Clapboard Siding Calculator
Calculate clapboard and lap siding for any wall - traditional cedar, beveled, Dutch lap, smooth lap, HardiePlank, LP SmartSide, or vinyl. Get exposure, courses, lineal feet, pieces by length, trim, fasteners, paint, and total cost in one click.
Wall & Material Inputs
Sum of all wall sections (perimeter).
Typical 8, 9, or 10 ft for one story.
Actual width: 5.50 in
1 in is standard. Larger overlap = tighter exposure.
Naturally rot- and insect-resistant. Holds paint or stain well; classic New England look.
10% default. Use 12-15% for many openings; 15-20% for short boards.
Quick Project Presets
Window & Door Cutouts
Wall Elevation Diagram
Enter wall dimensions and click Calculate Siding Takeoff.
Clapboard Siding: A Brief History From Colonial America to the Modern Wall
Clapboard siding is one of the oldest cladding systems in North American construction. The earliest settlers in seventeenth-century New England brought a Northern European framing tradition with them and quickly adopted the local practice of riving thin tapered boards from straight-grained oak, spruce, and later Eastern white pine. These hand-split boards - originally called "clapboards" from the Dutch klappen, meaning to split - were nailed horizontally to a wood- framed wall, each lapping the one below to shed wind-driven rain. The taper gave the wall its distinctive sloped profile and the lap created a positive drainage plane long before housewrap or rainscreens existed. Walk through Plymouth, Salem, Portsmouth, or Newburyport today and you will see houses that have been continuously clad in some version of clapboard for over three hundred and fifty years.
By the early nineteenth century, water-powered sawmills replaced the hand splitter. Boards became uniform in thickness, milled with a clean bevel from a heavy butt edge to a thin top edge, and could be ordered in 8-, 12-, and 16-foot lengths from any lumberyard in the country. The classic profile we now call "beveled siding" - the thick bottom edge laying over the thin top of the course below - emerged from this milling tradition. Variations followed: Dutch lap (also called German lap or cove lap) added a decorative rabbet or cove along the top edge of each board to throw a shadow line; smooth lap simplified installation by using a square-edge board with a simple overlap; and shiplap used a tongue-and-groove joint with a registered face. Each had a regional preference - Dutch lap dominated the Hudson Valley and Pennsylvania farm country, beveled clapboard the New England seaboard, smooth lap the West Coast and Pacific Northwest.
The twentieth century brought engineered substitutes. Aluminum siding arrived after World War II, then vinyl in the 1960s. Both promised the look of clapboard without the maintenance, and both succeeded at the second promise more than the first. In 1990 James Hardie Industries introduced HardiePlank fiber cement siding to North America, and the look-of-wood/durability-of-cement tradeoff finally tipped. Engineered wood products like LP SmartSide added a third path: real wood strands, factory-primed, with a long warranty. Today a serious siding contractor will work with all three families - traditional cedar for restoration and high-end custom, HardiePlank or LP SmartSide for new construction at scale, and vinyl for tight-budget rentals and remodels. The exposure math - board width minus overlap - is identical across every material. That single equation, more than any tool or technique, is the through-line that connects a seventeenth-century cottage in Plymouth to a 2025 production house in Texas.
Exposure by Board Width and Overlap
Reference chart for resulting exposure (in inches) given common nominal board widths and overlap amounts. Use it to plan course count for any wall height.
| Board (nominal) | Actual width | 0.75 in overlap | 1.0 in overlap | 1.25 in overlap | 1.5 in overlap |
|---|---|---|---|---|---|
| 1x4 | 3.5 in | 2.75 in | 2.50 in | 2.25 in | 2.00 in |
| 1x6 | 5.5 in | 4.75 in | 4.50 in | 4.25 in | 4.00 in |
| 1x8 | 7.25 in | 6.50 in | 6.25 in | 6.00 in | 5.75 in |
| 1x10 | 9.25 in | 8.50 in | 8.25 in | 8.00 in | 7.75 in |
| 1x12 | 11.25 in | 10.50 in | 10.25 in | 10.00 in | 9.75 in |
Material Comparison: Cedar vs HardiePlank vs Vinyl
| Property | Western Red Cedar | HardiePlank | Vinyl Lap |
|---|---|---|---|
| Typical $/LF (1x6) | $4.00 - $5.50 | $3.00 - $3.80 | $1.80 - $2.40 |
| Weight per sqft | ~1.5 lbs | ~2.3 lbs | ~0.5 lbs |
| Expected lifespan | 40 - 75 yrs | 50 yrs warranty | 25 - 40 yrs |
| Repaint cycle | 7 - 10 yrs | 10 - 15 yrs | Never (color integral) |
| Fire rating | Combustible | Non-combustible | Melts at 165 F |
| DIY-friendly? | Moderate | Difficult (heavy, dust) | Easy |
| Install productivity | ~75 sqft/day | ~60 sqft/day | ~150 sqft/day |
| Best for | Historic, custom | Production, paint look | Budget, low maintenance |
How to Install Clapboard Siding (5 Steps)
- Step 1: Sheathe the wall and install WRB. Install 7/16 in OSB or 1/2 in plywood sheathing over the framing. Cover with a continuous water-resistive barrier (Tyvek, Typar, or 30 lb felt) installed shingle-fashion - upper sheet laps over lower - and tape every vertical seam. Integrate the WRB with window and door flashings before any siding is loaded onto the wall.
