Planning a House Extension? Here’s What You Need to Know Before You Start

A rear extension project built by Austen Dawson in Great Bedwyn. Designed by Milton Architects.

If you’re feeling squeezed for space but love your home and location, a house extension might be the perfect solution. Whether you’re dreaming of a light-filled kitchen-diner, a new home office, or an extra bedroom for a growing family, extending your property can add real comfort and value.

At Austen Dawson (Construction & Mechanical) Ltd, we specialise in helping homeowners across the Cotswolds, Oxfordshire, and Gloucestershire transform their homes with expertly planned and beautifully built extensions. Here’s what you need to know before you begin your project — and how to avoid the common pitfalls along the way.

1. Define Your Goals and Budget

Before you even start thinking about plans or builders, it’s important to clarify what you want to achieve.

• Are you extending for more living space, better flow, or to increase resale value?

• Is it a single-storey extension, double-storey, side-return, or a loft conversion?

• Will it need to include plumbing (e.g. for a bathroom or utility room)?

Once your goals are clear, it’s time to think about budget. Be realistic — building costs in the South West can vary based on design complexity, material choices, and ground conditions.

Tip: As quantity surveyors, we can help you develop an early-stage cost estimate based on typical square metre rates and local construction costs. We always recommend including a 10–15% contingency for unexpected items.

2. Understand Planning Permission Rules

Many house extensions fall under permitted development rights, meaning they don’t require formal planning permission — but that’s not always the case.

You’ll need planning permission if:

• Your extension exceeds height or size limits.

• Your home is in a conservation area (common across the Cotswolds).

• You’re altering the roofline significantly (e.g. for a dormer loft conversion).

• Your planned materials differ greatly from the existing house.

Each local authority (like Cotswold District Council or West Oxfordshire) has its own guidance. Building Control approval is separate and always required, regardless of whether planning permission is needed.

Tip: Our team can advise you on what’s needed and even handle planning submissions on your behalf, saving you time and stress.

3. Good Design Is Worth It

A well-designed extension not only adds space but enhances how you live in your home. That’s why working with a team who understand both design and build is a huge advantage.

Some key design decisions:

• How will natural light be brought in? Roof lights? Bi-folds?

• How will the new space connect with the rest of the house?

• What heating, insulation, and ventilation systems are suitable?

At Austen Dawson, we offer a full design & build service — meaning your project benefits from a cohesive team from initial concepts through to the final finish. This approach helps avoid disconnects between architects and builders, and keeps budgets and timelines in check.

4. Know What to Expect During the Build

Once planning and design are complete, the construction phase begins. Here’s a rough idea of what the process involves:

1. Site setup – fencing, skip placement, material deliveries

2. Groundworks – foundations, drainage, utilities

3. Structure – walls, floors, roof

4. First fix – electrics, plumbing, heating

5. Windows & doors – installation of openings

6. Second fix & finishes – plastering, tiling, flooring, decorating

7. Snagging & handover – final touches, client sign-off

Depending on complexity, a single-storey extension might take 10–14 weeks, while a two-storey project could take 16–20 weeks.

Tip: We provide all clients with a clear build programme and regular progress updates — so you always know what’s happening and when.

5. Prepare for Disruption

Let’s be honest: any major construction project brings a degree of mess and disruption. But good planning can help reduce the impact on your daily life.

• Consider how builders will access the site (side gates? through the house?).

• Think about where materials and skips will go.

• Will your kitchen or bathroom be out of action temporarily?

At Austen Dawson, we pride ourselves on professional, tidy sites and proactive communication. We’ll work with you to minimise disruption and keep your home secure and clean throughout the build.

6. Avoid Common Pitfalls

We often get called in to fix issues caused by poor planning or rushed decisions. Avoid these mistakes:

• Going for the cheapest quote — it usually means corners will be cut or extras will pile up later.

• Skipping due diligence — always check the contractor’s credentials, reviews, and previous work.

• Starting without proper plans or approvals — this can lead to costly delays or enforcement notices.

Tip: Ask for a detailed, itemised quote — not just a single lump sum. We provide fully broken-down quotes with all labour and material costs clearly explained.

