Tile setting in the house requires the highest precision to avoid breakages. In some cases, the tiles are installed on rough concrete slabs. If the house is built in a water-prone area and the slab lacks a well-designed underlayment, water can rise through it. As a result, the adhesives between the tiles and the floor weaken, causing the tiles to slide and break. Tiles can also break if the wooden substrate absorbs water and swells. These phenomena can be minimized with a backer board.
So what is a backer board?
A backer board is a hard, flat sheet placed behind tiles to make the surface strong and even. It gives tiles a solid base to stick to and helps prevent them from cracking or falling off. Backer board is often used in areas with more moisture, such as kitchens and bathrooms.
What Are the Main Types of Backer Board?
There are different types of backer boards, each serving a distinct function on construction sites.
1. Cement Backer Board
Cement backer board is manufactured as a substrate for tiling. It is widely used in moisture-prone areas such as bathrooms and kitchens due to its water-resistant properties. Cement backer board is a composite material composed of Portland cement, cellulose or glass fibers, and mineral fillers, mixed with water. The role of Portland cement is to bind the materials and provide comprehensive strength. It ensures the board has the required rigidity for the construction sector. Cellulose helps the board gain tensile strength. Glass fibers serve the same role as cellulose in reducing the backer board’s brittleness. Some minerals, such as limestone and silica, are added in small amounts to enhance density. The minerals ensure the board maintains dimensional stability.
Cement backer boards are manufactured systematically in a controlled industrial process. First, the cement, fibers, and minerals are blended to form a homogeneous mixture. Second, water is added to the mixture to form a slurry ready for molding. The next step is forming the sheet. The mixture is fed to a series of rollers, which press it into flat sheets. The curing process, involving hydration and hardening, occurs before cutting to the desired sizes.
Cement backer boards exhibit unique behavior in water compared to other boards, such as gypsum. These boards maintain structural integrity without degradation under water. The boards do not swell or decompose when exposed to water, making them suitable for wet zones like showers. The most recognizable shortcoming of cement is its heavy weight. Compared to other boards like gypsum, these boards require high installation labor costs and high transportation costs.
2. Foam Backer Board
Beyond the structural strength provided by cement backer boards, foam boards offer thermal insulation. In foam backer boards, an extruded polystyrene (XPS) foam core is sandwiched between fiberglass facings. As a cost-effective alternative, the foam is sandwiched between reinforced cementitious facings. These boards can be easily installed due to their lightweight design. Their structural composition provides built-in waterproofing.
3. Gypsum Backer Board
In gypsum backer boards, the core is made of gypsum. It is chosen for dry areas or areas with very minimal moisture. The gypsum core, also known as calcium sulfate dihydrate, offers fire-resistant properties. When fire breaks out, the temperature rises. The gypsum materials absorb thermal energy, releasing chemically bound water in the form of steam. This steam significantly slows heat transfer.
The fibers also help the board maintain dimensional stability. Gypsum backer board has moisture-resistant additives to help it at least survive in some wet environments. The fiberglass makes these boards resistant to mold growth during moist setup. Further, these fibers enhance tile adhesion during installation.
How Do Different Backer Boards Compare?
The following table summarizes the comparison among the different backer boards.
| Type of Backer Board | Water Resistance | Weight | Ease of Installation | Best Use Area |
|---|---|---|---|---|
| Cement Backer Board | High | Heavy | Moderate | Showers, floors |
| Fiber Cement Board | High | Medium | Moderate | Walls, floors |
| Foam Backer Board | Very High | Light | Easy | Showers, waterproof systems |
| Gypsum Board | Medium | Light | Easy | Dry or light-moist areas |
How Do You Install Backer Board Correctly?
A series of steps must be followed when installing backer boards, starting with preparation. The methods include preparing the subfloor, cutting backer board, securing it, and sealing joints.
1. Prepare the Subfloor or Wall
The first step towards installing backer board is preparing the subfloor. Imperfections in the subfloor can cause stresses that are transferred to the backer board, leading to tile destruction. Backer boards are not designed to correct errors in subfloors, even though they offer a stable surface. If the subfloor is not well prepared, it can cause cracked grout joints, moisture penetration, and backer board movement. Preparation ensures surface flatness, structural integrity, and load-bearing capacity.
