Double-storey wraparound extension Greenwich, SE10
HOME EXTENSIONS · London, Essex & Herts
HOME EXTENSIONS
Add space for the changes you want to make.
When there isn’t enough room to move the kitchen, create a dining area or bring separate rooms together, an extension gives you the extra space to make those changes possible.
When there isn’t enough room to move the kitchen, create a dining area or bring separate rooms together, an extension gives you the extra space to make those changes possible.
30 Years In Construction
250+ Homes transformed
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Federation of Master Builders
Independently vetted & inspected
Insurance-backed warranty available
Find your extension
Find the right extension for your home
Three quick questions. Takes 15 seconds.
1 of 3
What shape is the back of your home?
2 of 3
Does your house have a side passage?
3 of 3
Do you want more space upstairs?
We’ve highlighted the relevant extensions below
Ways to extend your home
Ways to extend your home
The five main types of home extensions.
The right choice for you will depend on your home, the space around it and what you want to achieve.
Your home could be extended by June.
Not sure which of these you need? Tell us what isn’t working and we’ll plan the right changes with you.
Expert advice · No obligation
Homeowner interview
HOMEOWNER INTERVIEW
What’s it like to extend your home with Construct X Group?
Our client Genevieve talks through her home extension, why she chose Construct X Group and what it was like having us work on her home.
“You guys were just heads and shoulders apart from all the others. You were really good at listening, and you made it clear that you’d be doing what I wanted to do, not what you thought I should do.”
MORE FROM GENEVIEVE’S HOME
OUR transformations
See how we’ve extended homes like yours.
Explore real extension projects, the decisions behind them, what they cost and how long they took.
OUR transformations
OUR transformations
See how we’ve extended homes like yours.
Explore real extension projects, the decisions behind them, what they cost and how long they took.
Why extend your home?
WHY EXTEND
Why should you extend your home?
Most homeowners we’ve spoken to extend for at least two of these three reasons.
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LAYOUT
Make the layout work better for family life
Connect the rooms you use most and make it easier to move between cooking, eating, relaxing and spending time together.
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SPACE
Add extra space where you need it
Give the rooms that feel too small a little more space, so they can work the way you need them to.
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LOCATION
Stay in the home and area you love
Get the space and layout you need without giving up your street, schools, neighbours or the parts of your home you already love.
Extension costs
Extension costs
How much does it cost to extend a home?
An extension budget is made of three layers, and knowing what goes into each layer will make it easier for you to compare quotes and plan your spending.
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01 - The core
The essential building work
All the labour, materials and site management required to build your extension, from groundworks to an insulated and plastered space. It comes with our workmanship warranty. Typically £74,000+ including VAT
All the labour, materials and site management required to build your extension, from groundworks to an insulated and plastered space. It comes with our workmanship warranty.
Typically£74,000+including VAT
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02 - Fittings and finishes
What you choose to add
What you spend here is largely in your hands. Some clients keep things simple, while others choose high-spec kitchens, upgraded glazing and finishes. You can buy these yourself, or ask us to supply them. Examples include the kitchen, floor tiles, sanitaryware and finishes.
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03 - Optional extras
Other improvements you may want
While we're already working on your home, it can make sense to tackle other improvements too. With walls and floors already opened up, some work can be easier and cheaper to do now rather than as a separate project later. We can plan and manage everything together, from renovating other rooms to upgrading your heating.
How payments work
How payments work
You don’t pay for everything upfront.
How you pay: After an initial deposit, you pay in stages as we progress through the build.
How you’re protected: Before key stage payments, an independent inspector you appoint checks our work.
Extension Timings
Extension Timings
How long does it take to extend a home?
Allow approximately
5–8 months
for a single-storey extension requiring planning permission.
- Pre-build
- Around 3 months
- Build on site
- 2–4 months
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STEP 1
Architect’s survey
Usually arranged within 1–3 days
Our architect contacts you to arrange a survey of your home, depending on access and availability.
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STEP 2
Planning drawings
Usually 1–2 weeks
Our architect prepares the drawings for the planning application. You’ll have a chance to review them and request changes before they’re submitted.
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STEP 3
Planning application
Usually around 8 weeks
Once your application is validated, the council usually takes around 8 weeks to make a decision. It can take longer if they request changes or need more time.
Also at this stage: Party Wall (if needed)
If your extension needs a , we recommend starting the process as soon as we send in your planning application, as this can drag on quite a bit and risk delaying your start date.
