Proper waterproofing is critical in any bathroom renovation, and Schluter-Systems offers a range of solutions. Kerdi-Board, a lightweight and waterproof tile backer board, is often a top choice for showers and tub surrounds. The question, however, often arises: is kerdi-board waterproof? Understanding the correct thin-set mortar application techniques, as demonstrated by experienced installers at locations like the National Tile Contractors Association (NTCA) training facilities, ensures a truly waterproof barrier. This guide reveals the professional secrets to guarantee your Kerdi-Board installation protects against water damage, turning your DIY project into a durable and beautiful success.
Image taken from the YouTube channel Schluter-Systems North America / Amérique du Nord , from the video titled Schluter®-KERDI-BOARD over Framing .
Is Kerdi-Board Waterproof? A Pro’s Guide to DIY Success
Understanding whether Kerdi-Board is truly waterproof is crucial for successful bathroom and shower installations. While the answer is generally yes, the devil is in the details. This guide explores how Kerdi-Board achieves its waterproof rating and how to ensure your DIY project achieves the same level of protection.
What Makes Kerdi-Board Waterproof?
Kerdi-Board’s waterproof capabilities stem from its unique composition and design:
- Closed-Cell Structure: The foam core of Kerdi-Board is a closed-cell structure. This means the individual foam bubbles are sealed, preventing water from penetrating the material itself.
- Waterproof Coating: Both sides of the foam core are coated with a special modified polypropylene fleece that is specifically designed for tile adhesion and waterproofing. This coating acts as an additional barrier, reinforcing the waterproof nature of the board.
Key Areas to Focus on for a Waterproof Installation
While Kerdi-Board itself is waterproof, leaks can still occur if the installation isn’t done correctly. Pay close attention to these critical areas:
Seams and Joints
This is where most leaks occur. Proper sealing of seams and joints is vital.
- Kerdi-Band: Use Kerdi-Band waterproofing strip along all seams and joints. This fleece-covered sealing strip is bonded to the Kerdi-Board using thin-set mortar. Ensure full coverage and a strong bond.
- Thin-Set Mortar Application: Apply the thin-set mortar evenly and thoroughly, ensuring no gaps or air pockets. Use the correct type of thin-set recommended by Schluter (modified thin-set mortar).
- Overlapping: Overlap the Kerdi-Band at corners and intersections to create a watertight seal.
Fasteners
Fasteners are necessary to secure Kerdi-Board to the studs, but they also create potential entry points for water.
- Sealing Washers: Always use sealing washers under the heads of the screws or nails used to attach the Kerdi-Board.
- Fastener Spacing: Follow the manufacturer’s recommended fastener spacing. Over-fastening can damage the board, while insufficient fastening can lead to instability.
- Kerdi-Fix: After installation, consider applying Kerdi-Fix sealant over the fasteners for added protection.
Penetrations
Any penetration through the Kerdi-Board (e.g., pipes, showerheads) must be sealed properly.
- Kerdi-Kers-SB/-MV Valve Seal: Use preformed seals designed for valves. These seals are applied with thin-set mortar.
- Kerdi-Pipe: Use Kerdi-Pipe seals for pipes penetrating the Kerdi-Board. Available in different sizes to match pipe diameters.
- Tight Fit: Ensure a tight fit between the penetration and the Kerdi-seal. Fill any gaps with Kerdi-Fix or thin-set mortar.
Step-by-Step Guide to Sealing Kerdi-Board Seams
Here’s a simplified numbered list detailing how to properly seal Kerdi-Board seams using Kerdi-Band:
- Prepare the Surface: Ensure the Kerdi-Board surfaces are clean, dry, and free of dust and debris.
- Cut the Kerdi-Band: Cut the Kerdi-Band to the appropriate length, allowing for sufficient overlap at corners.
- Apply Thin-Set Mortar: Apply a generous layer of modified thin-set mortar to both sides of the seam using a notched trowel (size and type recommended by Schluter).
- Embed the Kerdi-Band: Carefully embed the Kerdi-Band into the thin-set mortar, ensuring it’s centered over the seam. Press firmly to create a strong bond.
- Smooth Out: Smooth out any air pockets or wrinkles in the Kerdi-Band using a grout float or similar tool.
- Cure Time: Allow the thin-set mortar to cure completely according to the manufacturer’s instructions.
Avoiding Common Mistakes
To ensure a truly waterproof installation, avoid these common mistakes:
- Using the Wrong Thin-Set: Standard thin-set may not bond properly to Kerdi-Board. Always use a modified thin-set recommended by Schluter.
- Skipping the Kerdi-Band: Never skip sealing seams with Kerdi-Band. It’s a critical component of the waterproofing system.
- Insufficient Overlap: Ensure adequate overlap of Kerdi-Band at corners and intersections.
- Poor Adhesion: Make sure the Kerdi-Band is firmly bonded to the Kerdi-Board with full thin-set coverage.
- Rushing the Job: Take your time and pay attention to detail. Rushing can lead to mistakes and compromised waterproofing.
Kerdi-Board Waterproof FAQ
Here are some frequently asked questions about Kerdi-Board to help clarify its waterproof capabilities and proper installation techniques.
How does Kerdi-Board achieve its waterproof seal?
Kerdi-Board is waterproof because it has a closed-cell, waterproof foam core. The critical element for a truly waterproof installation lies in properly sealing the seams and fastener penetrations with Kerdi-Band and thin-set mortar. This ensures that water cannot penetrate the system at joints.
Is Kerdi-Board waterproof even without Kerdi-Band?
No, Kerdi-Board itself is waterproof, but a Kerdi-Board installation is only fully waterproof when all seams, screw penetrations, and transitions are properly sealed with Kerdi-Band or Kerdi-Keba and unmodified thin-set mortar. These create a watertight bond.
Can I use any thin-set mortar with Kerdi-Board?
No, you must use unmodified thin-set mortar conforming to ANSI A118.1. Modified thin-set mortars can create an undesirable film between the Kerdi-Board and the tile which could cause problems with the bonding process.
What happens if I skip sealing the seams correctly?
If you skip or improperly seal the seams with Kerdi-Band and thin-set mortar, the installation will not be waterproof. Water can then seep through the unsealed joints, potentially causing mold growth, structural damage, and tile failure. Making sure to properly waterproof your installation is very important.
So, you’re armed with the secrets! Now get out there and make sure your Kerdi-Board installation is as waterproof as can be. Remember, a little extra care goes a long way to ensure that is kerdi-board waterproof and will stand the test of time. Happy tiling!