The 3 most common worries for people starting a home extension - backed by real homeowner data

Thinking about a home extension is exciting - more space, more light, more value. But before the drawings or builders arrive, almost everyone goes through the same three worries. These aren't theoretical fears - they come up again and again in homeowner surveys, online forums, Facebook groups and renovation communities across the UK.

If you've felt any (or all!) of these, you're not alone. Below, we break down why these worries are so common and what you can do to stay in control from day one.

Worry 1: "I'm worried the costs will spiral out of control."

For many homeowners, the biggest fear when starting an extension is that the cost will run away from them - and the data shows this isn't unfounded.

According to the 2025 Houzz UK & Home Report, renovation spending in the UK varies far more than most people expect. The median spend sits at £21,440, which already represents a significant investment for many households. But the real eye-opener is how steeply costs can climb at the upper end.

What's causing costs to spiral?

One of the biggest reasons extension budgets rise is the lack of clarity at the very beginning of the project. Many homeowners receive quotes that look straightforward but are missing key details such as scaffolding, waste removal, foundations, insulation upgrades or decorating. When these items appear later, the overall cost increases - not because anyone did anything wrong, but because the original quote didn't include the full picture. This makes it easy for a project that seemed affordable on paper to edge gradually beyond the planned budget.

Costs also rise because small decisions made during the build can have large financial consequences. Upgrading windows, choosing a different door style, moving internal walls or making last-minute layout adjustments all add time and materials. These changes often feel minor in the moment but accumulate quickly. Structural surprises contribute too: once floors are lifted or walls opened, builders often uncover issues such as damp, drainage problems, rotten timber or inadequate insulation - all of which need to be addressed for the extension to meet regulations.

There's also a wider market context that homeowners feel but don't always see directly. Material costs have increased significantly in recent years and labour shortages mean many builders have raised their prices simply to keep up with demand - something reflected in industry surveys. When a project takes several months, these cost increases can affect the budget even after work has begun. Add regional price differences into the mix and two seemingly identical extensions can end up costing very different amounts depending on where the homeowner lives.

Together, these factors create an environment where costs can escalate even when the homeowner is careful. It doesn't mean the project was mismanaged - it means extensions are complex, with many moving parts and each one carries a degree of uncertainty that needs to be planned for from the start.

What you can do to stay in control

The best way to prevent your extension costs from spiralling is to remove uncertainty before the build even begins. That starts with having a clear, realistic understanding of what your project is likely to cost in your area.

When homeowners go in with only a rough idea of pricing, they're far more vulnerable to vague quotes, unexpected add-ons and last-minute decisions that inflate the budget.

By contrast, when you begin with robust cost expectations, you're able to plan properly, set a realistic contingency and avoid being blindsided by items that weren't included in the initial quote.

Tools like Planning to Build are designed specifically to give you this clarity from day one. By understanding the full price of your extension - including typical regional labour rates, material costs and all the elements that often get missed in early builder conversations - you can budget confidently and negotiate from a position of strength.

This knowledge helps you compare quotes on a like-for-like basis, challenge unclear pricing and make informed choices about where to save and where to invest. In short, the more you understand upfront, the easier it is to keep your project on track and your finances under control.

Worry 2: "I'm worried planning permission will be complicated or rejected.

Many homeowners feel anxious about planning permission and with good reason. UK planning rules are complicated, inconsistent between councils and full of exceptions that aren't always obvious at the start of a project. Even straightforward extensions can hit unexpected delays if something isn't submitted correctly or falls foul of a local restriction.

Planning is one of the most commonly misunderstood parts of extending a home. Homeowners often discover too late that their property sits in a conservation area, has an Article 4 direction, or requires more documentation than they realised. Even under Permitted Development, rules about height, depth, eaves, materials and boundaries are tightly defined - and easy to get wrong.

What causes planning problems

One of the biggest causes of planning complications is simply not knowing which rules apply to your home. Conservation areas, Article 4 directions, flood zones, protected trees, overlooking constraints, height limits and boundary rules all affect what can be built - but they aren't always obvious without research.

