One of the most durable home siding materials is Hardie board, which is a fiber cement siding made from cellulose fiber, sand and cement. Hardie Board is paintable, which is good news for homeowners who want to change its color, or anyone whose previously-painted Hardie Board is beginning to flake and peel. If you’re one of those people, here’s how to proceed:
Step #1: Make sure that there are no open seams or cracks in the siding. If you find any, seal them with a high quality siliconized acrylic caulk. However, do not seal the bottom and side edges of the Hardie board without checking with the manufacturer or reading the manufacturer’s literature on recommended painting procedures.
Step #2: If any mildew is present, treat it with a solution containing one part bleach to three parts water. After applying the bleach solution to the mildew, leave it on the surface for 20 minutes or so, then rinse it clean. If your mildew is stubborn, repeat the procedure and scrub the surface.
Step #3: Clean the entire exterior by power-washing it, or scrubbing it down with a detergent solution using a long-handled brush. If you use a detergent solution for your cleaning, rinse the surface afterward with a garden hose.
Step #4: If you still see any flaking or peeling paint, use a wire brush to remove it, but work carefully. Brush the surface of the Hardie board in the direction of the wood-grain, not across it.
Step #5: After your surface preparation is complete, apply a liberal coat of latex masonry primer or stain-blocking primer to the Hardie board. The primer will help the new paint get better adhesion to the siding.
Step #6: Finish the job by applying one or two coats of top quality 100% acrylic latex exterior paint that is recommended for masonry surfaces (adding a second coat will help the paint job last longer). This type of paint is especially tough and durable; plus, it typically contains special ingredients to inhibit mildew growth.
That’s all there is to it. If you followed the directions carefully, your Hardie board should look good as new. And your new paint job will last for years!
[One note on personal protective equipment: Be sure to wear skin and eye protection when working with bleach solution and when wire-brushing.]
About The Author: Debbie Zimmer is editor-in-chief of the Paint Quality Institute blog. She’s a widely-cited authority on color, use of paints in interior and exterior design, and decorative painting techniques. She can be found on Twitter as @PaintQualityIns.