7. Why Homeowners Trust Austen Dawson

As a local contractor with deep roots in the Cotswolds and surrounding counties, we bring a personal, hands-on approach to every project.

• Full design, build, and mechanical expertise in-house.

• Clear communication and transparent costs.

• Trusted by homeowners, architects, and developers alike.

• Exceptional craftsmanship and attention to detail.

Whether you’re planning a rear kitchen extension in Lechlade, a two-storey build in Cirencester, or a full house renovation in Oxfordshire, we’re here to guide you from start to finish.

8. Ready to Get Started?

If you’re thinking about extending your home, the first step is a conversation. We’ll listen to your ideas, assess your property, and offer honest, expert advice — no hard sell.

Contact us today for a free consultation and estimate.

Top 7 House Extension Ideas to Maximise Space and Value

Thinking about extending your home? Whether your family is growing, your layout no longer works, or you’re looking to add value before selling — a well-designed extension is one of the smartest investments a homeowner can make.

At Austen Dawson, we’ve helped countless homeowners across the Cotswolds and beyond transform their properties with thoughtful, high-quality extensions. In this post, we’ll share 7 of the most popular and effective house extension ideas — all designed to increase usable space and long-term property value.

1. Rear Kitchen & Family Room Extension

One of the most sought-after upgrades in UK homes, a rear extension creates a spacious, open-plan kitchen-diner and living area — often with bifold doors opening onto the garden. It’s perfect for modern family life and entertaining.

Why it works:

• Connects kitchen, dining, and living into one open, sociable space

• Brings in natural light with rooflights or full-width glazing

• Creates a stunning focal point and improves indoor-outdoor flow

Planning tip: Many rear extensions fall under permitted development, meaning planning permission may not be required — as long as you meet certain size and height limits.

2. Wraparound Extension

A wraparound extension combines a rear and side return extension, usually seen on Victorian and Edwardian homes. It turns underused side alley space into valuable square footage.

Benefits:

• Adds width and depth to your ground floor

• Ideal for relocating the kitchen and adding utility rooms or larders

• Can radically improve layout flow in older homes

Design idea: Consider using Crittall-style glazing, internal crittall partitions, or exposed steelwork to add architectural flair.

3. Two-Storey Rear Extension

Want more space upstairs as well as downstairs? A double-storey extension might be the answer. While it does cost more, the additional square footage can dramatically increase your home’s value.

Typical additions:

• A larger kitchen/family space downstairs

• An extra bedroom and en-suite or bathroom upstairs

• Walk-in wardrobes or a home office

Things to consider:

You’ll need full planning permission, and designs must consider privacy (overlooking neighbours), matching materials, and structural impact.

4. Side Return Extension

If your home has a narrow, underused side alley (common in older terraces and semis), a side return extension can widen your kitchen or living space without sacrificing garden depth.

Advantages:

• Makes the most of wasted side space

• Ideal for galley kitchens and narrow plots

• Great light potential with roof glazing and open-plan design

Planning insight: Side returns often fall under permitted development, but always check if you’re in a conservation area or listed building.

5. Loft Conversion with Dormer

While not a ground-floor extension, a loft conversion is one of the most cost-effective ways to add space — especially for growing families or home workers.

What you can create:

• A generous master suite with en-suite

• A light-filled home office or creative studio

• A guest room or teenage retreat

Dormer conversions offer the most usable space and can often be done under permitted development rules.

6. Garden Room or Home Office Pod

Since 2020, remote work has become the norm for many, and demand for detached garden buildings has surged. A fully insulated garden room or office pod can give you space away from the main house.

Use cases:

• Home office

• Gym or yoga studio

• Guest accommodation (with en-suite/shower)

Key points:

Garden buildings under 2.5m high and under 30m² typically don’t need planning permission — but still require careful construction and insulation to meet Building Regs if used year-round.

7. Garage Conversion

If your garage is currently unused or acting as a glorified storage unit, converting it into a habitable room is a low-cost way to gain usable space.

Popular uses:

• Utility or boot room

• Ground floor WC or shower room

• Home office or studio

• Playroom or snug

Bonus: You retain your garden and external footprint while unlocking internal space.

How Much Value Can an Extension Add?

