Installation Guide

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FLOOR INSTALLATION
(Interior Application Only)
We recommend 1/4 in HardieBacker
®
board for floor applications, unless 1/2 in
thickness is needed for transition.
1 | Ensure subfloor is structurally
sound
On existing structures:
• Ensure subfloor is not damaged.
Replace any loose, warped, uneven or
damaged sections of floor.
• Make certain subfloor is a clean and flat
surface.
For all floors:
• Use minimum 5/8 exterior grade plywood or 23/32 OSB with Exposure 1
classification or better, complying with local building codes and ANSI A108.11.
• Joist spacing not to exceed 24 in on center.
• The floor must be engineered not to exceed the L/360 deflection criteria (L/720
for natural stone), including live and dead design loads, for the specific joist
spacing used.
2 | Determine layout of HardieBacker cement board
• Stagger all HardieBacker cement board joints. Do not align with subfloor joints.
• Never allow all four corners of boards to meet at one point.
• We recommend an 1/8 in gap between board edges.
• Keep sheet edges 1/8 in back from walls and cabinet bases.
• Score and snap boards to required
sizes and make necessary cutouts.
3 | Attach HardieBacker cement
board to subfloor
• Apply a supporting bed of mortar or
modified thinset to subfloor using a
1/4 in square-notched trowel.
• Embed HardieBacker cement board
firmly and evenly in the wet mortar.
• Use the fastener pattern as a guide. Fasten HardieBacker cement board with
specified nails or screws (as listed in “Materials Required”) every 8 in over the
entire surface. Keep fasteners between 3/8 in and 3/4 in from board edges and
2 in from board corners.
• Set fastener heads flush with the surface without overdriving.
4 | Tape joints prior to tiling
• Prior to setting the tile, fill all joints with the same mortar used to set the tiles.
• Embed 2 in wide high-strength alkali-resistant glass fiber tape in the mortar
and level.