How to estimate a siding job wall by wall, square by square
Siding is estimated from wall area: measure each side of the house (height times width), subtract large openings, add about 10 percent waste, then price the trim system (corners, J-channel, starter), house wrap, tear-off, and labor before dividing the total cost by one minus your target margin. Vinyl re-sides priced this way typically quote $6 to $8 per square foot; fiber cement runs higher on both material and labor. The trim accessories are a quarter of the material bill and the piece most first-time bids forget.
Step by step
- Measure each wall and subtract only the big openings. Measure height times width for every side of the house, including gable triangles at half base times height, and subtract garage doors and large window walls but not ordinary windows, which become cut waste rather than savings. Sum the sides into total square footage; siding crews and suppliers both talk in squares of 100 square feet. An 1,800 square foot wall area is an 18 square job in trade shorthand.
- Choose the product and price it with 10 percent waste. Vinyl runs about $1.68 a square foot, engineered wood $2.20, fiber cement lap $2.60, board and batten $3.15, and cedar bevel $4.85. Multiply the measured area by 1.10 for cut waste, more on complex homes with many gables and corners. Fiber cement also changes the labor line: it cuts slower, needs two sets of hands, and dulls blades, so the product choice moves both halves of the estimate.
- Take off the trim system, not just the field. Every inside and outside corner, window, door, and horizontal start needs its accessory: outside corner posts at $3.90 a linear foot, J-channel at $1.38, starter strip at $1.18, plus soffit at $2.20 a square foot and fascia wrap at $2.70 a foot if the eaves are in scope. On a typical house the trim system adds 20 to 30 percent to the siding material bill. Count it wall by wall; a lump-sum guess here is the most common siding estimating hole.
- Include the weather barrier and flashing. Building code (IRC R703) requires a water-resistive barrier behind siding, so house wrap at $0.17 a square foot covers the full wall area, with flashing tape at $0.87 a linear foot around every opening and metal flashing at $1.90 where roofs meet walls. These lines are cheap and non-negotiable. Skipping them fails inspection and, worse, rots the wall behind a beautiful re-side.
- Price tear-off and what you might find. Stripping old siding is real labor plus a dumpster, commonly $400 to $600, and the sheathing underneath is a mystery until it is exposed. Carry a written unit price for rot repair per square foot or per sheet of sheathing. Layered old siding (vinyl over wood over shakes) multiplies both tear-off hours and disposal weight.
- Estimate labor by squares per crew-day. A two man vinyl crew hangs roughly 4 to 6 squares a day on a walkable single-story with normal detail; second stories, many gables, and fiber cement cut that meaningfully. An 18 square strip-and-re-side is commonly a four day job, about 64 crew-hours, at a loaded rate covering wages, burden, staging, and brakes. Scaffolding or lift rental on tall walls is its own line.
- Divide by margin and check against the per-square market. Materials plus labor plus disposal equals cost; the quote is cost divided by (1 minus margin), so a 30 percent margin divides by 0.70. Cross-check the result per square: installed vinyl below $600 a square usually means the trim system or the wrap fell out of the bid. Multiplying by 1.3 instead of dividing by 0.7 gives away seven points of margin on a five-figure job.
- State the assumptions and send it same day. Name the product line and color, the trim system, the wrap, the rot allowance, and whether soffit and fascia are included, then exclude structural repairs beyond the allowance and painting. Send the line-item estimate as a text or email link the homeowner can e-sign that evening. Re-side decisions usually involve two or three bids and a spouse; the clearest same-day estimate is the one that gets discussed at dinner.
The siding pricing formula
(Wall area times 1.10 waste times siding price) plus the trim system (corners, J-channel, starter), house wrap, and flashing equals materials; crew-hours times the loaded rate plus the dumpster equals the rest of cost; quote equals total cost divided by (1 minus margin). A 30 percent margin means dividing by 0.70, and the difference from multiplying by 1.30 is about seven points of real margin, because markup is a percentage of cost while margin is a percentage of the price. Fiber cement bids use the same formula with heavier labor inputs.
