5 mistakes to avoid before renovating your home

Most bad surprises in a renovation don't come from a dishonest tradesperson or a faulty material — they come from decisions made too early, without the right information. Here are the mistakes that come up most often, in the order they generally occur.

1. Requesting quotes before you have a plan

Approaching contractors before you have a defined project seems like a time-saver. In reality, it produces quotes that can't be compared with each other, since each tradesperson fills in the blanks with their own assumptions. The time "saved" at the start ends up being spent on back-and-forth later.

2. Underestimating lead times for bespoke furniture

A piece of bespoke furniture generally takes 8 to 14 weeks between plan approval and delivery. If the order is only placed once the site work is finished, the apartment stays unusable for weeks longer than necessary.

3. Leaving lighting until the end of the project

The position of light points needs to be decided before the walls are opened, not after. Once the partitions are closed and the floors are laid, correcting poorly planned lighting means reopening everything.

4. Choosing finishes out of order

Flooring, walls and worktops all influence one another. Choosing each element in isolation, without seeing them together, frequently produces combinations that need correcting — meaning redoing — once the result is visible in real life.

5. Not building in a budget margin

In an existing building, opening the walls almost always reveals something — non-compliant wiring, a pipe that needs moving. A margin of 10 to 15% of the total budget prevents this kind of discovery from stalling the project.

These first five mistakes are the most common. There are at least five more, less visible because they get settled before the site work even begins — around permits, insurance and the contract — but which cost just as much when overlooked.

6. Starting work without checking whether a permit is needed

Most interior renovations don't require a building permit, as long as the load-bearing walls and the building envelope aren't touched: redoing a kitchen, a bathroom, the flooring or the electrics generally doesn't need authorisation. That changes as soon as the project alters the designated use of a room — turning an unheated box room into a bedroom, or a living space into a professional unit — or as soon as it touches fire safety.

This requirement isn't harmonised between cantons, nor always between communes within the same canton, which makes the generalities found online unreliable for a specific case. Works started without a prior check risk, in the worst case, a stop-work order or a requirement to restore the original state. The simple reflex: ask the commune before signing the first quote, not once the work has already started.

7. Underestimating insurance needs during the works

Standard household and private liability insurance, which covers an apartment day to day, isn't designed for a construction site. During the works, the risks change in nature: water damage linked to an open pipe, damage caused to a neighbour, theft of materials stored on site. These situations fall under separate types of cover, which need to be checked before the first hammer blow.

• Works insurance (site insurance): covers material damage to the works during the alteration
• Project owner's liability insurance: covers damage caused to third parties — a neighbour, a passer-by — during the works, even without personal fault
• Contractor's professional liability insurance: covers damage caused by the tradesperson themselves — get this confirmed in writing before signing

In case of water damage during the works, standard building insurance generally doesn't step in if the incident is linked to a construction defect: it's then the liability of the contractor, the architect or the project owner that's engaged, depending on the circumstances. Clarifying this cover before the works begin avoids discovering a contractual gap at the point where it costs the most.

8. Confusing a rough quote with a firm building contract

A quote, by default, remains an estimate — it doesn't automatically commit both parties to a firm price, precise deadlines or defined warranties. Many projects start on the basis of a simple email exchange, without ever formalising a building contract. This becomes a problem as soon as a disagreement arises: without a signed reference document, it's difficult to prove what was actually agreed.

In Switzerland, the SIA 118 norm governs this type of contract, but it doesn't apply automatically: the parties must explicitly include it in the contract for it to be binding. When it applies, it provides for a 2-year warranty period during which the contractor is presumed liable for reported defects, followed by a 5-year prescription period from handover of the works. Without this contractual reference, the more general regime of the Swiss Code of Obligations applies instead — to be clarified with the contractor before signing, not after.

9. Choosing the cheapest quote without checking references

Faced with several quotes, the temptation to pick the cheapest is natural — especially when the gap seems significant for services that look identical on paper. A quote noticeably lower than the others almost always hides something: an under-priced item, a lower-quality material than expected, or too thin a margin to absorb the unexpected — which often leads to extra charges during the works.

Asking for two or three references from recent, comparable projects — and visiting them or contacting the clients involved if possible — reveals in a few minutes what a quote never says: whether deadlines were kept, how the unexpected was handled, the quality of communication during the works. That's often more decisive for the final result than the price gap between two proposals.

10. Underestimating dust, noise and disruption to daily life

A renovation project, even a partial one, generates more dust and noise disruption than most people anticipate — particularly during demolition, drilling or sanding. Continuing to live in the apartment during these phases is rarely comfortable, and sometimes simply impossible if the kitchen or the only bathroom is out of service for several weeks.

Planning temporary housing, even for a few weeks, or at the very least a dust-protected zone for rooms still in use, avoids improvising under pressure once the works have started. This is an item to build into the schedule and, where relevant, into the budget from the outset — not something to discover on the first night without a working kitchen.