Contractor called basement water stain 'no big deal' — a year later, mildew smell won't go away

A persistent mildew smell has left a homeowner unsure whom to call for help with a basement water problem. Their contractor had previously dismissed a water stain as "no big deal."

With the contractor's warranty expired, the homeowner turned to Reddit for help figuring out their next steps.

Here's what to know

An upstairs bathroom was the suspected source of the trouble described in a post on Reddit. Directly below that room, a water mark was visible on the homeowner's finished basement ceiling.

The lingering odor has made the problem harder to ignore, despite the basement-finishing contractor's earlier dismissal. The homeowner said they first noticed the stain in 2025.

"Anyway, now, there's also a mildew smell that won't quit," the original poster wrote.

They were weighing a call to their insurer alongside the question of which professional to hire: a plumber or someone in another trade.

More background

"I don't trust the original contractor and the warranty period has passed anyway," they wrote.

The finished ceiling left the homeowner unsure what was happening behind the visible stain. Two commenters suggested opening the ceiling at the water mark to inspect the space.

One commenter recommended checking insurance coverage, though the thread did not establish whether the homeowner's policy would cover the damage or repairs.

What can be done?

The same commenter suggested using a dehumidifier to bring basement humidity below 50% while also checking the stained area for mold and dampness. A separate reply suggested using a humidity sensor to investigate the moisture.

The thread contained no follow-up confirming a repair, an insurance decision, or a quoted cost.

"Your first step is to find and stop the leak. Cut a hole in the ceiling, where you see the water and take a look. Call a plumber to repair the leak from the bathroom," one commenter recommended.

Where can I learn more?

Other homeowners have sought advice on musty smells, damp basements, and mold hidden out of sight. These stories cover basement insulation risks, waterproofing limits, crawlspace concerns, and mold discovered during a home purchase.

• A contractor's plan for mineral wool alone against basement blocks prompted mold warnings from builders.

• A homeowner blamed a waterproofing product for a wet basement, but the fix may start outside.

• A homeowner traced a musty smell to the crawlspace, prompting calls for a structural engineer.

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