Wall Repair Behind Tile
The shower corner that has been pulling away from the wall for two years. The single hollow-sounding tile near the valve that finally cracked open and revealed the gray, soft drywall behind it. The closet on the other side of the master shower wall whose paint has been bubbling at the baseboard since last winter. The mildew bloom that no amount of bleach will clear because it is coming through the porous substrate, not living on the surface. Wall repair behind tile is the trade for what is happening one layer in from the finish surface — wet drywall or backer board cut out, framing dried, mold treated, substrate replaced with cement board or Schluter KERDI-Board, real waterproofing membrane reinstalled, and the wall prepped for re-tile. Starting at $900 for a small drywall patch behind a single tile up to $3,500 for a full backer-board and membrane rebuild behind a shower wall. Honest scope — when the moisture source is an active in-wall plumbing supply or drain leak, a licensed Washington L&I plumber handles their portion FIRST, and Handis returns for the wall and waterproofing rebuild after.
Service
What Does Wall Repair Behind Tile Include?
Wall repair behind tile covers the substrate layer of a bathroom wet wall — the drywall, greenboard, cement backer board (Hardibacker, Durock), or Schluter KERDI-Board that sits behind the tile and either is or is not waterproof depending on which the original installer used. We open the failed tile section on arrival, inspect the substrate, cut out the wet or moldy material, treat any visible mold on the framing with a quaternary ammonium cleaner, replace the substrate with cement board or KERDI-Board, install a real waterproofing membrane (Schluter KERDI sheet or RedGard liquid), and prep the area for re-tile. Active in-wall plumbing supply or drain leaks route to a licensed Washington L&I plumber FIRST as the responsible licensed party — Handis returns for the substrate, waterproofing, and tile rebuild after.
Diagnostic Open and Substrate Inspection
Every visit starts with a diagnostic walk and a controlled opening. We tap-test the tile field around the failed area to identify additional hollows, press-test the substrate from any accessible back side (a closet or hallway wall behind the bathroom), and check the moisture meter on the wall surface. The controlled opening removes the smallest section of tile and substrate that gives us a look at the wall cavity — usually a 12-inch by 12-inch section centered on the failure. From the opening we can see the substrate (drywall, greenboard, cement board, or KERDI-Board), the framing (2x4 studs, typically 16 inches on center in a Seattle home), and any active wetness or mold.
Wet Substrate Cut-Out
Wet or moldy drywall, greenboard, or cement board comes out — cut with a utility knife or a small reciprocating saw, removed in panel sections, and bagged. We cut to the centerline of the nearest stud on each side and to a horizontal line above and below the wet area plus 6 inches of margin so the replacement panel has full bearing on framing. The framing under the wet substrate gets inspected — healthy 2x4 framing in a Seattle home is dry, light-colored, and rings solid when struck. Any soft spot on framing gets surfaced for the substrate replacement step.
Mold Treatment with Quaternary Ammonium
Visible mold on the framing or the back of the removed substrate gets treated with a quaternary ammonium cleaner (Spartan NABC, Diversey Virex, or hospital-grade equivalent) on the full ten-minute label dwell, rinsed, and dried with a heat gun on low until a moisture meter reads under 12 percent on the framing. Bleach alone fades the stain but does not kill the organism in porous wood. For extensive black mold visible through multiple stud bays, we will recommend a certified mold remediation contractor before we close the wall. The honest call is to surface the scope, not to bury it.
Substrate Replacement — Cement Board or Schluter KERDI-Board
The wet substrate gets replaced with either standard cement backer board (Hardibacker, Durock, USG Tile Backer) plus a real waterproofing membrane on top, or Schluter KERDI-Board (a waterproof foam panel that is the substrate and the waterproofing in one) installed with KERDI-Fix sealant at the seams. KERDI-Board is more expensive per panel but eliminates the membrane application step and integrates seamlessly with the rest of the Schluter system if the original install used it. Cement board plus membrane is the more common (and cheaper) path for most repairs.
Real Waterproofing Membrane Installation
Cement backer board is dimensionally stable under moisture exposure but water passes straight through it — it is not waterproof on its own. Every Handis wall repair gets a real waterproofing membrane bonded to the substrate before the tile goes back on. Schluter KERDI sheet membrane bonded with thinset, with seams overlapped and taped with KERDI-Band, is the gold standard for new tile work. RedGard liquid waterproofing membrane brushed on in two coats with fiber-reinforcement fabric at all changes of plane is the standard for repairs where the existing substrate is not Schluter-compatible. Either way, the membrane is the layer that stops water from reaching the cavity again.
