The average cost of a loft conversion in the U.K. is £41,000.
Small projects start at about £20,000. Large loft conversions can exceed £65,000, especially when premium materials are used and/or the roof structure is modified.
Per square metre, the cost is less than £1,000 to more than £1,600.
This summary table shows loft conversion prices for common requirements and their cost factors.
|Loft Conversion Cost & Prices|
|Low Cost||Average Cost||High Cost|
|Cost Range||£20,000 – £32,000||£33,000 – £46,000||£47,000 – £65,000+|
|Dormer||No||Up to 2||2+|
|Bath||No||No||Yes or No|
|Quality||Average||Average – Good||Good – Best|
|Architect||No||Yes or No||Yes|
|Roof Change||No||Yes or No||Yes or No|
Loft Conversion Overview
Each loft conversion is unique depending on what you’re starting with and what you plan to achieve.
The simplest conversions involve working with the space you already have and adding just the basics:
- Finished walls
- One or two roof windows
- Loft Insulation (Or moving the insulation from the floor of the loft to the ceiling)
- A few light fixtures
Some basic loft conversions don’t require the addition of heat, since heat from the house below will naturally rise. If anything, some lofts are too warm rather than cold, even in winter, especially when properly insulated.
This Improvement Costs posts includes cost factors needed to estimate the loft conversion cost you’re considering.
There’s much more:
- Cost factors
- A list of miscellaneous costs
- Permission information
- Advice on DIY loft conversion
- Time it takes for professional fitters to convert a loft
- The opportunity to get free quotes from experienced tradesmen in your area
Loft Conversion Cost Factors
The cost of your project will be impacted by these factors.
- Loft size: The larger the loft, the more of everything you need – Skylights or dormers, lighting fixtures, flooring, etc.
- Demolition required: The more material that must be removed from the loft prior to the conversion, the higher the cost will be for the work and skip hire.
- Roof window vs Dormers: Skylights and roof windows cost far less than dormers, but dormers can provide extra space and a larger view to the garden.
- Roof modifications: Any alteration to the roof structure other than installing skylights will raise the cost. Options are to expand outward with dormers or upwards by modifying the roof trusses. A hip roof can also be raised to a gable to create headroom.
- Materials quality: Your options range from cheap to very expensive flooring, windows, walls, decor, etc.
- Whether a bath is included: Cost goes up quickly when plumbing and fixtures for a bathroom installation costs are included.
- The company you hire: Small companies with fewer employees tend to have lower costs and give more competitive bids than large companies with loads of overhead costs. If you hire a small company, just be sure the fitters are certified and experienced.
- Hiring an architect or structural engineer: Many loft conversion companies roll these costs into their quotes. If you hire an architect or engineer separately, feels will exceed £2,000.
- Where you live: Costs in London are higher than in the South, Southwest, Midlands and North.
Here’s an itemised table that will help you put together your own estimate before getting quotes from loft conversion contractors.
Extent of work, number of outlets and lighting fittings
Number and quality of the fixtures
|Flooring||£15-£100 per /M²||
Common options are vinyl and laminate (£), wood and tile (££-£££)
|Dormer||£3,500 – £5,000||
Size, quality of the window
|Skylight||£850 – £1,700||
Size, type and quality
|Roof changes||£7,500 – £15,000||Extent of work|
|Finished walls||£2,500 – £5,000||
Wall dimensions, quality of finish material
|Bath||£3,500 – £7,000||
Size, quality/cost of the sanitary ware
Planning Permissions and Fees
Lofts are permitted development (PD) in most areas. However, you might want to get a Certificate of Lawfulness from the council.
- £75 – £115 | Certificate of Lawfulness
- £1670 – £300 | Planning Permissions fee
- £550 – £900 | Party wall agreement (attached homes)
- £450 – £700 | Building control charges for planning and inspections
This table brings together all the costs listed above. It includes the most typical loft conversions.
All the basics are included in these estimates: Walls, flooring, electrics, finish electric, etc.
|Size in m2||Project||Average Cost|
|16-22||2 or 3 Roof Windows||£16,000 – £20,000|
|16-22||4 Roof Windows||£21,000 – £25,000|
|16-22||Dormer & 1 or 2 Roof Windows||£28,000 – £33,000|
|24-40||2 or 3 Roof Windows||£23,500 – £34,000|
|24-40||4 Roof Windows||£27,000 – £37,500|
|24-40||Dormer & 1 or 2 Roof Windows||£33,000 – £41,000|
|24-40||2 Dormers & 2 or 3 Roof Windows||£38,500 – £46,000|
|44 – 68||3 or 4 Roof Windows||£42,000 – £58,000|
|44 – 68||Dormer & 2 or 3 Roof Windows||£50,000 – £62,000|
|44 – 68||2 Dormers & 1 or 2 Roof Windows||£55,000 – £64,500|
|44 – 68||2 Dormers & 3 or 4 Roof Windows||£58,000 – £70,000|
How long does a loft conversion take?
If the schedule goes as planned, here’s what you can expect. Keep in mind some work can be done simultaneously.
- Removing old materials (if needed): 1-2 days depending on loft size.
- Structural alterations (if required): 1-2 days for a dormer; 2-4 days for major roofline changes.
- Electric and plumbing first fixing: 1-3 days each. The work will be done consecutively rather than at the same time to prevent tradesmen from getting in each other’s way.
- Roof window installation: A 2-person crew installs 2-3 per day
- Plastering the wall: 2-4 days
- Installing flooring: 1-3 days
- Finish electric and plumbing: 1 day to install sockets, light fixtures, sink and handles
Compare Loft Conversion Costs
Would you like to compare prices from loft conversion contractors in your area?
Use our free service to compare costs. There is no obligation to accept any of the estimates. It is your opportunity to get questions answered and compare loft conversion costs for the type of conversion you require on your property.
Frequently Asked Questions for Loft Conversions & Planning Permission?
[ultimate-faqs include_category=’loft-conversion’ ]