I'm receiving conflicting 'information' on painting fiber cement siding. I have info from tech rep & web site each of two manufacturers.
The question is whether or not to back prime fiber cement siding. Has anyone any experience?
T
I've never done it. I just seal the cut edges. Then again I don't have several decades of experience with the stuff, so I can't say if there will be a long term problem if not back primes. I'd tend to doubt it though - back priming developed to keep wood siding from absorbing moisture, but fiber cement is far more stable, absorbs less moisture from the atmosphere, and I've taken down wood siding of all types that was not back primed and had no problems even though the wood was fifty years old or more. I'd tend to think that completely sealing the piece is unrealistic and would tend to trap moisture. Fiber cement siding drying out from the back would probably keep the paint from blowing off of the front.
R
Can only detail my dealing with James Hardie horizontal lap siding. Retail version, typically gotten at local big box store, is primed on the facing side. Unprimed on the backside. Details at their website don't mention priming the backside at all. They are very, very specific on the type of paint to use. This I experienced while building my own stand-alone garage.
The concrete siding the builder used on my home was not James Hardie brand. They had to prime it all before painting it. Was primed after the siding was installed.
Concrete siding wicks water, makes it soft. That's why they (James Hardie) require a minimum distance from the soil line. If installed, primed, and painted properly, there should be adequate enough ventilation to vent any moisture leakby with horizontal lap siding.
Thank you all. Job uses 4x8 sheets with battens. I'll go without priming or painting the back side. T
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