Two quotes, one budget, and only one of them is the one you want
Both prices arrived in the same week and both fit. The bathroom is the one the household has already voted for: a 1974 suite in a colour that has outlived its decade, a bath nobody has run in four years, and a shower fed off a gravity head that behaves exactly as you would expect. The other quote is for the two weather elevations — cladding stripped back, sheathing actually looked at, new siding — with a garage door added as a line item almost in passing, because the fitter noticed a broken torsion spring while he was measuring. Twenty-six thousand covers either one of these. It does not come close to covering both.
The house is a 1974 two-storey, 168 m² (1,808 sq ft) of finished floor area, and the plan is to be out of it in about eight years when the younger one finishes school. That last sentence is the one that turns a taste question into an arithmetic one, and it is also the sentence most kitchen-table versions of this conversation leave out. Nobody is choosing between a bathroom and some siding in the abstract. They are choosing what the house looks like for eight years and what it is worth on the day a stranger walks through it.
Three quantities follow whichever quote gets signed, and only the first is ever discussed. What share of the spend is still visible in the price at sale. What the assessor's office does with the work once a permit lands on their desk — which in some jurisdictions is a bill next year and in others is nothing whatsoever until completion day. And what the buildings sum insured on the policy should now say, given that neither of these projects makes the house one square foot bigger and both of them make it more expensive to put back. Figures below carry no currency symbol; the multiplication is identical in dollars, pounds or euros, and only the jurisdiction sections change with where the house stands.
The model only knows ratios, so price both jobs at the same number
The ROI calculator holds one recouped share per project type and multiplies your cost by it. Nothing else happens. That is a straight line through the origin, and it has a consequence worth stating before anything gets typed in: the calculator cannot tell you whether a 3,200 garage door beats a 26,000 bathroom, because the bathroom wins on size alone and would win at any percentage above about eleven. Absolute value added is not the comparison this tool can make honestly. The comparison it can make is between two ways of spending one fixed budget, and that happens to be the exact question on the table.
So hold the budget at 26,000 and run every route through it at that figure, splitting where a real job would split. The garage door costs what a garage door costs; the siding takes the balance. Concentrating the whole budget in the lowest-recouping option on the list gives up a little over three thousand against spreading it across the two highest, which is a real gap and a smaller one than most people expect after reading a headline percentage. Note also what the table quietly says about the kitchen: a minor kitchen remodel priced at the full budget lands within five hundred of the split route, which means the model is not actually confident about the ranking of its own top three at this budget. Treat gaps under a couple of thousand as noise inside a national average, and let the survey decide only where it is shouting.
| Route | Cost entered | Recouped share | Estimated value added | Against cost |
|---|---|---|---|---|
| Garage door replacement | 3,200 | 90% | 2,880 | −320 |
| Siding replacement, balance of budget | 22,800 | 75% | 17,100 | −5,700 |
| Split route — the two together | 26,000 | — | 19,980 | −6,020 |
| Minor kitchen remodel | 26,000 | 75% | 19,500 | −6,500 |
| Bathroom remodel | 26,000 | 65% | 16,900 | −9,100 |
| Window replacement | 26,000 | 65% | 16,900 | −9,100 |
| Deck addition | 26,000 | 65% | 16,900 | −9,100 |
Enter the same budget against each project type in turn and read the differences between the results rather than any single result. The share is fixed per type, so the absolute figures are only as good as the survey behind them — but the ordering they produce is the one piece of information the tool is actually offering. One thing to know before you compare: the calculator flags itself low confidence, and the headline figure is rounded to two significant figures to match, so at this budget the siding, bathroom, window and deck routes all print the same 17,000 and the differences in the table above disappear. Open "Show calculation logic" under each run and read the Final result line, which carries the unrounded figure.
Different project types typically recoup very different shares of their cost at resale.
Your total planned or actual cost for the project.
Estimated resale value added
$15,000
These are broad national averages from a specific point in time and vary significantly by local market, home price tier, renovation quality, and timing of sale — treat this as a rough planning reference, not a resale appraisal.
- Cost recouped
- 75 %
They open the calculator with your figures already in it
Home Improvement ROI Calculator: 15,000 $ (estimated value added) — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
What this calculation does not cover
- Each project type carries one stored percentage and nothing else, and the six options resolve to only three distinct figures: siding replacement and a minor kitchen remodel return an identical result for the same cost, as do window replacement, a bathroom remodel and a deck addition.