- Step 2: Install starter strip and corner boards. Rip a 1 to 1.5 in tapered starter strip (or use the manufacturer-supplied piece for fiber cement and vinyl) and nail it level at the base of the wall. This tilts the first course outward at the same angle as every course above. Install 5/4 x 4 or 5/4 x 6 corner boards on outside corners and a J-channel or trim board at any inside corners.
- Step 3: Snap layout courses. Use the exposure value from this calculator to mark every course up the wall with a level chalk line, or build a story pole and step the marks up the corner board. Verify courses break naturally at window heads and sills - adjust starter strip height by a half inch if needed to avoid awkward partial-row cuts at openings.
- Step 4: Install courses bottom-up. Set the first course on the starter strip and blind-nail just above the lap line into studs (8d ring-shank stainless or hot-dipped galvanized for wood; manufacturer-spec nails for HardiePlank and vinyl). Every following course laps the previous by your chosen overlap. Stagger butt joints so no two adjacent courses break over the same stud, and use scarf cuts (45-degree opposing miters) for nearly invisible joints. Cut around openings with a sharp jigsaw or carbide circular saw.
- Step 5: Install trim and finish. Install window and door casing, frieze board at the soffit line, water table or belt molding at story breaks. Caulk all joints with paintable acrylic latex sealant, prime every cut end before it goes up (this is the single biggest longevity factor on wood siding), and apply two finish coats of premium exterior latex or oil. Pre-finished products need only touch-up at field cuts.
Common Use Cases
Comparing Cedar vs HardiePlank for Whole-House Siding
Flip the material selector between Western Red Cedar and HardiePlank to see total cost, install time, and trim implications shift in real time. For a 2,400 sqft elevation, cedar typically runs 30-40% higher in material but installs faster than fiber cement. Use the comparison table above to weigh fire rating, lifespan, and crew makeup.
Use the Siding Material Calculator ->Pairing Horizontal Lap With Vertical Board and Batten Accents
A common modern-farmhouse detail mixes horizontal clapboard on the body of the house with vertical board and batten on gable ends or accent walls. Calculate the clapboard runs here, then jump to the board and batten siding calculator for the vertical accents.
Use the Board & Batten Siding Calculator ->Re-Siding a Rental With Maintenance-Free Vinyl
For rental properties where minimizing future repaint and maintenance is the driving constraint, switch material to Vinyl Lap. The exposure math is the same as wood; install productivity jumps to roughly 150 sqft per labor-day; and paint cost drops to zero because color is integral.
Use the Vinyl Siding Calculator ->Pairing Siding Work With Fence Refinishing
When you repaint or restain a cedar-clad house, the cedar fence in the back yard is almost always next on the list. Use the fence stain calculator to estimate gallons and labor for a coordinated yard-and-house refresh.
Use the Fence Stain Calculator ->Pro Tips From the Field
- Always start with a starter strip. The single most common cause of a "flat-looking" clapboard wall is a missing starter strip on the first course. Rip a 1 to 1.5 in tapered piece off the bottom of a board (or use the supplied piece for fiber cement/vinyl) and nail it level at the base before the first full course goes up.
- Level every course, not just the first. A 1/16 in error per course compounds. Across 16 courses you end up 1 inch out of level by the soffit. Snap chalk lines for every course, or use a story pole. The five extra minutes per course saves an hour of trim scribing at the top.
- Scarf joints over studs, never over open bays. A 45-degree opposing-miter scarf joint is nearly invisible when painted and weathers far better than a butt joint. Always land scarfs on a stud so both boards have solid backing, and stagger them so no two adjacent courses break over the same stud.
- Prime every cut end before it touches the wall. The single biggest longevity factor on wood siding is sealing the end grain at every cut. Keep a small can of primer and a brush right on the cut station; prime each end while the piece is still in your hand. Skipping this step is the main reason painted cedar walls fail at the joints.
- Use stainless or hot-dipped galvanized fasteners only. Electro-galvanized nails will bleed black streaks down a painted cedar wall within two seasons. Stainless ring-shank is the gold standard for cedar and redwood; hot-dipped galvanized is acceptable for HardiePlank and engineered wood. Never use staples.
- Keep the bottom edge at least 6 in above grade. Splash-back from a hard rain throws soil and grit several inches up the wall. Code is 6 in over earth and 2 in over concrete or paving; many siding warranties require 8 in. Adjust your starter strip up if the existing grade is too close.
What Siding Contractors Say
“I restore federal-era farmhouses in Vermont and we run a lot of cedar clapboard. This calculator finally gave me a clean takeoff sheet I can hand to my supplier - exposure, course count, lineal feet, and nail weight all on one page. The frieze and casing pull-down saved me a half-hour per elevation.”
“We bid almost exclusively HardiePlank ColorPlus. I love that I can flip the material and instantly see the cost shift to fiber cement rates and the install productivity drop to match a two-person crew. The 1.75 lbs of stainless per square assumption matched my actual job numbers within 5%.”
“Built a 2,800 sqft custom home this spring with 5/16 in fiber cement. Used the calculator for every elevation and our total ordered pieces were off by 11 boards on a job that needed 612. That is well within my 10% waste buffer, which is exactly the discipline I want from a takeoff tool.”
“Re-sided my detached garage in cypress lap this spring. I had no idea exposure was board width minus overlap until this page explained it. The shed preset got me 90% of the way to my final order in about two minutes. The repaint schedule FAQ was honest and helpful.”
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