In this article
- Why fiber cement is its own surface
- What type of paint to use
- New primed siding: paint it within 180 days
- Unprimed or bare board: prime first
- Repainting old fiber cement siding
- Painting over a factory finish such as ColorPlus
- Color, sheen and fire ratings
- Weather and application
- Fiber cement compared with the siding next to it
- How long the paint lasts
- Frequently asked questions
Quick answer: The best paint for fiber cement siding, including James Hardie board, is a high quality 100 percent acrylic exterior latex. James Hardie says its primed siding should get an acrylic top coat, and its technical bulletin on finishing primed siding rules out stain, oil or alkyd paint and powder coating. Primed boards should be painted within 180 days of installation. When you repaint, Sherwin-Williams says no primer is needed unless bare board is showing.
Fiber cement is one of the easiest sidings to paint well, because it is stable and holds paint better than wood. It is also easy to get wrong in small ways that shorten the life of the finish: the wrong product type, paint over a dirty or wet board, or primed boards left unpainted for too long. This guide covers what to use and why, how prep differs between new and old siding, and the points where the siding maker and the paint makers give specific instructions. For the money and quantity side, see how much paint a house exterior needs and the exterior painting calculator.
Why fiber cement is its own surface
Fiber cement board is made from cement, sand and cellulose fibers. It does not rot, it does not swell the way wood does, and it does not soften in the sun the way vinyl does. Those are the reasons it holds paint well. Two of its other traits shape how you paint it.
- It is cement based. Paint makers treat it like masonry rather than wood. Sherwin-Williams, for example, recommends an acrylic masonry primer on new boards, and its guidance notes that cement based products can attract mildew if they are not treated properly.
- It usually arrives with a finish already on it. Most fiber cement siding is sold either primed for field painting or factory finished, such as James Hardie siding with ColorPlus Technology. What you do next depends on which one you have.
Before you buy paint, find out which type is on the house. The builder, the installer or the original paperwork usually says. If the siding has never been painted on site and looks like a smooth, even factory color, it may be a factory finish rather than paint.
What type of paint to use
Use a 100 percent acrylic exterior latex, sometimes sold as acrylic house paint. James Hardie says in its siding FAQ that primed siding should be painted with an acrylic top coat, and its technical bulletin on finishing primed siding recommends a high quality waterborne 100 percent acrylic exterior paint.
The same bulletin lists what not to use:
- Stain. It is made to soak into wood. It does not build the protective film fiber cement needs.
- Oil or alkyd paint. James Hardie advises against it on its products.
- Powder coating. Also on the list of finishes not to use.
Treat any named product as an example of the category rather than the single best choice. Several manufacturers make premium 100 percent acrylic exterior paints. Sherwin-Williams, for instance, names its Duration exterior line as a top choice for new fiber cement and says its high film build means one coat over a primed surface, while a masonry topcoat such as Loxon needs two coats. Whatever you choose, check that the label says it is suitable for fiber cement or cement based siding, and follow the instructions for that product on primer, coats and temperatures.
New primed siding: paint it within 180 days
Primed fiber cement is not finished siding. The primer is there to make the board ready for paint, not to protect it for years. The James Hardie bulletin says primed products should be painted within 180 days of installation. Leaving primed boards bare for longer exposes the primer to sun and weather it was not designed to take on its own.
On new primed siding, the usual sequence is:
- Make sure the siding is clean and completely dry. The bulletin says not to paint wet siding.
- Caulk the butt joints and gaps at trim with a paintable exterior sealant, as Sherwin-Williams describes. How to do it cleanly is in how to caulk before painting.
- Apply the acrylic topcoat over the factory primer, following the paint maker on the number of coats.
- Seal any cut ends exposed during installation, following the instructions from the siding maker for the product you have.
Unprimed or bare board: prime first
Some fiber cement is sold unprimed, and older siding can wear back to bare board in places. Bare fiber cement needs a primer before the topcoat. Sherwin-Williams recommends a high quality exterior acrylic masonry primer, which it says improves how well the siding resists mildew and efflorescence. Spot prime any bare areas you uncover during prep on a repaint for the same reason. When primer is and is not needed on other surfaces is covered in do I need primer before painting.
Repainting old fiber cement siding
Most of the work in a repaint is cleaning and preparation. Sherwin-Williams gives a clear sequence for repainting fiber cement:
- Clean thoroughly. Its guidance is to pressure clean at a minimum of 2100 psi to remove dirt, chalk, grease, loose material and failing coatings, then rinse and let the siding dry. Keep the spray angled down so water is not driven up behind the laps, and follow any cleaning guidance from the siding maker.
- Remove failing paint. Scrape away peeling or cracked paint and sand those areas.
