Exterior Finishes

Cement backer board

The new kid under your tile 

To say that the home building industry adapts to changes in technology a bit slowly would be a vast understatement. Professional builders have to warrant their work, and they are also concerned about their reputation. As a result, they adopt new techniques only when they are fairly certain that the change won’t end up as a call back.

cement backer board
cement backer board

By building industry standards, Cement (backer) Board came onto the scene fairly recently. The first time I recall seeing it was in the mid 90’s when it appeared on the rack at one of our lumber yards. Cement board is a combination of concrete and reinforcing fibers formed into 3-foot by 5-foot sheets. These sheets are 1/4 to ½-inch thick and are typically used as a backing board for tile installations.

Cement board can be nailed or screwed across wood or steel studs. This creates a fast, really flat substrate for vertical floor tile or attached to plywood for stone or tile kitchen counters and backsplashes. It can also be used on the exterior of buildings as a base for exterior plaster (stucco) systems and sometimes as the finish system itself.

Cement board adds impact resistance and strength to the wall surface as compared to gypsum boards. Fabricating cement board in thin sheets allows bending for curved surfaces.

Thin set tile

Before cement board came along, many bathrooms in “tract” homes or spec-builds used a tiling method called “thin-set”. When it first got started, it was crap! Thin-set eliminated the traditional mortar layer beneath the tile. This saved time and material and required less skill. Thin-set was applied directly to a water-resistant version of gypsum sheetrock called “green” board because of its greenish color.

cement backer board options
Water resistant gypsum board

 

Unfortunately, “green” board did not resist impacts well nor did it stand up as a water-proof backing to the tile. Tile cracks, caulking or mortar failure could lead to water damage and sometimes mold.

Backer board makes Thin-Set tile acceptable

As a tile backing product, Cement Board has far better long-term performance than paper-faced gypsum core products. It is concrete after all, not gypsum. As a result, it will not mildew or physically break down in the continued presence of moisture or leaks. Also, cement board provides a stronger bond and support with tiles than typical gypsum board.  Cement Board has made thin-set tiling an acceptable building practice.

cement backer board
Thin set tile diagram

Tough but not waterproof

Cement board resists water damage but is itself not waterproof. It will actually absorb moisture, but it has excellent drying properties. In areas continually exposed to water like spray from showers, a waterproofing material is required behind the sheets, Plastic waterproofing sheets can be used or perhaps a trowel-applied liquid membrane.

Weight and installation

One major disadvantage of cement board is the weight per square foot. It is approximately twice that of gypsum board, making handling by one person difficult. Cutting of cement board must also be done with carbide-tipped tools and saw blades. Due to its hardness, and brittleness, pre-drilling for fasteners is recommended. Cement board is hung with corrosion resistant screws or ring-shank nails.

Cement board has very little movement under thermal stress. Still the boards are usually installed with a slight gap at joints in shower pans, bathtubs, and each other. These joints are then filled with silicone sealant  or the manufacturer’s taping compounds before applying a finish. Joints are taped like conventional gypsum board, but with fiberglass tapes that provide additional water resistance.

Summary

Combined with a water impermeable finish, cement board is a stable, durable backing board. Cement board is slightly more expensive than water-resistant gypsum board but will certainly provide better long term value.


Help me to help you

Thank you for taking time to use this free website. I hope you find the junk-free information here fun and useful? Please send me your comments and feedback.

Writing and maintaining the information in this manual is a lot of hard work. By sharing these pages with your friends, you help me to continue the effort.  You can easily share these pages to all your favorite social media sites via the shortcut buttons on the sidebar. You can also simply email the page link to your friends. Please share often.

The very best way to help me happens when you use the embedded links to buy things. Using a link is easy and free, yet it provides a great source of support for this site. The vendors I've chosen to link to have proven to be trustworthy and are the very best resources available. That is why I recommend them personally.

HomePreservationManual.com is the place to visit if you want information on

  • maintaining your home
  • how to improve air quality
  • ways to improve the real value of your home
  • what are the best housekeeping services
  • the problems with handymen services
  • how to plan and execute home renovation and home improvement projects
  • tips for spring cleaning; tidying up a messy house
  • and generally how to be a better homeowner.

Make sure you download your monthly maintenance checklist for this month.

Linking to this site

Do you want to link to anything on this site? Please do! Go right ahead. I appreciate it and am honored to be considered as a resource on your website. Always feel free to link to anything you find helpful. Of course, please never copy anything (everything is copyrighted and registered), but link away and thanks!

Thank you!

Copyright and permission to use information.

If you have questions or just want to say hi, please send me a note. If you are looking for help performing the work described and you are in the San Francisco area, go to HPS Palo Alto Inc.and request a free evaluation.

As a reminder, it is unlawful to make copies including cut and paste or especially in the form of making printouts for reuse. If you wish to make a print for personal use, I will happily grant you one-time permission if you will kindly send me a request in writing.

Thanks again!