Self-build budget spreadsheet (UK): trades, quotes, variations and stage payments
A self-build budget spreadsheet for the UK needs five things: one line per trade with planned, selected quote, committed, paid and forecast columns; a quote comparison on identical scope; a variations log that feeds the forecast; stage payments with a cap per stage and retention; and the official sources of the VAT, planning and building control rules. Below are the Excel layout, a fictitious example in pounds, and each rule attributed to its GOV.UK or Planning Portal source, checked on 19 and 20 October 2026.
What a self-build budget must track
The budget turns quotes and stage payments into four numbers recomputed every week:
- Planned: your estimate per trade before quotes, frozen once you have signed.
- Committed: signed contracts and approved variations only.
- Paid: stage payments actually made, with the date and the invoice.
- Forecast: selected quote (or plan) plus approved variations, the figure to compare with your funding (mortgage and savings).
The contingency reserve sits on a separate line and is consumed only when the total forecast exceeds the total plan.
Budget by trade
Use the trades your contractors will invoice, for example: architect and structural engineer; planning and building control fees; structural warranty and site insurance; groundworks and drainage; scaffolding; brickwork or timber frame; roofing; windows and doors; plumbing and heating; electrics; MVHR (mechanical ventilation with heat recovery); plastering; joinery; kitchen and bathrooms; decorating; driveway and landscaping; preliminaries. Each line has the same columns:
| Column | Typed or calculated | Rule |
|---|---|---|
| Planned | Typed | Estimate before quotes; do not edit after signing |
| Selected quote | Picked from the comparison | The quote you chose, which need not be the lowest |
| Committed | Calculated | Selected quote if signed, plus approved variations; otherwise nil |
| Paid | Sum of stage payments | Money actually transferred, invoice in hand |
| Forecast | Calculated | Selected quote (or planned) + approved variations |
| Variance | Calculated | Forecast − planned; positive is over budget |
| Status | Calculated | Not started, quoting, signed, on site, practical completion, snagging closed |
Three quotes, same scope
Three quotes are only comparable on the same scope: the same drawings revision, specification, allowances, exclusions and VAT treatment stated on the quote. In the sheet, each trade gets one block with up to three quotes; the lowest is shaded, the selected one is flagged, and the differences against the lowest and against the plan are calculated. If one builder adds VAT to work on a new dwelling and another does not, check the treatment against VAT Notice 708 before comparing totals.
Variations and expected final cost
A variation is any agreed change to the contract: extra work, an unforeseen ground condition, a selection above its allowance, or an omission. Log each one with the trade, the amount (plus or minus), the programme impact in days, its status and whether both parties signed it. Only approved variations enter the forecast:
Forecast = selected quote (or plan) + approved variations. Reserve remaining = reserve − (total forecast − total plan). The change-order version of this log is in our renovation budget template for change orders.
Stage payments
Self-build mortgages and main-contractor agreements commonly release money in stages whose names vary by lender and contract (foundations, wall plate, wind and watertight, first fix, second fix, practical completion), and the contract may hold back a retention until the release point it sets. Each payment request carries its stage, amount, percentage verified on site, invoice status and the stage cap, net of any retention. Two checks: the request must not exceed the cap, and cumulative payments must not run ahead of verified work.
VAT: where to check the rules
The spreadsheet should record amounts as you actually pay them and build in no VAT rate, because the rate depends on the work and on the contractor. The rules sit on these official pages:
- VAT Notice 708, Buildings and construction (HMRC, published 13 August 2014, last updated 26 August 2026). Section 2.1 lists the construction of new qualifying dwellings at the zero rate, and the renovation or alteration of empty residential premises at the reduced rate of 5% (section 8), for a dwelling that "has not been lived in during the 2 years immediately before your work starts" (paragraph 8.1.1). Other work to an existing building is normally standard-rated, at 20% (GOV.UK, VAT rates, consulted 19 October 2026).
- VAT refunds for DIY housebuilders (GOV.UK, consulted 19 October 2026). If you build a new home or convert a property into a home, you can apply for a refund of VAT on building materials and services; you can make only one claim, and for work completed on or after 5 December 2023 "you must apply no more than 6 months after finishing" (3 months for work completed before that date).
- Planning and building control. The Planning Portal has the tools to check whether a project needs planning permission or building regulations approval. GOV.UK (consulted 20 October 2026) adds that the two are separate, that outside higher-risk buildings you can choose your local authority's building control or a private registered building control approver, that without approval you may lack the compliance certificates needed when you sell, and that Scotland and Northern Ireland have their own rules.
Example (fictitious data)
Four trades of a fictitious self-build in England, mid-build. The plan for the whole house was £300,000 with a 10% reserve of £30,000, a total budget of £330,000.
| Trade | Planned | Selected quote | Committed | Paid | Approved variations | Forecast | Variance |
|---|---|---|---|---|---|---|---|
| Groundworks | £28,000 | £31,200 | £33,800 | £31,200 | +£2,600 | £33,800 | +£5,800 |
| Brickwork | £46,000 | £44,500 | £44,500 | £22,250 | £0 | £44,500 | −£1,500 |
| Roofing | £19,500 | £20,300 | £20,300 | £0 | £0 | £20,300 | +£800 |
| Plumbing and heating (not signed) | £24,000 | £23,400 | £0 | £0 | £0 | £23,400 | −£600 |
| Four trades | £117,500 | £119,400 | £98,600 | £53,450 | +£2,600 | £122,000 | +£4,500 |
Reading: the four trades are £4,500 above plan, so if the rest stays on plan the reserve remaining is £25,500 of £30,000. Committed includes the signed groundworks variation; plumbing and heating is not signed, so its £23,400 is a forecast only. Brickwork is half paid and site verification stands at 50%: the £22,250 paid matches the verified work, so any further brickwork request is flagged until a new verification raises that percentage.
The US version, with bids, change orders and draws, is our new home construction budget spreadsheet. If the finished house is to be let, the income side belongs in a landlord spreadsheet (UK) with SA105 categories.
FAQ
Should the self-build budget include VAT or exclude it?
Record what you actually pay, invoice by invoice, with a VAT column. Under VAT Notice 708 (section 2.1, conditions in section 3), building a new qualifying dwelling is zero-rated, including the building materials the builder supplies and incorporates (section 2.2), but architectural, surveying and consultancy services are standard-rated (section 3.4.1); VAT you pay on eligible materials you buy yourself may be refunded under the DIY housebuilders scheme, on one claim, within 6 months of finishing for work completed on or after 5 December 2023 (GOV.UK, consulted 19 October 2026).
How much contingency should a UK self-build carry?
None of the official pages cited here sets a figure: the amount is your choice. The spreadsheet described here defaults to 10% of the planned trades and lets you change it; keep the reserve on its own line, visible on the dashboard every week.
Does the spreadsheet replace a quantity surveyor or a warranty inspector?
No. It records what you planned, signed and paid; it does not measure work on site or certify stages. Building control and your warranty provider inspect the work for compliance; the percentage of a stage completed is the figure confirmed by whoever certifies stages under your contract or mortgage, and you type it into the stage-payment tab.