For a small bathroom, professional remediation cost varies significantly based on the mold’s penetration. Surface-level cleaning is less involved, but if the mold has spread behind tiles or into the drywall, the scope and cost increase as it requires removal of affected materials. The only way to get an accurate cost is to request an on-site assessment from a certified provider.

DIY is possible for very minor, surface-level spots. A stiff brush and a dedicated mold-removing cleaner from a hardware store can work. However, given the smell and that it’s spreading, the mold may have penetrated the porous grout. DIY often addresses the visible stain but not the root cause, leading to rapid regrowth.

For a case like yours, a professional inspection is recommended to assess the extent behind the walls. They can identify the moisture source (often poor ventilation or a tiny leak) and provide a remediation plan that includes fixing that issue to prevent recurrence. Look for a provider that offers before-and-after testing to verify the space is truly mold-free.