How Much Does a House Extension Cost?

By April 2, 2021July 7th, 2021General

How Much Does a House Extension Cost?

Basic Single Storey Extension

£1,200 – £1,500 per m2
Example – 4m x 5m extension
£24,000 – £30,000
10-15% for professional fees (design / drawings, planning application, building regs, structural engineer)
£ 2,400
Single storey extension = £32,000

Basic Two Storey Extension

Approx. 50% extra to the build cost of a single storey extension.
£ 30,000 +50% = £45,000
+ Add on 10-15% for professional fees (design/ drawings, planning application, building regs, structural engineer)
+ VAT
£ 3,000
Two Storey Extension = £48,000

These costs do not include the following (if required): –

Kitchen
Bathroom
Structural Steel
Vaulted ceiling with roof lights
Stairs other than standard straight softwood
Bay window
Balcony
Glazed balustrades
Folding / sliding doors – UPVC
Folding / sliding doors – Aluminium powder coated
Roof covering- other than standard concrete, slate small clay tiles metal
Electrics – downlighters
Light fittings
Feature radiators
Underfloor heating
Wall tiles and splash backs
Fitted joinery – example cupboards
Hardwood joinery – example skirting architrave
Internal doors other than standard
Door handles / locks other than standard
Floor finishes
Curtains / blinds
Coving

Work to existing property

New boiler existing boiler may not have capacity to heat increase in size of property
New RCB electric box (may have an old fuse box that requires replacement)
New electric circuit a new circuit may be required to the extension this can sometimes mean a new RCB
Remedial work to existing structure example the existing structure may not comply to building regulations / structural standards
Remedial work to existing electrics – existing electrics may not comply to present day standards – as a matter of safety and this may need updating
Removal of asbestos – As a matter of safety this may need to be removed possibly by licensed contractors
Levelling of existing floor for new flooring – existing floor may not be even or level enough to lay some flooring to manufacturer’s specification

Associated works

Demolition and removal of existing structures including paved areas
Breakthrough for new access and making good
Removal of existing fittings and possible replacement
Removal of any structural walls
Moving any pipework, drainage, gas meters

Site and Ground Conditions

Limited access to the site requiring more labour time
Soil type and ground conditions requiring more expensive foundations / ground floor construction
Raised floor from ground level requiring more brickwork / blockwork
Reduced ground level – increasing soil or material to be taken away
Re – direction of underground drainage or services

External Works

Paths
Paving
Decking
Landscaping

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