How to Lay Tapes for Hardibacker Floor Installations

Hardibacker cement composite board provides a stable surface for the installation of tile, vinyl and laminate flooring. The seams between installed Hardibacker panels create voids that will cause applied flooring to crack over time. Applying tape over the seams fills those voids. This provides a solid connection between neighboring panels. Installing seam tape incorrectly will cause a multitude of problems that will damage the finished floor. Paying attention to detail during all stages of the taping process will ensure a long-lasting, crack-free floor.

Stiff-bristled broom
Damp rag
4-inch spackling knife
Mixed mortar
2-inch-wide fiberglass tape

Instructions

- 1
  Sweep the installed Hardibacker panels thoroughly with a stiff-bristled broom to remove all debris from the floor. Wipe over each seam with a damp rag.
- 2
  Drag the blade of a 4-inch spackling knife through pre-mixed mortar. Pull the blade from the mortar to load the knife. For tile installations, use the same mortar to seal Hardibacker seams and set the tile.
- 3
  Pull the spackling knife across the seam with the knife blade sitting at a 30-degree angle to the Hardibacker seam. Reload the blade with mortar as needed. Drag the blade over the seam until the mortar is between 1/32 and 1/16 inch thick.
- 4
  Align one end of a roll of 2-inch-wide fiberglass tape with one end of the mortared seam. Push the tape end firmly into the mortar with the end of the spackling knife blade. Pull the tape along the seam while dragging the blade behind the tape to embed it in the mortar.
- 5
  Hold the spackling knife perpendicular to the floor. Apply downward pressure on the knife. Pull the tape away from the seam to tear it from the roll.
- 6
  Pull the spackling knife over the seam to remove excess mortar from the area.
- 7
  Allow the mortar to dry for 24 hours before installing flooring over the Hardibacker.

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