This Moldy Shower Looked Like a Remodel Problem Until the Grout Was Cleaned
Dark mold had spread across the shower floor, corners, grout lines, and built-in seat, making the lower section look like it needed more than a cleaning. Reddit user u/Mikealicious2k5 tackled about 12 inches above the floor and the shower seat first, rather than cleaning the entire enclosure in one session.
He sprayed Clorox Tilex Mold and Mildew onto the affected areas, left it for five minutes, then used an electric scrubber across the corners, pebble tile floor, and seat for about 15 minutes before rinsing with hot water. Much of the dark buildup disappeared, exposing pale grout and individual stone pieces that had been obscured by staining.
Mold Had Spread Across the Shower Seat
Dark buildup covered much of the grout between the small stone pieces on the triangular shower seat, with heavier staining concentrated where the seat meets the tiled walls. Cracked material along the front edge also remained visible, making the area look damaged as well as dirty.
The owner said the shower sits in an older house with a foundation that shifts, which has contributed to cracked grout and caulk that still need repair. Cleaning changed the surface, but it did not address those damaged joints.
One Cleaning Pass Exposed the Original Grout
After treatment, the individual stone pieces and pale grout became much easier to distinguish across the seat. Dark staining remained in a few joints and along the damaged front edge, but the difference showed how much of the discoloration came from surface buildup rather than the tile itself.
The owner plans to replace the caulk and repair the cracked joint at the seat, describing those repairs as temporary because the shower will need a larger renovation.
Dark Buildup Collected Where the Floor Meets the Walls
Another section showed black and brown buildup concentrated along the perimeter of the pebble floor and inside the corner. Discoloration extended into the wall grout, while the floor grout had shifted from pale beige to orange-brown around several stones.
The problem was not limited to one dirty grout line. Moisture had affected several adjoining surfaces, with some of the darkest deposits sitting where water can remain around changes in plane.
Cleaning Made the Corner Joints Visible Again
Once cleaned, the same corner lost most of the black surface buildup and the pale grout around the pebble tile returned. Some discoloration remained along the floor-to-wall joint, which is also an area the owner intends to recaulk.
One commenter, u/Puzzled-Band-4538, who identified themselves as an architect, pointed out that shower joints where walls and floors meet should use silicone caulk because movement can cause grout in those locations to crack.
Another Corner Had Mold Running Along Both Edges
Black buildup followed the rear wall and continued into the vertical corner, while brown staining spread through the floor grout. With dozens of small stones packed into the floor, the shower also contains far more grout joints than a floor finished with larger tile.
The owner traced the recurring problem to high humidity in a small bathroom with poor ventilation and said he was working on ways to address that source rather than relying on repeated cleaning alone.
The Pebble Floor Looked Different After Scrubbing
Cleaning removed much of the dark perimeter buildup and reduced the orange-brown staining between the stones. Pale grout once again separated the gray pieces, while the wall joint went from a dark continuous line to a much cleaner transition.
The electric scrubber handled the floor and corners during the 15-minute scrubbing portion of the process, reducing the amount of hand scrubbing required across the many small grout lines.
Grime Extended Across the Back Wall of the Shower
A wider view before cleaning showed brown staining stretching across the floor perimeter, with darker patches concentrated at the corners. The square drain and pebble tile remained exposed, but the grout near the walls had changed color across much of the shower.
This view also shows why the transformation goes beyond one isolated mold spot. Several feet of grout and floor-to-wall joints needed attention before the original lighter finish returned.
Twenty Minutes Changed the Look of the Shower Floor
After the cleaner, electric scrubber, and hot-water rinse, the back section of the shower floor appeared much lighter. The gray stones stood apart from the pale grout again, and most of the dark line that had followed the base of the wall disappeared.
The owner acknowledged that a few areas still needed another pass, but said he was pleased with what the first cleaning session accomplished. The remaining cracked grout, failing caulk, and humidity problem will require separate fixes beyond cleaning.
Heavy Staining Was Still Visible Near the Shower Entrance
Near the raised entrance, orange-brown grout and dark buildup followed the wall and corner before cleaning. Black deposits were concentrated around the change in plane, while staining extended farther into the pebble floor.
The combination of small stones and numerous grout joints creates many recessed edges for residue to collect, which made the difference between the untreated and cleaned sections easy to see.
Cleaned Grout Brought Back the Gray-and-White Floor
After treatment, the same area showed pale grout surrounding the gray stones and far less discoloration along the wall. Some marks remained near the edge and raised entrance, consistent with the owner’s plan to make another cleaning pass and replace deteriorated caulk.
The first session covered only the lower portion of the shower and the seat, but it showed what five minutes of cleaner dwell time followed by about 15 minutes with an electric scrubber could remove before the larger repairs begin.
Our experience with a pebble shower floor followed a similar pattern. Mold returned between the stones despite repeated cleaning, leaving dozens of grout joints that needed attention each time. After cleaning the floor again and again, we replaced the pebble surface with large-format tile.
Fewer grout lines gave water and residue fewer joints to collect in and made routine cleaning much easier. If a pebble shower floor develops recurring mold problems, replacing it may be worth considering during a future renovation, especially when the grout and caulk already need repair. Several commenters reached the same conclusion, recommending larger tiles and fewer grout joints when this shower is eventually rebuilt.
Image credits to Reddit user: u/Mikealicious2k5