Here is a excerpt from the hardie board web site.
Does hardie board siding need primed.
All you should have to do is rinse your siding use a garden hose no pressure washers here to clean off any dust or dirt.
Paint hardiplank siding within installation time frame after installation of primed hardiplank siding it is recommended to have it painted within 180 days or roughly 6 months.
Do not use stains or oil based alkyd paints on james hardie products.
Primed products if your james hardie siding was originally painted after it was installed on your home then check the original paint manufacturer s recommendations for reapplication of paint.
If your siding is unprimed the time frame shortens to 90 days or 3 months to have surfaces painted.
The main thing with hardie board isnt so much what brand of paint you use but what type 100 acrylic latex is what you need.
Hardie board is awesome to paint looks great when done right and it is so easy to work with.
All sides of the hardie board are painted even the edges and therefore the entire board is completely sealed.
And there are definite benefits when choosing james hardie primed siding.
James hardie does not specify paint and will not warrant or accept liability for the performance of field applied finishes.
Limited 30 year non prorated transferable siding substrate warranty.
Siding is factory primed using a primer with a yellow hue paint with an acrylic exterior house paint within 180 days of install complies with astm e136 as a noncombustible cladding that is recognized by fire departments across the u s.
Although hardie board comes from the factory without the back of the board primed according to james hardie s support department they say you can prime and paint the entire board.
More colors because colorplus boards get their tint in the factory they are limited to 33 preset colors.
An exclusive primer for an exceptional product.