In article , rgammon51
@yahoo.com (Robert Gammon) says...

Be aware, priming and painting is a all side proposition. Hardie siding
panels are ONLY primed/painted on the Top Side. All cuts and the back
side need to be primed for long life and any exposed nail heads and
seams need paint/caulk.

Why in the world would you back-prime cement siding? I can see it with
wood, where you nail the siding up against the sheathing, but cement
board needs an air gap to keep condensation from rotting out the
framing. With proper ventilation, painted one side should be fine.

--
For email, replace firstnamelastinitial
with my first name and last initial.