An 1,800 square foot vinyl re-side: 1,980 square feet of siding after 10 percent waste at $1.68 is $3,326.40, house wrap at $0.17 a square foot is $306, 280 feet of J-channel at $1.38 is $386.40, 160 feet of starter strip at $1.18 is $188.80, 80 feet of outside corner post at $3.90 is $312, and nails plus caulk add about $117. Materials total $4,636. A two man crew strips and hangs it in four days, 64 hours at a $55 loaded rate, so labor is $3,520, plus a $400 dumpster. Job cost is $8,556. Divide by 0.70 for a 30 percent margin and you get $12,223, quote $12,225, which is about $6.79 a square foot.
Cost factors siding contractors price for
Stories and staging
Second and third story walls need scaffolding, lifts, or pump jacks, and every piece travels up before it goes on. Tall work can add 30 to 50 percent to labor and a rental line to materials. Walk all four sides before quoting; the street-facing wall is rarely the hard one.
Gables, corners, and detail density
Every gable adds angled cuts and waste, and every corner adds posts at $3.90 a foot plus fitting time. A simple rectangle and a cottage with six gables can share square footage and differ 25 percent in cost. Count corners and gables at the measure, not from the curb.
What is under the old siding
Rotten sheathing, missing wrap, and past leaks only show up at tear-off. A written rot allowance with a per-sheet or per-square-foot unit price turns discovery into a documented change instead of a fight. OSB sheathing repair runs about $0.73 a square foot in material plus labor.
Product and profile choice
Fiber cement at $2.60 a square foot costs more than vinyl at $1.68 and installs slower, with silica dust controls and two-person handling, while cedar at $4.85 adds finishing. Premium profiles also mean premium trim accessories. Quote the chosen product and one alternative tier so the customer can trade money for material honestly.
Openings and penetrations
Every window, door, light, outlet, and hose bibb is J-channel, flashing tape, blocks, and cut time. Window-dense walls take meaningfully longer per square than blank walls. Mounting blocks and light fixture blocks are small parts that read as craftsmanship when priced and as corner-cutting when absent.
Frequently asked questions
How do I measure a house for siding?
Measure each wall's height times width, add gable triangles at half base times height, and subtract only large openings like garage doors, since normal windows become cut waste. Sum it, then add 10 percent waste, more on gable-heavy homes. Suppliers sell siding by the square (100 square feet), so an 1,800 square foot measurement with waste is an order of about 20 squares.
Vinyl or fiber cement, and how different is the price?
Vinyl material runs about $1.68 a square foot against $2.60 for fiber cement lap, and fiber cement adds labor: slower cutting with dust control, two-person handling, and paint or caulk detailing, so installed prices commonly differ by 40 to 80 percent. Fiber cement buys fire resistance, paintability, and a premium look. Quote both honestly when a customer is on the fence and let the house's exposure and budget decide.
What margin do siding jobs need?
Between staging, disposal, weather days, and the rot you have not seen yet, siding overhead and risk justify a 30 to 40 percent gross margin, meaning cost divided by 0.60 to 0.70. The unit-price rot allowance protects the margin from discovery, and the margin protects the business from everything else. A 10 percent markup on a five-figure re-side is a rounding error away from working for free.
Is house wrap actually required?
Yes, the residential code (IRC R703) requires a water-resistive barrier behind exterior cladding, and at about $0.17 a square foot plus flashing tape at openings it is among the cheapest lines on the whole estimate. The wrap, not the siding, is the wall's real water management layer. Any bid that omits it is either non-compliant or planning to skip it after the contract is signed.
How does Staxen help a siding contractor bid faster?
Walk the house talking: wall areas, product, corners, gables, tear-off, and Eddie the Estimator drafts a priced line-item estimate you review and send as a text or email link with e-signature and optional deposit collection. Eddie is $59 per month and your first job is free with no card required. Ivy can then invoice the job in draws and chase payment automatically, at $59, or all three employees for $149 per month.
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