- The recouped shares are national averages, so the same constant is applied whatever currency the cost is entered in and whatever market the money was actually spent in — there is no regional term behind the percentage at all.
- Project Cost is the only figure the estimate scales from, and it is limited to between 100 and 500,000 in steps of 100, so a programme of work beyond that ceiling has to be split and each part run against its own option.
- Nothing checks the cost against the scope named in the dropdown, because the percentage never moves with the size of the spend: a modest deck and one costing a hundred times as much are both returned at 65 per cent.
- The figure is gross value added rather than a return, since the arithmetic subtracts nothing — not your outlay, not financing interest, not agent or closing fees — and as no option recoups more than 90 per cent it always lands below the cost entered.
- Only a label and a cost are read, so the condition of what is being replaced never enters: swapping a failed garage door and upgrading a serviceable one are the same job to this estimate, though only one of them removes a defect a buyer would price.
Every row on that table is a loss, and the model is right about that
Not one option returns more than it cost. Even the garage door, top of the list at ninety per cent, gives back 2,880 of 3,200. That is not pessimism baked into the calculator; it is what the underlying surveys report and what a valuer's adjustment grid tends to produce, and a guide that let you read these numbers as profit would be doing you a disservice on the most important line of the page. The residual — 6,020 on the split route, 9,100 on the bathroom — is what it costs to live in the improvement. That is a legitimate thing to buy. It is simply not an investment, and the two get confused because the word return is in the calculator's name.
The reason the shares sit where they do is visible in how residential valuation actually works. A sales comparison starts from recent sales of similar properties and adjusts line by line for the differences, and the heaviest line on that grid is size. In the United States the measurement itself is standardised: ANSI Z765, American National Standard for Single-Family Residential Buildings — Square Footage Method for Calculating, is required by the Fannie Mae Selling Guide for appraisals of most one-unit properties, and it reports gross living area as above-grade finished area only, with below-grade space stated separately. In the UK and much of the rest of the world the equivalent conventions live in RICS Property Measurement, incorporating IPMS: Residential Buildings. Neither the bathroom nor the siding adds a square foot to that number. They compete for the smaller adjustment lines underneath it, which is precisely why every share on the list is under one hundred.
There is a second distinction the percentages blur, and it decides how the money behaves rather than how much of it comes back. A broken garage-door spring and failed cladding are not improvements; they are deferred maintenance, and a comparison approach prices them as a deduction against a property otherwise in market condition. Repairing them recovers a deduction, which is why that kind of work sits at the top of the list and why the recovery has a ceiling — you cannot get credit twice for a door working. The bathroom is both things at once. The 1974 suite is a stated objection and removing it recovers a deduction; the specification above what the comparable properties carry is an improvement and gets adjusted separately, usually for less than it cost. Whoever is producing the opinion works to a standard — the Uniform Standards of Professional Appraisal Practice in the United States, RICS Valuation – Global Standards in the UK and internationally — and neither standard contains a table of recoup percentages, because both require an opinion built from the comparables actually available in that market on that date.
Then there is the limitation that decides whether this calculator is any use to you at all. There are six project types and no generic option, and the six are the ones the survey covers. Roof replacement is not there. Neither is an addition, a heat pump or furnace replacement, solar, landscaping, or a pool. If the two quotes on your table are a rear extension and a loft conversion, this tool cannot rank them and the nearest label is not a substitute — dropping an extension's cost against the deck row returns a number with nothing behind it. Work that changes the footprint or the mechanical systems is judged on the individual property, which means an appraiser or an agent who has closed sales on your street this year, not a national average. Leave the resale line blank until you have that opinion rather than filling it with a figure that looks like one.
What the assessor does with it next — and where nothing happens at all
The property tax calculator runs the value forward one step: added value, multiplied by the share of market value your jurisdiction actually assesses on, multiplied by the rate. Take an effective rate of 1.2 per cent against a ratio of 100 as the illustration and the split route's 19,980 becomes 239.76 a year, while the bathroom's 16,900 becomes 202.80. Over the eight years to sale that is 1,918 against 1,622 — the route that comes back better also costs about three hundred more to hold, which shaves the advantage from 3,080 to roughly 2,780 and reverses nothing. That is the honest shape of this cascade in most cases. It trims a ranking; it rarely flips one.
