5 hidden costs of renovation that you should know

So, you’ve got your quotes from the builder. You’ve chosen your dream kitchen and the perfect bathroom tiles. You have your “magic number,” and you’re ready to start.

Not so fast.

One of the biggest mistakes in renovation is assuming your builder’s quote is your total budget. It’s not. It’s merely the largest part of it. The real budget-breakers are the costs everyone forgets—the ones that turn a dream project into a financial nightmare.

Based on our data and experience with thousands of UK projects, here are the top 5 hidden costs you need to plan for before work begins.

1. The “Paperwork” & Professional Fees

Before a single hammer swings, there’s a chain of essential “pre-construction” costs. These are non-negotiable and add up quickly.

• Architect/Designer: If you’re changing the layout, you’ll need plans. Fees can range from a few hundred pounds for simple drawings to 5-12% of the total project cost for full architectural services.
• Structural Engineer: Removing a chimney breast or knocking through a wall? You’ll need a structural engineer to provide calculations. Expect to pay £500 – £1,000 for their report and site visit.
• Planning Permission: Your extension or loft conversion might need planning permission from your local council, which carries a fee (currently £206 for a homeowner application in England).
• Building Regulations: This is not the same as planning permission. It covers the technical side of your build (e.g., insulation, fire safety, structural integrity). You’ll pay for a Building Control Officer from your council or a private approved inspector to sign off on the work. This can cost anywhere from £300 to £1,500+ depending on the project’s scale.

2. The “Surprise” Costs (The Contingency Fund)

We call this “The Pandora’s Box” cost. In UK housing stock, especially Victorian and Edwardian properties, you never truly know what’s behind a wall or under a floorboard until you open it up.

This is what your 10-15% contingency fund is for. It’s not “extra money” to spend on nicer taps; it’s a critical safety net for:

• Discovering asbestos (common in Artex ceilings, floor tiles, and pipe insulation in pre-2000 homes). Specialist removal is mandatory and expensive.
• Finding rotten joists or damp that was hidden by the previous owner.
• Uncovering dodgy old wiring (like old rubber-cased cables) that isn’t safe and requires a full rewire.
• Realising the existing plumbing is failing and needs to be replaced.

If your budget is £50,000, you must have £5,000 – £7,500 set aside purely for these inevitable surprises.

3. Waste Management & Site Setup

Your builder’s quote may include waste removal, but it’s crucial to check. If it doesn’t, you’re on the hook.

• Skip Hire: This isn’t just a few quid. A large 8-yard skip can cost £250 – £400 per fill, and a full house refurb might need 5-10 of them.
• Skip Licences: If the skip needs to be on a public road, you’ll need a permit from your local council, which costs extra.
• Specialist Waste: By law, you cannot mix all waste. Plasterboard, for example, must be disposed of separately. Asbestos and other hazardous materials have their own costly disposal streams.

4. The Cost of Living Without a Home

This is the silent budget-killer. If you’re renovating your whole house, you probably can’t live in it.

• Alternative Accommodation: Renting a similar property, even for just 3-4 months, can add £4,000 – £8,000+ to your project, especially in the South East.
• Storage Fees: You’ll need to move all your belongings out. A self-storage unit can cost £150 – £300 per month.
• Increased Living Costs: With no kitchen, your food bill will skyrocket. The cost of takeaways or eating out every night adds up incredibly fast.

5. The “Final 5%” — The Finishing Touches

A builder’s quote often stops at what’s called “second fix.” This means they’ll install your light fittings (the plastic pendants) and your sockets (the white plastic ones). They’ll paint the walls with a “mist coat,” not the final designer colour.

The budget for the “final finish” is almost always forgotten:

• Paint: That specialist, wipe-clean paint in a designer colour costs 3x more than standard white emulsion.
• Hardware: New handles for all your doors and kitchen cabinets (£200 – £500).
• Light Fittings: Swapping the plastic pendants for the designer lights you want (£50 – £300 per room).
• Window Dressings: New curtains and blinds for freshly plastered walls.
• Final “Deep Clean”: After the builders leave, the entire house will be coated in a fine layer of dust. A professional “post-builder clean” is essential and can cost £300 – £600.

How to Stop These Costs from Being “Hidden”

A builder’s quote is a part of your budget, not the whole budget.

The only way to avoid these nasty surprises is to have a professional-grade, detailed report before you even ask for quotes. This is the core of the Refurbmate service.

Our data-driven platform analyses your project and produces a detailed breakdown that includes labour, materials, and specification tiers. This report gives you a realistic, comprehensive budget—one you can use as a benchmark to compare the quotes you receive from Checkatrade professionals. You can spot what’s missing from their quote before it becomes a £5,000 problem.

Don’t start your renovation blind. Get the full picture first.