Prep for Re-Tile
Wall repair scope ends at the prepped membrane surface — tile and grout reinstall is a separate scope under tile and grout repair. We level the membrane surface, mark out the tile layout matching the existing field, and stage the wall for tile reset. Most customers book the tile and grout repair scope together with the wall repair as a single coordinated project; we name both portions on the quote.
How Wall Repair Behind Tile Works
Seven sequential steps from the on-arrival diagnostic open through substrate cut-out, mold treatment, dry-down, substrate replacement, membrane install, and prep for tile reset — the sequence we follow on every wall-behind-tile repair.
Diagnostic Walk and Controlled Opening
Tap-test the tile field around the failed area for additional hollows. Press-test the substrate from any accessible back side. Moisture meter on the wall surface. Remove a 12-inch by 12-inch controlled opening centered on the failure to inspect substrate, framing, and any active wetness or mold.
Diagnose the Moisture Source — Plumber or Handis Scope
Source tracing from the opening. Failed caulk seam letting water through the joint for years (Handis scope). Failed waterproofing or original substrate that was never waterproofed (Handis scope). Active in-wall plumbing supply or drain leak (licensed Washington L&I plumber FIRST). When the source is plumbing we name the licensed sub on the quote and stage the rebuild for after their portion closes.
Cut Out the Wet Substrate
Wet or moldy drywall, greenboard, or cement board comes out. Cut to the centerline of the nearest stud on each side, and to a horizontal line above and below the wet area plus 6 inches of margin. The framing under the wet substrate gets a visual and struck-with-a-hammer test for water damage.
Treat Mold with Quaternary Ammonium and Dry Down
Visible mold on framing or substrate gets a quaternary ammonium cleaner (Spartan NABC, Diversey Virex, or equivalent) on the full ten-minute label dwell. Rinse, dry with a heat gun until the moisture meter reads under 12 percent on the framing. For extensive black mold across multiple stud bays we will recommend a certified mold remediation contractor.
Replace Substrate with Cement Board or Schluter KERDI-Board
Standard cement backer board (Hardibacker, Durock, USG Tile Backer) fastened with cement-board screws every 6 inches on the panel field and 8 inches on the perimeter — or Schluter KERDI-Board (waterproof foam panel) installed with KERDI-Fix sealant at the seams when integrating with an existing Schluter system. Panel sized to the opening with full bearing on framing.
Install Real Waterproofing Membrane
Schluter KERDI sheet membrane bonded to the cement board with thinset, seams overlapped and taped with KERDI-Band. Or RedGard liquid waterproofing brushed on in two coats with fiber-reinforcement fabric at all changes of plane (corner, curb, niche). The membrane is the continuous barrier that stops water from reaching the cavity again.
Prep the Wall for Tile Reset
Level the membrane surface. Mark out the tile layout matching the existing field. Stage the wall for tile reset (a separate scope under tile and grout repair). Most customers book the tile and grout repair scope together with the wall repair as a single coordinated project; we name both portions on the quote.
Wall Repair Behind Tile Pricing
Final pricing depends on the size of the wet area, the substrate type behind the tile, whether mold remediation is required, whether a licensed plumber is in the loop for an active in-wall leak, and whether the tile reset is bundled with the wall repair. Licensed-plumber sub fees pass through transparently with the line item named. Request a free estimate for an accurate quote.
Send us photos of the failed tile area and any visible bubbling paint on adjacent walls — we will tell you the scope.
Why Handis for Wall Repair Behind Tile
The most-common mistake on any shower or tub-surround repair is the rebuild that uses cement board as if it were waterproofing. Cement board is dimensionally stable under moisture exposure (it does not swell, crumble, or rot the way drywall does), but water passes straight through it. The original 1995-to-2010 standard was cement board with mastic-set tile and no waterproofing membrane behind — and that install has a 10-to-15-year service life before the moisture reaches the framing and the wall has to come out. Every Handis wall-behind-tile repair gets a real waterproofing membrane bonded to the cement board (Schluter KERDI sheet with KERDI-Band seams or RedGard liquid brushed on in two coats with corner reinforcement fabric). The membrane is the layer that turns a 10-year repair into a 25-year one.