The larger risk is putting the wrong number in the first field. The office that opens your permit file usually prices the job from its declared cost and the construction schedules it keeps for work of that class, not from a resale uplift somebody estimated. Both of our routes declare the same 26,000, so on that basis both produce 312 a year and the tax cannot discriminate between them at all — which is worth knowing, because it means the tax line is not a tiebreaker unless your jurisdiction genuinely assesses on market uplift. Put the uplift and the declared cost through separately and keep the pair as a span rather than a point. And keep the rate and the ratio on one basis: an effective rate worked back from your own bill already has the assessment ratio inside it, so applying a ratio below 100 on top of it discounts the same thing twice.
Whether any of this happens is a question about your jurisdiction, and the calculator's model — value added, assessed, taxed — is a US-shaped model. In California, Proposition 13 caps annual growth in the base year value of existing property, but new construction is separately valued and added on top, so an improvement arrives as a fresh increment against an otherwise restrained base; the California Revenue and Taxation Code carries the definition of what counts as newly constructed along with a set of exclusions, and the county assessor's office is the place to establish which of them your work touches. In England the answer is stranger and much better news for the person doing the work: council tax bands are set under the Local Government Finance Act 1992, and a material increase in value from an improvement is not reflected while you own the house — the Valuation Office Agency picks it up on a relevant transaction, which in practice means a sale, under the Council Tax (Alteration of Lists and Appeals) (England) Regulations 2009. The extension you build is banded for the buyer, not for you. In New South Wales, council rates are struck on land value determined under the Valuation of Land Act 1916, so a refitted bathroom does not move them by a cent. In Ireland, Local Property Tax is self-assessed against fixed valuation dates set by the Finance (Local Property Tax) Act 2012, and improvements between those dates wait for the next one. Establish which of these describes your address before you carry an annual figure into an eight-year plan.
| Where | What the charge is struck on | What an improvement does | The governing instrument |
|---|---|---|---|
| Much of the United States | Assessed value of land and improvements | Permit is a public record; assessor may add value, often from declared cost and their own schedules | State and county assessment law; the assessor's office states the local practice |
| California | Capped base year value, plus new construction at full value | New construction is valued separately and added; the existing base stays capped | Proposition 13 and the new construction provisions of the Revenue and Taxation Code |
| England | A council tax band fixed at 1991 values | Nothing while you own it; a material increase is picked up on sale, and the buyer pays | Local Government Finance Act 1992; Council Tax (Alteration of Lists and Appeals) (England) Regulations 2009 |
| New South Wales | Land value, excluding the buildings on it | Nothing — dwelling improvements are outside the base being rated | Valuation of Land Act 1916 (NSW) |
| Ireland | Self-assessed value at a fixed valuation date | Nothing until the next valuation date, then included in the self-assessment | Finance (Local Property Tax) Act 2012 |
Run it once on the resale uplift and once on the declared cost of the works, and hold the two results as a range. Keep the rate and the ratio on the same basis while you do it: an effective rate taken off your own bill already carries the ratio, and discounting it again understates the answer by exactly the ratio you applied twice.
The estimated increase in resale value from your project.
Your local effective property tax rate.
The percentage of market value your jurisdiction actually taxes on.
Assessed value increase
$15,000
Figures that depend on a rate wait for yours — this page does not assume one.
They open the calculator with your figures already in it
Property Tax Increase Calculator: 15,000 $ — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
What this calculation does not cover
- The assessment ratio is applied to the added value on its own, so the estimate assumes your jurisdiction assesses newly added value at the same percentage it already applies to the rest of the property rather than on a separate schedule reserved for improvements.
- Local Property Tax Rate is a single field, so a bill assembled from overlapping levies — county, school district, municipal, special district — has to be totalled by hand before it goes in, and the breakdown reports only the assessed value increase, never the share each levy contributes to it.
- Both steps are plain multiplications, which leaves no room for a graduated rate band, a minimum charge, or the flat per-parcel and special-assessment fees that sit alongside the value-based portion of many bills.
- Nothing asks when the work finishes and the answer carries a per-year unit, so an improvement completed part-way through a tax year is shown at its full twelve-month amount rather than prorated to the months it actually stood.
- What comes back is gross tax: there is no field for income, filing status or itemising, so any offset from deducting property tax on a return sits outside the figure entirely.
