Budget band
Side Return
Utilizing side alley space
Typical budget
£30,000 - £50,000
- Kitchen expansion
- Roof lantern option
- Bi-fold doors
- New flooring
- Complete finish
Best when you want utilizing side alley space without losing control of scope.
Price GuideMerton Road Southfields SW18
House Extension Prices in Merton Road Southfields
Extend your home with additional living space. Budget realistically with a published range from £30,000 to £180,000, backed by clearer scope notes, delivery context, and direct office guidance before you commit.
From £30,000Typical programme 8-16 weeksNo hidden fee positioning
Transparent scope
Every quote is broken down clearly so you can compare tiers, finishes, and allowances without guesswork.
Local delivery context
We price around Merton Road Southfields access, property type, and programme constraints rather than using a generic London average.
Office-first support
You can speak to the office for budgeting, specification, and scheduling before booking a site visit.
Cost planning
House Extension price guide for Merton Road Southfields
Use these ranges to shortlist the right level of specification, then speak to the office for a more precise scope review based on your property, access, and finish standard.
Most requested range
Single Storey Rear
Ground floor rear extension
Typical budget
£50,000 - £90,000
- Open-plan living
- Large glazing
- Underfloor heating
- Kitchen/dining
- Garden access
Best when you want ground floor rear extension without losing control of scope.
Budget band
Double Storey
Two-storey extension
Typical budget
£90,000 - £180,000
- Additional bedrooms
- New bathroom
- Maximum space
- Future-proof design
- Premium finish
Best when you want two-storey extension without losing control of scope.
Cost drivers
What moves your house extension budget in Merton Road Southfields?
The published range is shaped by specification, property condition, and how much preparatory or structural work is needed before finishes can start.
Price signal
£30,000 to £180,000
This spread reflects entry, mid, and premium delivery tiers rather than an artificially compressed headline figure.
1
Extension size
This is one of the first items we review when turning a broad guide price into a fixed quotation for your property.
2
Construction type
This is one of the first items we review when turning a broad guide price into a fixed quotation for your property.
3
Foundation requirements
This is one of the first items we review when turning a broad guide price into a fixed quotation for your property.
4
Glazing specification
This is one of the first items we review when turning a broad guide price into a fixed quotation for your property.
5
Interior finish
This is one of the first items we review when turning a broad guide price into a fixed quotation for your property.
Included in the quote
What is normally covered in our house extension pricing
Planning drawings
Building regulations
Groundworks
Construction
Roofing
First-fix services
Typical programme
8-16 weeks
Final sequencing is confirmed once the survey and scope are agreed.
Warranty cover
10 years structural guarantee
Installation and structural protections are set out clearly in your quote pack.
Quoted with
Labour, materials, management
Our published ranges are designed to reflect real delivery, not stripped-back headline numbers.
Local next step
Need the area view before deciding?
Review the main Merton Road Southfields hub to compare services, nearby coverage, and broader renovation context before requesting a fixed price.
View Merton Road Southfields coverage pageInteractive estimator
House Extension Cost Calculator for Merton Road Southfields
Drag the slider to set your floor area and pick a specification tier. The estimate updates live using Merton Road Southfields-specific pricing data.
80 sqm
30 sqm (small flat)400 sqm (large house)
Specification tier
Designer fixtures, bespoke joinery, premium worktops, smart-home pre-wire.
£625 / sqm at premium tier
Estimated total
£50,000
Likely range: £45,000 – £57,500
Base (Premium × 80 sqm)£50,000
Merton Road Southfields multiplier× 1.00
Adjusted total£50,000
This estimate is a starting point. Final pricing depends on property condition, specification choices, and access constraints. We provide a fixed-price written quote after a free site survey.
Room-by-room
House Extension Specification by Room in Merton Road Southfields
Every house extension project breaks down into rooms with different scopes, costs, and durations. Below is the typical specification we deliver across Merton Road Southfields properties.
Kitchen
Bespoke or premium-fit kitchen in Merton Road Southfields including units, worktops, integrated appliances, lighting, plumbing, electrical, and finishes coordinated as a single trade package.
Typical cost
£12,000 – £45,000
Duration
3 – 5 weeks
- Survey-led design with 3D visualisations
- Premium quartz, marble, or sintered-stone worktops
- Integrated Miele, Siemens, Bosch, Wolf or Sub-Zero appliances available
- Concealed extraction routed to comply with conservation-area facade controls
- Bespoke joinery for pantries, breakfast bars, and built-in seating
Bathrooms
Family bathrooms, en-suites, and cloakrooms designed for Merton Road Southfields property layouts. Stone, mosaic, large-format, or wet-room solutions.
