Home Renovation Mistakes to Avoid: 7 Errors That Can Cost You Dearly

ETNA STUDIO · Architecture & Interior Design in Barcelona

Commissioning a full home renovation is one of the most significant financial decisions a homeowner can make. It is also one with the most room for things to go wrong when approached without the right information. The good news is that the most common mistakes are not unpredictable — they recur from project to project with a consistency that makes them entirely avoidable.

At ETNA STUDIO, an architecture and interior design studio in Barcelona, we have guided dozens of clients through every stage of the renovation process. In this article, we share the 7 most common mistakes when planning a full apartment renovation so you can make the right decisions from the start — with no unpleasant surprises along the way.

1. Choosing the Cheapest Renovation Quote

This is, by far, the most frequent mistake in any full home renovation. It is also the one that tends to cost the most in the long run.

When you receive three quotes and one of them is noticeably lower than the rest, the initial reaction is relief. But before signing anything, there is one essential question to ask: why is it so cheap?

Trimming a renovation budget on paper is remarkably easy. A contractor can cut their figure in a number of ways that the client will not see until the work is already underway:

• Lower-grade materials. The tile or flooring you had in mind can be swapped for something that looks similar but is industrial quality — with a lifespan that will make itself known within just a few years.
• Less experienced tradespeople. Skilled craftspeople charge higher rates. A heavily discounted quote almost always means less experienced or less careful labour on site.
• “Extra” line items appearing mid-build. The initial budget is set at a bare minimum, and as the renovation progresses, “unforeseen issues” emerge — which, somewhat predictably, are always charged to the client. The final cost ends up matching or exceeding the most expensive quote, but with a lower-quality result.
• Constant pressure on material choices. When it comes time to select finishes, the contractor persistently steers towards the cheapest options because the appropriate ones simply do not fit within the agreed price.

The cheapest quote is rarely the most economical option. The gap between serious proposals is not a calculation error — it is what doing a quality full renovation actually costs. Comparing quotes properly means verifying that they describe exactly the same scope: same line items, same quality standards, same working methodology.

2. Splitting the Renovation Into Phases to Spread the Cost

The logic seems sound: if the total renovation budget is high, you do the kitchen this year and the bathrooms next. In theory, it distributes the financial pressure. In practice, a phased full home renovation typically costs more, takes longer, and delivers worse results than tackling it all at once.

The reasons are concrete:

• Repeated mobilisation costs. Every time a team of professionals starts work in a home, there are set-up costs — transport, preparation, protective measures — that double or triple when the project is carried out in separate stages.
• Technical incompatibilities between phases. Plumbing, electrical, and HVAC systems are interdependent. Intervening in one area without considering the whole almost always means undoing work that has already been completed when the next phase begins.
• Repeated permits and neighbour disruption. Municipal licences, skips on the street, noise complaints — these do not disappear when you divide the work; they multiply.
• Inconsistency in finishes. Manufacturers discontinue product lines every season. The flooring chosen in the first phase may not be available when the second begins, breaking the visual coherence of the entire project.

The solution is not to fragment the full home renovation, but to plan the financing properly from the outset and negotiate payment terms with the studio that allow the whole project to be tackled in one go, with full guarantees.

3. Skipping the Architectural Project and Site Management

One of the most costly mistakes — sometimes literally — is treating the architectural project as an expendable expense in a full home renovation.

Without a project, there are no detailed drawings, and every trade interprets the brief in its own way. The inconsistencies between contractors — the electrician who didn’t coordinate with the plumber, the joiner who arrived without knowing the finish detail at the tiling junction — generate rework that the client ends up paying for.

Without site management, no one with technical authority verifies that execution is correct. Structural issues, unresolved damp, or deficient installations go undetected until it is too late to fix them without demolishing finished work.

Furthermore, many full home renovations require a municipal building permit. Carrying them out without the appropriate technical oversight can result in fines, restoration orders, or serious complications when selling the property.

A good architectural project is not a luxury — it is the guarantee that what you pay for is what you get.

4. Starting on Site Before All Decisions Have Been Made

Beginning a full home renovation without having defined materials, finishes, and layout is one of the most common causes of delays and budget overruns.