The floor area did not change; the cost of putting it back did
Rebuild cost is finished floor area multiplied by a local cost to rebuild per square foot, and the interesting thing about both of our projects is that they leave the first term completely alone. 168 m² before the work, 168 m² after it. What moves is the rate, because a rebuild reproduces the specification standing at the time of the loss — new cladding on two elevations and a refitted bathroom are what a builder would be putting back, not the 1974 versions. So the field that has to change is the one nobody ever revisits, and the field everybody looks at is the one that stays still. That is the whole reason this step gets skipped.
Two mechanics before you type. First, the rate is always read as cost per square foot even when the area is entered in square metres — the calculator converts your area to square feet and then multiplies, so a rebuild rate a local builder quoted per square metre has to be divided by 10.764 first, or the answer comes back very nearly eleven times too large. Second, watch what you counted as area: an attached garage, an unfinished basement or a covered porch rebuilds for markedly less per square foot than finished living space, and rolling them into one figure against a single blended rate overprices them. Carried through with 168 m² — 1,808.34 sq ft — an illustrative 150 per square foot gives 271,250, and a rate ten per cent higher gives 298,376. The 27,000 between them is what two projects and a few years of construction inflation can put on a sum insured without a single square foot appearing anywhere.
The consequence of leaving it stale is not that a total loss pays short, because total losses are rare. It is that partial losses — which is nearly all of them — pay short too, through the condition every buildings policy carries under one name or another. In the ISO Homeowners 3 (Special Form), the loss settlement condition pays replacement cost on buildings only where the dwelling limit is at least eighty per cent of full replacement cost at the time of loss, and pays the greater of actual cash value or a proportion below that threshold. UK household policies do the same job with an average clause, and the Association of British Insurers points householders at the RICS Building Cost Information Service rebuild figures rather than at market value. On our numbers, a limit still set at 271,250 against a true 298,376 is a shade over ninety per cent and still clears the test — one bathroom does not trip it, and saying otherwise would be scaremongering. A decade of unreported work plus construction inflation is what trips it. Tell the insurer what was done, which in the UK sits inside the duty a consumer owes under the Consumer Insurance (Disclosure and Representations) Act 2012 and in Australia under the Insurance Contracts Act 1984 and the General Insurance Code of Practice. And read the figure for what it is not: area times a rate does not include debris removal, demolition of what is left standing, design and permit fees, or the cost of rebuilding to the code in force today rather than the one the house was built to — that last gap is what ordinance or law cover addresses, granted in a limited amount by the standard form and bought larger by endorsement.
Put the same finished floor area through twice — once at the rate that suited the house before the work, once at the rate a builder would now quote to reproduce what is standing — and treat the difference as the amount your sum insured has silently fallen behind. The rate field is per square foot whichever way the unit switch is set. Take the difference from the Final result line under "Show calculation logic" rather than from the headline: this calculator is low confidence too, so the headline rounds to two significant figures and the two runs above read as a flat 270,000 and 300,000, which overstates the gap by three thousand.
The total conditioned floor area of the home.
The cost to rebuild from scratch in your area, per square foot.
House area
1,600 sq ft
Figures that depend on a rate wait for yours — this page does not assume one.
They open the calculator with your figures already in it
Homeowners Insurance Replacement Cost Calculator: 1,610 sq ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
What this calculation does not cover
- This is a dwelling figure and not a policy. Personal property, detached structures — garage, shed, fence, pool, driveway — and the cost of living somewhere else while the house is rebuilt are separate coverages, generally written as a percentage of the dwelling limit rather than priced from anything on this page. Insuring to this number covers the shell and nothing that was inside it or standing beside it.
- The dwelling limit this feeds also sets what you pay before the policy does. Wind, hail and hurricane deductibles are commonly written as a percentage of that limit rather than a flat sum, so a 2% deductible against a 400,000 limit is 8,000 out of pocket on a claim, and every increase in the limit raises that deductible with it.
The certificate is part of what you are selling
Work that cannot be evidenced is discounted, and the discount is usually decided by somebody with no interest in defending your workmanship. A buyer's solicitor asks for the paperwork; a US appraiser inspecting to the Uniform Residential Appraisal Report notes what looks like unpermitted alteration; and the answer is a retention, an indemnity policy, or a chip off the price on the week you are least able to argue. None of that appears in a recouped-cost percentage, and it can comfortably exceed the gap between the two routes on the table above.
