The signs that come up most often
The most common red flags when choosing a contractor are five: a price given without measuring, a quote with no line items or nothing in writing, most of the payment upfront or cash only, company details that cannot be verified, and pressure to sign quickly. One on its own proves nothing; two or three together are a reason to stop.
Each has its own article in this guide: the verbal quote, cash payment, checking the tax number (NIF), civil-liability insurance, the registered address, pressure to decide and the suspiciously cheap quote. Here we explain how to spot them in order, from the first call to the signature, and how to weigh them together.
Before the visit: what you can check from home
With the company name alone you can check several things in ten minutes. That it exists as a company with a tax number and registered office in a public register. That the address on its website is a real office or premises and not a mailbox. That the projects it shows have a location, dates and progress photos, not just catalogue images.
How they respond also counts. A company that takes a week to return a call before signing is unlikely to be faster once work is under way. We answer every enquiry within an hour; it is not a special merit, it is what you should expect from anyone.
At the visit: how they measure and what they ask
A serious contractor measures, opens the electrical panel, looks at visible pipework, asks about the comunidad de propietarios, the lift and working hours, and wants to know what finishes you have in mind. In an Eixample flat they will ask about downpipes and floor structure; in a Castelldefels house, about damp and the roof.
Be wary if they give a firm figure in the hallway without measuring, ask nothing about the building, or promise to start next week on a renovation that needs a municipal permit. A fast reply is good; a fast price without information is not.
In the quote: what must be in writing
A reliable quote is broken down into line items with quantities and units, identifies the main materials by brand or range, states what is and is not included (permits, skip, protection of common areas, final cleaning) and shows VAT. A single line saying "full renovation" with a total cannot be compared or claimed against.
The other sign is a price far below the rest. If three quotes are around one figure and one is a third lower, ask what it leaves out. The difference is almost always a missing item, a material from another range, or a figure that will grow during the works. How to compare quotes line by line is explained in another article.
In payment terms and the contract
Reasonable payment goes by stages tied to finished, checkable work: demolition, services, partitions, finishes. Asking for most of the money upfront, insisting on cash without an invoice or refusing to sign a contract are signs that on their own justify a serious conversation.
The contract should attach the quote, set out timelines, stage payments, how changes are approved and who the site manager is. If the contractor says "between us we don't need paperwork", the right answer is that this is exactly why you do. We work with a contract and stage payments; it is the minimum that protects both sides.
Five questions that separate a good contractor
Ask them all and compare how each candidate answers. Who will manage my project and how do I reach them? Which work does your own team do and which do you subcontract? What municipal procedure does this job need and who files it? What happens if something unexpected turns up when walls are opened, how is it priced and who approves it? Can I see a finished or ongoing job of yours?
A good contractor answers with names, dates and examples. For instance, in our case our own crew does the work, very specific jobs go to trusted subcontractors, and there is a single manager per project who speaks Russian and Spanish. Vague answers, "we'll see" and changes of subject tell you more than any review.
How to weigh the signs
A single sign calls for a question: a serious self-employed builder may have no website and a small firm may prefer immediate transfer over deferred payment. Two signs call for everything to be put in writing before going on. Three or more, especially a large upfront payment combined with no contract, justify looking elsewhere, however good the price seems.
What decides it is the reaction to your questions. People who work well appreciate a client who asks, because it saves them disputes later.