Hardie board is not wood. At its core it is a concrete board, and that changes how you should prime and paint it. If your home is a new spec build with unpainted board and comb face pine trim, here are the practical product recommendations and application tips that will give you long lasting protection and a clean finish.
Why Hardie Board Needs the Right Primer
Because Hardie board is a cementitious product, you want a primer that does more than just stick. The right primer will bond to the surface and prevent issues later like efflorescence and adhesion failures. Before you start, do a simple water test to tell if the siding is already pre-primed.
“If it’s beating and the water’s rolling down even like just a little bit you most likely have some sort of primer on those boards. If you’re throwing water at the side of the house and it’s absorbing right in it’s probably not primed.”
Recommended Products
Primer for Hardie board
Use a masonry/concrete primer that is formulated to bond to cementitious substrates. A product like Loxon Concrete and Masonry Primer is the go-to recommendation. It provides a strong bond and helps stop staining or salt migration that can occur with concrete-based boards.
Topcoat Options
For topcoats you have two smart routes depending on budget and desired performance.
- Self-cleaning topcoat: A Loxon self-cleaning paint provides the highest level of protection. It uses a technology where the paint film dries with an inverted surface profile that makes it harder for dirt to cling. When it rains the surface sheds dirt more effectively so the siding stays cleaner longer.
- 100 percent acrylic system: If self-cleaning is outside your budget, a 100 percent acrylic coating such as A100 is an excellent alternative. Many builders use A100 for durable, breathable finishes on Hardie board.
Painting Comb Face Pine Trim
Comb face pine trim behaves more like MDF or other engineered trim than concrete. For the best results:
- Prime with an alkyd blocking primer such as an Extreme Block Alkyd Primer. This prevents edge swelling that can occur if you used a water based primer and it gives superior adhesion to the wood.
- Apply your chosen topcoat over the alkyd primer. If using A100 on the body, using it on the trim gives a consistent overall finish.
Windows, Soffits and Surfaces Not to Paint
Do not paint vinyl windows or aluminum metal soffits. These manufactured surfaces are best left as is, and painting them often causes adhesion issues or voids warranties. Focus your painting on the concrete board and the wood trim.
Choosing Sheen: Durability and Design
Sheen is both a design choice and a durability choice. Here are the common approaches and the recommended combo for longevity:
- Common pairing: Flat or satin body with semi-gloss trim. This is used about 85 percent of the time and balances appearance with durability.
- Durability pick: Semi-gloss on trim and satin or low luster on the body. Semi-gloss tends to be more resistant to scratches and cleaning and sheds moisture more easily than flat finishes.
- Design trends: Some modern looks use flat walls with eggshell or satin trim for a more subdued contrast. This is a stylistic choice and is perfectly acceptable if you are prioritizing look over ease of cleaning.
Step by Step Painting Process
- Perform a water test on the siding. If water beads and runs off you likely have pre-dipped primer. If it absorbs, plan to prime.
- Prime bare Hardie board with a concrete and masonry primer such as Loxon.
- Prime comb face pine trim with an alkyd block primer to prevent edge swelling and improve adhesion.
- Topcoat the siding with either a self-cleaning Loxon finish for maximum dirt resistance or a 100 percent acrylic A100 for a durable, cost effective finish.
- Use a higher sheen on trim for longevity. Semi-gloss trim with a satin or low luster body is the best all around recommendation.
- Do not paint vinyl windows or aluminum soffits.
Final Recommendations
- Always prime raw Hardie board before topcoating. The correct primer prevents long term issues.
- Use Loxon concrete and masonry primer for the siding. Consider the Loxon self-cleaning finish for reduced dirt build up or A100 100 percent acrylic as a strong alternative.
- Prime comb face pine with an alkyd block primer then topcoat. This protects edges and improves adhesion.
- Choose semi-gloss for trim and satin or low luster for the body for the best combination of durability and appearance.
