Putney House Extension Cost 2026: What Does a High-Spec Extension Really Cost?
2026-09-18 12:55
Quick Answer
A house extension in Putney can broadly cost £2,300–£4,800+ per m² for construction in 2026, with the finished project potentially moving well into six figures once structure, glazing, kitchens, professional fees and high-quality finishes are included. A 20–30m² extension might therefore sit around £75,000–£150,000+, depending on the property and specification.
There is a moment in almost every extension project when someone asks:
“So… how much is this actually going to cost?”
Not the optimistic number from a calculator.
Not the figure someone remembers paying in 2019.
The real number.
The one that accounts for the steel, foundations, glazing, kitchen, electrics, plumbing, flooring, plastering, decorating and all the other things that mysteriously appear once you stop looking at the floor plan and start looking at the actual building.
If you are researching house extension cost Putney 2026, this guide is designed to give you a much more useful starting point.
Because in Putney, the number can change dramatically depending on the house, the street, the access, the planning constraints and how ambitious the finished space is.
How Much Does a House Extension Cost in Putney in 2026?
For 2026, a sensible broad construction benchmark for London extensions is around £2,300–£4,800+ per m², depending on specification and complexity.
For Putney, that means a project might broadly look like:
ExtensionBroad 2026 construction budget
15m² smaller extension
£50,000–£80,000+
20m² extension
£75,000–£110,000+
25m² extension
£85,000–£130,000+
30m² extension
£100,000–£150,000+
Larger / high-spec extension
£150,000–£200,000+
These are budgeting ranges rather than quotations.
And there is an important point here.
A 25m² extension with basic finishes is not the same financial proposition as a 25m² extension containing a bespoke kitchen, large-format glazing, rooflights, structural steel, stone worktops, engineered timber flooring and bespoke joinery.
The square metres are identical.
The project isn't.
Why Putney Extensions Can Cost More Than You Expect
Putney has a mixture of property types, from Victorian and Edwardian houses to later suburban homes and larger properties around areas such as West Putney and Putney Heath.
That variety matters.
An extension has to respond to the existing building.
And old London houses have a habit of keeping a few secrets.
You might uncover:
awkward drainage
old foundations
redundant pipework
chimney structures
uneven floors
complicated wall construction
difficult access
neighbouring structures very close to the proposed extension.
The drawings might look beautifully simple.
The building might disagree.
Rear Extension Cost Putney
A rear extension is one of the most popular ways to improve a Putney home.
The basic idea sounds simple:
Build out → add kitchen → add glazing → connect to garden.
In reality, there is considerably more going on.
A typical rear extension can involve:
excavation
foundations
drainage
structural steel
brickwork
insulation
roofing
rooflights
windows
sliding or bifold doors
plumbing
electrics
heating
flooring
plastering
decorating
kitchen installation
external landscaping.
For a good-quality 20–30m² rear extension, a broad budgeting range of £75,000–£150,000+ is realistic depending on the specification.
The kitchen alone can make a considerable difference.
Kitchen Extension Putney: Where the Budget Starts Moving
This is where homeowners sometimes get caught out.
They search:
“How much does a 25m² extension cost?”
Then choose a kitchen with a large island, stone worktops, bespoke cabinetry, integrated appliances, feature lighting and full-height storage.
Suddenly the extension isn't just a construction project.
It's also a kitchen project.
A premium kitchen extension can include:
Structural work
Steel, foundations, openings and roof construction.
Glazing
Large sliding doors, bifold doors, rooflights or fixed panels.
Kitchen
Cabinetry, island, worktops and appliances.
Services
New plumbing, electrical installation, extraction and heating.
Finishes
Flooring, lighting, joinery, plastering and decorating.
This is why kitchen extension Putney is a much more specific search than simply asking what one square metre of building costs.
Side Return Extension Putney
If you own a traditional London terrace, the side return can be one of the most useful pieces of underused space.
It can also be one of the most technically interesting.
A side return extension may involve:
removing an existing lean-to
excavation
new foundations
opening up the rear wall
structural steel
a new roof
glazing
drainage alterations
insulation
kitchen relocation.
The finished extension might not add a huge number of square metres.
But it can change how the ground floor functions.
And that is often the point.
Putney Wraparound Extension Cost
A wraparound extension combines a rear extension with the side return.
It can create a much larger kitchen-dining area and make better use of the full width of the property.
But it also introduces more construction.
You may be dealing with:
multiple structural openings
larger steelwork
more extensive foundations
more roofing
more glazing
additional drainage
larger kitchen installations
more complicated junctions with the existing house.
