How to Budget an Apartment Renovation (and Where Design Fits)

Budget a renovation in four parts: the design project (typically 8–12% of the total), construction work, materials and fixtures, and furniture with appliances. Then add a 10–15% reserve. Most overruns don't come from prices rising. They come from decisions made on site, redoing work, and items nobody listed. A good budget is mostly a good list.

Renovation prices per m² vary too much by country to quote a universal number. What doesn't vary is the structure, and that's what this article is about.

The four parts of a renovation budget

Shares for construction, materials and furniture depend on country and choices more than on anything a designer can promise. The design share and the reserve are the two numbers you can plan with confidence.

Where the money actually leaks

Decisions made on site. The builder asks where the socket goes. You guess, on the phone, from another city. Multiply by a hundred.

Redoing. The kitchen arrives and doesn't fit because a wall was plastered 3 cm thicker than planned. The shower tray doesn't line up with the tile grid. Each fix is small; together they are the overrun.

Missing items. Nobody put skirting boards, door handles, ventilation grilles or the underfloor heating thermostat on the list. They get bought last, fast and expensive.

Scope creep. "While we're at it, let's also…" — every time without a drawing, and without a new number.

Renovations without a project commonly run 20–30% over. That figure comes mostly from the four points above, not from inflation.

Why a project makes a budget possible

A budget is only as accurate as the list behind it. A design project produces that list:

• Drawings give builders exact quantities: metres of wall, square metres of tile, number of sockets. Quotes become comparable.
• A specification with part numbers gives a price for every item before you buy. You can see the total and trade down where it matters least.
• Visualizations mean you approve the result before spending, so there is less "let's change it" during the build.

The project fee is visible. The savings are the problems that never happen, which is why they're easy to underestimate.

A worked example

An 80 m² apartment at our rates:

• Basic project (layouts and visualizations of every room): 80 × €35 = €2,800
• Full project (plus drawings and specification): 80 × €50 = €4,000

If that €4,000 is about 10% of the renovation, the total is around €40,000. A 20% overrun on that is €8,000 — twice the project fee. The arithmetic only works in the project's favour if the project is used: builders quote from the drawings and buy from the specification.

How to build your budget, step by step

1. Fix the scope. Which walls move, which rooms get a full renovation, what stays. 2. Get a layout. Scope isn't real until it's drawn. 3. Choose finishes at three price levels for the big areas: floor, tile, kitchen. Pick per room, not per apartment. 4. Get construction quotes from drawings, from at least two crews. 5. Price the specification item by item. 6. Add 10–15% reserve and don't spend it on upgrades. 7. Track changes in writing, each with its cost.

Frequently asked

Is 8–12% for design expensive? Compared with the overruns it prevents, usually not. And you can start with the layout only, which is a fraction of that.

Can the designer design to my budget? Yes, if you name the number at the start. Materials and products are then chosen to fit it, with cheaper equivalents where they matter least.

What's the minimum project? At our studio the minimum is about 50 m². See pricing and how much an interior designer costs.