House Extensions In Essex
Planning a house extension in Essex? Belvia Construction designs and builds single-storey, double-storey, side, rear, and wrap-around extensions for homeowners across Chelmsford, Colchester, Brentwood, Southend-on-Sea, and surrounding areas. With over 20 years of experience and a fixed price guarantee, we manage every stage, from planning applications through to final handover, so you get the extra space your family needs without the stress.
Fully Insured20+ Years ExperienceFree Quotes
Experienced House Extension Builders in Essex
Quality · Experience · Trust
As one of Essex’s established house extension companies, we specialise in high-quality residential extensions that add real living space and long-term value to your property. Whether you need a rear kitchen extension, an extra bedroom above with a double-storey build, or a full wrap-around redesign, our team handles the structural engineering, Building Control liaison, drainage, electrics, and finishing, end to end.
Two decades on site means we’ve seen the pitfalls that derail timelines and budgets, and we’ve built the systems, supply chains and standards to avoid them.
We handle everything end-to-end – surveys, structural engineering, Building Control liaison, and fully compliant plumbing and electrics via Gas Safe and NICEIC partners – so you don’t have to juggle multiple contractors or carry the risk. You get a single point of contact who manages scope, schedule and spend, keeps you updated weekly with photos and progress notes, and signs off each stage with you before we move on.
We’ve completed over 25 extension projects across Essex, and every one was delivered on a fixed price with no hidden extras.
Peace of Mind
Our on-site quality control manager oversees all operations and you sign off at every stage before we move on to the next.
Stress Free Process
Getting a house extension shouldn’t be stressful. We manage every step, from planning and design to construction and finishing.
Built to Last
We use high-quality materials and trusted construction techniques to deliver durable and stylish extensions that stand the test of time.
Our Specialities
Types of House Extensions We Build
Every property is different. We tailor our single-storey, double-storey, side, rear and wrap-around extensions to your home, budget style, and planning constraints.
Single-Storey Extensions
From £2,250 +VAT per m²Ideal for creating open-plan living areas, extending kitchens, or adding additional ground-floor living space. Single-storey extensions are perfect for homeowners who need extra space without dramatically altering the property’s structure.
- End-to-end project management
- Structural openings (RSJs/goalposts) to spec
- First & second fix: electrics, plumbing, plaster, finishes
Double-Storey Extensions
From £4,500 +VAT per m²Add substantial living space across two floors. Double-storey extensions are perfect for growing families, offering the opportunity to add additional bedrooms, bathrooms, or even home offices.
- Planning & Building Control coordination
- Engineered structure with verified load paths
- Can add kitchens, bathrooms, living spaces with end-to-end finishing.
Wrap-Around Extensions
Single from £2,750 · Double from £5,500 +VAT per m².Maximise your space with a wrap-around extension, combining both side and rear expansions. This type of extension offers ultimate flexibility and is often used to create large open-plan kitchens with dining areas or multi-functional spaces.
- Daylight strategy (rooflights/lanterns/sliders)
- Drainage reroutes & thresholds detailed flush where feasible
- UFH, upgraded electrics, tested and certified
Side and Rear Extensions
From £2,250 +VAT per m² (single storey)Perfect for semi-detached and detached homes, side and rear extensions make the most of unused garden or side return space. These extensions are ideal for adding light-filled rooms without the need for a larger footprint.
- Daylight strategy (rooflights/lanterns/sliders)
- Drainage reroutes & thresholds detailed flush where feasible#
- UFH, upgraded electrics, tested and certified
Kitchen Extensions
From £3,000 +VAT (install only)Our kitchen extensions combine structural expertise and high-quality kitchen installation, giving you one seamless project from foundations to finished cabinetry.
Whether you’re extending to the rear, side, or creating a wrap-around kitchen-diner, we manage the full build and fit-out, including structural steel, glazing, insulation, services, and final finishes, so your new kitchen feels fully integrated with your home.
What we Deliver
Rear, side & wrap-around kitchen extensions
Structural alterations with RSJs & Building Control sign-off
Foundations, shell, glazing & insulation
Full kitchen fit-out incl. plumbing, electrics & ventilation
Ready for cabinetry, appliances & lighting
Loft Conversions
Starting from £45k + VATWe offer a range of loft conversion options perfect for situations where a complete extension isn’t possible or is working out too expensive. Whether you’re looking for dormer, hip-to-gable, or a full roof construction, we can help. Our loft conversions include:
- Steel beam installation to support the new structure
- Structural alterations to extend the roof if needed
- New staircase if required
- Plumbing and fitting for en-suite if required
- Velux or dormer windows for natural light
- New gable wall construction (matching existing materials)
- Roof tile reinstatement
- Windows, insulation, and full internal fit-out
Happy Customers Across Essex
We're committed to delivering exceptional customer service and we're proud to showcase our client testimonials.
