Search “single storey extension London” and you’ll get pages of companies that all look, on the surface, remarkably similar. Same promises. Same stock phrases about “quality craftsmanship” and “stress-free process.” The problem isn’t finding companies — it’s telling them apart before you’ve signed anything and committed real money to one of them. So here’s a practical way to actually do that, rather than picking based on whoever answered the phone fastest.
Start With Whether They Actually Do Design AND Build
This sounds obvious, but it’s worth checking properly rather than assuming. Plenty of companies market themselves as a “design and build” outfit while actually subcontracting the architectural work out to a freelancer they use occasionally, with no real ongoing relationship or shared accountability. Ask directly: are the architects, structural engineers, and construction team all part of the same company, working from the same information throughout the project? A genuine London design and build company should be able to answer that clearly and specifically, not vaguely gesture at “we work with trusted partners.”
The reason this matters more than it might seem is that single storey extensions, while simpler structurally than a double storey job, still involve decisions — wall removals, roof design, drainage routing — that need design and structural thinking to happen together, not in sequence with gaps in between.
Ask to See Real, Local Projects — Not Just Any Portfolio
A polished portfolio full of beautiful photography tells you a company can hire a good photographer. What actually tells you something is whether they’ve completed single storey extensions specifically, ideally in boroughs similar to yours, with real addresses and real case studies you can look into. Every council in London has its own quirks around planning, conservation areas, and what’s acceptable on a typical rear extension, so a company with genuine local experience in your specific area is worth more than one with an impressive but geographically scattered portfolio.
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Insist on a Proper Site Visit Before Any Pricing Discussion
Any company willing to give you a price, even a rough one, before actually visiting your property and seeing your garden, your boundaries, and your existing structure, is guessing. A proper first conversation involves someone walking the site, understanding how you actually use your home, and being upfront about what’s realistically achievable given your specific plot and your council’s track record with similar applications.
This is also the point where you find out whether a company is honest rather than simply telling you what you want to hear. If every idea you raise gets an enthusiastic yes with no caveats, that’s a red flag rather than reassurance.
Get Clarity on Planning Permission From the Start
Some single storey extensions fall under permitted development and don’t need full planning permission — others don’t, and it depends entirely on your property’s planning history and your borough’s specific rules. A company worth hiring should tell you clearly and early which situation applies to you, and roughly how long the process is likely to take if permission is needed. Vague reassurance without specifics (“don’t worry, we’ll sort it”) isn’t the same as an honest, informed answer.
Ask How Pricing Actually Works
This is where a lot of homeowners get caught out. Ask for an itemised, fixed quote covering structural work, professional fees, and finishes — not a rough estimate that’s likely to grow as “unforeseen issues” appear throughout the build. Genuine unforeseen issues do happen occasionally, especially with older properties, but they should be the exception a good company flags honestly, not a pattern built into how they price jobs from the outset.
Be particularly wary of the lowest quote among several you’ve collected. If one company comes in noticeably cheaper than the others for what’s supposedly the same project, ask specifically what’s included, because it’s rarely a genuine bargain — it’s usually something significant left out of the number.
Check How They Communicate During a Build
Ask what happens once construction actually starts. Will you have a single point of contact, or will you be chasing different people for different questions? A proper London design and build company should assign a dedicated project manager who knows exactly what stage your project is at and what’s happening next, rather than someone reading off a schedule they’ve never actually visited.
It’s also worth asking previous clients directly, if you can, whether communication held up through the middle of the build — that’s usually where less organised companies go quiet, once the exciting early stages are behind them and the finish line still feels a long way off.
Ask About Aftercare
A finished single storey extension isn’t just “the builders have left and taken the skip.” There should be a proper snagging process before the job’s called complete, and the company should still be reachable weeks or months later if something needs attention — a door that’s sticking, a tap that needs adjusting. Ask directly what aftercare looks like, because this is often where the difference between a good company and an average one becomes obvious, well after the invoice has been paid.
Trust Your Own Read of the Conversation
Beyond all the practical checks, pay attention to how honest and specific the answers actually feel. A company that’s confident enough to say “that particular idea probably won’t get planning permission on your street” or “that finish would push your budget up more than you’re expecting” is generally more trustworthy than one that agrees with everything you suggest. Straight answers, even when they’re not what you hoped to hear, are usually a good sign.
In Conclusion
Finding the right company for a single storey extension comes down to asking specific, practical questions rather than judging on marketing alone — genuine design and build integration, real local project history, honest planning advice, and fixed, transparent pricing. London Design & Build are happy to answer every one of these questions directly, and offer a free site visit to talk through what’s realistic for your specific property. Get in touch and judge us against exactly the standards laid out here
