Hardie Plank Lap Siding

Fiber cement lap siding is a noncombustible exterior cladding built to outlast wood and resist the things that wreck siding in this climate. Crafted with fiber cement and engineered for climate resilience, it offers the warmth and texture of wood with durability — without the rot, the repaints, and the woodpecker holes that come with cedar.

Here’s the one thing Montana buyers cannot get wrong: be sure you’re using the right instructions for your Hardie Zone — HZ5 or HZ10. Montana sits in HZ5 — cold winters, freeze-thaw cycling, snow. HZ10 product is engineered for hot, humid, coastal regions. Spec the wrong zone and you can void the warranty and run afoul of code. That mistake is invisible on install day and expensive later.

What it is and why it holds up

The material itself explains the durability. Made from a proprietary blend of cement, sand, and cellulose fiber, this siding is highly durable and resistant to warping, cracking, and swelling. That dimensional stability matters here. Wood siding moves with every freeze-thaw swing — and most valleys cycle through 100-plus of those a year. Fiber cement doesn’t.

On fire, the spec is plain. Hardie siding is noncombustible — it will not burn. It resists damage from moisture and holds no appeal for pests like woodpeckers or termites. More precisely, it is noncombustible and complies with ASTM E136 standards. While it does not ignite, applied paints or coatings may still char when exposed to flame. In the WUI zones — and most of western Montana qualifies — noncombustible cladding earns its keep.

The pest angle is real money in forested country. Woodpeckers drill cedar and grooved plywood chasing carpenter ants. Fiber cement gives them nothing. Unlike wood, this siding resists pests, moisture, and rot, significantly reducing the need for repainting or frequent upkeep. A simple rinse is often enough to keep it looking great.

And the climate engineering is purpose-built. The fiber cement siding and trim products are formulated to offer superior performance based on your region’s unique climate needs, and help protect against damage from weather extremes, hurricanes, winter storms and more.

Sizes, textures, and finish options

Texture is where you set the look. The lap siding comes in six profiles: Select Cedarmill, Smooth, Beaded Select Cedarmill, Beaded Smooth, Custom Colonial Roughsawn, and Custom Colonial Smooth. Cedarmill is the workhorse — a natural cedar look with a soft texture that mimics wood. Smooth reads modern. The Beaded and Custom Colonial profiles lean traditional.

Spec	Detail
Material	Cement, sand, cellulose fiber
Thickness	5/16 inch
Fire	Noncombustible, ASTM E136
Climate zone	HZ5 (Montana) or HZ10
Substrate warranty	30-year non-prorated, transferable
ColorPlus finish warranty	15-year prorated

On finish, you’ve got two roads. Buy it primed for paint and field-paint on site, or order it prefinished with ColorPlus. The factory finish is the better bet against UV at elevation, which fades field paint faster than most folks expect. The factory-applied, baked-on color is cured between coats for superior color consistency, adhesion and durability.

ColorPlus comes two ways. The Statement Collection products are curated and tailored to your home’s region, locally stocked, making it easier to find a color. If nothing fits, the Dream Collection features a palette of nearly 700 ColorPlus finishes, made to order — and may incur additional cost and production time.

One catch worth knowing: not every width comes in every finish. In HZ5, the wider 9-1/4 and 12-inch widths come primed only.

Western Building Center carries an 8.25-inch by 12-foot primed Cedarmill plank — the standard length across the line is 12 feet.

Warranty — and the strings attached

The warranty is a real value point, but it’s conditional. The substrate carries a 30-year non-prorated limited, transferable substrate warranty. The finish is separate: ColorPlus Technology finishes have a 15-year prorated limited finish warranty.

Non-prorated on the substrate means full coverage that doesn’t shrink year over year. Transferable means it follows the house to the next owner — a selling point. But all of it hinges on doing the install by the book, with the correct zone product. Wrong zone, sloppy install, no coverage.

Installation basics

Lap siding lives or dies on water management and the starter course. Behind it you need a code-compliant water-resistive barrier. Then the first course gets set right.

Hardie Plank lap siding requires a starter strip beneath the first course. You can make your own or find acceptable prefabricated third-party starter strips for purchase. To make your own, rip a piece of Hardie Plank into 1-1/4-inch strips.

Lay out before you fasten. For accurate fastening, snap vertical chalk lines on the water-resistive barrier at the center of every stud location. Blind nailing is the recommended method.

Long walls need staggered joints. For walls longer than 12 feet, you’ll need to butt additional lengths of siding together. It’s best to stagger the joints in each successive course to avoid noticeable patterns. The spacing rule: butt joints in adjacent courses should be spaced apart by at least two stud bays for 16-inch o.c. framing or one bay for 24-inch o.c. framing. A progressive stagger works clean — the cut-off piece for one course becomes the first piece in the course above, making efficient use of materials and ensuring all butt joints land on studs.

Flash those joints. Flashing behind butt joints is an effective, low maintenance way to comply with building code and help protect against water intrusion. James Hardie recommends 6-inch-wide flashing that overlaps the course below by 1 inch, though some local codes may require different sizing. Joint flashing must be durable, waterproof material that does not react with cement products. Match the flashing to the finish — light-colored joint flashing with light finishes, dark flashing on dark finishes.

If you’re running ColorPlus, handle it carefully. It ships with a protective laminate slip sheet, which should be left in place during cutting and fastening to reduce marring and scratching. The sheet should be removed immediately after each plank is installed. And take silica safety seriously when cutting fiber cement — proper blades and dust control are not optional.

Frequently Asked Questions

Which Hardie Zone does Montana need? HZ5. The product line is engineered by climate, and you need to be sure you’re using the right instructions for your Hardie Zone — HZ5 or HZ10. HZ5 is built for cold winters, freeze-thaw, and snow. HZ10 is for hot, humid, and coastal regions. Specifying the wrong zone can void the warranty and violate code.

Will it work in cold, wet Montana winters? Yes. It’s Engineered for Climate to handle specific regional weather challenges, from harsh winters to high humidity, making it a durable choice across climates. The fiber cement is moisture resistant, rot-resistant, and dimensionally stable — it will not swell, crack or warp due to moisture or precipitation.

Is it really fireproof? Not fireproof — noncombustible. It complies with ASTM E136 standards. While it does not ignite, applied paints or coatings may still char when exposed to flame. The board won’t feed a fire, which is what matters in WUI country.

How long does the color last? With the factory finish, a long time. The baked-on color is factory-applied and cured between coats, ensuring superior color consistency and resistance to peeling, chipping, and fading over time.

What’s the difference between Select Cedarmill and the other textures? Select Cedarmill offers a woodgrain texture that resembles real cedar, while options like Smooth or Beaded feature different finishes. Select Cedarmill is ideal for achieving a natural wood appearance without the maintenance.

Do I need flashing on every joint? On walls longer than 12 feet you’ll have butt joints, and yes — flash them. James Hardie recommends 6-inch-wide flashing that overlaps the course below by 1 inch. It keeps water out and keeps you code-compliant.