Rating
Chris Warwick
November 4, 2025
James and his team at Belvia were responsible for overseeing a refurbishment of our main family bathroom. This is the second time we’ve had Belvia in our home, previously it was for a rear extension of our property some 5 years ago.Whilst this project is nowhere near the size of our first with James, the attention to detail and communication level was second to none. Belvia combined multiple trades to ensure a smooth transition as the project progressed and we couldn’t be happier with the finished product.Couldn’t recommend enough.Chris Warwick
Norman Lee
November 4, 2025
We would be very confident about recommending Belvia construction to anyone planning a building or renovation project. James has been extremely helpful throughout. The team are conscientious and hard working . The standard of work is very high. Comments from neighbours were that the team were polite and considerate. Belvia Construction have made this project as stress as free as possible.
Linda Morss
October 11, 2024
So impressed with Belvia construction,we moved to a property that needed new kitchen, bathroom and en suite. James gave great advice with the planning of the works. All work was done to a very high standard from stripping the rooms back,moving door frames and walls to the fitting of new kitchen,bathroom suite and en suite also new unvented hot water cylinder/system and flooring throughout. A big shout out to the lads Ryan,Ellis,Barry,John Jo and Ryan (sorry if forgotten anyone) very reliable and friendly team and hard working and did an amazing job. I would highly recommend Belvia construction if you want an excellent job done. We will definitely be using this company again for future plans for our property.
Drew Whiting
September 15, 2024
Belvia installed the trade counter at our new Branch in Colchester. Worked with us to design an install that suited the new showroom and was cost effective for the project. During the install James worked with other contractors on site seamlessly and in a clean and tidy manor.Would recommend.
Cathy McGrath
June 12, 2024
Outstanding 5 star building services from Belvia Construction.From the start Jim gave us total confidence that Belvia were an incredibly professional and capable building company. They always arrived when they promised, they left everything tidy, the lads (Ryan, Ellis & Luke) were very polite and knew exactly what they were doing. Every aspect of the build was undertaken with the highest level of quality. Things we mentioned early on in the process were remembered and implemented exactly as we required. Our friend (also a builder) visited and was really impressed with the finish, which is no mean feat.We are overwhelmed with the final result - it is even better than we expected and there is nothing we would change. We would 100% recommend Belvia Construction. Many thanks to Jim and the team.
anthony carlyle
February 7, 2024
Had a patio, new composite fencing, garage conversion and internal work including a walk-in wardrobe. The Belvia team were professional and courteous the whole time, turned up when they said they would and took a real pride in their work, which looked superb at the end. Many thanks to James and his team for the finished results, we would highly recommend them.
MELLANIE POTTER
December 1, 2023
James and his team made a fantastic job of our bathroom and garage refit. James kept us updated on all aspects, and what was going to happen each day. Whenever I messaged him he replied straight away. The quality of work he provides is outstanding and all of his team are first class tradesmen. I would have no hesitation in recommending Belvia Construction, and we will definitely be using them again.
Julia Chisholm
May 23, 2023
Great service and great quality. We would definitely recommend Belvia. James made the whole process simple and stress free. Always very helpful answering questions and making suggestions. James and his team are very polite, tidy workers and finished the project to a high standard. We’re over the moon with the final result.
Sam Greenhalgh
May 15, 2023
Excellent from start to finish Very professional and extremely high-quality of work will use them again and would highly recommend
David Elwick
May 5, 2023
We were recommended to James, after looking for a reliable builder .He is one of a kind who actually does what he says , on time , with care, and with a pride in his work.From initial contact, to quote, to agreeing a start date and then completing the works ( on time) he gave an excellent service and we would highly recommend him and his company for your construction projects large or small.We look forward to using him again on our next projectThanks James to you and your teamRegards Michele & David.
Felicity Collingwood
March 16, 2023
James and the whole team at Belvia are first class - super helpful , super responsive and amazing attention to detail and quality workmanship ! We have used many builders in the past and would not use another now - we wouldn’t hesitate to recommend Belvia to anyone that needs work big or small! A great company all round!!
Frances R
September 4, 2022
Belvia just completed a full kitchen/utility/dining room re-fit for us and we are absolutely delighted with the results! The team was professional, well organised, respectful, friendly and always left things tidy at the end of the day. James kept us fully informed throughout and oversaw everything closely even when he was not onsite himself. Excellent job all round and we would not hesitate in recommending Belvia!