The first approach to preparation is to evaluate the structural condition of the floor systems and the walls. Examination of the floors involves determining floor joints and subfloor panels. Any possible damage must be noted and repaired. Cleaning is also another preparation approach. Cleaning involves the removal of dust, dirt, oil, grease, and loose mortar, among other unwanted materials. All contaminants must be removed, even if they are too small to detect. This helps maintain the bond strength.
In summary, the following table outlines the areas installers should inspect before installing the backer boards.
| Inspection Item | Requirement |
|---|---|
| Surface Cleanliness | Free of dust and debris |
| Structural Integrity | No damaged framing or subfloor |
| Moisture Condition | Within acceptable limits |
| Surface Flatness | Meets tile industry tolerances |
| Fastener Security | Loose components repaired |
| Load Capacity | Adequate for intended finish |
| Surface Stability | No excessive movement |
2. Cut Backer Board
Proper cutting of the backer board helps conserve materials and reduces installation time by ensuring the panel fits well. Cutting techniques vary depending on the type of backer board. In all cases, the edges must be clean to avoid micro-cracking.
Cutting cement backer board and gypsum backer board requires the greatest care because of their brittleness. To cut these boards, installers should first score the surface. They then snap the board along the score line. Cutting these boards generates dust that must be controlled for health reasons. Dust can be controlled through wet cutting systems, HEPA filtration, or vacuum extraction. If these technologies are unavailable, installers can choose outdoor cutting stations. When using machines to cut the backer boards for large-scale production, operators should consider all machining tolerances.
Cutting foam backer boards is easier than cutting cement backer boards. This is because XPS material is lightweight. Tools used to cut these boards include a handsaw, a utility knife, and a hot wire cutter.
3. Secure Backer Board
The third step of installing backer board is securing. At this stage, installers secure the mechanical connection between the board and the supporting structure. Backer boards are not meant to function independently; rather, they require fasteners to form a composite. In this composite, the board serves as the substrate. Proper fastening is required to secure the board, prevent tile cracking, keep the board in place against movement, eliminate surface unevenness, and prevent grout joint failures.
The primary fasteners used are alkali-resistant backer board screws or heavily galvanized roofing nails designed for cementitious materials. Proper fastening ensures that the load is transferred effectively to the subfloor. When a person walks on the tile surface, the load is transmitted to the thin-set mortar, which binds the tiles to the board. The mortar layer transmits the load to the backer board. The board absorbs this load and then transfers it to the fasteners. If the fasteners are poorly set, they can crumble, leading to board shearing and the effects transferred to the tiles. The fasteners later transfer the load to the subfloor and then to the structure’s foundation.
4. Seal Joints
The last process the installer undertakes is sealing the joints. When installing backer boards, installers leave small gaps between panels. These gaps allow installers to adjust any dimension and make changes before installation. These reinforcements are necessary to prevent the build-up of stress concentrations. Unsealed joints contribute to cracked tile surfaces and cracked grout lines, leading to water penetration.
Choosing the Right Backer Board
Every backer board suits different needs in the construction sector. The choice of the backer boards depends on what the installer or the constructors want to achieve. One factor builders consider is moisture level. When choosing backer boards for moisture- or water-prone areas like showers, contractors must select boards that are highly water-resistant. The most suitable type of backer board for these applications is a cement or foam backer board.
Second, constructors choose backer boards based on the structural load requirements. Backer boards installed on the floor are subject to consistent loading from human movement, furniture, water vessels, and other household components. For floor installations, contractors prefer cement backer boards over other boards due to their greater load capacity. Another factor is installation speed. In emergency situations where the speed of installation does not compromise load-bearing capacity, contractors choose foam backer boards over cement backer boards. These boards serve well where labor is minimal. For instance, in fast-track commercial projects where minimizing labor time is critical, contractors often specify foam backer boards for rapid installation.
Lastly, the budget is another consideration. The costs vary from board to board. With more resources available, constructors can opt for foam backer boards. However, if resources are limited, contractors can use cement backer boards, which are less expensive than foam backer boards.