A Practical Guide to Fiber-Cement Siding

Picking the right siding for your house is a delicate balancing act between good looks, durability, maintenance, and affordability. With wood, vinyl, stone, brick, or stucco, you might get only two or three of these. But with fiber cement, a resilient mix of wood pulp and portland cement, you get all four. It’s the only siding that combines the performance of masonry—minimal upkeep; rot-, fire-, and termite-proof; unaffected by wind or cold—with the look of painted wood clapboards, shingles, even stone or brick. Yet fiber cement goes for just a fraction of the cost of these other materials. No wonder nearly 15 percent of new homes—and many TOH TV projects—are clad with the stuff.
All this has happened in just 25 years, since fiber cement was first introduced. Now architects regularly specify the siding because it holds down costs without compromising aesthetics. It’s even accepted for use in many historic districts.

What’s in Fiber Cement?
The basic recipe has just four ingredients.
Water: Dissolves the wood pulp; activates and hardens the cement.
Wood pulp: Improves flexibility and resilience.
Fly ash: Acts as a filler. (Some makers use silica sand instead.)
Portland cement: Binds the ingredients. Made with limestone, clay, and iron.

What’s it cost?
Clapboards, the most common type of fiber-cement siding, range from 70 cents to about $5.25 per square foot uninstalled. Shingles sell for about $2 to $8. Pricing depends on finish, size, and where it’s sold.

DIY or hire a pro?
Because of its weight—about 2½ pounds per square foot—its tendency to crack if mishandled, and the specialized tools needed to cut and nail it, fiber-cement installation might be best left to pros.

How long does it last?
Warranties against defects range from 25 years to limited lifetime. Factory finishes carry a 15-year warranty against flaking and fading.

How much care?
As with wood siding, spray it with a garden hose every 6 to 12 months; inspect caulked joints every few years, and be sure to keep foundation plants pruned back so that siding can dry out.

Trimming and Finishing
Finish: Fiber cement has to be painted or stained. This can be done before it’s installed—either by the manufacturer or by a paint shop hired by the lumberyard where you order the siding—or after it’s up. Manufacturers charge about $1 per square foot and offer a 15-year warranty, but color choice is limited and you get only one coat. Paint shops provide two coats, 25-year warranties, and hundreds of hues for about $2 per square foot, not including the cost to ship your order to and from the lumberyard. On-site painters generally offer one- or two-year warranties on their work.
Trim: For minimal maintenance, use trim made of fiber cement or cellular PVC. Both are rot-proof and come in standard ¾- and 1-inch thicknesses for use as corner, frieze, and fascia boards. Crown moldings are also available. You can also use wood trim with fiber-cement siding. Wherever trim and siding meet, there should be a 1/8-inch gap, concealed with caulk.

Layout and Installation
Layout: Fiber-cement panels butt together at the edges, making layout a relatively simple matter. With clapboards and shingles, each course overlaps the next by at least 1¼ inches. The portion that’s visible—not overlapped—is called the exposure. (A 6¼-inch-wide clapboard with a 1¼-inch overlap has a 5-inch exposure.) Exposure has to be decided before you order because it determines how wide your siding will be, how much you will need, and how it will look once it’s installed.
Installation: Make sure your contractor uses rustproof stainless-steel nails, primes all cuts, and caulks joints with a paintable exterior-grade sealant that will remain flexible. To reduce water absorption, fiber cement has to be installed at least 2 inches above steps, decks, and roofs, and at least 6 inches above grade. Check joints every few years and recaulk as needed.

Fiber Cement vs. Mother Nature
Inland: In arid locales that are prone to wildfires, particularly in the western U.S., some insurance companies offer a discount for homes sided in fiber cement because it’s noncombustible. It’s also unaffected by the strong UV radiation typical at high altitudes.
Coastal Environment: Salt air, high humidity, and bright sun are constant challenges in seaside environments but have no effect on this siding. With a proper nailing pattern, it will also withstand winds up to 130 mph.

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