Transparent Pricing
How Much Does a House Extension Cost in Essex?
House extension costs in Essex depend on the type of build, the size in square metres, and the level of structural and finishing work involved. Below is a guide based on our recent project pricing across Chelmsford, Colchester, Brentwood, and surrounding areas.
House Extension Cost Guide (2026/27 Prices)
| Extension Type | Price Per m² (+ VAT) | Typical Project Cost |
|---|---|---|
| Single-storey rear extension | From £2,250 | £30,000 – £65,000 |
| Side return extension | From £2,250 | £25,000 – £55,000 |
| Single-storey wrap-around | From £2,750 | £50,000 – £90,000 |
| Double-storey extension | From £4,500 | £80,000 – £160,000 |
| Double-storey wrap-around | From £5,500 | £120,000 – £200,000+ |
| Kitchen extension (build + fit-out) | From £3,000 (install only) | £40,000 – £80,000 |
These figures cover the construction build itself. Final costs vary based on your property's specific requirements - we provide a fixed-price quotation after surveying your home, so there are no surprises once work begins.
What Affects the Cost of a House Extension?
Several factors influence the final price of an extension project in Essex:
- Size and footprint – Larger extensions require more materials, deeper foundations, and longer build times.
- Structural complexity – Wide structural openings (RSJs/steel goalposts), load-bearing wall removals, and underpinning work add cost.
- Number of storeys – Double-storey builds need engineered load paths, additional scaffolding, and more extensive Building Control involvement.
- Ground conditions – Properties on clay soil (common across Essex) may require deeper or reinforced foundations.
- Drainage and services – Rerouting existing drains, upgrading electrics, or installing underfloor heating increases the scope.
- Finishes and specification – Higher-spec glazing (bi-fold doors, roof lanterns), premium flooring, and bespoke joinery affect the final figure.
- Access – Restricted site access for machinery or materials delivery can affect logistics and timelines.
What’s Included in Our Extension Pricing
Every Belvia Construction quote covers the full build scope so you can compare like for like:
- Foundations, structural shell, and roofing
- Structural steelwork and Building Control applications
- Windows, doors, and glazing to your specification
- First and second fix electrics (NICEIC certified)
- First and second fix plumbing (Gas Safe registered partners)
- Plastering, decoration preparation, and internal finishes
- Drainage connections and reroutes where required
- Waste removal and site management throughout
Items such as kitchen units, bathroom suites, and bespoke joinery are quoted separately based on your selections. We’re happy to guide you through specification choices at the design stage.
Want an accurate figure for your project? Get a free, no-obligation quote – we’ll survey your property and provide a fixed-price breakdown.
Want an accurate figure for your project?
We'll survey your property and provide a fixed-price breakdown.
Planning Permission & Building Regulations for Extensions in Essex
Know Before You Build
One of the most common questions homeowners ask before starting an extension project is whether they need planning permission. In many cases, single-storey rear and side extensions in Essex can be built under Permitted Development rights – meaning no formal planning application is needed, provided the build stays within set limits on size, height, and materials.
However, planning permission is typically required for double-storey extensions, front extensions, wrap-around builds that exceed PD limits, properties in conservation areas, listed buildings, and homes where Permitted Development rights have been removed (which is common on newer housing estates across Essex).
Regardless of whether planning permission is needed, Building Regulations approval is always required. This covers structural safety, fire resistance, insulation, drainage, and electrical compliance. We handle the full Building Control process on your behalf, including applications, inspections, and final sign-off.
Every Essex district council from Chelmsford City Council to Basildon, Colchester, Brentwood, Castle Point, and Rochford has its own planning team and processing timelines. We know the local requirements and can advise you on the right route for your property before any work begins.
House Extension Builders Across Essex
Local Expertise
We build house extensions across Essex, from urban areas like Chelmsford and Southend-on-Sea to market towns and villages across the county. Our team is based in Essex and works locally, which means shorter travel times, faster site visits, and familiarity with local council planning processes.
Chelmsford & Mid Essex
Chelmsford, Writtle, Great Baddow, Springfield, Danbury, Maldon, Witham, Braintree
Colchester & North Essex
Colchester, Marks Tey, Tiptree, West Mersea, Wivenhoe
Brentwood & West Essex
Brentwood, Shenfield, Ingatestone, Epping, Loughton, Ongar
South Essex
Southend-on-Sea, Basildon, Rayleigh, Benfleet, Canvey Island, Rochford
Tendring & East Essex
Frinton-on-Sea, Clacton, Harwich, Manningtree
If your area isn't listed, get in touch - we cover most of Essex and will let you know if we can help.
