By Andrew Hunt
Most everyone knows that a strong subfloor is ideal when installing ceramic tile. But to really do the job right, nothing beats a layer of backerboard over the top of the subfloor. Besides making for a more even surface, backerboard can provide many advantages to the floor, backsplash or tub surround to help reduce the chance of cracking. Knowing which backerboard to use and understanding a few of the fundamental tricks of installation can help ensure a quality job that will stand the test of time.
The basics of backerboard
Whether installing stone, ceramic or porcelain flooring, having a solid foundation to which you'll adhere the tiles is critical. A properly installed backerboard helps your tiling project in three ways:
- Creates a uniform, smooth surface that will make for a better, more even finished surface
- Prevents cracking by providing a more stable foundation for tiles and won't expand and shrink with temperature changes
- When used with a proper water barrier, helps protect the rest of the home from water damage
For years the standard when installing tiles in water-prone areas was water-resistant drywall or green board. While this was better than standard, untreated drywall, the problem with green board is that it is only water-resistant, not waterproof. Over time and repeated wettings, the board could swell and become weak. Also, green board alone can't act as a barrier to keep water from seeping beyond the tub surround or back splash. Changes in the International Builder Code have pretty much ruled out green board in traditional situations, but it is still an acceptable backerboard in areas not exposed to excessive amounts of water.
Cement backerboards were developed to replace the classic mortar and mesh (or lathe) style underlayment; they are arguably the most popular choice today. Regardless if they are cement granules covered in mesh or simply sheets of concrete, these boards offer stability, durability and are pretty easy to work with. Cement backerboards come in various thicknesses depending upon the application. For floors and countertops, a 1/4- inch thickness is usually best. For walls and other vertical installations, 1/2-inch backerboards are recommended.
Updated versions of cement board are now hitting the market and include styles made of treated gypsum core with a fiberglass coating, which serves as an onboard water barrier. These styles install like the standard cement backerboards, but their water-resistant properties offer additional peace of mind for areas often water soaked.
Tips for installation
Here are few tips on installing backerboard:
- Cement is tough on tools! Score and break the board like drywall, or use a carbide blade and a skill saw. Making your cuts outside and wearing a dust mask is a very good idea.
- Wear eye protection whenever working with backerboard.
- Make sure the walls are perfectly plumb and the floors true and level before installing backerboard. That extra layer could exaggerate any off angles and, if you are attaching it directly to studs (wall applications only), a twisted stud will put a bow in the board.
- Allow a 1/8-inch gap between all backerboard sheets, and fill/tape the joints to create an even transition between sheets.
- When securing backerboard to the subfloor, use roofing nails, corrosion-resistant screws or fasteners specifically designed for cement backerboard. Make sure fasteners counter-sink into the board to keep the tiles even.
- Stagger your backerboard sheets to avoid a room-long seam. Also stagger the seams when putting backerboard over a plywood subfloor.
- Backerboards do not increase the structural strength of floors.
- Fifteen-pound roofing felt paper can be used as a water barrier behind backerboards in tub and shower surrounds. Simply install by stapling the paper to the studs and overlap (top to bottom) by at least 4 inches.
- Some backerboard manufacturers require the use of modified thinset mortar for the tiling process, so be sure to check the fine print on your materials.
Easy to use and providing a perfect surface for ceramic tiles, backerboard is a no-brainer for improving the quality, durability and appearance of tiling projects.
Andrew Hunt is a freelance writer who specializes in building technology and green building. He formerly worked for BuildIQ.
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