Diagnostic open before any tear-out
Every visit starts with a controlled 12-inch by 12-inch opening centered on the failure. We see the substrate, the framing, and any active wetness or mold before we commit to the rebuild scope. From the opening we tell you on arrival whether the repair is a $900 small patch, a $2,200 multi-stud-bay rebuild, or whether the moisture source is in-wall and needs a licensed plumber sub first.
Honest plumber handoff when the source is in-wall
An active in-wall plumbing supply line drip behind the shower valve, a hairline pinhole in a copper line, a slow drain leak inside the wall — any of these means a licensed Washington L&I plumber is the responsible licensed party for the leak fix. We do not do in-wall plumbing supply or drain repairs ourselves. We name the plumber and their portion on the quote, schedule their site visit, and return for the wall and waterproofing rebuild after their portion closes.
Real waterproofing — Schluter KERDI or RedGard, not cement board alone
Cement board is not waterproof. Every Handis wall repair gets a real waterproofing membrane bonded to the substrate before the tile goes back on. Schluter KERDI sheet membrane (the gold standard) or RedGard liquid membrane (the more common repair-scope choice) — installed correctly with corner reinforcement at every change of plane. The waterproofing inspection happens before any tile resets. You see it. You sign off on it.
Mold treatment with quaternary ammonium, not bleach
Visible mold on framing or substrate gets a quaternary ammonium treatment on the full ten-minute label dwell, rinsed, and dried with a heat gun until the moisture meter reads under 12 percent on the framing. Bleach alone fades the stain but does not kill the organism in porous wood substrate. For extensive black mold across multiple stud bays, we will recommend a certified mold remediation contractor — the honest call is to surface the scope, not to bury it.
Coordinated tile reset — one project, one warranty
Most wall-behind-tile repairs end at a prepped membrane surface and need the tile reset on top to close the project. We name the tile reset bundle on the quote when scope warrants it so you book one coordinated project, not two. The wall repair and the tile reset both carry the same one-year project warranty when bundled.
Estimate
Tell us where the failed tile area is (master shower corner, hall tub surround, niche, valve area), any visible bubbling paint on the back side of the wall, and the approximate age of the tile install if you know it. Send phone photos of the failure and any adjacent-wall paint damage. We will tell you on the response whether it is a Handis-only visit or needs a licensed plumber sub in the loop, and we will quote both portions line by line.
Customer Reviews
Recent wall repair behind tile reviews from verified Handis customers.
Mildew bloom behind the master shower wall in the closet. Tech opened the shower corner, found the original cement board had never been membraned and the drywall behind it was wet and moldy two feet up. They cut out the wet drywall, treated the studs with a quaternary cleaner, replaced with KERDI-Board, did fresh Schluter membrane, prepped for tile. The tile bundle came next visit and the closet wall has been bone dry for over a year.
Single cracked tile near the valve. Tech opened the area, found about one square foot of soft drywall behind, no active plumbing leak just a years-long failed caulk path. Replaced the drywall with cement board, RedGard membrane in two coats with corner fabric, prepped for the tile reset they did the following day. Bundled the tile and grout repair so it was one project, one warranty.
Active leak inside the wall behind the guest-bath shower valve. Handis was honest on arrival — said it was a licensed plumber call first, not theirs. They named a Washington L&I plumber, the plumber came in for the supply line repair, then Handis returned to rebuild the substrate with new KERDI-Board, a fresh Schluter membrane, and prepped for the tile reset. Two contractors, one coordinated project, transparent line items.
1998 shower with the cement board install that had no membrane. We had been getting mildew at the same corner for years and no amount of bleach would clear it. Tech said the substrate was probably wet, opened it, confirmed — full two-stud-bay rebuild with KERDI-Board upgrade and Schluter membrane. The mildew has not come back.
Bubbling paint on the bedroom wall behind the master tub surround. Tech said the source was almost certainly the tub-surround caulk path, opened the surround side, confirmed wet drywall, did the substrate rebuild and membrane on the bathroom side, then patched the bedroom drywall after the cavity dried. Two-sided repair, one visit, one warranty.
Frequently Asked Questions
Common questions about Handis wall repair behind tile.