Avoiding Costly Mistakes When Planning a Property Extension

Planning a property extension is thrilling, but it can quickly spiral into a budget-busting nightmare if you're not careful. Whether you're considering a home extension, a dreamy kitchen extension or even a bespoke conservatory, there's a lot to juggle before swinging a hammer. Below, we've outlined the most common pitfalls and how you - working with trusted building contractors like Christie's Carpentry & Construction in Guildford - can dodge them.

1. Skipping Planning Permission (or Getting it Wrong!)

It's tempting to dive into work, especially if it all seems straightforward. But different types of extensions carry different permissions. For instance, a modest kitchen extension might fall under "permitted development," but you still need to check out height, footprint and neighbour impact limits.

On the other hand, larger property extensions and bespoke conservatories often do need full planning permission, and getting it wrong can lead to enforced removal or expensive reworks.

What to do:

●      Always check with Guildford Borough Council and/or hire a prep-savvy surveyor.

●      Get your building contractors (like Christie's) to guide you; we’ve handled the red tape many times before!

●      Factor planning fees and application time (usually 8–13 weeks) into your timeline.

2. Under-Budgeting

A council-approved design is just one cost in the process. A modest home extension can balloon if you're not thorough - think materials, labour, scaffolding, VAT, insulation, electrics, plumbing…

Relying on the first quote you receive is also risky. Every contractor interprets scope differently.

What to do:

●      Ask for at least three detailed quotes, covering everything from groundwork and carpentry to joinery and decoration.

●      Include a 10–15% contingency for surprises (like rotten joists or poor soil).

●      Use Christie's experience to get transparent costs and avoid hidden extras.

3. Overlooking Design Practicalities

Visions of lofty ceilings and grand conservatories are tempting, but are they realistic?

Common design oversights include:

●      Poor flow between old and new spaces.

●      Insufficient structural support for your ideas.

●      Conservatories that end up too cold in winter, too hot in summer.

What to do:

●      Work with architects or structural engineers where needed.

●      Get your building contractors involved early—they can help you balance wow-factor with reality and value.

●      Consider hiring a specialist for bespoke solutions like a bespoke conservatory to ensure thermally efficient glazing.

4. Choosing Materials by Price Alone

Cutting costs on materials might seem smart at first, but cheap insulation, second-rate windows or low-grade timber can compromise longevity and energy efficiency.

What to do:

●      Insist on quality: double- or triple-glazed windows, recommended roofing membranes and eco-friendly insulation.

●      Talk material longevity as those composite doors and hardwood floors pay off over time.

●      Christie's locally sourced timber and time-tested suppliers mean they can strike that sweet spot between cost and quality.

5. Ignoring Phases & Timeline Management

A kitchen extension means you might be without your kitchen for weeks. Underestimating this can cause household chaos.

What to do:

●      Map out project phases: demolition, foundations, structure, roofing, interior fit-out.

●      Allow for tradesmen availability, e.g. electrics after plastering.

●      Ask Christie's team to produce a Gantt-style schedule so you know exactly when things will happen (and when to prepare dinner elsewhere!).

6. Skimping on Communication

A major home extension involves countless subcontractors - plumbers, joiners, plasterers, roofers, electricians. This means that miscommunication is guaranteed chaos.

What to do:

●      Choose a building contractor who provides a single point of contact (like Iain at Christie's).

●      Regular updates and open lines of communication reduce mistakes and stress.

●      Weekly check-ins - live feedback saves future cost and time overruns.

7. Underestimating Health & Safety

Construction isn’t glamorous. It’s loud, dusty and potentially dangerous.

What to do:

●      Make sure your building contractors follow regulations and are insured (Christie’s is FMB and Guild of Master Craftsmen accredited, meaning full public liability, employer’s liability and compliance).

●      Create safe walkways, ventilation and consider dust-sealing zones.

●      Book a final site clean and inspection before moving in.

8. Forgetting Future-Proofing

Extending your home isn’t just about present enjoyment, it can also be about future resale value (or making space for a growing family).

What to do:

●      Think about insulation, solar panels and energy efficiency from Day 1.

●      Include USB sockets, home office space, wheelchair accessibility if relevant.

●      A well-planned property extension, like a bespoke conservatory, can enhance resale value - but only if built to last.

9. Overlooking Legal & Neighbour Agreements

Particularly in semi-detached or terraced homes in Guildford, overlooking party walls and neighbour approvals can backfire.

What to do:

●      If close to a boundary, serve Party Wall notices well in advance.

●      Keep neighbours informed and offer courtesy measures (like dust-sheets).

●      Christie's team is famed on Checkatrade for neighbour diplomacy, saving you potential disputes.

Why Christie's Should Be Your First Port of Call

Christie’s Carpentry & Construction has been delivering trusted builds across Guildford since 2010. We offer a full turnkey solution - from property extensions and kitchen extensions to loft conversions and bespoke conservatories - so you don’t need to manage multiple trades . Chuck in our FMB/Guild of Master Craftsmen/Checkatrade accreditations, and we’re a safe pair of hands! When you work with us, you get a single integrated team, a transparent schedule, quality materials and a single point of contact.

Ready to Build Without the Headaches?

Don’t let your dream property extension turn into a costly regret. Chat to the team at Christie's Carpentry & Construction today for expert advice, quotes you can trust and projects delivered on time and within budget. Give us a ring on 01483 608100 or email sales@christiescc.co.uk - you’ll soon wonder why you didn’t call sooner!