Apply Waterproof Membrane
Paint on liquid membrane or install sheet membrane on all wet areas per manufacturer specifications. This creates the critical waterproof barrier that protects your home from water damage.
Quick Summary
4-6 hours
$100-$300
Medium
Roller, trowel
Choosing Your Waterproof System
Liquid Membrane Systems
Paint-on waterproofing that dries to a flexible rubber-like coating.
RedGard, Hydroban, AquaDefense
- • Easy to see where you've applied
- • Great for complex shapes
- • DIY-friendly application
- • Easy to fix missed spots
- • Requires 24-48 hour cure time
- • Two coats needed
- • Temperature sensitive
$100-200 for typical shower
Sheet Membrane Systems
Fabric or foam sheets installed with thinset mortar.
Schluter Kerdi, Wedi, Laticrete Hydro Ban Sheet
- • Tile immediately - no cure time
- • Fast for large flat areas
- • Physical barrier you can see
- • Integrates with pan systems
- • Requires thinset experience
- • Cutting and fitting takes time
- • Pre-formed corners needed
$150-300 for typical shower
Matching Systems
Important: If you used a Schluter pan, use Schluter Kerdi membrane. If you used a Wedi pan, use Wedi membrane. Manufacturers design their systems to work together and provide warranties only when you use matching components. Mixing brands isn't necessarily unsafe, but it voids warranties and may have compatibility issues.
Before You Start
Surface Preparation Checklist
Tools and Materials
For Liquid Membrane
- • Liquid waterproof membrane (1-2 gallons)
- • Paint roller with 3/8" nap cover
- • Roller tray
- • 2-3 inch paintbrush for corners
- • Fiberglass mesh tape (4" width)
- • Primer (if required by system)
- • Clean rags and water for cleanup
- • Painter's tape for masking
For Sheet Membrane
- • Sheet membrane rolls (measure your area)
- • Pre-formed inside/outside corners
- • Unmodified thinset mortar
- • 1/4" square notch trowel
- • Flat trowel for smoothing
- • Utility knife with fresh blades
- • Straightedge for cutting
- • Wallpaper roller or grout float
Application: Liquid Membrane
Apply Primer (if required)
Some systems (like certain versions of Hydroban) require primer. Check your product's technical data sheet. If primer is needed, apply it first and let it dry per instructions (typically 30 minutes to 2 hours).
Reinforce Corners and Seams First
Using a paintbrush, apply membrane to all inside corners, outside corners, and wall-to-floor transitions. While the membrane is still wet, press fiberglass mesh tape into these areas. Then apply another coat of membrane over the tape, ensuring it's fully embedded.
Key areas to reinforce: All inside corners (wall-to-wall and wall-to-floor), around the mixing valve, around niches, and where the membrane meets the shower pan flange.
Apply First Coat to Walls
Pour membrane into roller tray. Roll onto walls in thin, even coats. Work from top to bottom in sections. The coat should be thin enough that you can see the substrate through it. Don't try to achieve full coverage in one coat - two thin coats are better than one thick coat.
Coverage rate: Most liquid membranes cover 50-75 square feet per gallon per coat. A typical 36" x 60" shower (3 walls plus floor) needs about 1.5-2 gallons total for two coats.
Integrate with Shower Pan
Roll or brush the membrane to overlap onto the shower pan flange or bonding surface. This should overlap at least 2-3 inches onto the pan. Check your pan manufacturer's specs for exact requirements. This creates a continuous waterproof envelope.
Allow First Coat to Dry
Wait for the first coat to dry completely before applying the second coat. Drying time depends on temperature, humidity, and ventilation. Typical times:
- • RedGard: 1-4 hours between coats
- • Hydroban: 1-2 hours between coats
- • AquaDefense: 1-2 hours between coats
The membrane changes color as it dries (RedGard goes from pink to dark red). If it's still tacky to the touch, it's not ready for the second coat.
Apply Second Coat
Roll the second coat perpendicular to the first (if you rolled vertically first, roll horizontally second). This ensures complete coverage. Again, keep it thin and even. Pay special attention to corners and seams.
Cure and Inspect
Allow the membrane to cure fully before tiling:
- • RedGard: 24-48 hours (longer in cold/humid conditions)
- • Hydroban: 4-16 hours depending on conditions
- • AquaDefense: 4-24 hours depending on conditions
Inspect under bright light for thin spots, missed areas, or gaps. Use a flashlight at an angle - properly coated areas reflect light differently than thin spots.
Application: Sheet Membrane
Mix Unmodified Thinset
Mix unmodified thinset to a smooth, lump-free consistency. It should hold ridges from the notched trowel but still be workable. Work in batches - you have about 30 minutes before it starts to set.
Always unmodified: Sheet membrane systems require unmodified thinset. Modified thinset won't cure properly and can cause membrane failure.
Install Corner Pieces First
Apply thinset to inside and outside corners using the flat side of your trowel. Press pre-formed corner pieces into the thinset. Smooth out air bubbles with a grout float or wallpaper roller. These corners are critical - take your time to get them flat and well-bonded.
Apply Thinset to Wall
Using the notched trowel, apply thinset to a manageable section of wall (about 3-4 feet). Hold the trowel at a 45-degree angle to create consistent ridges. Don't apply more thinset than you can cover in 15-20 minutes.
