Specification level affects materials, finishes and allowances across the build.
Essential / rental-spec
Standard materials and basic finishes. Works for tight budgets and rentals.
Comfortable family home
Good quality materials, branded appliances, solid finishes. Most common choice.
Premium specification
Higher end materials and fixtures, stronger design focus and details.
Bespoke / luxury
Top tier finishes, bespoke joinery and detailed architect led specification.
4
Structural & groundwork
Foundations and structure based on ground conditions and the level of opening up.
Standard foundations
Strip foundations to 1m depth for typical ground conditions.
£8,000-12,000
Piled foundations
For clay soils, trees nearby or poor bearing ground.
+£15,000-25,000
Structural steelwork
Typical beams for knock throughs and open plan spaces.
£6,000-10,000
Demolition works
Removing existing structures, internal walls or outbuildings.
£3,000-8,000
Tight access / restricted site
Rear access through house, limited storage, or narrow street access. Increases prelims, labour
time and plant costs.
+£7,000-12,000
Party wall & neighbour matters
Allowance for surveyor fees and temporary support/works to adjoining property.
+£3,000-6,000
Complex scaffolding / protection
Full wrap scaffolding, crash decks, and protection to neighbouring roofs or pavements.
+£5,000-10,000
Basement waterproofing & tanking
Cavity drain membranes, sump pump and tanking to below-ground areas.
+£8,000-20,000
5
External envelope (shell)
Walls, roof and glazing, effectively the weather tight shell of your build.
Standard (approx. 20%)Feature (approx. 35%)Very glazed (50%+)
6
First fix (services in the walls)
Core plumbing, electrics and heating infrastructure before plastering.
Electrical first fix
Wiring for sockets, lighting and consumer unit upgrades.
£4,000-6,000
Plumbing first fix
Hot and cold feeds, waste pipes and radiator pipework.
£3,000-5,000
Heating system
New boiler or upgrade, radiators, controls and cylinder if needed.
£5,000-8,000
Underfloor heating
Wet UFH system for the ground floor with controls.
+£80-120/m²
MVHR system
Mechanical ventilation with heat recovery for airtight builds.
+£6,000-10,000
Smart home pre wire
CAT6 data, speaker cabling and smart lighting infrastructure.
+£2,000-4,000
7
Internal finishes
Plastering, flooring and internal joinery, the things you live with every day.
Includes door, frame, ironmongery and fitting.
Note that adding items also increases fees and contingency, so the overall total moves by more than this item alone.
8
Kitchen (optional)
Complete kitchen including units, worktops, appliances and installation if required.
Include a fitted kitchen
Add a full kitchen package to your build.
Configure below
Integrated appliances
Oven, hob, extractor, dishwasher and fridge freezer.
£3,000-5,000
9
Bathrooms (optional)
Bathrooms, ensuites and cloakrooms with full sanitaryware and tiling.
Include bathrooms
Add bathrooms and ensuites to your build.
Configure below
Includes bath or shower, WC, basin, tiling and towel rail.
Indicative allowance: £3,000-6,000 per ensuite.
10
Second fix (final fit out)
Final electrical and plumbing connections, fittings and commissioning.
Electrical second fix
Sockets, switches, light fittings, testing and certification.
£2,000-3,000
Plumbing second fix
Connecting sanitaryware, radiators and taps, plus testing.
£1,500-2,500
Designer lighting package
Architectural lighting, feature pendants and layered lighting.
+£3,000-6,000
Smart home setup
Smart heating, lighting, security and voice control.
+£4,000-8,000
11
External works & landscaping (optional)
Patios, driveways and basic landscaping around your new space.
Patio area
Approx. 30m² porcelain patio including sub base and drainage.
£3,000-5,000
Driveway
Block paved or resin drive with drainage, approx. 40m².
£5,000-8,000
Basic landscaping
New turf, simple borders and fencing repairs.
£2,000-4,000
Bi fold / terrace package
Approx. 4m bi fold doors plus matching terrace works.
£8,000-12,000
12
Professional fees & management
Essential design, approvals and oversight to safeguard quality and compliance.
Architectural services
Design, planning, building regulations and tender information.
Est. 10% of build
Structural engineer
Calculations, drawings and liaison with building control.
£2,500-4,000
Project management
Professional coordination of trades and programme.
Est. 6% of build
Building control
Inspections and approvals via local authority or inspector.
£1,500-2,500
Warranties
Structural warranty or similar latent defects cover.
£1,000-2,000
13
Risk & contingency
Practical allowance for unknowns, especially important on existing properties.
10% (new build)15% (typical)20% (older / complex)
Higher contingency is sensible for older properties or tricky sites.
Important note on estimates
This calculator provides order of magnitude estimates only, based on typical UK build costs and assumptions at 2025 prices. Actual prices will vary with site conditions, access, structural complexity, specification and market conditions. VAT is additional where applicable and finance costs are not included.
Rates are compiled from industry benchmark data (including BCIS indices, quantity surveyor cost plans and anonymised tender returns) and are intended as a starting point for discussion, not as a quotation or offer to carry out work. You should always obtain firm quotations from contractors and allow a 10-20% contingency.
Nothing on this page constitutes financial, legal or technical advice. Before committing to a project you should take professional advice that is specific to your property and circumstances. Professional fees in this tool include architectural design, structural engineering, building control and (if selected) project management and warranty-related costs but are indicative only.
Live cost summary
Tap to collapse • updates in real time
On track against budget.
Include professional fees & contingency
Professional fees cover architectural design, structural engineer, building control and, if selected, project management and warranties. Contingency is a risk allowance for unknowns. You can switch these on or off in the total here for comparison.
Main construction£0
Structural items£0
Services (M&E)£0
Kitchen & bathrooms£0
Internal finishes£0
External works£0
Professional fees£0
Contingency£0
Estimated project total
£0
VAT is additional where applicable.
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