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How to Install Cement Board Floor Underlayments

You plan to install a new ceramic floor or a vinyl floor and the thickness of the underlayment is a concern. Cement boards provide a less thicker, exceptionally hard, and durable underlayment. It is better than plywood and efectively prevents the growth of mold and mildew.

What is a Cement Board?

A rigid substrate made of Portland cement, aggregate and glass mesh
Withstand prolonged exposure to moisture
Does not rot, disintegrate or swell when exposed to water
Provides execent support and robustness to the floor
Ideal for ceramic underlayments or backing surfaces around bathtubs, showers and countertops
Available in various widths, lengths and thicknesses
Easy to cut with a untility knife

Typical Cement Boards Applications

Floor underlayment in kitchens, foyers, laundry rooms, mud rooms, bathrooms
Countertops
Backsplashes
Bath tub and shower enclosures
Saunas and steam rooms
Garden and whirlpool tubs
Swimming pool and whirlpool decks and enclosures

Steps to Installing Cement Board Floor Underlayments

Spred thin-set mortar strating at the longest wall using a 1/4″ notched trowel
Set the cement board on the mortar with the rough side up
Fasten the cement board using 1 1/4″ cementboard screws every 6″ at 8″ intervals in the filed of the cement board
Cut cement board as required to follow the surface of the floor
Place alkali resistant fiberglass mesh tape over the seams and fill all the gaps with thin-set mortar by using a putty knife
Allow the thin-mortar to cure per maufacturer’s instructions before starting tile installation

Tips for Installing Cement Boards

Make sure the edges are offset from the subfloor seams
Flush all the screw heads with the surface of the boards
Leave 1/8″ expansion gaps at all joints and 1/4″ around the walls
Do not use conventional paper drywall tape, joint compound and drywall nails or screws fro cement board installations
Do not use cement boards as a moisture barrier, use proper moisture barriers instead
Do not expose cement boards to temperatures exceeding 225°F (107°C)