The right extension, designed well and built to a high standard, can add 10%–25%+ to your property’s market value — especially if it improves layout, bedroom count, or kitchen space.

For example:

• A rear kitchen extension in a 3-bed semi could push the value up by £40,000–£70,000+

• A two-storey extension could move a house into a completely new price bracket

• A loft conversion can often add 1.5x–2x the build cost in value

Of course, this depends on local demand, build quality, and overall finish — but the returns can be substantial.

Need Help Planning Your Extension?

At Austen Dawson (Construction & Mechanical) Ltd, we offer full design and build services, including:

Advice on permitted development and planning

• Accurate cost estimates and budgeting

• Structural calculations and building control

• High-quality construction with a focus on detail and finish

Whether you’re planning a kitchen extension, loft conversion, or full house remodel — our experienced team is here to guide you from concept to completion.

Let’s talk about your project – Contact us today or call 01367 248417 or fill out the form below and we’ll get back to you.

The Biggest Mistakes Homeowners Make During Extension & Renovation Projects and How to Avoid Them

Renovating or extending your home is an exciting opportunity to create the space you’ve always wanted — but without the right planning and advice, things can quickly go off track. At Austen Dawson, we’ve seen first-hand the most common pitfalls homeowners face. Here are the biggest mistakes people make during renovations — and how to avoid them.

1. Underestimating the Budget

The Mistake: Many homeowners plan for ideal costs without factoring in hidden issues, material increases, or design changes.

The Fix: Always build a 10–15% contingency into your renovation budget. Work with a quantity surveyor early to cost up different design options and understand what’s realistic.

2. Not Getting the Right Permissions

The Mistake: Starting work without checking whether planning permission or Building Regulations approval is needed.

The Fix: Speak to your local authority or hire a company that handles this for you. Even permitted development has rules — especially for rear extensions, lofts, or conservation areas.

3. Rushing the Design Phase

The Mistake: Jumping into construction before finalising design and specification details leads to delays, cost overruns, and rework.

The Fix: Take the time to work through a clear brief, drawings, and a specification schedule with your architect or design-and-build team. Good planning saves time and money.

4. Hiring Based on Price Alone

The Mistake: Going with the cheapest builder without checking their experience, past work, or insurance cover.

The Fix: Choose a reputable builder with relevant experience in extensions or renovations — ideally one who can show you previous projects and offer detailed estimates.

5. Trying to Project Manage Alone

The Mistake: Taking on the management of trades, schedules, deliveries, and inspections without experience often leads to chaos.

The Fix: Hire a professional project manager or work with a design-and-build firm who handles everything from planning through to handover.

6. Not Considering How You’ll Live During the Works

The Mistake: Staying in the house during messy and noisy works can be incredibly disruptive.

The Fix: If your renovation or extension is major, plan for temporary accommodation or create a clear living zone with your builder that minimises disruption.

7. Ignoring Energy Efficiency and Long-Term Value

The Mistake: Focusing only on short-term aesthetics without considering insulation, lighting, or heating systems.

The Fix: Use the renovation or extension as an opportunity to upgrade your home’s energy performance — which saves money and adds resale value.

Final Thoughts

Renovating or extending your home doesn’t have to be stressful. With the right team, planning, and advice, it can be one of the best investments you ever make. If you’re planning a home extension or renovation, get in touch with the team at Austen Dawson— we’re here to make it straightforward, high-quality, and hassle-free.

The Biggest Mistakes Homeowners Make During Extension & Renovation Projects and How to Avoid Them

Renovating or extending your home is an exciting opportunity to create the space you’ve always wanted — but without the right planning and advice, things can quickly go off track. At Austen Dawson, we’ve seen first-hand the most common pitfalls homeowners face. Here are the biggest mistakes people make during renovations — and how to avoid them.

1. Underestimating the Budget

The Mistake: Many homeowners plan for ideal costs without factoring in hidden issues, material increases, or design changes.

The Fix: Always build a 10–15% contingency into your renovation budget. Work with a quantity surveyor early to cost up different design options and understand what’s realistic.

2. Not Getting the Right Permissions

The Mistake: Starting work without checking whether planning permission or Building Regulations approval is needed.

The Fix: Speak to your local authority or hire a company that handles this for you. Even permitted development has rules — especially for rear extensions, lofts, or conservation areas.

