Building Project Budget Planner

Add up all available funds: savings, remortgage amount, or loan facility. Deduct 10–15% for contingency before you start dividing the rest between builder costs, professional fees, and everything else.

Every building project hits unexpected costs — hidden rot, asbestos, supply delays, design changes. A 10% contingency is the minimum for straightforward work; 15–20% is wiser for older properties or complex projects.

Building costs vary significantly by region. London and the South East can be 30–50% more than the Midlands or North. Use MyBuildAlly's estimators to get a realistic range before committing to a budget.

Some projects add more value than they cost (loft conversions, extensions); others don't (swimming pools, ultra-high-spec kitchens). Check local sold prices to understand what your improved home would be worth.

Know what you absolutely must have versus what's nice to have. If the budget gets tight, you'll need to make trade-offs — deciding these upfront prevents emotional spending during the project.

This is your main construction cost — the builder's quote for structural work, carpentry, plastering, and general labour. Get at least three itemised quotes to establish a realistic range.

Some homeowners buy their own kitchen, bathroom suite, tiles, or flooring to save money or get exactly what they want. If so, budget for these separately from the builder's quote.

Typically 7–15% of the build cost for a full service (design, planning, construction supervision). A design-only service is cheaper but leaves you managing the build yourself.

Required for structural alterations — removing walls, steel beams, underpinning. Expect £400–£1,500 for calculations and drawings, depending on complexity.

Currently £258 for a householder application in England (2026). Some projects fall under permitted development and don't need planning — check before you pay.

Varies by council and project size — typically £200–£900 for domestic work. Covers plan checking and site inspections throughout the build. Required for most structural work.

Only needed if your work affects shared walls or is near a neighbour's property. If your neighbour dissents, expect £1,000–£2,000+ per neighbour. You pay both surveyors' fees.

A typical extension generates 3–5 skips of waste. Budget £250–£400 per skip depending on size and your area. Some builders include this in their quote — check.

Required for any work above ground floor. A typical domestic scaffold costs £600–£1,200 to erect, with weekly hire charges of £50–£100 on top. Longer projects cost more.

If the builder isn't supplying these, budget separately. A mid-range kitchen costs £5,000–£12,000 for units and worktops; a bathroom suite £1,000–£4,000 before fitting.

Many builders exclude final decoration from their quote. Budget for a decorator (£150–£250 per room) or materials if you're doing it yourself. Don't forget flooring — it adds up fast.

A new extension or loft room needs furnishing. It's easy to overspend here after months of building work — set a limit and stick to it.

Driveways, patios, fencing, and planting to restore your garden after the builders leave. Often forgotten in the initial budget but can easily cost £2,000–£10,000.

If you can't live in the house during the build, you'll need somewhere to stay. Even a month of Airbnb or staying with family has costs — travel, storage, lost routine. Budget realistically.

During a kitchen renovation, you might need a temporary setup — a microwave, mini fridge, and kettle in another room, or a camping stove in the garage. Some people budget for more takeaways and eating out too.

You'll likely need to clear rooms before work starts. Self-storage units cost £50–£200 per month depending on size and location. Book early — units near you may fill up.

It sounds trivial, but two weeks of takeaways and restaurant meals for a family can easily cost £300–£500. Factor it in or set up a temporary cooking space to reduce the impact.

These are separate from the initial Building Control application. You'll pay for each stage inspection — foundation, drainage, structural, and final completion. Costs are usually included in the initial fee, but check.

Moving a gas meter, adding a new electrical supply, or upgrading water mains can cost £500–£3,000 per utility. If your project requires relocating services, budget for this early as lead times can be long.

Trees with preservation orders (TPOs) or in conservation areas need council permission to prune or remove. An arborist report costs £300–£600, and tree removal can cost £500–£2,000 depending on size.

Properties built before 2000 may contain asbestos. A survey costs £150–£400, and removal is significantly more. Drainage surveys (£200–£400) and detailed structural surveys (£500–£1,000) may also be needed.

A reasonable deposit covers the builder's initial material costs. Never pay more than 15% upfront — if a builder demands more, ask why. If they can't give a good reason, that's a red flag.

Once the groundwork and foundations are done and inspected, a payment of 20–25% is typical. Only pay when the work is complete and you're satisfied — get Building Control sign-off at each stage.

When the structure is up, the roof is on, and the building is weathertight, another 20–25% is due. This is a significant milestone — the hardest part of the build is usually done.

First fix means pipes, wires, and plaster are in but nothing is connected or finished. This stage payment of 15–20% reflects the progress towards a liveable space.

Sockets, switches, radiators, kitchen, bathroom — everything fitted and working. Pay 10–15% when the project is practically complete and you can use the space.

Retain the final 5% until you've lived with the finished work and completed a snagging inspection. This gives the builder a financial incentive to return and fix any defects promptly.

Record every payment with the date, amount, and what stage it relates to. Keep receipts and bank transfer confirmations. This is your evidence if there's ever a dispute.

Design changes happen — a different tile, an extra socket, a bigger window. Record every change, get the additional cost agreed in writing before the work is done, and update your running total.

A quick weekly check against your original budget reveals creep early. If you're 10% over budget at the halfway point, you need to make decisions now — not when the money runs out.

Multiple small variations that individually seem reasonable but collectively add up; the builder suggesting upgrades you didn't ask for; materials being substituted for more expensive alternatives without discussion.

Approach it factually, not emotionally. Show them your records: 'The original quote was £X, we've agreed £Y in variations, and now the total is £Z. Can we review what's left?' Good builders respect organised clients.