Preventing Mold and Moisture Damage with Fiber Cement Underlayment


A lot of people assume that simply tiling the walls and floors in wet areas like kitchens and bathrooms is enough to prevent moisture damage. After all, most types of tile including ceramic, porcelain, and glass are inherently water resistant, and those that aren’t, like stone, can be sealed. What many people don’t realize, however, is that the tile itself is not enough to prevent moisture damage to the areas beneath the tile. Installing tile right on plywood may be acceptable in hallways or on a kitchen backsplash, but wet areas need more protection than tile alone can bring. That’s where using fiber cement backerboard as an underlayment can help.

Where Moisture Issues Come From

Tile itself is fairly water resistant. Materials like porcelain and vitrified ceramic tile are non-porous and do not absorb any moisture, which is why so many people use them in wet areas. If you take the time to think about what surrounds your tile, however, you’ll see where the issues can arise from.

Grout and caulk are both integral parts of the tile installation. Both are necessary to help absorb movement and protect the edges of the tile, as well as to help seal out moisture. Unfortunately, because of the fact that both materials need to flex to do their jobs, they can both develop cracks or holes over time. It’s extremely common in wet areas, for example, for the caulk that fills the expansion gap where the tile meets a tub or shower pan to eventually come loose and need to be replaced. Caulk that surrounds a shower valve, tub spout, or shower head also can frequently come loose, allowing moisture to seep around these areas and into the walls behind.

Even if the amount of moisture seeping into these areas is minimal, it can do real damage over time. Moisture can lead to mold and mildew growth behind the walls where it can be difficult to eradicate. At the same time, moisture can cause wood to swell and even rot as time goes by, breaking down the integrity of your walls and subfloor.

Obtaining Protection from Backerboard

A lot of tile installers like to use cement backerboard beneath their tile installation for a number of reasons. Backerboard can help prevent issues such as lippage or abnormal amounts of flex in the subfloor, which can lead to large format tiles cracking over time. Not all backerboards are the same, however; many are only rated for dry use applications only, meaning that they can make a great addition to your sunroom floor or fireplace surround, but they can’t be used in wet areas like a shower.

Fiber cement underlayment can be used in these wet areas to help solve several problems at once:

1. Fiber cement backerboard provides the same protection against lippage and against excessive movement in floors that can cause cracks in large format tiles.

2. Fiber cement does not expand or disintegrate on contact with moisture or water, so it can be installed below grade, in showers, or on kitchen floors – all areas where moisture can cause problems.

3. Fiber cement also does not contribute to the growth of mold, mildew, and other issues that can come from exposure to moisture over a long period of time.

Fiber cement backerboard is also easy to use and install. It doesn’t require special tools; it can score and snap like other types of backerboard and can be screwed down to the subfloor or wall studs like other underlayments. Fiber cement is also lightweight and flexible enough to handle any tile application including natural stone and ceramic tile. It installs like any other backerboard with a layer of thinset covering the substrate first, followed by the backerboard. The tile itself can be installed right on top of the backerboard with or without back buttering.

Best of all, in areas like bathrooms that may have two or three different coverings on the walls, fiber cement backerboard can be used on every surface. Unlike other backerboards that may have to change from the sink area to wall areas to the tub area to accommodate the different surfaces being installed, fiber cement can easily handle paint, wallpaper, and various types of tile seamlessly. So you can tile a backsplash above the sink, and paint the area above that with no interruption and the same protection against humidity and moisture throughout the space. You can even use the same material on tiled countertops and tub decks to provide the same great protection.

Protect Your Home from Mold and Moisture Damage

Mold and moisture damage in wet areas are a serious problem. Installing tile alone is not enough to help protect your walls and floors from moisture damage in wet areas. Couple your tile installation with a fiber cement underlayment to provide the best protection possible in your home.