For installing Hardie® Backer Board, you should use either unmodified thinset (ANSI 118.1) or acrylic modified thinset (ANSI 118.4). This application is crucial for the layer placed between the Hardie® Backer Board and the subfloor.
Why the Right Thinset Matters
The correct thinset is specified for use between the Hardie® Backer Board and the subfloor primarily to eliminate any deviations between the backer board and the underlying surface. This critical step significantly decreases the probability of tiles popping or cracking later, which can be caused by deflection in the subfloor or the presence of air pockets beneath the backer board.
Recommended Thinset Types
Choosing between unmodified and modified thinset depends on the specific project requirements and environmental conditions, though both are acceptable for Hardie® Backer Board installations.
- Unmodified Thinset (ANSI 118.1)
- Description: This type of thinset is primarily a Portland cement-based dry mix that is mixed with water on site. It relies on the water in the mix to hydrate the cement, creating a strong bond.
- Application: It is a reliable choice for standard installations where no additional flexibility or enhanced bond strength beyond the cement's inherent properties is required.
- Acrylic Modified Thinset (ANSI 118.4)
- Description: Modified thinsets contain polymer additives, such as acrylics, either pre-blended in the dry mix (requiring only water) or added as a liquid component during mixing. These polymers enhance the thinset's performance.
- Benefits:
- Enhanced Bond Strength: Provides superior adhesion to various substrates.
- Increased Flexibility: Offers better resistance to deflection and movement, which can be beneficial in certain installations.
- Improved Water Resistance: While not waterproofing, the polymers can improve resistance to moisture penetration.
- Application: Often preferred for installations in wet areas like showers, or where extra bond strength and flexibility are desired.
Thinset Standards at a Glance
For clarity, here's a quick reference for the specified thinset types:
| Thinset Type | ANSI Standard | Key Characteristics |
|---|---|---|
| Unmodified | ANSI 118.1 | Cement-based, mixed with water; good for basic, stable installations. |
| Acrylic Modified | ANSI 118.4 | Contains polymers for enhanced bond strength, flexibility, and moisture resistance; often preferred for demanding conditions. |
Key Considerations for Proper Application
Achieving a durable and stable tile installation on Hardie® Backer Board requires meticulous attention to the application process:
- Subfloor Preparation: Ensure the subfloor is clean, dry, level, and structurally sound before applying thinset and the backer board. Any existing imperfections can lead to future issues.
- Mixing Consistency: Always follow the thinset manufacturer's instructions precisely for mixing. Proper consistency is vital—it should be smooth and spreadable, not too wet or too dry. Incorrect mixing can compromise bond strength.
- Full Coverage: Use the appropriate notched trowel size as recommended by Hardie and the thinset manufacturer to achieve full coverage beneath the Hardie® Backer Board. This ensures maximum adhesion and eliminates air pockets that could lead to weak spots or tile failure.
- Manufacturer Guidelines: Always consult the official installation guides provided by James Hardie for their Hardie® Backer Board products, as well as the specific thinset manufacturer's instructions, for the most accurate and up-to-date recommendations.
