Siding Replacement Cost Calculator: Check the Wall Behind the Panels
Siding is the one exterior job where almost nothing you are paying for is visible when it is finished. The panels are the cheap part. The barrier behind them, the flashing at every roof and every opening, and the gaps at the bottom decide whether the wall stays dry for thirty years or rots quietly for five. This page gives you a total to measure your quote against, works out the material takeoff, and shows you the handful of details that separate a wall from an expensive mistake.
What you can check, and what you can't
| Line item | Can you verify it? | How |
|---|---|---|
| Wall area and squares | Yes | Geometry. Perimeter, height, gables, minus openings. |
| Trim quantities | Yes | Corners, starter and J-channel all follow from the same measurements. |
| Water-resistive barrier | Yes | Published code. It is required, and so are its laps. |
| Kick-out flashing | Yes | Published code, and the manufacturer asks for more. Go and look at your roof-wall corners. |
| Clearances at grade and roofs | Yes | Manufacturer's written instructions. A tape measure settles it. |
| Permit | Yes | Re-siding needs one in code-following jurisdictions. Ask. |
| The total | Yes, against a benchmark | A published, scope-defined national and regional figure, scaled to your wall area. |
| Labour hours and wages | Mostly | Federal wage data, plus a stated productivity assumption. |
| Panel prices | No | Not published as open data. Ask for brand, line and profile. |
| Overhead and profit | No | The contractor's business. But it should be disclosed. |
Calculator
Your walls, by the numbers
The house
Measure at ground level around the outside. This assumes a rectangular footprint; bump-outs add area and corners.
Count every place a sloped roof runs into a wall — a porch roof, a dormer side, a garage. Each one needs kick-out flashing.
Openings
Material and place
Clearances you can measure fiber-cement
Waste and labour
2025 U.S. national median for carpenters. Siding crews often mix carpenters with labourers, whose median is $22.44 — see sources.
Your total
| Siding area | — |
| Benchmark rate, — | — |
| Benchmark total | — |
| of which field labour, our model | — |
| of which everything else | — |
Area
| Perimeter | — |
| Wall area | — |
| Gable area | — |
| Openings deducted | — |
| Net siding area | — |
| Squares to order (with waste) | — |
What the quote should list besides panels
| Water-resistive barrier | — |
| Starter strip | — |
| Corner posts | — |
| J-channel at openings | — |
| Kick-out flashing | — |
Clearance check
| Required at grade | — |
| Required at roofs, decks, paths, steps | — |
| Verdict | — |
Labour
| Labour-hours | — |
| Crew days | — |
| Direct wages | — |
| + burden | — |
| Labour as billed to you | — |
Where the total comes from
Siding panel prices are not published as open data, and the retailers that carry some of them block automated access — we tested six and every one refused. So the total starts from a published, scope-defined benchmark for the finished job instead.
The 2025 Cost vs. Value Report, published by Zonda through the Journal of Light Construction, prices two siding jobs every year. Both replace 1,250 square feet — 12.5 squares — of existing siding, include factory trim at all openings and corners, and call for a continuous water-resistive barrier beneath. The 2025 national averages:
| Material | National job cost | Per square |
|---|---|---|
| Vinyl | $17,950 | $1,436 |
| Fiber-cement, factory primed and painted | $21,485 | $1,719 |
Fiber-cement carries a 19.7 percent premium over vinyl for the same 1,250 square feet. That is the whole material decision in one number, before anyone argues about looks.
Siding costs more per square than a roof. That surprises people.
Hold the two benchmarks side by side. A roof, in the same report and the same year, runs $1,062 a square. Vinyl siding runs $1,436 — about 35 percent more for the same 100 square feet of surface.
Most people assume the opposite, because a roof feels like the bigger, more dangerous job. Three things explain it, and all of them show up in your takeoff:
- Siding is mostly edges. A roof is a few large planes. A wall is interrupted by every window, every door, every corner, every hose bib and every light fixture. Each interruption is a cut, a piece of trim and a flashing detail.
- The trim is not a rounding error. Run the calculator on a plain 40-by-30 house and you get roughly 140 feet of starter, 36 feet of corner post and nearly 200 feet of J-channel — before a single panel goes up.
- You cannot walk on a wall. Everything above head height needs staging or a lift, and it has to move around the building.
If you have already read our roof replacement cost breakdown, this is the same arithmetic pointed at a vertical surface.
