I got my conversion done. The overall quality of the work was good. But I experienced two leaks, poor aftercare, and some stressful conversations along the way. Here's what I'd do differently.
Choosing a contractor is the single biggest decision in the whole process. Get it right and the build is smooth, the quality is there, and you sleep at night. Get it wrong and you're dealing with problems for months - or years. This guide is everything I wish I'd known before I signed anything.
I'm happy that my conversion is done and I use the space every day. But the process was at times stressful, especially with topics that were completely new to me - waste pipe routing, insulation types, certificates, fire safety. This entire website is a brain dump of everything I learned so you can go in with your eyes open.
Get at least 3 quotes - and compare properly
Don't just compare the bottom-line price. A quote of €18,000 and a quote of €24,000 might include completely different things - our full cost breakdown guide explains what to expect. The cheaper one might exclude flooring, certificates, blinds, or have a vague scope that leads to "extras" mid-build.
For each quote, check what's actually included:
Is VAT included?
Some quotes are ex-VAT. A 13.5% surprise on top of the quoted price is a nasty shock. Always confirm the final price is VAT-inclusive.
Is flooring included?
Many quotes only cover OSB subfloor. The floor finish (laminate, LVT, carpet) is often extra. Clarify this upfront.
Is the certificate of compliance included?
Most quotes don’t include engineering certification. Budget €750 separately if not. See our certificates guide.
What about Velux blinds?
Blinds are often excluded from the base quote. Electric blackout blinds add €200–400 per window. Ask.
What happens if unexpected issues arise?
Roof structure problems, hidden wiring, rotten joists — these things happen. How does the builder handle unexpected costs? Get this in writing.
Payment schedule
Never pay 100% upfront. A typical payment schedule is 30% deposit, 40% at midpoint (e.g. when the structural work is done), and 30% on completion. Some builders want more upfront - anything over 40% as a deposit should give you pause. The final payment is your leverage to make sure everything is finished properly before you pay the balance.
Questions to ask every contractor
These are the questions that separate a contractor who knows what they're doing from one who's winging it. You don't need to be confrontational - just ask them clearly and see how they respond.
"What insulation type do you use and why?"
They should be able to explain their choice clearly. If they push spray foam without discussing alternatives or the UK mortgage concerns, that’s worth noting.
"How will you handle the waste pipe for the ensuite?"
This is a genuinely technical question. A good builder will explain the routing, the fall, and whether a macerator is needed. Vagueness here is a concern.
"What size and brand of Velux windows are included?"
Get the exact size code (MK04, CK04, etc.). “Standard size” is not an answer. And confirm the brand — alternatives exist but Velux has the best accessory ecosystem.
"Will you arrange the certificate of compliance, or do I?"
This tells you whether they understand the certification process. If they seem unaware of different cert types, that’s a red flag.
"Will you allow an independent engineer to inspect during the build?"
A during-build inspection gives a much stronger certificate. If the builder resists this, ask yourself why.
"What’s your timeline, and what causes delays?"
Honest builders will tell you what can go wrong. “Three weeks, no problem” with no caveats is less trustworthy than “Usually four weeks, but weather can push it to five.”
"What warranty or aftercare do you provide?"
Ask what happens if something goes wrong after the build. Leaks, cracks, issues with plumbing — how do they handle callbacks? Get it in writing.
"Can I speak to a previous customer?"
Any builder proud of their work will be happy to connect you with a past client. Reluctance is a red flag.
Red flags
None of these are automatic deal-breakers on their own, but if you're seeing several of them, trust your instincts.
Won’t commit to a written contract with a detailed scope of work
Wants full payment upfront or a deposit over 40%
Can’t show you a recent completed conversion (photos or in person)
Won’t let you speak to a previous customer
Gets vague about certificates — “Ah you don’t really need one”
No Google Business reviews, or only reviews on their own website
Quotes significantly lower than everyone else — they’re either cutting corners or will add costs later
Pushes spray foam without discussing alternatives or the UK mortgage situation
Green flags
These are the signs you're dealing with someone who takes their work seriously.
Happy to let an independent engineer inspect during the build
Has genuine Google reviews from real homeowners (not just testimonials on their website)
Provides a written contract with a detailed scope, timeline, and payment schedule
Uses rigid board insulation or can clearly explain their spray foam choice and the trade-offs
Includes fire doors and interconnected smoke alarms as standard
Can walk you through the waste pipe routing before you commit
Is upfront about what’s included and what’s extra
Has a clear aftercare/warranty process for issues after completion
What I'd do differently
Looking back, I'd spend more time vetting upfront. I'd ask more of the questions listed above. I'd push harder on the certificate process from the start, rather than dealing with it after the build. And I'd have a clearer written agreement on aftercare - what happens when something goes wrong six months later.
The build quality itself was good. I use the attic every day and it's genuinely transformed how we use the house. But the two leaks, the chasing for callbacks, and the stress of navigating topics I didn't understand at the time - all of that could have been reduced with better preparation.
That's why this site exists. I want you to go in knowing what I didn't.
The bottom line
Get three quotes. Compare what's included, not just the price. Ask the hard questions. Check Google reviews. Agree a sensible payment schedule. Get everything in writing. And trust your gut - if something feels off during the quoting stage, it won't get better once they have your money.
A good contractor makes the whole experience manageable. A bad one makes it miserable. The time you spend vetting upfront is the best investment you'll make in the entire project.
Our planning report includes the full builder vetting checklist
Every question you need to ask, every thing to check, in one printable report. We can also introduce you to a contractor I've seen great work from firsthand - but always do your own due diligence.
Try the Planning Tool