Most renovation nightmares in Dublin are not caused by bad luck. They are caused by warning signs the homeowner spotted early, then talked themselves out of. Builders who quote without a site visit. Demands for half the deposit in cash before a tool turns up.
The seven red flags below cover the patterns that show up again and again when jobs go wrong. Watch for missing CIRI registration, vague quotes, cash-only deposits, no insurance, references you cannot verify, pressure tactics with suspiciously low pricing, and poor communication from day one. Any one of these on its own should give you pause. Two or more is a reason to walk away.
2026 is the year the Construction Industry Register Ireland (CIRI) becomes a statutory requirement for builders, which gives Dublin homeowners a stronger filter than ever before. If you are about to spend €40,000 to €300,000 on a build or extension, the next ten minutes of reading is worth your time.
Red Flag #1: No CIRI Registration or Verifiable Trade Credentials
Construction Industry Register Ireland is the official, government-backed register of competent builders, and registration is becoming a legal requirement for residential builders during 2026 under the Regulation of Providers of Building Works Act 2022. If a builder cannot point you to their listing, that is a serious problem.
You can search the register at CIRI.ie in under a minute, and any builder bidding for your job should welcome you doing so. While the rollout is phased and some legitimate smaller contractors will appear later, you should still expect to see Voluntary Construction Register membership, Construction Industry Federation membership, or comparable Safe-T-Cert accreditation in the meantime. A flat refusal to discuss credentials is not a small thing.
Red Flag #2: Vague Quotes With No Written Breakdown
If your quote arrives as a single round figure on a one-page email, you do not have a quote. You have a guess. A proper Dublin builder will price the work line by line so you know exactly what you are paying for, and so variations later can be costed against the original brief.
A real quote should include the following at a minimum:
- Detailed scope tied to drawings or a written brief.
- Separate costs for structure, plumbing, electrics, heating and finishes.
- Stated allowances for kitchens, bathrooms, tiles and sanitaryware.
- VAT shown clearly, with the 13.5% reduced rate applied to qualifying construction services.
- Payment stages tied to progress milestones rather than calendar dates.
- What is excluded as well as what is included.
If you are unsure what to look out for in a written scope, Clarcon’s guide to 10 common house extension mistakes walks through where homeowners typically under-allow, and it gives you the language to push back on a vague quote without sounding awkward.
Red Flag #3: Cash-Only Payments and Big Upfront Deposits
Cash payments are not illegal in Ireland, but a builder who insists on cash and refuses to issue a VAT receipt is telling you something. They are likely operating outside the system, which means no VAT trail, no Revenue paperwork, and almost certainly no recourse if the work goes wrong.
Deposits in Ireland for residential building work typically sit between 10% and 25% of the contract sum, with the balance paid in stages tied to completed milestones. A builder asking for 50% upfront, or a five-figure cash sum before any materials arrive on site, is asking you to take all the risk. Walk that one back.
Red Flag #4: No Insurance or Refusal to Provide Documentation
Every reputable Dublin builder carries public liability insurance covering damage to your property and to neighbouring properties, plus employers liability covering anyone working on site. For most domestic projects, expect to see public liability cover of around €6.5 million and employers liability of around €13 million, though exact requirements can vary by insurer and project size.
Ask to see current certificates, not photocopies from three years ago. If walls are coming out or roofs being opened, you should also ask about contract works (all-risks) cover. Clarcon’s piece on budgeting for unexpected costs in construction explains why insurance gaps are one of the worst surprises a homeowner can hit, because the cost of an uninsured incident can dwarf the entire build budget.
Red Flag #5: No Verifiable References or Past Projects
Photos of completed work are easy to fake. Phone numbers of three “happy clients” passed across a kitchen table are easy to invent. What is not easy to fake is a finished project you can drive past, or a homeowner you can ring without the builder in earshot.
Ask for at least three recent projects of a similar type and scale, ideally completed within the last two years and within Dublin or surrounding counties. If the builder hesitates, names go missing, or every reference is “doing a job in Spain at the moment”, you have your answer. Ask the references about communication, about overruns, and about what they would do differently. Most homeowners will tell you the truth.
Red Flag #6: Pressure Tactics and Quotes Far Below the Rest
If three builders quote in the €120,000 to €140,000 range for a two-storey extension and the fourth comes in at €82,000, the cheap quote is not a bargain. It is either a missing scope, an underestimate that will balloon through variations, or someone who plans to disappear after the deposit clears. None of those endings are pleasant for the homeowner.
What “Too Cheap” Usually Means
Suspiciously low quotes almost always have one of three explanations. The builder has not priced the full scope and will issue a series of “extras” once you have committed. They have priced the labour at unsustainable rates and will pull the team mid-job for a higher-paying client. Or they intend to skip steps you cannot see, like proper damp proofing, foundations, or insulation depth.
Pressure tactics travel with low quotes. Be wary of “decide today and I will hold the price”, “my lads have a gap next week so I can fit you in”, or any builder who rings you repeatedly chasing a yes before you have time to compare. A builder who is busy and reputable does not need to push.
Red Flag #7: Poor Communication From the First Phone Call
How a builder communicates before you sign is exactly how they will communicate during the job, only worse. If calls take three days to return now, expect a week once the deposit is in. If they cannot give you a clear named contact for the site, no one is going to be accountable when something goes wrong.
Watch for vague timelines, refusal to put answers in writing, and any reluctance to do a proper site visit before pricing. Clarcon’s post on the top mistakes homeowners make during renovations covers communication breakdowns in detail, and it shows how the same patterns play out across different project types.
A good Dublin builder will visit your home, take measurements, ask probing questions about the brief, follow up with a written quote within a week or two, and give you a single named point of contact for everything that follows. If you are not getting that on day one, the rest of the project will not get easier.
Hiring a Dublin Builder You Can Actually Trust
Three quotes, full credentials, written contracts, and a buyer with their eyes open is how most Dublin renovations stay on the rails. If you are planning building or civil works in Dublin, Kildare, Meath, Louth or Cavan, get in touch with Clarcon for a proper site visit and a written breakdown. Call 01 437 0645 or email info@clarcon.ie to start the conversation.