Another common issue is incomplete or inaccurate submissions. Councils regularly reject applications because drawings don't show correct measurements, elevations lack detail, or supporting documents such as location plans, heritage statements, or neighbour impact assessments are missing. Even small errors can reset the clock on a project.

Council interpretation also varies. Two homeowners in different local authorities can submit almost identical extensions and receive completely different outcomes, depending on local policy, design guidance, or even neighbourhood context.

What you can do

The most effective way to reduce planning stress is to understand your property's constraints before you do anything else. Knowing whether you're in a conservation area, subject to Article 4, or within specific boundary or height limits helps you design a proposal that is far more likely to be approved.

This is where Planning to Build plays a crucial role. By checking your postcode and highlighting relevant restrictions upfront - such as conservation areas, flood zones, listed status and PD limitations - you can make informed decisions early and avoid costly redesigns later. With the right knowledge, you can brief your designer properly, manage expectations and submit an application with a far higher chance of success.

From there, providing accurate drawings, supplying all required documents and understanding the local design guidelines will help prevent unnecessary delays. A clear, complete and compliant submission gives you the best possible chance of getting planning permission approved the first time around.

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Worry 3: "I'm worried about choosing the wrong builder."

For most homeowners, choosing a builder is the part of an extension that feels riskiest. A build is expensive, disruptive and emotionally significant - and once the work begins, you're committed. It's completely understandable that people worry about picking a builder who may deliver poor workmanship, exceed the budget, delay the project, or disappear altogether.

Builder selection is one of the most commonly cited sources of stress in UK renovation forums and consumer surveys. The quality of your builder has a bigger impact on cost, timeline and overall experience than almost any other factor. Homeowners often feel unprepared to judge whether a quote is fair, whether a builder's experience is suitable, or what should be included in a contract.

What causes these problems

One of the biggest issues is the lack of standardisation in quotes. Two builders might quote the same job but include completely different things - some will include scaffolding, waste removal, insulation upgrades or plastering, while others won't. Homeowners then pick a builder based on a price that doesn't reflect the full cost.

Another major cause is poor communication or unclear expectations. If the scope isn't defined before work begins, the builder is left to make assumptions and homeowners often assume more is included than actually is. Add in the fact that many homeowners only undertake one major project in their lifetime and it becomes clear why the process feels unpredictable.

Finally, some issues arise simply because homeowners don't know what to ask: about timelines, payment schedules, materials, insurance, disputes, or references. Without a clear framework, it's easy to overlook important checks.

What you can do

The best way to choose the right builder is to start with clarity. That means understanding the full cost of your project and the elements that should appear in a detailed quote. When you know what your extension should cost - including typical allowances for labour, materials, preliminaries and contingencies - you're in a far stronger position to compare builders fairly.

This is where Planning to Build supports homeowners. By giving you a realistic estimate of costs for your extension type and region, you can identify quotes that are unusually low (a warning sign) or unusually high and you can challenge missing or unclear pricing. Clear expectations lead to clearer conversations with builders - about what's included, what isn't, how long the work should take and how payments should be staged.

From there, always request itemised quotes, check references and previous work and agree on a written contract that outlines scope, timeline and payment milestones. With the right preparation, choosing a builder becomes far less intimidating - and far more about making a confident, informed decision.

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Starting a home extension is a big step, and it's completely normal to feel worried about costs, planning permission, or choosing the right builder. These aren't abstract fears - they're grounded in real homeowner experiences, data and the complexities of the UK planning and building system. But the good news is that each of these worries becomes far more manageable when you replace uncertainty with clarity. The more you understand upfront, the fewer surprises you'll face later.

With the right preparation, you can take control of your project from the very beginning. That means knowing what your extension should cost, understanding the planning rules that apply to your property, and being able to compare builder quotes confidently and fairly. Tools like Planning to Build exist to make those early decisions simpler and more informed, so you can move forward feeling prepared rather than overwhelmed. When you start with knowledge, you start with confidence - and that's the foundation of a successful extension.