How to Paint a Hardie Board
- 1). Clean raw or painted Hardie board before painting, if necessary, with a low pressure stream of water and a non-metal scrub brush. If you need a detergent, use a solution of 1 part muriatic acid to 5 parts water. Avoid acid washing and power washing as they can damage the surface of the cement.
- 2). Cover unpainted Hardie board with a latex primer before you apply a top coat. Use a high-quality, exterior-grade primer intended for use on cement or stucco to enhance the moisture resistance of the board. You can brush, roll or spray the primer.
- 3). Apply the primer within 90 days of installation to maintain the manufacturer's warranty. If the Hardie board is pre-primed, apply a top coat within 180 of installation by brushing, rolling or spraying.
- 4). Top-coat primed Hardie board with latex paint or an opaque latex stain. You can apply oil-based paint on Hardie board that has been primed, but not on the raw product, because it creates defects like surface roughness, poor adhesion, chalking and cracking. Products with linseed oil are intended for wood and the manufacturer does not recommend their use on Hardie board.