What is behind the siding matters more than the siding
Siding is not waterproof and was never meant to be. It is a rain screen: it takes the beating, and the layer behind it does the actual keeping-water-out. The code is explicit about that layer.
| Requirement | What the code says |
|---|---|
| Water-resistive barrier | Required behind the covering — one layer of No. 15 asphalt felt or an approved equivalent |
| Horizontal laps | Not less than 2 in |
| Joint laps | Not less than 6 in |
| Lap over flashings | Not less than 2 in |
| Drainage | The wall envelope must provide a means of draining water to the exterior |
| Flashing at openings | Required at the heads and sides of windows and doors |
| Permit | Required to re-side an existing dwelling |
Two consequences worth acting on. First, a quote that lists panels and labour but never mentions house wrap is either hiding it in the labour line or not doing it — ask which. Second, this is work you can only inspect while it is happening. Once the panels are on, nobody can tell you whether the laps ran the right way. Walk the site on the day the wrap goes up, and take photographs.
The cheapest part that prevents the most expensive damage
Where a sloped roof runs into a wall — a porch, a dormer, an attached garage — the water running down that roof edge has to be thrown clear of the wall. The part that does it is a small bent piece of metal called a kick-out flashing.
Leave it out and every rainfall pours a concentrated stream behind the siding at exactly the point where nobody will look for twenty years. It is the single most common cause of hidden wall rot on otherwise well-built houses.
| Source | What it requires |
|---|---|
| Building code | Kick-out flashing at roof-to-wall intersections, not less than 2.5 in long, corrosion-resistant metal not less than 0.019 in thick |
| James Hardie written instructions | Not less than 4 in by 4 in, angled 100 to 110 degrees |
Notice that the manufacturer asks for more than the code does. A 3-inch kick-out passes inspection and still fails the instruction sheet — and James Hardie states plainly that failing to follow its written instructions may affect warranty coverage.
This is the general shape of the thing: passing inspection and keeping your warranty are two different tests, and the manufacturer's is usually stricter. Ask which one your installer is building to.
You can check this yourself in five minutes without a ladder. Stand where a roof edge meets a wall and look at the bottom corner. If there is no metal tab bent out and away from the wall, there is no kick-out flashing.
The gaps at the bottom
Fiber-cement is a cement product. Left in contact with wet ground or a wet deck it wicks water, swells and fails, and the manufacturer's instructions are correspondingly specific:
| Where | Required clearance |
|---|---|
| To the ground | 6 in minimum |
| To roofs, decks, paths, steps, driveways and other solid surfaces | 1 to 2 in |
| Above horizontal flashing | 1/4 in, and not caulked |
That last line is the one installers get wrong most often, because caulking a gap looks like care. It is the opposite: the gap above a flashing is a drainage path, and sealing it traps water in the wall. If you can see a bead of caulk sitting on top of a flashing, that is a defect, not a finish.
These are the two easiest faults for a homeowner to find. Take a tape measure to the bottom edge of the siding and to any place it meets a deck or a path. Some product instruction sheets ask for more than the general guide — the sheet for your specific product governs.
Three trades, one pattern
This is the third of these breakdowns we have built, and something has become visible across all three that is worth more than any single number in them.
The same report publishes the same projects for each of the nine US Census divisions. Divide the most expensive division by the cheapest and you get how much a job's price depends on where you live:
| Project | Most expensive ÷ cheapest division |
|---|---|
| Siding replacement, vinyl | 1.45× |
| Roofing replacement, asphalt shingles | 1.43× |
| Siding replacement, fiber-cement | 1.41× |
| Window replacement, vinyl | 1.19× |
| Window replacement, wood | 1.17× |
The three jobs built on your walls and roof cluster tightly around 1.4. The two jobs that consist of carrying a factory-made object to your house and fitting it sit near 1.18. Nothing about the buildings changed. What changed is how much of the price is made on site.
These are the publisher's own figures with none of our assumptions in them, which is what makes the pattern worth trusting. It gives you a practical rule: the more of a job that is manufactured elsewhere, the less shopping around your area can save you — and the more the brand and product line decide the price. For siding and roofing, getting three local bids is worth real money. For windows, arguing about the product line is worth more than arguing about the installer.
Our window replacement breakdown works through the other end of that line.
What the labour is actually worth
The benchmark says 12.5 squares of vinyl siding costs $17,950. Our labour model — 12.5 squares at three hours each, at the federal median carpenter wage, with burden and markup on top — puts the field labour inside that at about $1,916, or 10.7 percent.
