Building a Realistic Budget for Your Renovation

Start With the Figure You Already Know Is Too Low

Almost every renovation conversation begins the same way: someone has a number in mind, and it is usually the one on the cheapest builder's quote. That quote is real, but it is not your budget. A realistic budget covers everything from the first design sketch to the last coat of paint, including the costs that never appear on a builder's invoice at all. Getting that full picture before you commit is the single most useful thing you can do — it is what separates a project that finishes well from one that stalls halfway through with the roof off.

So let's build it up, line by line.

The Build Cost Is Only the Middle of the Story

Your builder's price for the physical work — demolition, structure, plaster, services, kitchen or bathroom installation — is the biggest single item, and usually the easiest to compare. What is often left out is the long tail.

• VAT. Most renovation work is standard-rated at 20%, and labour, materials and plant hire all count. A few energy-saving installations attract a reduced rate, but never assume. Check whether every quote is inclusive or exclusive of VAT, because a £40,000 quote can become £48,000 very quickly.
• Making good and finishing. Decorating, flooring, tiling, skirting, door furniture, curtain tracks, and the cost of putting right the mess left behind. These are rarely in the build quote and can easily run to several thousand pounds.
• Exterior work. Patios, drainage, guttering, fencing, turf and lighting. If the garden is a building site for four months, it will need attention at the end.
• Professional fees and statutory charges. Covered below, but they are part of the build, not an optional extra.

Professional Fees Are Owed Whatever Happens

Design and compliance costs arrive early and are paid in stages, often before a single brick is touched. For a full-service renovation, it is sensible to allow somewhere in the region of 8–15% of the build cost.

• Design fees. Architect or architectural designer, measured survey, planning drawings.
• Engineering. A structural engineer's calculations and drawings are essential for most openings, steels and extensions.
• Statutory fees. Planning application fees are non-refundable even if permission is refused, and building control charges apply to the work itself. Some projects also need a party wall surveyor — commonly around £700–£1,500 per neighbouring property — or a specialist report on drainage, trees or asbestos.
• Contract administration. If you want someone to inspect the work, certify payments and chase defects, that is a separate service with a separate fee.

None of this is wasted money. It is what keeps the build lawful, insurable and properly priced.

Contingency Is Not Doubt — It Is Experience

Contingency is the pot you hope never to use. For a straightforward cosmetic refit in a modern home, 10% of the build cost is a reasonable starting point. For anything involving structure, or any house built before about 1980, plan on 15–20%. Older properties hide things: a wall that is not load-bearing as drawn, damp behind plaster, outdated wiring, non-standard construction, an asbestos board in a cupboard, drains that lead nowhere useful.

Keep this money genuinely available. It is not the budget for the nicer worktop, and if you spend it in month one you will be paying for it in month four. If the project completes under budget, you have a pleasant surprise; if it does not, you have a way to keep going.

Where Will You Actually Live?

Temporary accommodation is the cost most often forgotten, and it is not a small one.

• Moving out. Rent on a similar-sized home for the duration, plus council tax, utilities and insurance on two addresses. Add storage, removals in both directions, and possibly kennel or cattery fees.
• Staying in. Cheaper on paper, but you may lose the kitchen or the only bathroom, which means eating out, takeaways, launderette trips and a slower build as trades work around you. Budget a few hundred pounds a month for this, and be honest about how long you can tolerate it.
• Insurance. Tell your existing insurer before work starts. Standard home policies often exclude buildings under renovation, and a dedicated policy or extension is usually required.

Doing the Sums in the Right Order

Take a mid-sized project — a kitchen extension and internal refit on a 1930s semi-detached house — and the shape of a true budget becomes clear:

• Build cost, including VAT: £95,000
• Professional fees: £9,000
• Planning, building control and party wall: £2,300
• Contingency at 15% of build cost: £14,250
• Temporary accommodation, storage and removals for four months: £6,500
• Realistic total: around £127,000

If that number is beyond your means, the answer is not to trim the contingency or skip the engineer. It is to reduce scope — a smaller extension, a phased approach, or doing the decorating yourself later. A budget that assumes everything will go well is not a budget; it is a hope. A budget that expects a few surprises, and has the money set aside to meet them, is what lets you enjoy the finished house instead of worrying about it.