The Shower Walls Turned Bright Red Before the Tile Went Up
Most homeowners expect cement board to be the final surface before tile installation begins. Homeowner Brittney Smart’s bathroom remodel reveals one more step that changes the entire shower before the first tile is set. Instead of reaching for thinset, she covers every seam, screw hole, corner, edge, and plumbing opening with a thick waterproof membrane that transforms the gray cement board into a bright red surface.
The color is only temporary. Once tile covers the walls, this waterproof layer disappears from view, yet it continues protecting the shower behind every tile for years. The result looks like fresh paint, but its job has nothing to do with appearance.
Every Seam Receives the First Coat
The waterproof membrane goes on where two cement board panels meet. A brush pushes the material into the joint before spreading it across both sides, covering one of the most common places where moisture could travel behind the tile.
Instead of treating the seam as a simple gap, this step turns two separate panels into one continuous waterproof surface.
Screw Holes Don’t Stay Exposed
Every fastener that holds the cement board to the studs creates a small opening in the surface. Those screw heads receive the same waterproof coating as the seams.
By the end of this step, the wall begins to fill with bright red circles and lines that mark every place where water could reach beneath the tile.
Small Gaps Get Filled Before Tile
Not every cement board joint closes perfectly. Small spaces between panels receive another layer of waterproof membrane before the shower moves to the next stage.
The thick coating bridges shallow gaps instead of leaving them exposed beneath the finished tile.
Thick Coating Covers More Than the Surface
The membrane spreads well beyond the visible crack. Brushing across both sides creates a larger waterproof area instead of sealing only the narrow opening.
This wider coverage helps tie neighboring sections together into one continuous layer.
The Ceiling Becomes Part of the Waterproof System
Waterproofing continues across the ceiling joint, inside corners, window edges, horizontal seams, and every exposed screw head. The gray cement board begins to disappear beneath bright red bands that connect one section to the next.
By this point, the waterproofing reaches nearly every place where two materials meet.
Window Edges Receive the Same Protection
The narrow space between the cement board and the window frame receives careful attention before tile installation begins. The brush carries the membrane into the edge instead of stopping at the face of the wall.
Windows introduce more corners and transitions than flat walls, making these details important parts of the waterproof layer.
Plumbing Openings Stay Sealed
Large openings for the shower valve also receive a complete coat around the exposed cement board. The waterproof membrane reaches the cut edge instead of ending at the flat surface.
Although the trim plate hides this area later, the waterproofing remains underneath.
The Entire Shower Turns Bright Red
After every seam, screw hole, corner, edge, and opening has been coated, the shower looks completely different from the gray cement board installed only a short time earlier. Bright red waterproofing now outlines nearly every connection across the walls.
Once tile covers the shower, none of this work remains visible. The color disappears forever, but the waterproof membrane continues protecting the wall behind the finished tile, making it one of the last hidden layers installed before the transformation is complete.