That lands between roofing at 11.5 percent and windows at 4.6 percent, which is where a job of this kind should land. Push the assumptions and it stays a minority:
| Scenario | Hours/square | Burden | O&P | Billed labour | Share |
|---|---|---|---|---|---|
| Fast crew, modest markup | 2.0 | 30% | 35% | $1,278 | 7.1% |
| Our defaults | 3.0 | 30% | 35% | $1,916 | 10.7% |
| Slow, high comp state, heavy markup | 5.0 | 65% | 60% | $4,805 | 26.8% |
| Implausibly slow and expensive | 7.0 | 80% | 75% | $8,026 | 44.7% |
Be careful with this comparison, including ours: the hours per square are our assumption, so a labour share is only ever as good as that number. The regional-spread table above has no such weakness, which is why we lead with it.
The assumptions, stated plainly
| Input | Our default | What moves it |
|---|---|---|
| Waste | 12% | Complex elevations, many openings, board-and-batten or shake patterns, long runs that reduce offcuts |
| Labour-hours per square | 3.0 | Two storeys, staging, fiber-cement instead of vinyl, how much trim there is |
| Crew size | 2 | Two is standard for residential siding |
| Labour burden | 30% | State workers' compensation rates |
| Overhead and profit | 35% | Company size, local market, whether they carry their own crews |
| Barrier lap allowance | 10% | Wall height and how many courses of wrap it takes |
The calculator also assumes a rectangular footprint. Bump-outs, wings and porches add both area and corners, and corners are where the money is.
Questions to take to the contractor
- What brand, product line and profile? Not "premium vinyl".
- Is a water-resistive barrier included, which one, and can I see it before the panels go on?
- Will kick-out flashing be installed at every roof-to-wall intersection? How many are there on my house?
- What clearance will you hold at grade and at the deck?
- Is the permit in this price, and who pulls it?
- What is the price per square? Ask every bidder the same way.
- How much trim is in this quote — corners, starter, J-channel — and is it itemised?
- Are you following the manufacturer's written installation instructions? Which document?
- What happens to the price if rotten sheathing turns up? Get the unit rate in writing now.
- Who holds the labour warranty, and for how long?
Warning signs
- No mention of house wrap or a water-resistive barrier. It is required. Its absence from the quote is a question, not a saving.
- Siding installed over the old siding without a discussion of what is underneath. Sometimes acceptable, sometimes covering rot.
- No kick-out flashing at a roof-wall corner. Go and look.
- Caulk on top of a horizontal flashing. That gap is meant to drain.
- Siding touching the deck, the path or the ground.
- No permit where the jurisdiction requires one, especially if it is offered as a discount.
- A total with no square-foot or square figure. You cannot compare bids without it.
Sources and method
- Cost benchmark — Zonda, Cost vs. Value Report 2025, published through the Journal of Light Construction. Projects: Siding Replacement, Vinyl (national $17,950) and Siding Replacement, Fiber-Cement (national $21,485), each replacing 1,250 sq ft with factory trim at openings and corners over a continuous water-resistive barrier; the nine US Census division figures from the same edition are used to derive a regional index, and the roofing and window figures quoted for comparison come from the same edition. Read from the publisher on 31 August 2026. jlconline.com/cost-vs-value
- Wages — U.S. Bureau of Labor Statistics, Occupational Outlook Handbook: Carpenters (SOC 47-2031) median $29.12 per hour; Construction Laborers and Helpers median $22.44 per hour, $46,680 per year, 1,674,400 jobs. Both May 2025. Siding crews commonly mix the two. bls.gov/ooh
- Water-resistive barrier, flashing, kick-out flashing and permit — International Residential Code R703.1, R703.2 and R703.4 as adopted, via a city building department re-siding handout for the 2020 Minnesota Residential Code, which adopts the 2018 IRC. Verify the edition your jurisdiction has adopted.
- Fiber-cement clearances — James Hardie, Best Practices Installation Guide for Siding and Trim Products: 6 in to the ground; 1 to 2 in where products meet roofs, decks, paths, steps and driveways; 1/4 in above horizontal flashing, not caulked; kick-out flashing not less than 4 in by 4 in at 100 to 110 degrees. The guide states that failing to follow the written instructions may affect warranty coverage. Individual product instruction sheets can be stricter and govern.
- Siding square — 100 sq ft, the standard unit of measure in the trade.
- Panel prices — not used, because we could not source them. Automated retrieval from six major retailers was attempted on 31 August 2026 and refused by all of them. No price on this page is a retail product price.
- Waste, labour-hours per square, crew size, labour burden, overhead and profit, barrier lap allowance — assumptions set by Home Repair Ledger and adjustable in the calculator. They are not measurements and are not sourced.
Code citations are to the model code as adopted by one jurisdiction; your jurisdiction governs. Manufacturer requirements are quoted from the publisher's own current guidance.
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