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STEP 4
Structural drawings
Usually 1–2 weeks
Once planning is approved, the structural engineer works out what steel beams, foundations and other supports your extension needs, and prepares the drawings.
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STEP 5
Building Control notice
At least 5 working days before building starts
Building Control checks that your extension meets building regulations. You can use the council or a private provider, which we usually recommend because inspections are easier to arrange. We can help with the application. The private provider notifies the council, and once the required notice periods have passed, we can usually start building while they continue reviewing the drawings.
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STEP 6
Build on site
Typically 12 weeks
Some straightforward extensions can be built in as little as 8 weeks. Larger or more structurally involved projects can take up to 16 weeks.
What could affect the timeline? Planning decisions, , design changes and unexpected site conditions can affect timings. While not common, these things can happen, and from our end, we’ll flag potential delays as early as possible.
During construction
During construction
What actually happens during the build?
Here’s how a typical single-storey rear extension progresses, from digging the foundations to finishing the new space.
Typically 12 weeks on site.
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01
Site setup & foundations
Weeks 1–3 · Protecting your home, digging the foundations and pouring concreteOn site
We start by setting up the site, arranging waste collection and protecting the areas we’ll need to use. If there isn’t a side passage, that can mean protecting the route through your home to the back garden.
We mark out where the extension will go and dig the foundations. Building Control checks the excavations before we pour the concrete.
We also check where the existing drains run and arrange the structural steels needed for the next stage. The concrete needs time to gain strength before it can support the work above.
At home
Before we start, we’ll explain which areas we need access to, how we’ll protect them and which rooms you’ll be able to use.
This stage involves digging and moving materials, so expect noise and regular deliveries. If we need to work through your home, we’ll explain how that will be managed.
Building Control: The excavated foundations are inspected before concrete is poured. If the ground requires deeper foundations or a change to the design, we’ll explain what’s needed, including how it affects cost and timing, before proceeding.
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02
Structural steelwork & external walls
Weeks 4–6 · Opening the rear wall, installing the steel beams and building the new wallsOn site
Before we remove part of the existing rear wall, we install temporary supports to hold the house safely in place.
The opening is then formed and the structural steel beams are installed. These support the parts of the house above the new opening.
Once that work is complete, we build the extension’s external walls, including the insulation that goes between the layers of brickwork or blockwork. We also form the openings for the new windows and doors.
At home
Opening the rear wall is one of the more disruptive parts of the build, particularly if we’re connecting the extension to your existing kitchen or living room.
We’ll explain when this work is planned, how we’ll separate the building area from the rest of the house and what it means for access to those rooms.
Building Control: The structural steelwork is checked at the appropriate stage, before it’s covered over. Other wall and damp-proofing details may also need inspection.
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03
Roof structure & weatherproofing
Weeks 6–7 · Building the roof frame and putting on the covering that keeps the rain outOn site
Once the walls are high enough, we build the timber roof structure, including any openings for rooflights.
The roof covering then goes on. Depending on the design, that might be tiles or a flat-roof waterproofing system.
By the end of this stage, the roof will be watertight, although some window and door openings may still need temporary protection until the glazing is installed.
At home
You can now start to see the shape of the finished extension.
If you’ve chosen large sliding or bifold doors, these may be made to measure once the opening is ready. They aren’t necessarily installed at the same time as the roof.
Building Control: The roof structure and relevant details are inspected when required, before work that needs checking is covered over.
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04
Drainage, first fix & plastering
Weeks 7–9 · Building the new floor, running pipes and cables, insulating and plasteringOn site
We complete the underground drainage and build the new extension floor, including the concrete base and damp-proofing.
Our plumber and electrician then run the pipes and cables for the new room. This is called first fix.
We install the required insulation, including the roof and floor insulation, before plasterboarding and plastering the walls and ceiling, and screeding the floor.
Some of these jobs overlap, and the plaster and screed need time to dry before certain finishes can be fitted.
At home
Before the cables and pipes are covered, we’ll confirm the positions of sockets, switches, lights, radiators and any other agreed connections with you.
This is also when the new room starts to look more finished, although there will still be work to do before you can use it.
Building Control: Inspections may be needed for drainage, damp-proofing and insulation before those parts of the work are covered up. We arrange the relevant checks as the work progresses.
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05
Second fix & handover
Weeks 10–12 · Connecting the fittings, completing agreed finishes and checking the work togetherOn site
We connect the lights, sockets, radiators and other agreed fittings. Skirting boards, doors and the remaining carpentry work are also completed.
