When tiling walls or floors, installing a tile backer board as the substrate provides a stable, water-resistant surface for the tile. But is backer board always required for a successful tile installation? Here we’ll examine when you need backer board, when you can tile directly over existing materials, and the best practices for installing tile backer board.
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When is Tile Backer Board Required?
In most tile installations, a backer board is required or highly recommended as the underlayment. Backer board, usually made of cement or fiber cement, provides a rigid, stable layer that resists moisture damage. Tiling directly over drywall, plywood, or concrete can lead to failure or damage over time. Here are some examples where tile backer board is essential:
- Walls – Backer board is required when tiling tub/shower surrounds or anywhere tiles will be exposed to moisture. Cement backer boards like Durock or HardieBacker are ideal.
- Floors – For floor tile, backer board is recommended for wood subfloors. Cement board or fiber cement boards add durability and prevent moisture issues.
- Countertops – Concrete backer board makes a great substrate for tiling over plywood counter substrates. This prevents moisture damage to the cabinets.
- Exterior applications – Fiber cement or polymer-modified cement backer boards are best for exterior wall tile installations.
- Wet areas – Anywhere tile will be exposed to water regularly, use a water-resistant backer board rated for wet areas.
In summary, a backer board designed for tile provides a stable, rigid layer that resists damage from moisture over time. Backer board is required by code for tiling wet areas and recommended for nearly all tile applications.
When is Backer Board Not Necessary?
There are some cases where you may be able to tile successfully without a backer board:
- Concrete substrates – Installing tile over concrete generally does not require a backer board. The concrete just needs to cure fully and be free of contaminants.
- Existing tile – You can often tile over existing well-bonded tile with a proper tile prep product like a skim coat or bonding agent.
- Cement board siding – Siding boards like HardiePlank can be tiled over directly since they are already stable and water-resistant.
- Interior vertical surfaces – If tiling a non-wet area wall with minimal moisture exposure, you may be able to tile directly over drywall.
Even in these situations, it is still a good idea to consider a backer board for added stability and moisture protection. But in general, a backer board is not absolutely necessary when tiling over very stable, water-resistant surfaces.
How to Install Tile Backer Board
When your tile project does require a backer board, be sure to install it properly. Here are some tips for installing tile backer board:
- On walls – Install vertically using backer board screws placed every 8 inches along studs. Seal seams and corners with mesh tape and thinset.
- On floors – Fasten sheets to subfloor using backer board screws, nails, or glue. Offset seams between sheets and leave a 1/8 inch gap.
- In bathrooms – Waterproof the backer board using a membrane or moisture barrier paint like RedGard.
- Around tubs/showers – Extend the backer board 2 feet past the shower dimensions and wrap it around corners.
- Preparation – Fill any gaps or low spots with modified thinset and allow to fully cure before tiling.
Following manufacturer instructions for installation and using fibercement backer board screws or galvanized roofing nails ensures a secure, rigid surface for tiling. Allowing proper curing time for thinset and membranes creates a water-resistant layer.
Backer Board Options
There are several good backer board options available for tile installations:
| Backer Board | Description | Uses |
|---|---|---|
| Durock | Fiberglass mesh reinforced cement board, waterproof and durable | Wet areas, flooring, countertops |
| HardieBacker | Fiber cement backer, moisture resistant and fireproof | Bathroom walls, kitchen backsplashes |
| PermaBase | Cementitious backer board, coated fiberglass face | Tub/shower walls, ceilings, floors |
| WonderBoard Lite | Foam backer board with fiberglass reinforcement | Walls, floors, exterior applications |
Always choose a backer board recommended for tile rather than using regular plywood or drywall. Consider moisture resistance for wet area applications. Thicker boards provide more rigidity for floor installations.
Pros of Using a Tile Backer Board
Installing a proper tile backer board provides many benefits compared to tiling directly over drywall or plywood:
- Prevents cracks and damage from tile shifting or moisture
- Offers a smooth, uniform surface for tiling over uneven substrates
- Does not break down or deteriorate like wood or drywall
- Adds stability and structure to help support tile weight
- Waterproofing ability resists mold, mildew, and rotting
- Fireproof rating improves safety in the event of a fire
- Allows for a thinner profile than a mud bed substrate
The rigidity, moisture resistance, and durability of cement or fiber cement backer boards offer major advantages over common sheathing boards. Tile installation over a proper backer board will last much longer than tiling directly over drywall or plywood.
Cons of Backer Board
There are a few potential disadvantages to keep in mind with tile backer boards:
- Higher cost than drywall or plywood sheathing
- Heavier than other boards, making them challenging to lift and install
- Prone to crumbling at corners and edges if not handled carefully
- Cutting and drilling cement boards requires carbide blades
- Joint tape and thinset add time and cost to the installation
The extra labor and cost involved with installing a backer board can seem unnecessary for a simple weekend tile project. But the longevity and performance gains make cement backer boards well worth the investment for most tile jobs.
Conclusion
Tile backer board provides a stable, water-resistant layer for tile installations. While backer board may not be an absolute necessity for tiling over concrete or existing tile, it is required by code for wet areas. Its durability and moisture resistance offer significant advantages over drywall or plywood for most tile applications. With proper preparation and installation, a good fiber cement, polymer-modified, or concrete backer board will provide a crack-resistant, long-lasting substrate for beautiful tiled surfaces.