3. Rushing the Design Phase

The Mistake: Jumping into construction before finalising design and specification details leads to delays, cost overruns, and rework.

The Fix: Take the time to work through a clear brief, drawings, and a specification schedule with your architect or design-and-build team. Good planning saves time and money.

4. Hiring Based on Price Alone

The Mistake: Going with the cheapest builder without checking their experience, past work, or insurance cover.

The Fix: Choose a reputable builder with relevant experience in extensions or renovations — ideally one who can show you previous projects and offer detailed estimates.

5. Trying to Project Manage Alone

The Mistake: Taking on the management of trades, schedules, deliveries, and inspections without experience often leads to chaos.

The Fix: Hire a professional project manager or work with a design-and-build firm who handles everything from planning through to handover.

6. Not Considering How You’ll Live During the Works

The Mistake: Staying in the house during messy and noisy works can be incredibly disruptive.

The Fix: If your renovation or extension is major, plan for temporary accommodation or create a clear living zone with your builder that minimises disruption.

7. Ignoring Energy Efficiency and Long-Term Value

The Mistake: Focusing only on short-term aesthetics without considering insulation, lighting, or heating systems.

The Fix: Use the renovation or extension as an opportunity to upgrade your home’s energy performance — which saves money and adds resale value.

Final Thoughts

Renovating or extending your home doesn’t have to be stressful. With the right team, planning, and advice, it can be one of the best investments you ever make. If you’re planning a home extension or renovation, get in touch with the team at Austen Dawson— we’re here to make it straightforward, high-quality, and hassle-free.

How AI is Transforming the Architectural and Construction Industries – What It Means for Your Home Extension Project

An AI generated image of a rear extension.

The construction industry is on the brink of a technological revolution, and artificial intelligence (AI) is leading the charge. From planning and design to project management and on-site operations, AI is streamlining processes, improving accuracy, and enhancing outcomes across every stage of the build.

At Austen Dawson, we’re always looking ahead – adopting modern technologies to deliver the highest standards in building. As a Cotswolds-based builder specialising in house extensions, renovations and bespoke new builds, we understand that our clients expect both quality craftsmanship and forward-thinking solutions.

So, what exactly does AI mean for construction and architectural services in the UK? And how will it affect your next home extension project in areas like Lechlade-on-Thames, Cirencester, Burford, and the wider Cotswolds?

Let’s explore how artificial intelligence is helping to shape the future of construction – and why it matters for you.

What Is AI and Why Is It Relevant to Construction?

Artificial intelligence refers to a range of technologies that allow machines to learn from data, make decisions, and automate tasks. In construction, this can mean:

• Predicting costs and timelines more accurately

• Identifying design issues before building begins

• Managing on-site logistics more efficiently

• Enhancing collaboration between teams

• Reducing waste and environmental impact

AI isn’t about replacing people. Instead, it’s about giving experienced builders, designers, and quantity surveyors like us at Austen Dawson the tools to work smarter, safer, and more cost-effectively.

1. Smarter Design with AI-Powered Architecture Tools

In the design phase of a house extension or loft conversion, AI is proving to be a game-changer. Tools like generative design software and intelligent 3D modelling use machine learning to explore a wider range of layout options based on your goals – whether that’s maximising light, improving flow, or increasing energy efficiency.

These tools can:

• Rapidly generate multiple design concepts

• Simulate how natural light will move through your space

• Spot planning or compliance issues early

• Reduce time spent in the design phase

By integrating AI into the architectural workflow, designers can present clients with more options – and refine those designs faster. That means fewer delays and a smoother journey from concept to construction.

At Austen Dawson, we work closely with architects who embrace this technology to bring our clients cutting-edge, buildable designs that meet both aesthetic and practical needs.

2. Improved Project Planning and Cost Estimating

One of the most common concerns when planning a house extension is cost. AI helps here too – especially in the realm of quantity surveying and cost management, where it can:

• Analyse data from similar projects to generate more accurate estimates

• Flag cost overruns before they occur

• Automatically track material and labour costs in real-time

• Provide better budget control from start to finish

As an experienced builder in the Cotswolds, our quantity surveying team at Austen Dawson is already using AI-assisted tools to improve forecasting accuracy and ensure clients stay informed at every stage.

