Guide · Renovation mistakes · Barcelona
Most renovation problems don't come from the building work itself, but from decisions made before it starts. These are the ten costliest mistakes when renovating a flat in Barcelona — especially in the old buildings of the Eixample and Gràcia — and how to avoid them from the very first quote.
By Vladimir Petrov, founder of TrueHomeBuild · 18 years running renovations · updated June 2026.
RENOVATION MISTAKES · 2026
The costliest one. In pre-1940 buildings many internal walls are load-bearing and the floor rests on Catalan vaulting. Opening a gap without redistributing the load with a calculated lintel or beam causes cracks — in your flat and the neighbour's. Before demolishing anything, an inspection defines what is a partition and what is structure. It's the basis of any apartment renovation that changes the layout.
Renovating without the correct procedure risks fines, a stop-work order and being unable to legalise it afterwards. Each renovation has its permit — minor-works notice, responsible declaration or major works. Knowing which you need before starting avoids the worst surprise. The Spanish guide to building permits in Barcelona covers each case.
An indicative quote commits no one: the price climbs with "extras" during the works. Demand a closed, line-by-line quote with units and unit prices. The figure signed in the contract should be the final one, unless you request changes in writing. That's how a serious turnkey renovation works.
In flats with pre-code wiring or lead/iron plumbing, renovating only "what you can see" is throwing money away. If the cabling and pipes aren't renewed during the works, the problems come back soon and force you to open freshly finished walls.
Old buildings have cast-iron drain stacks with decades of use, plus damp from capillarity or leaks. Renovating a bathroom without checking the communal stack is the number-one cause of stains that keep reappearing on the neighbour's ceiling. Waterproofing and stack condition are checked before, not after.
When the client hires electrician, plumber and builder separately, each blames the other for delays and no one owns the result. A single site manager coordinating every trade removes the dead time and leaves one point of contact for any problem.
An abnormally low price almost always hides something: excluded items, lower-grade materials, unlicensed trades or no warranty. Compare closed quotes with the same scope — not loose prices — and check licences, references and a written warranty.
A full renovation of 70-90 m² takes 8-14 weeks; with structure and a major-works licence, add the permit time. Promising very short timelines usually means missing items or badly overlapped work. Allow a 10-15% buffer, especially in old buildings where surprises appear once walls are opened.
Choosing finishes for looks without thinking about real use is a mistake you pay for over time: floors that scratch, joints that stain, paint that won't survive Mediterranean humidity. In a major renovation the right material for each area lasts years; the cheap one, months.
Without a completion certificate you can't obtain the habitability certificate or legalise the renovation. And without a written warranty, any later defect is your problem. Always demand a workmanship warranty (24 months minimum) and, on structural work, the 10-year LOE cover.
FAQ · Renovation mistakes
Touching a load-bearing wall without calculation or a project. In the pre-1940 buildings of the Eixample and Gràcia many internal walls are structural; opening a gap without redistributing the load can crack your flat and the neighbour's.
It doesn't commit the contractor: the price climbs with extras during the works. The right approach is a closed, line-by-line quote where the signed figure is the final one, unless you request changes in writing.
Almost never. A very low price usually hides excluded items, worse materials, unlicensed trades or no warranty. Compare closed quotes with the same scope and check licences and warranty.
A full renovation of 70-90 m² takes 8-14 weeks; with structure and a major-works licence, add the permit time. Allow a 10-15% buffer, especially in old buildings with surprises once walls are opened.
Renovation without surprises · Barcelona
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