Ready to Start Your Extension Project?
Contact us today for a free consultation and let's get started on your next extension project.
Get A QuoteRecent Extension Projects
Our Portfolio
Discover how we've transformed our clients' homes with expertly built extensions.
View All Projects →Complete Ground Floor Refurbishment & External Facade Uplift In Writtle
Budget
£155,000 + VAT
Timeline
14 Weeks
Ground-floor refurbishment with open-plan kitchen/living, new bathrooms, plus external rendering and garage part-conversion Writtle, Essex.
Whole-House Expansion & First-Floor Addition
Budget
£300,000
Timeline
8 Months
Comprehensive side-and-rear extensions plus a new first floor turned an irregular bungalow into a spacious, energy-efficient family home with upgraded services and high-quality finishes.
Full House Renovation & Extension - Frinton On Sea
Budget
£260,000
Timeline
6 Months
A full-house renovation and rear extension in Frinton-on-Sea, delivering open-plan living, modernised services and three new bathrooms.
Ground Floor Extension and Layout Transformation
Budget
£60,000
Timeline
12 Weeks
A single-storey ground floor extension createing a spacious, light-filled area for kitchen and living spaces.
We chose Belvia for our extension and kitchen redevelopment project and couldn’t be happier with the end result and their approach from start to finish. James and his team have a friendly and professional style, providing valuable input to help us finalise the design, manage the building control process and undertaking the build to a high standard of workmanship with great attention to detail. We really appreciated the communication throughout the project and the site management – keeping things clean and tidy along the way. We would highly recommend Belvia.
ST
Steve ReadHomeowner,
Double-Storey Side Extension with Ground Floor Expansion
Budget
£150,000
Timeline
18 Weeks
Extensive double-storey extension and single-storey rear extension, adding a master bedroom, en suite, kitchen, and living areas.
Property Extension with Master Bedroom, Kitchen, and Garage Addition
Budget
£130,000
Timeline
16 Weeks
Comprehensive property extension featuring a master bedroom, kitchen dining room, and garage.
Single-Storey Rear Extension for Kitchen/Dining Space
Budget
£65,000
Timeline
12 Weeks
Single-storey rear extension to create a spacious kitchen and dining area, enhancing the ground floor layout.
Single Storey Rear Extension
Budget
~£55,000
Timeline
10 Weeks
Ground floor renovation and extension, including kitchen relocation and open-plan living area transformation.
From the start Jim gave us total confidence that Belvia were an incredibly professional and capable building company. They always arrived when they promised, they left everything tidy, the lads (Ryan, Ellis & Luke) were very polite and knew exactly what they were doing. Every aspect of the build was undertaken with the highest level of quality. Things we mentioned early on in the process were remembered and implemented exactly as we required. Our friend (also a builder) visited and was really impressed with the finish, which is no mean feat.
We are overwhelmed with the final result – it is even better than we expected and there is nothing we would change. We would 100% recommend Belvia Construction. Many thanks to Jim and the team.
ST
Cathy McgrathHomeowner,
Our Simple Process for a Stress-Free Extension
How It Works
Extending your home should be an exciting and seamless experience. Our structured process ensures that every project runs smoothly, from the initial consultation to the final handover. Here’s what you can expect.
Consultation & Survey
We start with a free consultation to discuss your ideas, needs, and goals. Our experts will visit your property to assess the space, listen to your requirements, and provide initial advice on feasibility, design options, and budget.
- Personalised consultation
- Obligation-free expert advice
- On-site survey & feasibility analysis
Design & Planning
We put you in contact with our design team to create your detailed plans and drawings to reflect your vision. We handle all planning permissions and liaise with local authorities, ensuring your project complies with regulations. At this stage, you’ll have the opportunity to finalise materials, layouts, and finishes.
- Tailored design process
- Planning permissions & Building Regulations
- Material Selection Support
Construction & Project Management
Our skilled construction team gets to work. Led by a dedicated project manager, we ensure that every aspect is carefully coordinated and executed, from foundations to final finishes. We keep you updated throughout, maintaining clear communication so you’re never left in the dark.
- Dedicated Project Management
- Skilled & Reliable Team
- Transparent Timeline
Inspection & Handover
After construction is complete, we conduct a thorough inspection to ensure everything meets our high standards. We’ll walk you through your new space and address any questions or last-minute adjustments. Once you’re completely satisfied, the project is signed off and ready for you to enjoy.
- Detailed Quality Assurance Check
- Customer Walkthrough
- 100% Satisfaction Guarantee
Frequently Asked Questions
How long does a house extension take to build?