Whether it’s a kitchen extension in Bibury or a double-storey addition in Fairford, AI allows us to give more confidence in both budgeting and scheduling.

An internal image generated by AI.

3. Enhancing On-Site Safety and Efficiency

Construction sites are complex environments, with many moving parts and potential risks. AI is increasingly being used to enhance safety and logistics through:

• AI-powered cameras and sensors that detect hazards

• Drones that survey sites and track progress

• Predictive models that prevent accidents

• Smart scheduling tools that optimise daily workflows

This is particularly useful in projects involving renovations and extensions, where existing structures may present unique challenges.

By using AI to monitor real-time conditions and streamline operations, we’re able to deliver safer, faster, and more efficient results – minimising disruption to you and your family during the build.

4. Sustainable Building Through AI

Sustainability is at the heart of modern construction – and AI plays a major role in reducing environmental impact.

With AI, builders can:

• Optimise material usage to reduce waste

• Design energy-efficient heating, lighting, and insulation systems

• Choose low-carbon materials based on lifecycle data

• Simulate energy performance before construction begins

At Austen Dawson, we take a sustainable approach to every project. Whether we’re specifying mechanical systems, installing smart heating, or designing passive energy features, we’re using AI-backed insights to reduce your home’s carbon footprint without compromising comfort or style.

This is especially important in the Cotswolds, where preserving natural beauty and heritage is part of every build.

5. Better Communication and Collaboration

AI-powered platforms are also improving communication between homeowners, architects, engineers, and contractors. These platforms help everyone stay aligned and informed, with benefits including:

• Centralised access to updated plans and documents

• Automated task tracking and scheduling

• Instant updates on progress or delays

• Transparent reporting for peace of mind

When you choose Austen Dawson for your house extension, you’re choosing a team that values clear communication – and uses the latest tools to keep your project on track.

6. AI and Smart Homes: Designing for the Future

As smart homes become more popular, AI is helping to design and integrate intelligent systems from day one. This includes:

• Smart lighting, heating and security systems

• AI-enabled ventilation and mechanical systems

• Voice-activated or app-controlled appliances

• Home energy management tools

When we design and build your extension or loft conversion, we can incorporate these technologies seamlessly. The result is a home that’s not only beautiful and functional – but also future-ready.

What Does This Mean for You?

If you’re planning a house extension in the near future, you might be wondering – how does all this innovation benefit you, the homeowner?

Here’s what you can expect when working with a modern, tech-aware builder like Austen Dawson:

• Faster design and approvals – AI speeds up the early phases, helping you get started sooner.

• More accurate budgeting – Predictive modelling and cost tracking reduce surprises.

• A higher quality finish – Intelligent tools support better design, planning and execution.

• Reduced disruption – Streamlined logistics mean fewer delays and a smoother build.

• Sustainable results – AI helps us build greener, more energy-efficient homes.

AI may sound futuristic, but the benefits are already here – and we’re using them to deliver even better outcomes for our clients.

Why Choose Austen Dawson for Your Next Home Project?

We’re more than just a local builder. At Austen Dawson (Construction & Mechanical) Limited, we combine traditional craftsmanship with modern innovation. Based in Lechlade-on-Thames, we serve clients across the Cotswolds who want beautifully designed and expertly delivered:

• House extensions

• Renovations

• Loft conversions

• New builds

Our team brings together skilled builders, experienced project managers, and in-house quantity surveyors who use data-driven tools and AI-assisted insights to make your dream home a reality.

Whether you’re extending your kitchen, creating an open-plan living space, or building upwards with a loft conversion, we bring precision, reliability, and future-focused thinking to every project.

Final Thoughts: Embracing the Future of Construction

The construction industry is evolving – and artificial intelligence is becoming a vital part of that journey. For homeowners in the Cotswolds, that means more efficient projects, better value for money, and smarter, more sustainable homes.

At Austen Dawson, we’re proud to be part of this transformation. We’re investing in technology, refining our processes, and continually improving how we deliver for our clients.

If you’re planning a home extension or renovation and want a builder who blends craftsmanship with innovation – get in touch with us today.