The cost nobody invoices
When a kitchen is stripped out, the household does not stop eating. It eats differently, and more expensively: takeaway two or three nights a week, lunches bought rather than made, a microwave on a folding table in the dining room, coffee from a shop because the kettle is boxed. When a bathroom goes, the household still washes — at a gym, at a relative's house, or in a hotel. When the furniture has to come out of a room, it goes into a storage unit that bills by the month whether the project is on schedule or not.
None of this appears in a contractor's quote, and almost none of it appears in a homeowner's budget. It is nonetheless money leaving your account because of the renovation, and it belongs in the same arithmetic as the tiles. On a six-week kitchen for a family of four it commonly reaches four figures.
Pricing it changes two decisions. First, it changes the budget: the disruption line usually deserves to sit alongside permits and disposal in the renovation budget. Second, and more usefully, it prices time. Once you know a week of disruption costs you $438, you can evaluate a contractor's offer to finish a week earlier for $300 as an unambiguously good deal, and an identical offer at $900 as a bad one. Without the number, that argument is decided by feel.
Four lines, three different billing rhythms
Food accrues per person per day, and the figure to enter is the increase. If you normally spend $12 a day per person on groceries and you now spend $30, the disruption cost is $18, not $30 — you would have eaten either way. Getting this wrong is the most common error in disruption budgeting and it typically doubles the food line. Fifteen to twenty-five dollars a person a day is what most households find when they actually measure it, but measure it rather than assume it: a family that already ate out three nights a week has a much smaller increment than one that cooked everything.
Storage bills in whole months, and that discontinuity matters. Self-storage is sold as monthly periods, not pro rata days, so a project that runs from day 30 to day 31 costs a full extra month. On a $150 unit that is a $150 step for one day of delay. The calculator uses a ceiling function for exactly this reason, and it is why the cost-per-day figure understates the cost of the specific delay that crosses a billing boundary.
Laundry and similar recurring costs accrue weekly and are simply scaled by days ÷ 7. This line is a catch-all: laundromat trips, a temporary gym membership taken out for the showers, extra fuel for the drives to a relative's house, a second parking permit for the trades.
Accommodation is per night, for the household. Enter only nights you actually pay for. Staying with family is free in cash even though it is expensive in other currencies. This line is separated out because the stay-or-go decision is the biggest single lever in the calculation, and reporting the total both with and without it lets you see exactly what you are buying.
The cost per week is the number that does the work. It is the total divided by the days, times seven — the marginal value of time on this project. It reads in both directions: it is what a week of overrun costs you, and it is the ceiling on what a week-shorter schedule is worth. Compare it against the premium in any quote that promises a faster programme, and against the saving from a slower one.
Worked example: a family of three, kitchen out for 30 days
Three people, kitchen out of action for 30 days. You reckon on $18 per person per day more than your normal food spend. Furniture and the contents of the units are in a $150 a month storage unit. Laundry and extra driving come to about $25 a week. You stay in the house throughout, so no nights away. The project itself is budgeted at $40,000.
- Food. 30 × 3 × $18 = $1,620.
- Storage. 30 days is ceil(30 ÷ 30) = 1 whole month × $150 = $150.
- Laundry and weekly costs. $25 × 30 ÷ 7 = $107.14.
- Accommodation. None: $0.
- Total. 1,620 + 150 + 107.14 = $1,877.14.
- Cost per day. $1,877.14 ÷ 30 = $62.57.
- Cost of a week. $62.57 × 7 = $438.00.
- Share of the project budget. $1,877.14 ÷ $40,000 = 4.69%.
Two readings follow immediately. The disruption adds nearly five per cent to a $40,000 kitchen — more than the permits, and about the same as a mid-range set of taps. And a week of delay costs $438, which is now a number you can put in front of a contractor. If the schedule slips by a fortnight, that is $876 of cost that appears nowhere in anybody's quote.
Note the storage discontinuity. At 30 days you pay one month. At 31 days you pay two, so the total jumps to $1,877.14 + $150 + (1 × 3 × 18) + (25 ÷ 7) = $2,084.71 — a $207.57 step for a single day. Days that cross a storage billing boundary cost far more than the average day.
What to do with the number
Below about 3% of the project budget, note it and move on. It is real but it will not change any decision, and the effort of managing it is not repaid.
