Installation Guide

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2 | Basements and crawl spaces
• Crawl spaces must be well ventilated
with a minimum of 18 in between the
ground and joists. A vapor barrier over
the ground is required.
Underlayment Installation
1 | Determine layout of HardieBacker
®
cement board
• Install smooth side up.
• Install HardieBacker boards perpendicular to subfloor panels.
• Stagger all HardieBacker board joints. Do not align HardieBacker board joints with
subfloor joints
• Never allow all four corners of boards to meet at one point.
• Lightly butt the board joints. Do not leave a gap or force edges together.
• Join factory-cut edges together in the body of the floor.
• Keep board edges 1/8 in back from walls and cabinet bases.
2 | Attach HardieBacker boards to subfloor
• Fasten one board at a time. HardieBacker boards must be flush with subfloor
during installation.
• Begin the fastening pattern in a corner of the board, then fasten the two adjacent
edges. Return to the corner and fasten in a diagonal pattern from that corner until
the board is completely fastened.
• Place fasteners in a random, staggered pattern across HardieBacker board. Avoid
fastening in a straight line.
• Fasten HardieBacker boards with proper fasteners (as listed in “Materials
Required”) a maximum of 3 in on center around the perimeter and 6 in on center
in the field.
• Keep fasteners between 3/8 in and 3/4 in from board edges and 2 in in from
board corners.
• Fastener heads/crowns must be flush with or slightly countersunk a maximum of
1/16 in below the surface.
3 | Finishing surface and joints (not necessary for carpet or wood flooring)
• If necessary, lightly hand-sandseams to achieve a smooth transition between
boards. Avoid over-sanding. Sanding will generate significant respirable silica
dust and those in the immediate area must wear NIOSH-approved respiratory
protection (e.g. N95) in accordance with applicable government regulations.
• Thoroughly clean HardieBacker board surface to remove all debris prior to
patching.
• Using a wide flat trowel, apply a skim coat of patch (as listed in “Materials
Required”) to all seams, sanded areas, hammer indentations, holes, gaps,
gouges, chips and voids to achieve a smooth surface. Avoid building a ridge over
the seams by feathering the patch out several inches on both sides of the seams.
• Obtaining a perfectly smooth surface may require more than one coat of patch.
• After the patch has thoroughly dried, lightly sand or scrape off any surface
imperfections caused by the patch to achieve a smooth surface.
• Wait until patch is thoroughly dry before installing the floor covering.
4 | Flooring installation
• Prepared HardieBacker cement board surface must be free of all debris, oil, paint,
caulk, joint compound and other foreign substances.
• Do not install floor covering seams directly over the HardieBacker board seams.
• Install floor covering according to the adhesive and floor
covering manufacturers’ instructions.