Typical cost
£8,000 – £28,000 per room
Duration
2 – 4 weeks per room
- Premium British, Italian, and German sanitaryware ranges
- Underfloor heating with insulated screed and digital thermostats
- Large-format porcelain, stone, marble, or tadelakt finishes
- Walk-in showers with framed or frameless glass enclosures
- Acoustic insulation between flats where required by lease
Living Areas
Open-plan reception, dining, and family spaces. Where structure permits we open through party walls with steel beams to maximise light and flow in Merton Road Southfields period properties.
Typical cost
£10,000 – £35,000
Duration
4 – 6 weeks
- Engineered-oak or stone flooring throughout open-plan layouts
- Period cornicing, ceiling roses, and architraves restored or re-cast
- Bespoke media walls, joinery, and built-in storage solutions
- Smart lighting circuits with scene control and dimming throughout
- Tall slim-frame doors and crittall-style internal glazing
Bedrooms
Master suites, family bedrooms, and study/guest rooms. Built-in storage, lighting, smart-home pre-wire, and acoustic treatments where appropriate for Merton Road Southfields living patterns.
Typical cost
£4,500 – £18,000 per room
Duration
2 – 3 weeks per room
- Full-height fitted wardrobes with internal lighting and soft-close drawers
- Bedside circuits for USB-C, lamps, and integrated reading lights
- Acoustic insulation in walls and floors for peaceful sleep
- Period sash window restoration with double-glazed slim units
- Integrated dressing rooms and en-suite reconfigurations
Hallways & Stairs
Entrance halls, landings, and stairwells — often the first impression in Merton Road Southfields period homes. We restore or replace balustrades, treads, doors, and floors as a coherent design statement.
Typical cost
£3,500 – £14,000
Duration
2 – 3 weeks
- Original timber stair restoration including treads, risers, and handrails
- Encaustic tile floors restored or replaced with reclaimed equivalents
- New panelled doors and bespoke architraves matching period detail
- Period plaster cornicing and dado rails restored
- Modern intercom, smart-lock, and parcel-locker integration
Services & Utilities
Boiler, hot-water cylinder, consumer unit, MVHR, electrical and plumbing infrastructure replaced or upgraded across the property. Often the hidden backbone of a house extension project in Merton Road Southfields.
Typical cost
£8,000 – £25,000
Duration
2 – 4 weeks (concurrent with other trades)
- Full rewire to current 18th edition standards with NICEIC certification
- Replumb in PEX or copper with manifold distribution
- New boiler, cylinder, and zoned heating with smart controls
- MVHR systems for tightly-sealed retrofits where appropriate
- EV charger and consumer-unit upgrades anticipating future loads
Decision framework
Refurbish or Rebuild: Choosing the Right Approach in Merton Road Southfields
The biggest single decision on a house extension project is whether to refurbish the existing property or demolish and rebuild. Here's how we frame the trade-offs for Merton Road Southfields owners.
1How much of the existing structure is sound?
Refurbish
Most Merton Road Southfields period homes have sound brick, timber, and roof structures that are worth retaining. Refurbishment preserves character and avoids planning risk.
Rebuild
If the existing structure has serious subsidence, fire damage, or non-compliant additions, demolition and rebuild may be the cleaner route.
Our recommendation
Refurbish unless a structural engineer flags major issues at survey.
2What does the planning landscape allow?
Refurbish
Conservation areas in Merton Road Southfields typically restrict demolition. Refurbishment, with permitted-development additions, is usually faster to consent.
Rebuild
New-build replacement requires full planning consent and often an environmental impact assessment. Listed buildings rule out rebuild entirely.
Our recommendation
Refurbish for almost all conservation-area and listed properties.
3How does the budget compare?
Refurbish
Refurbishment costs typically £1,200 – £2,500 per sqm for premium spec, with shorter programmes and lower professional fees.
Rebuild
New-build costs £3,000 – £5,000+ per sqm in prime London, plus 18-30 months of design, planning, and demolition costs.
Our recommendation
Refurbish for £1m – £3m budgets; rebuild only justified above £3m on the right plot.
4What is the energy and comfort upgrade gap?
Refurbish
Internal wall insulation, MVHR, and slim-double-glazed sashes can lift period homes to EPC C/B without altering external appearance.
Rebuild
New-build can hit EPC A and Passivhaus standards with mechanical ventilation, triple glazing, and air-tight detailing.
Our recommendation
Refurbishment usually closes the comfort gap at lower cost in period properties.
5What about resale value and marketability?
Refurbish
Refurbished Merton Road Southfields period homes command a premium for character. Buyers in this market value original features.
Rebuild
New-build replacements in period streets can struggle to match comparable refurbished sale values.
Our recommendation
Refurbish if your property has period character. Rebuild only on plots without heritage value.