Between 3% and 10%, put it in the budget as a line. This is where most kitchen and sole-bathroom projects land. Treating it as a budget line rather than as background spending changes behaviour: you notice it, and you can trade against it.
Above 10%, the schedule is worth buying. When disruption is a tenth of the project, a contractor who can finish materially sooner is worth a real premium, staging the work to keep the space usable is worth real inconvenience, and the specification is worth simplifying to avoid long-lead items. Long-lead procurement is the usual culprit — a made-to-order worktop can hold a kitchen shut for three weeks after the work is finished — so check where your project duration is actually going before assuming the trades are the problem.
Compare the with- and without-accommodation totals honestly. Moving out is expensive in cash and cheap in everything else: the work usually goes faster with an empty house, the dust does not matter, and the trades can start early and finish late. Staying is the reverse. The difference the calculator reports is the price of that trade; whether it is worth paying depends on whether you have a working bathroom, whether anyone in the house works from home, and how long the disruption runs.
Use the weekly figure in the schedule conversation, not the total. Contractors respond to "a week is worth $438 to me" far better than to "please hurry". It converts an emotional request into a commercial one, and it occasionally reveals that a week can be bought for less than you expected — an extra labourer, a faster-setting product, or paying express freight on the item everything is waiting for.
How long spaces are typically out of use
| Project | Space unusable | What drives the tail |
|---|---|---|
| Repaint a room | 1–3 days | Recoat intervals and furniture return |
| Replace flooring in one room | 2–7 days | Acclimation before, adhesive cure after |
| Bathroom refit (sole bathroom) | 10–20 days | Tile adhesive, grout and silicone cure in sequence |
| Kitchen refit | 21–45 days | Worktop template and fabrication after units are fitted |
| Whole-floor refurbishment | 30–90 days | Trade sequencing and inspection waits |
| Extension, existing house occupied | 60–180 days | Structural work, weather, and the break-through at the end |
Enter the days the space is unusable, not the days trades are present. On a kitchen the two differ by the worktop lead time, which is commonly one to three weeks of a finished-looking room you cannot cook in.
Ways to cut the disruption rather than the budget
- Set up a temporary kitchen properly. A microwave, a kettle, a two-ring induction hob, a table and the old fridge relocated to another room will cut the food line by more than half, and costs almost nothing if you already own the appliances.
- Order long-lead items before demolition. Templating a worktop the day the units are fitted, then waiting three weeks, is three weeks of disruption bought for nothing.
- Keep one bathroom working. Where there are two, phasing them so they are never out together removes the single most disruptive condition in a renovation.
- Move out for the noisy, dusty phase only. Demolition and first fix are the worst days; a few nights away at the right moment often beats a month of them.
- Sell or donate rather than store. Six months of storage for furniture you were ambivalent about costs more than replacing it.
- Ask for a firm date on the last item, not the last trade. The room is unusable until the last item lands, and that is rarely the last trade to leave.
- Take the storage unit for the right number of whole months. Finishing on day 29 rather than day 31 saves a full month's charge.
What is left out, and where it fits
This calculator prices cash costs only. Three real costs sit outside it, and you should hold them in mind rather than in the total.
Lost time and lost productivity. Waiting in for a delivery, supervising trades, driving to a laundromat, and working badly from a house full of noise are all costs, but converting them into dollars requires a rate for your time. If you want them in the total, use the same hourly value you would use in the DIY versus contractor calculator, and add the hours to the weekly line.
Financing. A project running two months late carries two extra months of interest on whatever is funding it. On a $40,000 renovation loan, that is a real number and it scales with the same delay this calculator prices.
Wear on the household. Sleep, stress, meals eaten standing up and the arguments that follow are excluded because they cannot be priced honestly. They are, in most people's experience, the reason renovations feel expensive well beyond their invoices.
Put the total into the budget as its own line, and use the weekly figure whenever you evaluate a schedule. Two other pages complete the picture: the duration calculator tells you how many days you are actually pricing, including the waiting days that keep a space unusable after the trades leave, and the contingency calculator sizes the money buffer. A schedule buffer and a disruption cost are the same idea seen from two sides: one asks how long the overrun might be, the other asks what it will cost when it happens.