A broad starting budget for a Putney wraparound extension can therefore move into the £110,000–£180,000+ territory, with highly specified projects going beyond that.
Double Storey Extension Putney
Want another bedroom upstairs as well as a larger kitchen downstairs?
A double-storey extension could be worth considering.
It can provide:
Ground floor:
Kitchen, dining, family room or utility space.
First floor:
Bedroom, bathroom, dressing room or office.
The construction cost is higher, but the additional floor area can make the overall project much more substantial.
A typical London double-storey extension can easily move beyond £120,000–£220,000+, depending on size, access, structure and specification.
And once you start adding premium glazing, bathrooms, joinery and finishes, the budget can move considerably further.
Putney Conservation Areas: Why Location Matters
Putney is not simply one planning environment.
Different parts of the area have different planning considerations, including conservation-area designations and, in some locations, additional restrictions affecting permitted development rights.
That can matter when you are considering external alterations.
Depending on the property and location, planning considerations can affect:
extensions
roof alterations
windows
doors
external materials
dormers
side extensions
boundary treatments.
For Putney homeowners, checking the property-specific planning position early is therefore an important part of the process.
The postcode matters.
Victorian House Extension Putney
A Victorian house gives you something modern new-builds don't:
character.
It may also give you:
original fireplaces
sash windows
timber floors
cornicing
high ceilings
chimney breasts
brick detailing
awkward rear additions
narrow side passages.
The extension should respond to those existing features.
That does not necessarily mean copying the old house.
In fact, a well-designed contemporary extension can work extremely well against a traditional London façade.
The trick is getting the relationship right.
Old house at the front.
New architecture at the back.
One property.
What Is Usually the Most Expensive Part of a Putney Extension?
But these are the areas that can make a significant difference.
Foundations
Especially where ground conditions or proximity to neighbouring structures make the design more complicated.
Structural Steel
Large openings need proper structural support.
That means calculations, fabrication, installation and associated works.
Glazing
A modest window and a six-metre opening are two very different purchases.
Kitchen
Cabinetry, stone, appliances and bespoke details can quickly become a major part of the budget.
Bespoke Joinery
Utility storage, media walls, shelving, wardrobes and cabinetry all add labour and material costs.
Bathrooms
Particularly where plumbing needs to be relocated or high-quality sanitaryware and finishes are specified.
Landscaping
The extension may be complete, but the garden might look like it has hosted a small archaeological excavation.
Don't forget the outside.
How to Make a Putney Extension Feel Bigger
More space isn't always about building more.
It's about making the space you have work harder.
Bring the garden into the room
Large glazed openings can create a strong visual connection between the kitchen and garden.
Use rooflights intelligently
A rooflight can pull daylight into areas that side windows can't reach.
Keep sightlines open
Avoid unnecessary partitions if the floor plan doesn't need them.
Use built-in storage
Good storage makes a room feel larger because everyday clutter disappears.
Think about flooring early
A continuous floor between the existing house and extension can help the two spaces read as one.
Don't forget the ceiling
Roof structure, rooflights and ceiling height can have a surprisingly large effect on the finished feeling of the room.
What About Planning Permission for a Putney Extension?
Some extensions can fall within permitted development rights, while others require planning permission.
The answer depends on the individual property and proposal.
You need to consider:
property type
size
position
previous extensions
conservation area status
Article 4 restrictions
whether the building is listed
local planning requirements.
For Putney homeowners, checking the property-specific planning position early is an important part of the process.
Don't Forget Building Regulations
Planning permission and Building Regulations are not the same thing.
An extension also needs to satisfy technical requirements covering areas such as:
structural stability
insulation
fire safety
ventilation
drainage
electrical installation
energy performance.
This is where structural design and proper construction detailing become particularly important.
A pretty drawing isn't enough.
The building has to work.
How Long Does a Putney Extension Take?
A straightforward single-storey extension may take around 10–16 weeks on site, while more complicated extensions and combined renovation projects can take considerably longer.
But don't confuse construction time with the entire project timeline.
Before the first brick is laid, there may be:
Design → surveys → structural engineering → planning → Party Wall → Building Regulations → procurement → construction
And if your extension is part of a larger renovation, the programme can become considerably more involved.
Should You Extend or Renovate the Whole House?
This is a question worth asking before construction starts.
Imagine the extension is finished.
New kitchen.
New floor.
Beautiful glazing.
Then you walk into the original hallway.