Know which side of the line each job sits on before it starts. Under the International Residential Code, Section R105 sets out when a permit is required and R105.2 lists the work exempt from one; siding replacement and a garage door are the kind of items where practice varies by adopting jurisdiction, so the building department decides this question, not the contractor's opinion of it. In England and Wales the Building Regulations 2010 set out notifiable work and the classes outside it, and several trades discharge the obligation through competent person schemes that issue their own certificate — FENSA for replacement windows and doors, an approved scheme operator for electrical work under Approved Document P, Gas Safe Register for gas appliances. That certificate is the document the conveyancer wants years later, and it is issued once, to the address, at the time of the work.
- Ask the building department, before signing, whether each element of the quote is permitted work in your jurisdiction — and get it in writing rather than in a phone call nobody logged.
- Keep the permit, the inspection sign-offs and the final certificate together in one file with the contract and the itemised quote, scanned as well as filed on paper.
- Collect competent person scheme certificates at completion, not at sale — FENSA for windows, the electrical scheme's certificate for Part P work, Gas Safe for anything burning gas.
- File manufacturer warranties with the serial numbers and installation dates recorded, and register them where registration is what activates the longer term.
- Photograph the sheathing, the flashings, the wall build-up and any rot cut out while the cladding is off, because that is the only chance anyone gets to see it.
- Send the insurer a note of what changed and what it cost, and ask them to confirm the buildings sum insured they now hold.
How long you stay is the input nobody types in
None of the three calculators on this page has a time field, and time is doing more work here than any of them. The survey shares behind the ROI model describe work sold not long after it was done. A bathroom fitted this spring and sold in eight years is not that bathroom: the fittings are eight years into their life, the tiling choices are eight years into a fashion cycle, and the buyer is pricing a bathroom in use rather than a bathroom just completed. Cladding and a garage door age far more slowly against the same clock, which is a real difference between the two routes that appears nowhere in the percentages.
Run the eight years properly and the picture holds its shape. The split route gives 19,980 of value and carries roughly 1,918 of extra tax over the period on the illustrative rate; the bathroom gives 16,900 and carries about 1,622. Both are still losses against 26,000 spent, and the ordering does not move. If your assessor prices from declared cost, both carry the identical 2,496 and the tax stops being a variable in the decision at all. Discount none of it if that is how you think about eight-year money, or discount all of it consistently — what you must not do is discount the value and take the tax at face value, which is the version that quietly makes every project look better than it is.
So the case for the split is not that a national average ranked it first by three thousand. It is that both halves of it are deferred maintenance a buyer would otherwise price as a deduction, both have a slow clock, and both are things the surveyor's report would have flagged anyway. The bathroom is a different kind of purchase and deserves to be argued for on its own terms: eight years of using it. If that argument wins, take it and stop calling the decision financial — and if it wins narrowly, consider doing it in the year you list, when it is closest to the condition the survey averages were actually measuring. What none of these routes is, on any row of any table above, is money back.
Before you sign either quote
Six things to establish while both prices are still live and neither has become the decision. Three are calculator runs and three are phone calls that cost nothing.
- Both routes priced at the identical budget — The ROI model scales linearly with cost, so a comparison at different costs measures size rather than merit; hold the spend fixed and read the gap between results.
- The reassessment basis, from the assessor's office — Market uplift or declared cost of works, and whether an improvement triggers anything at all before sale — the answer changes the tax line from a decision input to a non-event.
- Two tax runs, kept as a span — One on the resale uplift, one on the permitted cost. Keep the rate and the assessment ratio on a single basis so the ratio is not applied twice.
- The rebuild rate before and after, per square foot — Finished floor area does not move on either job; the rate does. Divide any rate quoted per square metre by 10.764 before it goes in the field.
- Permit status for every element, in writing — Confirmed with the building department rather than the contractor, and separately for each item — a garage door and a re-clad are not always treated alike.
- An agent's opinion where the model has no row — Roofs, additions, mechanical systems, solar, landscaping and pools are absent from the six project types, and the nearest label carries a percentage that was never measured against work like yours.
Opens the calculators above on one screen with the dimensions from this article already filled in. Quantities only — this site publishes no price list, because local prices vary too much to publish honestly.