How to Install HardieBacker: Floor Preparation Guide

Floor Preparation

• Remove any existing flooring down to the subfloor
• Ensure subfloor is dry, clean and free of debris
• Fix any squeaks or loose sections with screws
• Verify subfloor is minimum 5/8″ thick plywood or 3/4″ OSB
• Locate and mark floor joists for reference

Cutting HardieBacker

• Measure space and mark your cuts
• Score one side with utility knife using straight edge
• Snap board along score line
• For holes (like for toilet flange), use hole saw or jigsaw
• Tip: Cut outdoors or in well-ventilated area with dust mask

Dry Fitting

• Test fit all pieces before mixing mortar
• Leave 1/8″ gap at walls for expansion
• Ensure proper fit around any plumbing fixtures
• Stagger joints between sheets
• Don’t place joints over subfloor seams

Mortar Application

As shown in Image 2:

• Mix modified thinset mortar according to instructions
• Use 1/4″ x 1/4″ notched trowel
• Apply in curved sweeping pattern
• Only spread enough for one board at a time
• Ensure full coverage with no bare spots

Board Installation

• Place HardieBacker onto wet mortar
• Press firmly and evenly across surface
• Start fastening from center, working outward
• Use HardieBacker screws or 1-1/4″ galvanized roofing nails
• Space fasteners every 8″ on center
• Keep fasteners 3/8″ from edges
• Countersink slightly but don’t break surface

Joints and Seams

• Fill all joints with mortar
• Apply alkali-resistant mesh tape over joints
• Cover tape with thin layer of mortar
• Let cure completely before tiling

Required Tools

Visible in Image 1:

• Notched trowel
• Vacuum/cleanup equipment
• Drill/screw gun
• Measuring tools
• Utility knife
• Safety equipment (mask, glasses, gloves)

Important Tips

• Don’t reuse old backer board
• Always use modified thinset mortar
• Keep surface clean as you work
• Allow proper cure time before next steps
• Use proper ventilation
• Clean tools frequently

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