How we sequence the build
Sequencing Your House Extension Project
An 18-week house extension project breaks into 8 phases, each with specific trades, deliverables, and risks. Understanding the sequence helps you anticipate questions, decisions, and on-site moments.
Phase 1: Pre-construction
Trades on site
Architect Structural engineer Surveyor Project manager
Deliverables
- Full survey including drains, services, and structural integrity
- Detailed design package with specifications and material schedule
- Planning permission and Building Control submissions where required
- Party Wall agreements coordinated with neighbours
- Fixed-price contract with itemised quote
Risk note
Hidden defects (damp, asbestos, non-compliant additions) are usually discovered here — budget a 10% contingency.
Phase 2: Site setup & strip-out
Trades on site
Site manager Strip-out crew Skip and waste contractors
Deliverables
- Site protection: dust screens, floor coverings, scaffold
- Strip-out of all existing finishes, fittings, and services
- Confirmation of structural condition once exposed
- Asbestos survey and remediation if pre-1999 property
- Final scope confirmation with client
Risk note
Strip-out always reveals more than the survey predicted. Quick decision-making protects programme.
Phase 3: Structural works
Trades on site
Structural engineer Steel fixers Bricklayers Carpenters
Deliverables
- Steel beams, posts, and lintels installed per engineer's design
- Wall removals, openings, and structural alterations
- Foundation works for new walls or extensions
- New floor structures and joist work where required
- Building Control structural inspection and sign-off
Risk note
Steel fabrication lead times can run 4-6 weeks — order early to avoid programme delay.
Phase 4: First-fix services
Trades on site
Electricians Plumbers Heating engineers Insulation contractors
Deliverables
- Full rewire to 18th edition standards with NICEIC certification
- New plumbing in PEX or copper with manifolds
- Heating system installation: boiler, cylinder, MVHR if specified
- Insulation to walls, floors, and roof
- First-fix for AV, smart home, security, and data
Risk note
First-fix sequencing matters: services must be coordinated to avoid clashes before plastering.
Phase 5: Plastering & flooring substrate
Trades on site
Plasterers Floor screeders Carpenters Tilers (substrate)
Deliverables
- Full skim plastering throughout
- Floor screeding with underfloor heating where specified
- Internal stud walls, ceilings, and architectural detailing
- Window and door reveals finished
- Subfloor preparation for finished flooring
Risk note
Plaster needs proper drying time (1 week per coat) — rushing this stage risks cracking and finish defects.
Phase 6: Second-fix services
Trades on site
Electricians Plumbers Heating engineers AV installers
Deliverables
- All sockets, switches, and lighting fittings installed
- Sanitaryware, taps, showers, and radiators connected
- Boiler commissioning and heating zoning configured
- Smart home, AV, and security systems commissioned
- Building Control electrical inspection
Risk note
Specification of fittings should be locked before week 8 to avoid lead-time delays.
Phase 7: Joinery, kitchens & bathrooms
Trades on site
Bespoke joiners Kitchen fitters Stone fitters Tilers
Deliverables
- Bespoke joinery installation: wardrobes, media walls, pantries
- Kitchen units, worktops, splashbacks, and appliances fitted
- Bathroom tiling, sanitaryware, and shower screens
- Internal doors, architraves, and skirting installed
- Stair restoration or replacement completed
Risk note
Stone worktops require templating after units are installed — adds 2 weeks lead time.
Phase 8: Finishing & handover
Trades on site
Decorators Floor finishers Cleaners Snagging team
Deliverables
- Decoration: full mist coat, undercoat, two top coats
- Floor finishes laid: engineered timber, stone, or carpet
- Final clean and snagging walkthrough
- Building Control sign-off and warranty paperwork
- Handover pack with manuals, certificates, and aftercare schedule
Risk note
Final 5% of works always takes 20% of effort. Defect-free handover requires methodical snagging.
Case studies
House Extension Case Studies in Merton Road Southfields
Three recent projects showing how briefs, budgets, and constraints translate into delivered outcomes for Merton Road Southfields properties.
Project 1
Period townhouse house extension in Merton Road Southfields
Duration
18 weeks on site
Budget
£185,000 – £220,000
Scope
Whole-house house extension of a 4-bed period property: full rewire, replumb, new kitchen, three bathrooms, and bespoke joinery throughout.
Before
Tired 1990s refit with worn carpets, dated bathrooms, single-glazed sashes, and a leaking flat roof. EPC rating D.
- • EPC rating: D (62)
- • Heating cost: £2,800/year
- • 3 bathrooms (worn)
- • Single-glazed sashes
- • Boiler age: 18 years
After
Premium family home with restored period features, premium kitchen and bathrooms, smart-home integration, and EPC rating C.