Every change of mind once work has started has a cost — sometimes financial, always in time. Changes during construction can inflate the renovation budget by 10% to 20% compared to the original agreed figure.

The design phase exists precisely to prevent this: to define and sign off on every decision — materials, furniture, taps and fittings, lighting, appliances — before the first wall comes down. Everything confirmed, every delivery lead time locked in, before work begins.

5. Overlooking Material and Furniture Lead Times

Closely related to the previous point, one of the most common bottlenecks in a full home renovation is the late arrival of materials or furniture.

A bespoke kitchen typically has a manufacturing lead time of 10 to 14 weeks. Certain imported ceramic flooring or custom joinery can involve similar timelines. If orders are not placed well in advance, the build comes to a standstill at the most critical moment — tradespeople waiting on site, time ticking, and costs mounting.

Procurement planning must begin in parallel with the design process, not once work is already underway.

6. Underestimating the Impact of the Renovation on Daily Life

A full home renovation means, in most cases, that the property is not liveable for weeks or months. This is something most clients are aware of — but very few plan for with sufficient rigour.

The result is making important decisions under the pressure of living on a building site, accepting compromise solutions out of exhaustion, or absorbing the cost of temporary accommodation that was never budgeted for.

Before starting any full renovation, it is essential to have a clear plan for life during the process: where the family will live, what the realistic duration of the works actually is, and what the contingency plan looks like if timelines run over.

7. Proceeding With a Vague or Informal Contract

Starting a full home renovation with an informal quote or a poorly drafted contract is a mistake with potentially serious consequences.

A well-written construction contract should cover at a minimum:

• The exact scope of works and what is expressly excluded.
• The agreed materials, with specific brands and product references.
• The execution schedule with verifiable intermediate milestones.
• Payment terms linked to actual progress on site, not arbitrary dates.
• Warranties on completed works and remediation timeframes.
• The procedure for handling unforeseen issues or disputes.

Without this framework, the client is left unprotected against unjustified delays, unilateral material substitutions, or disagreements about what was actually included in the project.

Conclusion: The Best Home Renovation Is a Well-Planned One

A well-executed full home renovation can radically transform a property and represents an investment that pays back in quality of life and in the value of the home. But that outcome does not happen by chance — it requires making the right decisions before the first stage of work begins.

At ETNA STUDIO we work alongside our clients from the very first conversation, helping them understand the process, accurately size their renovation budget, and build a solid project that reaches the construction phase with every variable under control.

👉 Are you thinking about renovating your home in Barcelona? Tell us about your project — no obligation.

Frequently Asked Questions About Full Home Renovations

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Why do full home renovations go over budget?

A full home renovation involves simultaneous work across installations, structure, finishes, and fittings throughout the entire property. The most common overruns occur due to the absence of an upfront design project, changes of mind during construction, choosing the cheapest quote without properly analysing its conditions, and poor planning of material delivery lead times.

What should a full home renovation quote include?

A rigorous full renovation quote should break down every work item by chapter — demolition, structure, installations, wall and floor finishes, joinery, furniture, and final finishes — specify the quality level and product references for all materials, and set out the execution timeline. A lump-sum quote without that level of detail cannot be meaningfully compared with others and offers the client no real protection.

Do I need an architect for a full apartment renovation?

In many cases, yes — it is a legal requirement, particularly when the renovation affects the building’s structure, involves a change of layout, or requires a municipal building permit. Beyond the legal obligation, having a proper architectural design project and site management is the best guarantee that the renovation is carried out correctly, on time, and with the agreed materials.

How long does a full home renovation take?

The duration of a full apartment renovation depends on floor area, the existing condition of the property, and the scope of works. As a rough guide, a full renovation of an apartment between 80 and 120 m² in Barcelona typically takes between 3 and 6 months from the start of construction — provided the design is fully defined and materials ordered well in advance.

Why is it a bad idea to carry out a renovation in phases?

Splitting a full home renovation into separate phases generates repeated mobilisation costs, technical incompatibilities across installations, multiple rounds of permits and neighbour disruption, and inconsistencies in finishes. In most cases, tackling the renovation all at once works out more cost-effective and guarantees a coherent final result.

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