How to Install Backerboard Expansion Gaps

Depending on the material used for the backerboard, it will change shape over time. Your tile and countertops will begin to show wear and could move out of place. To avoid this, you should leave room for the expansion. An eighth-inch is a good size for most expansion gaps between the boards. However, a quarter-inch is better for backerboards on showers and tubs and bathroom walls and floors.

Difficulty: Moderately Challenging

Instructions

1. Know the ingredients of the backerboard. The compounds carry different expansion rates and will affect the look of your tile or countertop if not used correctly.

2. Check the manufacturer's instructions for expansion rates. Take into consideration the area in which it is used. Bathrooms require larger expansion gaps because of the constant moisture.

3. Utilize a measuring tape for the width. Eyeballing a space leaves too much room for error. An eighth or three-sixteenths is a very small space and easily mistaken.

4. Keep a metric conversion chart handy, as many of the most common measuring tools will not correspond with the manufacturer's recommendations. Every kind of conversion can be found at onlineconversion.com (see Resouces below).

5. Include the measurement for the gap when planning the job. Add one-eighth-inch between every board on in the bathroom or other moisture-prone rooms.

6. Use a sealant or grout to fill the gaps after the backerboard is secured. Make sure the sealant is even with the backerboard before installing the tile or counter.

7. Wait at least 24 hours before sanding to make sure sealant is completely dry. Light sanding will even out any irregularities.

Resources

• Convert measurements using this tool.