The gap between butt joints should never be more than 1/8 inch.
Credit: Photo: JLC | Tim Uhler The gap between butt joints should never be more than 1/8 inch.

Terry Stamman, co-owner of Twin Cities Siding Professionals, in St. Paul, Minn., knows what a good fiber-cement siding job looks like and how it's put together. And he knows what a great fiber-cement job looks like. One testimonial on the company's Web site ( calls his work: “Awesome.”

So what makes for an awesome fiber-cement job?

  • Make sure everything lines up. “You start at the lowest point of the house,” Stamman says, and take into consideration “where that window header will end up and where that sill ends up.” Get it wrong and you end up covering your mistake with an inch or two of lap siding at the top.
  • Stagger butt joints. Scott Barr, owner of Southwest Exteriors, in San Antonio, is adamant that installers vary the width between butt joints. “When you see a butt joint pattern repeating itself, it really jumps out at you.”
  • Mind the gap. Speaking of joints, Laura Tinsley, a Texas home inspector certified to specialize in exterior cladding, says that the gap between joints should be uniform throughout and never be more than 1/8 inch. “It's a small thing, and doesn't affect performance,” she says, “but it affects appearance.”
  • Overlap. Tinsley says she sometimes sees situations where “to save money on materials, installers will barely overlap one plank with another.” She suggests a 1½ -inch minimum overlap.
  • Mark stud locations. “Guys don't hit the studs,” Stamman says, “so when the house moves, the siding moves with it.” Solve that problem by marking stud locations in pencil on the soffit and foundation before putting on your building paper.
  • Nail properly. Tinsley says improper nailing is the single biggest cause of defective installation of fiber cement. Nailing woes include nailing too close to the edge of the plank (could cause cracking) and not enough nailing to properly fasten the material to studs.
  • Caulk carefully. “The last thing you do on a job is caulk, and guys are in a big hurry to get out of there,” Stamman says. Use an acrylic latex caulk, a good one, and make sure it fills the joint to keep it watertight. “The whole point of siding is to keep water out of the house.”