- • EPC rating: C (74)
- • Heating cost: £1,400/year
- • 3 premium bathrooms
- • Slim-double-glazed sashes
- • New A-rated combi
Challenge
Conservation-area consent required for sash window upgrades and new dormer at rear. Family wanted to remain in property for first 4 weeks.
Solution
Phased works with ground-floor rooms completed first as habitable zone. All planning consent secured before strip-out.
"They handled the conservation officer brilliantly and the period detailing is better than the original. We could not be happier."
Project 2
Mansion-block flat house extension in Merton Road Southfields
Duration
12 weeks on site
Budget
£95,000 – £125,000
Scope
Premium flat house extension: full rewire, replumb, new kitchen, two bathrooms, acoustic insulation, and managing-agent coordination.
Before
Tired 1980s refit, electric storage heaters, no acoustic insulation, dated kitchen and bathrooms.
- • EPC rating: E (52)
- • Heating cost: £2,200/year
- • No acoustic insulation
- • 2 bathrooms (1 worn)
- • Electric storage heaters
After
Premium apartment with new gas central heating, acoustic insulation, designer kitchen, and stone bathrooms. EPC C.
- • EPC rating: C (76)
- • Heating cost: £950/year
- • Full Part E acoustic insulation
- • 2 stone bathrooms
- • Gas central heating
Challenge
Strict managing-agent rules: 8am–5pm working hours, lift bookings, no Saturday work, deposit £5k for communal-area damage.
Solution
Detailed method statement and risk assessment submitted upfront. Lift and porter slots booked weeks ahead. Communal areas protected daily.
"The managing agent said they'd never seen a contractor coordinate so well. Worth every penny for that alone."
Project 3
Family extension and refurb in Merton Road Southfields
Duration
22 weeks on site
Budget
£235,000 – £275,000
Scope
Side-return extension, full kitchen replacement, ground-floor reconfiguration, plus full upstairs refurbishment.
Before
Closed-off Victorian layout with narrow galley kitchen, cellular reception rooms, and tired upstairs bathrooms.
- • Floor area: 142 sqm
- • EPC: D
- • Original layout: 7 rooms
- • £0 added value
After
Open-plan kitchen-dining-family living across rear, restored front reception, three new bathrooms, and converted loft bedroom.
- • Floor area: 178 sqm (+25%)
- • EPC: C
- • New layout: 9 rooms
- • £420k added value (estimated)
Challenge
Permitted-development limits, party wall agreement with two neighbours, and a tight side-return access.
Solution
Crane delivery for steels over rear roof. Both party wall agreements secured pre-start. Architect-led design package.
"They turned a tired family house into the home of our dreams without losing the character. Best decision we made."
House Extension Pricing FAQs - Merton Road Southfields
Find answers to common questions about our services.
House Extension in Merton Road Southfields typically ranges from £30,000 to £180,000. The exact price depends on: Extension size, Construction type, Foundation requirements. HAMPSTEAD RENOVATIONS provides free, no-obligation quotes for Merton Road Southfields properties.
Our house extension price includes: Planning drawings, Building regulations, Groundworks, Construction, Roofing, First-fix services. There are no hidden extras - we believe in complete transparency. The quote you receive is the price you pay.
House Extension typically takes 8-16 weeks. The exact duration depends on project complexity and any specific requirements for Merton Road Southfields properties. We provide detailed timelines with every quote.
HAMPSTEAD RENOVATIONS provides 10 years structural guarantee. We stand behind our work with comprehensive guarantees that give you complete peace of mind.
HAMPSTEAD RENOVATIONS offers transparent pricing with no hidden fees, local expertise in Merton Road Southfields properties, comprehensive warranties, and published review evidence across London. Our current aggregate rating is 4.9 from 183 published reviews.
More price routes
Compare other service budgets in Merton Road Southfields
These guides use the same transparent structure, so you can compare scope and budget before building a broader project brief.
Merton Road Southfields
Full House Renovation
Complete property renovation including structural work, electrical, plumbing, and finishes.
From £80,000
Merton Road Southfields
Kitchen Renovation
Complete kitchen transformation from design to installation.
From £15,000
Merton Road Southfields
Bathroom Renovation
Complete bathroom design and installation services.
From £8,000
Merton Road Southfields
Loft Conversion
Transform your loft into valuable living space.
From £30,000
Merton Road Southfields
Basement Conversion
Create additional living space with a basement conversion.
From £50,000
Merton Road Southfields
Electrical Rewire
Complete electrical rewiring for safety and modern standards.
From £3,000
Speak to the office
Get a sharper house extension quote for Merton Road Southfields
Call the office for budgeting and programme guidance, or send your brief for a fuller written quotation. We will explain what is included, what can move cost, and which tier best fits your property.
Typical start point
£30,000
Published rating
4.9 / 5
Across 183 published reviews.
Best first call
Office for budgeting, mobile for quick response