Kitchen fitting, flooring and decorating are your choice. We can do them towards the end of the build, or you can use your own suppliers.
Large sliding or bifold doors may also be installed during this period, depending on the glazing supplier’s lead time.
We then walk through the finished work with you, identify anything that needs putting right and complete the agreed snagging.
At home
You’ll walk through the extension with your site manager so we can check the work together.
We’ll go through anything outstanding, explain what happens next and provide the relevant documentation as it becomes available.
Building Control: Building Control carries out their final checks. The formal completion certificate will follow the inspection once all the required information and certificates have been received.
Building Control checks the work at key stages, which can include the foundations, drainage, steelwork, insulation and final completion. We arrange these inspections as the build progresses and combine visits where possible.
Ready to talk through your project?
You’ll speak with Eddie
Planning & approvals
Planning & approvals
Will I need planning permission for my extension?
Not every extension needs planning permission, but every project needs the right approvals in place before work begins.
We’ll identify what applies to your home and guide you through the process.
- Read our planning permission guide
Planning permission
When do I need planning permission?
A full planning application is required when your extension falls outside permitted development rights, or where other restrictions apply (for example, conservation areas or listed buildings).
- Read our permitted development guide
Permitted development
Could my extension be permitted development?
Some extensions can be built without a full planning application if they meet the permitted development rules and conditions.
- Read our lawful development certificate guide
Lawful development certificate
Should I get a lawful development certificate?
Even when planning permission isn’t required, we normally recommend getting formal confirmation from the council that your proposed work is lawful.
What other approvals might I need?
Depending on the scope of your extension, you may need additional approvals alongside planning permission.
- Read our party wall guide
Party wall
Do I need a party wall agreement?
The Party Wall Act may apply if the work affects a shared wall, boundary or nearby foundations.
- Read our building regulations guide
Building regulations
What building regulations apply?
Most extensions require Building Regulations approval. This covers structure, insulation, fire safety and other technical standards.
- Read our structural engineering guide
Structural engineer
When do I need a structural engineer?
A structural engineer is normally required where structural changes need to be designed and calculated, such as new openings or steelwork.
“I can’t imagine having a renovation completed with anyone else as it really felt like being part of the family whilst they were doing the work.”
ConstructX Group did a rear extension on our house which took about 3-4 months. The work moved quickly and the end result is absolutely beautiful. We couldn’t be happier with the end result.
We had a 2 and 4 year old at the time and we were anxious about living in the house whilst renovating, but honestly Eddie, his brother and Dad were absolute delights and made it so much nicer. They always made sure at the end of the day everything was in a safe way and were so accommodating.
I can’t recommend them enough; we have used their services since to do some work on our front garden and will definitely use them in the future.
Our family
Who will be working on your home?
Construction has been our family trade for the past 30 years. Your project is led by our family alongside professionals we’ve worked with for years.
We’re one family managing the whole build
Building work involves a lot of different people. Our own trades work alongside the architects, engineers and specialists your project needs, all managed by our family. You have one point of contact throughout your project, without having to coordinate everyone involved yourself.
Meet the family
OUR FAMILY
Who will be working on your home?
Construction has been our family trade for the past 30 years. Your project is led by our family alongside professionals we’ve worked with for years.
We’re one family managing the whole build
Building work involves a lot of different people. Our own trades work alongside the architects, engineers and specialists your project needs, all managed by our family. You have one point of contact throughout your project, without having to coordinate everyone involved yourself.
Meet the family
HOMEOWNER EXPERIENCES
HOMEOWNER EXPERIENCES
What do homeowners say about extending with us?
100% of our home extension reviews have received 5‑star ratings.
Recent homeowner reviews
Homeowner guides
HOMEOWNER GUIDES
Prefer to read up on things before speaking to us?
Explore our human written guides on planning, approvals, costs and the decisions that come up during home extension projects.
“All our articles were written by me with Eddie’s input, not AI.”
FAQs
FAQs
Questions that come up on most home extension projects.
Ready to get a clear plan for your home extension?
Get a realistic picture of what’s possible for your home, likely costs, timings, planning requirements and what the project would involve.
You’ll speak with Eddie
Managing Director
150+ projects delivered
Expert advice · No obligation

Ready to get a clear plan for your project?
Get a realistic picture of what’s possible for your home, likely costs, timing, planning requirements and what the project would involve.

You’ll speak with Eddie
Managing Director
150+ projects delivered
Expert advice · No obligation