Press Membrane into Thinset
Roll out the membrane sheet and press it firmly into the thinset, starting from the center and working outward. Use a grout float or wallpaper roller to smooth out the membrane and remove air pockets. You should see thinset slightly squeeze through the fleece backing.
Good bond indicators: The membrane should be completely flat against the wall with no air pockets or loose areas. You should see thinset coverage through the fleece when you press firmly.
Overlap Seams Properly
When installing multiple sheets, overlap them by at least 2 inches. The thinset between sheets creates the waterproof bond. Make sure overlaps are well-pressed and air-free.
Integrate with Shower Pan
Overlap the membrane onto the shower pan's bonding flange per manufacturer specs (typically 2 inches minimum). Apply thinset to the flange first, then press the membrane down firmly. This connection is critical for a watertight shower.
Tile Immediately or Next Day
Sheet membrane can be tiled immediately - no cure time needed. However, many installers wait 24 hours to ensure the thinset behind the membrane has set properly. Check your system's specifications.
Waterproofing Coverage Requirements
Shower Enclosures
Waterproof all walls from floor to at least 6 feet high, or to the ceiling. Cover the entire shower floor (pan). Overlap onto pan flange by 2-3 inches minimum.
Tub Surrounds
Waterproof to at least 6 inches above the tub rim on all tiled walls. Many pros go higher (to ceiling) for extra protection from splashing.
Sink and Toilet Areas
Waterproof 3 feet around sink and toilet if walls will be tiled. Some codes don't require this, but it's good practice for areas that get regular water exposure.
Floor Areas
Waterproof entire bathroom floor if using tile flooring. Water from showering and cleaning can travel across floors. Floor waterproofing adds minimal cost but significant protection.
Common Mistakes to Avoid
One thick coat instead of two thin coats
For liquid membranes, always do two thin coats. One thick coat doesn't cure properly, can crack, and won't provide proper waterproofing. Follow manufacturer specifications exactly.
Not reinforcing corners and seams
Corners and seams are stress points where cracks form. Always use fiberglass mesh tape (liquid systems) or pre-formed corners (sheet systems). Don't skip this step.
Tiling before membrane is fully cured
Liquid membranes need full cure time before tiling. If it's tacky or soft, wait longer. Moisture from thinset can damage uncured membrane. When in doubt, wait an extra day.
Poor integration with shower pan
The connection between wall membrane and shower pan is critical. Overlap onto the pan flange per specs (usually 2-3 inches). This is the most common leak point if done incorrectly.
Using modified thinset with sheet systems
Always use unmodified thinset for sheet membranes. Modified thinset contains polymers that prevent proper curing when sandwiched between impermeable layers.
Frequently Asked Questions
Should I use liquid membrane or sheet membrane?
Both work excellently when properly installed. Liquid membranes (RedGard, Hydroban) are easier for DIYers - paint on like thick paint, can easily see where you've applied it, and you can do complex shapes without cutting. Sheet membranes (Schluter Kerdi, Wedi) are faster for large areas once you get the hang of it, and some prefer the assurance of seeing a physical barrier. Cost is similar ($100-300 for typical shower). Choose liquid if you're nervous about application; choose sheet if you want speed and have experience with thinset. If using a foam shower pan system, use the matching membrane from the same manufacturer.
How many coats of liquid membrane do I need?
Always apply two coats of liquid membrane. The first coat is applied, then allowed to dry completely (usually 1-4 hours depending on temperature and humidity). The second coat goes on perpendicular to the first (if you rolled vertically first, roll horizontally second). Total dry thickness should be 20-30 mils. One thick coat is NOT the same as two thin coats - you risk cracking and poor curing. Each coat should be thin enough that you can still see the substrate through it. The color change from wet to dry helps you see coverage.
Do I need to waterproof the entire bathroom or just the shower?
Minimum waterproofing requirements: Full shower enclosure (walls and floor), tub surround to 6 inches above tub rim, and areas directly around sink and toilet to 3 feet. Building codes vary, but best practice is to waterproof all walls that will have tile and can get splashed. Many professionals waterproof the entire wet wall (floor to ceiling) in any area with a shower or tub. It doesn't cost much more and provides better protection. Overkill is better than underkill when it comes to waterproofing.
Can I tile the same day I apply waterproof membrane?
It depends on the system. Sheet membranes (Kerdi, Wedi) can be tiled immediately - they're installed with thinset and you tile right over them. Liquid membranes need drying time. RedGard requires 24-48 hours cure time before tiling. Hydroban needs 4-16 hours depending on temperature and humidity. Check your product's technical data sheet. Never tile over liquid membrane that hasn't fully cured - the moisture from thinset can cause problems. If membrane is tacky to the touch, it's not ready. It should be completely dry and firm.
What happens if I miss a spot or get a thin area?
Thin spots or gaps are future leak points. Before tiling, inspect your work carefully under good light. For liquid membranes, you can touch up thin spots with another coat (let it cure fully). For sheet membranes, overlap a patch piece with at least 2 inches of overlap on all sides, setting it in thinset. The most common missed spots are: behind mixing valve plates, inside corners where walls meet, the transition from wall to shower pan, and around niches. Use a bright flashlight at an angle to spot thin areas in liquid membrane - they'll look different than properly coated areas.