Old floor.
Old electrics.
Old lighting.
Old heating.
Old plaster.
Suddenly the new extension looks rather lonely.
For some Putney properties, combining an extension with a wider renovation can make sense.
Before committing to a project, make sure your budget has considered:
Construction
Foundations
Excavation
Structural steel
Brickwork
Roofing
Insulation
Windows
Doors
Rooflights
Internal works
Plumbing
Heating
Electrical
Plastering
Flooring
Decorating
Kitchen
Joinery
Professional costs
Architectural work
Structural engineering
Planning
Building control
Party Wall matters
External works
Drainage
Patio
Garden
Fencing
Landscaping
Waste removal
That is a much more useful checklist than:
“25m² × £3,000 = done.”
It isn't.
What Should You Ask a Putney Extension Builder?
Before accepting a quotation, ask:
What exactly is included?
You need to know what the price actually covers.
Is VAT included?
Never assume.
Are structural works included?
Check the steel, temporary supports and associated making good.
What happens if the ground conditions change?
Understand how unforeseen works are handled.
Who manages the project?
A single point of responsibility can make a complicated project much easier to coordinate.
How are variations handled?
Get the process agreed before construction starts.
What is the expected programme?
A realistic programme is much more useful than an optimistic promise.
[PHOTO 2: Completed Putney kitchen extension with contemporary cabinetry, stone island, rooflights and large glazed doors opening onto a landscaped garden.]
Suggested alt text: High-spec Putney kitchen extension with rooflights, stone island and garden glazing
Why the Cheapest Extension Quote Can Become the Most Expensive
There is a familiar pattern in construction.
Quote A:
£92,000
Quote B:
£118,000
Quote C:
£137,000
The instinct is obvious.
Pick £92,000.
But first ask what each contractor has actually included.
If one quotation excludes:
structural steel
kitchen installation
flooring
decoration
professional fees
drainage
landscaping
certain electrical works
then the three numbers aren't really comparable.
A quotation is only useful when you understand the scope behind it.
What Makes a High-Quality Putney Extension Work?
It isn't necessarily the most expensive material.
It is the details.
A rooflight positioned where the room actually needs light.
A steel opening that allows the kitchen and garden to connect properly.
Joinery that hides the things you don't want to see.
A kitchen that works at breakfast time, not just in photographs.
Heating that doesn't turn the room into a greenhouse.
Doors that open properly.
And a junction between old and new that looks intentional.
That's where good construction starts to matter.
Planning a House Extension in Putney?
Dominant Construction LTD works across London on house extensions, kitchen extensions, renovations and design-and-build projects, with experience working on complex residential properties where structural work, services and high-quality finishes all need to come together.
If you're considering a Putney house extension, whether it's a rear extension, side return, wraparound or larger renovation, we can discuss the project and the practical considerations before construction begins.
How much does a house extension cost in Putney in 2026?
A broad 2026 London construction benchmark is around £2,300–£4,800+ per m², although the final cost depends on the property, structure, access and specification. A 20–30m² Putney extension can therefore move from around £75,000 into the £150,000+ range.
How much does a 20m² extension cost in Putney?
A 20m² extension could broadly start around £75,000, with the final cost increasing according to structural work, glazing, kitchen specification, professional fees and finishes.
How much does a 30m² extension cost in Putney?
A 30m² extension could broadly fall around £100,000–£150,000+, although a highly specified kitchen extension or structurally complicated project can cost more.
Do I need planning permission for a Putney extension?
Not necessarily. Some projects may fall within permitted development rights, while others require planning permission. Conservation areas, Article 4 Directions, listed buildings and the specific design of the extension can affect the requirements.
Can I build an extension in a Putney conservation area?
Potentially, yes, but additional planning controls can apply. The planning position should be checked for the individual property before finalising the design.
Is a kitchen extension worth considering in Putney?
It depends on the property, budget and how you want to use the house. A well-designed kitchen extension can improve the relationship between the kitchen, dining area and garden while providing additional usable floor space.
How long does a Putney house extension take?
A straightforward single-storey extension may take approximately 10–16 weeks on site, although the full process from design through planning, approvals, procurement and construction can take considerably longer.
Thinking About a Putney House Extension?
Don't start with the cheapest number you find on Google.
Start with the property.
The existing structure.
The planning position.
The access.
The foundations.
Then the specification.
If you're planning a rear extension, kitchen extension, side return, wraparound extension or full house renovation in Putney, speak to Dominant Construction LTD about your project.