Most single-storey extensions take 10–14 weeks from breaking ground to handover. Double-storey and wrap-around builds typically take 14–20 weeks depending on complexity. We provide a detailed project timeline before work starts. For a full stage-by-stage breakdown, read our house extension building process guide.
Do I need planning permission for a house extension in Essex?
Many single-storey extensions can be built under Permitted Development without formal planning permission. Larger builds, double-storey extensions, and properties in conservation areas usually require a planning application. We assess your property and advise on the correct route before any work begins. Read our full planning permission guide.
How much does a house extension cost in Essex?
Single-storey extensions typically start from £2,250 + VAT per square metre, while double-storey builds start from £4,500 + VAT per m². Final costs depend on size, structural complexity, and finishes. We provide fixed-price quotations after surveying your property – see our full cost breakdown above.
Will a house extension add value to my property?
In most cases, yes. A well-designed extension in Essex can add between 5% and 15% to your property’s value, depending on the type of extension and local market conditions. Open-plan kitchen-diners and additional bedrooms with en-suites tend to deliver the strongest returns.
Can I live in my house during the extension build?
Yes – the majority of our clients remain in their homes throughout the project. We plan the build sequence to minimise disruption, and we keep the site clean and secure at the end of each working day. We’ll discuss any temporary arrangements (such as kitchen access during a kitchen extension) before work starts.
Do you handle Building Regulations for extensions?
Yes. Building Regulations approval is required for every house extension regardless of whether planning permission is needed. We manage the full Building Control process, including applications, site inspections, and obtaining your completion certificate.
Can you build an extension on a semi-detached or terraced house?
Absolutely. We regularly build side return, rear, and single-storey extensions on semi-detached and terraced properties across Essex. Party wall agreements may be required, and we’ll guide you through that process.
What is a Party Wall Agreement and do I need one?
A Party Wall Agreement is required under the Party Wall etc. Act 1996 if your extension is built on or near a shared boundary with a neighbouring property. This applies to most semi-detached and terraced house extensions. We’ll advise you on whether one is needed and help you serve the correct notices.
Can you help me with the design and planning phase?
While our core strength lies in construction, we recognise the importance of seamless collaboration. We have a network of trusted architects and designers we can recommend to assist with your project’s initial design and planning stages. We’ll work closely with these professionals to ensure a smooth transition into construction and that your vision is fully realised.
What measures do you take to ensure my project stays on budget?
Transparent pricing and proactive cost management are cornerstones of our approach. We’ll provide a detailed, itemised quote upfront, outlining all anticipated costs. Throughout the project, we’ll closely monitor expenses, track any changes or additions, and communicate with you transparently to ensure your project stays within budget.
How often will I receive updates on my project’s progress?
We believe in open and transparent communication. You’ll receive regular updates on your project’s progress, including detailed reports, photos, and on-site visits as needed. We also encourage open dialogue throughout the build, so you’re always aware of what’s happening and can address any questions or concerns promptly.
Will there be a dedicated project manager for my project?
Yes, every project at Belvia has a dedicated project manager who will serve as your main point of contact. Your project manager will oversee the entire process, ensuring seamless coordination, clear communication, and timely execution. They’ll be readily available to answer your questions, address any concerns, and keep you informed every step of the way.
How do you handle waste disposal?
We take environmental responsibility seriously. We manage waste disposal in accordance with all local regulations and industry best practices. We strive to minimise waste wherever possible and recycle or repurpose materials whenever feasible. We’ll ensure your site remains clean and organised throughout the project, and we’ll leave your property in pristine condition upon completion. We will discuss any skip requirements with you before starting the project.
The Latest From Our Blog
Insights & Guides
Expert advice, inspiration, and practical guides for your extension project.
How Long Does a House Extension Take? The Complete Build Process Explained Stage by Stage
How long does a house extension really take? We break down the complete build process stage by stage, with real photos from an Essex project and insider tips from our team.
Planning Permission for House Extensions in Essex – What You Need to Know
Planning a home extension in Essex? You might not need full planning permission. Read our 2026 guide to Permitted Development rights, local council timelines (from Chelmsford to Southend), and how to avoid costly enforcement mistakes before you build.
Let's Talk
Ready to Transform Your Home?
Tell us about your project and we'll get back to you with a free, no-obligation quote. Whether you're at the early planning stage or ready to start, we're here to help.
- Free consultation and property survey
- Transparent, fixed-price quotation
- Detailed, upfront scope with no hidden costs
- Skilled team delivering exceptional results
- Quick Responses