upgrading to something newer that moves more air around. Some homes were built with undersized fans.
With the new fan in place, give the shower a thorough cleaning, and then see if the mold returns more slowly, or not at all.