Painting Fiber Cement: Is It Like Wood?
Before I purchase paint and begin finishing my addition, is there anything I need to know about painting fiber cement? Or do I proceed as I would with preprimed wood clapboards?
James Kauffman, Alexandria, VA
Editor Brian Pontolilo replies: I recently re-sided some of my house with James Hardie’s fiber-cement siding, and I assumed I could treat it like preprimed wood. Your question challenged my assumptions, though, so I called James Hardie to investigate.
Like preprimed wood siding, cut ends of fiber cement need a coat of primer before the siding is installed. James Hardie specifies 100% latex acrylic paint and primer, though they did not specify a brand, as they did when I asked about filling nail holes. In this case, the Hardie representative recommended using OSI’s Quad sealant, but only with the caveat that there shouldn’t be nail holes unless I had overdriven a fastener. Because overdriven nails may not hold, he said I should properly drive a nail adjacent to the overdriven fastener before filling the hole. He specified Quad for all caulking.
I only have weekends to work on my house, so I paint as I go. I got this part right, as Hardie recommends painting as soon as possible. I lightly sanded the surface, but wish I had done a more careful inspection. Blemishes such as nicked edges and splotches hide in the flat, textured primer, but stand out when the siding is painted.
It’s OK to brush, as I did, or spray-paint the siding, which takes paint so well thatexcept for some flashing where I had sanded and touched up the primer, one coat looked finished. The second coat went on quickly, though not nearly as quickly as my neighbors’ project. Their builder used a prefinished product and left me wishing I hadn’t already bought the siding for my whole house.