Build your budget from the work, not from a wish list

Most renovation budgets fail before a single skip arrives, because they start with a number someone likes the sound of rather than the work that actually needs doing. Flip that around. Walk the property room by room and write a schedule of works: strip out, first fix, plaster, second fix, kitchen, flooring, decoration. Every single line gets a job description and a price.

Then price it three ways: a builder's quote, a materials estimate from a supplier, and your own worst-case guess. The highest of the three becomes your baseline. It sounds pessimistic. It is also the reason some projects finish on budget.

• List works room by room, including the boring bits — waste removal, access, making good.
• Separate labour, materials, and hire costs so you can see where money really goes.
• Add a line for the things you have not decided yet. They will cost something.

Contingency: the line nobody wants to fund

Contingency is not spare cash for a nicer worktop. It is the money that pays for the joist nobody knew was rotten, the chimney that needs repointing, and the wall that turns out to be lathe and plaster. Treat it as spent from day one and you will never be tempted to raid it.

For a straightforward modern property, allow 10 per cent of the build cost. For a Victorian terrace, a 1930s semi with original pipework, or anything listed, allow 15 to 20 per cent. If the house has been empty for years, go higher still.

Keep contingency separate from your main budget in the spreadsheet, and only release it when a genuinely unforeseen problem appears. If you get to the end without touching it, you have a lovely problem on your hands.

Professional fees and the costs that hide in plain sight

Builders' quotes rarely include the professional work that makes a project legal and buildable. These fees catch people out because they arrive in small, separate invoices spread across months.

• Architect or designer, often charged as a percentage of build cost for a full service.
• Structural engineer, typically needed for knock-throughs, loft conversions and anything load-bearing.
• Planning application fees, plus building control and Building Regulations approval.
• Party wall surveyor, if you share a wall or are excavating near a neighbour's foundations.
• Energy assessments, SAP calculations, and any asbestos or damp surveys.
• Project management, if you would rather not run the trades yourself.

Then the practical extras: scaffolding licences, skip permits, temporary accommodation, storage, and buildings insurance while works are underway. Add them to the spreadsheet as individual lines. A single "sundries" column is where budgets go to die.

VAT: do the sum before you sign anything

VAT at the standard rate of 20 per cent applies to most renovation work on an existing home, including labour and materials supplied by the builder. Many homeowners mentally add it later, then discover it adds thousands to the total.

Two things to check carefully. First, whether a quote is inclusive or exclusive of VAT — ask in writing, every time. Second, whether any reduced or zero rates apply. Qualifying conversions, such as turning one dwelling into two or a non-residential building into a home, can attract a 5 per cent rate, and some energy-saving material installations are treated differently. Rules are specific, so confirm your own position with an accountant before you budget on it.

If you are buying materials yourself, VAT still applies. If you are managing the project, you may be able to reclaim some of it — again, get proper advice. Build the VAT into your baseline figures rather than bolting it on at the end.

Track spending weekly, not monthly

A budget is only useful if it is live. Set aside twenty minutes every Friday and update a simple spreadsheet with four columns: item, budgeted, committed, spent to date. Committed spend matters as much as paid spend — a quote you have accepted is money gone, even if the invoice has not arrived.

Keep every receipt and invoice in one folder, digital or paper, and reconcile it against your bank account. If you are paying in stages, agree clear milestones: foundations, first fix, plaster, completion. Hold back a retention of around 5 per cent until you are satisfied with snagging.

• Update the sheet weekly and note the running total in bold.
• Compare the total to your contingency balance, not just your overall budget.
• Flag any line more than 10 per cent over before it doubles.

Where budgets quietly break — and how to protect yours

Budget creep rarely comes from one big disaster. It comes from a hundred small upgrades: the better tiles, the deeper bath, the extra socket, the upgraded boiler. Each feels trivial. Together they can add 20 per cent.

Decide your fixed points before work starts — the boiler, the glazing, the floor — and refuse to change them. For everything else, set a modest "choices" allowance and once it is gone, it is gone.

Finally, plan the order of spending so the non-negotiables (structure, roof, electrics, plumbing) are paid for before the finishes. A beautiful kitchen in a house with a leaking roof is not a renovation. It is an expensive lesson.