- Dull glossy areas. Sand any glossy surfaces so the new paint can grip.
- Prime only where needed. Unless bare board is exposed, Sherwin-Williams says no primer is required when repainting fiber cement.
Check for mildew while you clean. Green or black staining that comes back after washing needs a mildew treatment before painting, or it can grow through the new finish. Replace or repair cracked boards and fix any leaks behind them first, because paint will not stop water getting into a damaged board. If the job includes pressure washing as a priced line, how to price pressure washing before painting covers how painters quote it.
Painting over a factory finish such as ColorPlus
Factory finished fiber cement does not need painting to stay protected. James Hardie says its ColorPlus finishes are cured onto the boards at the factory, and it sells touch-up kits for nicks and scrapes. It also says the siding can be repainted if you want to change the color.
If you are repainting a factory finish, treat it like a repaint: clean it, dull any gloss, prime any bare spots and use a 100 percent acrylic exterior topcoat. One practical point: once a factory finish is painted over, color matched touch-up products from the siding maker no longer match the house, so future touch-ups come from the paint you used.
Color, sheen and fire ratings
Vinyl siding has a strict rule against going darker, because vinyl softens and warps with heat; that rule is explained in best paint for vinyl siding. Fiber cement is a cement based board, and neither the James Hardie nor the Sherwin-Williams guidance cited here sets a color limit for it. Dark colors still fade faster in strong sun, so expect to repaint sun facing walls sooner if you choose a deep shade. Help choosing a color is in how to choose exterior paint colors.
For sheen, satin and low luster finishes are the usual choice for siding, because they shed dirt better than flat paint while hiding surface texture better than gloss. Trim is often painted a step glossier. More on sheen is in the paint sheen guide, and trim products are covered in best paint for exterior trim.
One note for homes in wildfire areas: James Hardie states that the fire resistance of fiber cement does not extend to applied paints or coatings, which can be damaged or char in a fire. The board itself is the fire resistant part.
Weather and application
Paint on a dry day within the temperature range on the paint can, and keep off walls in hot direct sun so the paint does not dry before it levels. Never paint siding that is wet from rain, dew or washing. Two thinner coats, or the coats the paint maker specifies, last longer than one heavy coat. Fiber cement can be brushed, rolled or sprayed; on textured board such as a wood grain finish, back brushing or back rolling after spraying works the paint into the texture. Timing around weather is covered in best weather conditions for exterior painting and the best time of year to paint a house exterior.
Fiber cement compared with the siding next to it
| Siding | Paint type | The rule that matters most |
|---|---|---|
| Fiber cement | 100 percent acrylic exterior latex | Paint primed boards within 180 days; no stain, oil or alkyd paint (James Hardie) |
| Vinyl | Vinyl safe 100 percent acrylic | Do not go darker than the original unless the paint is rated for it |
| Aluminum | Acrylic exterior latex over a bonding primer where needed | Remove the chalky surface first |
| Wood | Acrylic exterior latex over the right primer | Block tannin bleed and seal end grain |
| Stucco | Masonry or elastomeric coating | Let new stucco cure and deal with cracks first |
The full guides are best paint for vinyl siding, best paint for aluminum siding, best paint for wood siding and best paint for stucco.
How long the paint lasts
A good acrylic finish on fiber cement usually outlasts the same paint on wood, because the board does not swell, shrink or rot under it. How long it lasts in practice depends on sun exposure, climate, prep and the paint quality. The factors and what to expect are set out in how long exterior paint lasts.
Frequently asked questions
What is the best paint for Hardie board siding?
A high quality 100 percent acrylic exterior latex. James Hardie says primed siding should get an acrylic top coat, and its finishing bulletin rules out stain, oil or alkyd paint and powder coating.
Do you need to prime Hardie board before painting?
Not if it is factory primed and painted within 180 days of installation. Bare or unprimed board needs an exterior acrylic masonry primer. On a repaint, prime only where bare board is showing.
Can you use oil based paint on fiber cement siding?
James Hardie advises against it. Its bulletin on finishing primed siding lists oil and alkyd paints among the finishes not to use, along with stain and powder coating.
How long can primed Hardie board go without paint?
James Hardie says primed products should be painted within 180 days of installation. The primer prepares the board for paint; it is not a finish on its own.
Can you paint over ColorPlus siding?
Yes. James Hardie says ColorPlus siding can be repainted if you want to change the color. Clean it, dull any gloss, prime bare spots and use a 100 percent acrylic exterior paint.
Can you paint fiber cement siding a dark color?
The guidance cited here sets no color limit for fiber cement, unlike vinyl, which can warp under dark colors. Dark shades fade faster in strong sun, so expect earlier repaints on sunny walls.
