How to Track Your Renovation Budget and Costs

From building your first budget to staying on top of every invoice — a practical guide for UK homeowners.

RenoHub · 18 June 2026 · 6 min read

Start with a realistic budget — not a wish list

The first mistake most people make is writing a budget before they have any real numbers. A budget built on guesswork isn't a budget — it's a wish list that will disappoint you.

Before you commit any figures, get written quotes from at least two or three contractors for each trade involved. That means separate quotes for the builder, electrician, plumber, plasterer, and anyone else doing specialist work. Verbal estimates are useful for a rough sense of scale, but only written quotes give you something to hold a contractor to.

Once you have quotes in hand, add up the hard costs — labour and materials as quoted. Then layer on the things that often get forgotten:

• VAT. Most VAT-registered contractors quote exclusive of VAT unless they say otherwise. At 20%, that adds £4,000 to a £20,000 project. Always ask whether a quote is plus VAT before you accept it. For certain work on properties that have been empty, a reduced rate may apply — check with HMRC or a tax adviser if that could be relevant to you.
• Fixtures, fittings, and materials you supply. If you're buying your own kitchen, tiles, or sanitaryware, those costs belong in the budget.
• Fees. Architect fees, structural engineer fees, planning application fees, and Building Regulations application fees all add up.
• Skips, deliveries, and temporary facilities. Easy to overlook; very real costs.

Contingency: a buffer, not a slush fund

Renovations rarely go exactly to plan. Walls come down and reveal rotten joists. Floors come up and expose old pipework that needs replacing. A quote that seemed complete turns out not to include the plasterwork after the electrics are re-routed.

A contingency exists for these surprises. The commonly cited range is 10–20% of your total project cost, but there is no universal rule. A light cosmetic refresh in a recently-built property might only need 10%. A Victorian terrace with original plumbing and wiring, or a house where you don't know what's behind the walls, justifies more. Your RICS surveyor, if you have one, is well placed to give a view.

The important discipline is to treat the contingency as a separate pot — not as money you can dip into for spec upgrades. If you finish the project and haven't needed it, that's a win. If you spend it on a better kitchen tap because it was "roughly there," you've left yourself exposed for the surprises that come later.

Where overspends actually come from

Three things cause the vast majority of renovation overspends in the UK.

Variations. A variation is any change to the agreed scope after the contract is signed. You ask the builder to move a wall while they're already in. You decide to add a downstairs WC that wasn't in the original plan. Each variation should be agreed in writing — with a price — before the work is done. Without that, you're at the mercy of whatever the contractor thinks is fair when the invoice arrives.

Surprises behind walls and under floors. Especially common in older properties. Asbestos in the artex. Dampness in the external wall. Undersized joists that don't meet current Building Regulations for the new load. None of these are the contractor's fault, but they all cost money. This is exactly what the contingency is for.

Spec creep. You planned for a standard bathroom suite but by the time you're at the tile shop, you've upgraded to large-format porcelain and a freestanding bath. Small upgrades compound. Keep a running total of every spec change and ask yourself whether the aggregate still fits inside the budget — not whether this individual item seems affordable.

Quoted, invoiced, and paid — three numbers you must track separately

These three figures tell you fundamentally different things, and conflating them is a common cause of nasty surprises.

Quoted is what the contractor originally agreed to do the job for. It's your baseline. Every variation agreed since the original quote should adjust this figure upward (or occasionally downward).

Invoiced is what the contractor has actually billed you. A contractor typically invoices in stages — a deposit upfront, milestone payments at agreed points, and a final payment on completion. When an invoice arrives, compare it to the quote. If it's higher than you expected, ask for an itemised breakdown before you pay.

Paid is the money that has actually left your account. In the middle of a project, this may be significantly different from what has been invoiced — and your outstanding liability (invoiced minus paid) matters for your cash flow.

The gap between quoted and invoiced is where variations live. If your invoiced total is creeping above the original quote without agreed variations to explain it, that's a conversation you need to have before the final payment.

How RenoHub helps

Keeping a running budget across multiple contractors, stages, and trades is exactly where spreadsheets start to fall apart. RenoHub's Document archive is designed specifically for this.

When you upload an invoice, receipt, or quote, RenoHub's AI reads it and pulls out the key details: the amount, supplier, purpose, and whether it's a quote, invoice, or payment receipt. It then tracks each document against a paid / invoiced / outstanding status — so you always know where you stand across the whole project, not just for one trade at a time.

Alongside the document archive, the Contractor Works Tracker lets you import a contractor's PDF quote and have it broken down line by line. As work progresses, you tick off sections and see the budget vs quoted price in real time. If a variation comes in, you can see exactly how it shifts the picture.

Everything stays on your iPhone and in your iCloud — no account, no data on RenoHub's servers. The AI features use your own OpenAI or Gemini key, stored in the iOS Keychain. It's currently free for life for anyone who downloads before 30 September 2026.