Home & Garden cost guide

Loft Conversion Cost Guide

Cost estimates and information on loft conversions

To convert the space you have in your loft is perhaps the cheapest option for adding extra living space to your home. They are not suitable for all types of property but the extra space can have many different uses. Let’s look at what some of the issues and how the costs involved add up.

Skip to our prices 

Planning permission

In many cases if the loft conversion doesn’t add to the volume of the house (that is extend it upwards or outwards) then you probably won’t need planning permission. If in doubt, as always talk to your builder and/or local planning office. There are circumstances in which you will almost certainly need planning permission.

  • If you wish to extend the roof by any amount in a Conservation Area, Area of Outstanding Natural Beauty or National Park.
  • If the conversion will at any point be higher than the existing roof.
  • If you have a dormer installed and it’s not set back further than 200mm from the original eaves (unless impossible to do so).
  • Any extension protrudes further than the outer wall of the original house, or if it has platforms or balconies.

As with normal house extensions you can add to your property without planning permission if the volume of the additional space is less than a given amount. You cannot add more than:

  • Terraced property 40m3 and 50m3 on semi-detached and detached.
  • These figures are with respect to the original size of the property before any extensions or previous loft conversions were added.
  • Consult a planning officer or ask a professional if in doubt.

The volume constraints are based upon the external dimension of the conversion you are planning. 

Even if you do not need to seek planning permission (but be careful getting permission retrospectively is tricky) then the modification to the property will need to comply with building regulations for loft conversions.

Building regulations

The main aim of these is to ensure that the property is still safe for the occupants after the conversion has been adding. In summary this includes

  • Structural Safety
    • Is the new floor in the loft strong enough to support the additional weight?
    • The existing properties load bearing wall, interior joists and foundations were designed without a loft conversion in mind and its extra loading, new floor joists will probably be needed. These will normally run alongside your existing joists spanning between walls, which may need to be reinforced.
  • Fire Safety
    • The materials used in the construction of the outer skin of the conversion (walls, roof, flooring, doors) should be able to act as fire breaks for a reasonable amount of time to allow for any persons trapped within the room to be rescued.
    •  At least one window must meet dimensional guidelines in terms of is size and location to aid escape via easy access from a ladder.
    • A fire door must be installed at either the top or bottom of the new staircase to separate the loft room.
  • Stairs
    • In addition to the fire regulations mentioned above, there are additional regulations pertaining to staircases that must be followed.
  • Insulation
    • Both in terms of sound insulation and heat insulation. If you are part of a terraced or semi detached than you will also need to consider the join between the two houses as well as the floor and roof.

If the loft conversion is going into a 3 storey building then the rules are similar but stricter.

Types of loft conversion

  • Rooflight (Velux)
    In this type of conversion no additional space is added to the loft. At least one of the windows is placed into the roof tiles and is often of the type Velux, hence the name, though there are alternatives. This is common among smaller loft conversions.
  • Dormer
    The living space in the loft is extended out. This is usually because without it there would be insufficient space. It requires additional building work especially in how it structurally joins the existing rafters. This extra work and materials mean that dormer projects cost between £5-8k more than ‘Velux’ ones.
  • Mansard
    The mansard roof typically has a flat top and is known for its distinct box-like appearance. This type of loft conversion often provides more space compared to other loft conversion types, making it popular in urban areas where maximizing living space is crucial. Mansard conversions are commonly found in historical or older buildings, but they can be applied to various architectural styles. The construction of a mansard loft conversion is more involved and may require planning permission due to the significant alterations to the roof structure and the overall appearance of the building.
  • Hip to gable

    This type of conversion will entail changing a hip roof to a gable roof to accommodate a loft. The construction work to be done with this kind of conversion is pretty much extensive that a building permit is necessary. The structural stability of a hipped roof is insufficient to carry the load of the new floor beams of the proposed loft conversion. The headroom that is available in a hipped roof does not meet the minimum 2.10 meters in most cases therefore there would not be enough room for a habitable space in a hipped roof loft conversion.

    Changing a hip to a gable roof will make it feasible to convert the roof space into a habitable loft. If the hip to gable roof change is too much in terms of cost and effort, then the best option is to opt for a dormer loft conversion.

Time taken

Obviously varies with the size and complexity of the project but one could expect it to take between 4-12 weeks to complete, not including any planning permission etc (if required). 

Loft conversion prices

  • Plans
    • Whilst many loft conversion companies will survey and plan it out for you it’s also possible to employ an architect and structural engineer and then contract a builder to construct it for you. Plans can start at around £750 ranging to over £2,000 depending on complexity.
  • Building Control Officer
    • The plans have to submitted to the BCO who inspects them and will also have to do a site inspection. There are two fees you will have to pay which are combined together into a single Building Notice Charge.
      • Plan Fee – £190-250
      • Inspection Fee – £400-500
      • Both exclude VAT.
  • Misc
    • Typically things like scaffolding for working at height and skips to remove the rubbish can cost in the region of £3,000-5,000.
  • Party Wall Agreement
    • If you share an adjoining wall with another property you may need a Party Wall agreement, this will cost around £1,500.
  • Staircase
    • Straight forward off the shelf staircases start at about £1,000 but can quickly approach £2,000. If it needs to be a bespoke staircase then start looking at more than £3,000 (unless it’s perhaps done by your joiner as part of another larger job).
  • Windows
    • Often Velux™ these windows come in a variety of sizes and finishes but typically start in price at about £300 per window.
    • Escape windows that meet building regulations cost more starting at around £400 per window.
    • Blackout blinds for the windows can be expensive for the size of windows starting at around £90 whilst simpler roller blinds are about £60 per window.
  • Complete Project Costs
    • This includes the scaffolding, any insulation, joinery, structural check, usually liaising with the authorities if needed and builder labour charges. One can expect to pay around £1,000 per m2 for a straightforward rooflight (velux window) conversion. Try our loft conversion calculator to generate an estimated price for your project.

User submitted loft conversion costs

The table below shows the latest prices received from WhatPrice users, who have either had a conversion done or received a quote for one.

Job typeDescriptionPriceUnitsRegionUpdated
Loft conversion

Full dormer conversion with a single large bedroom, ensure and dressing area. All construction, insulation plumbing and wiring, 2 velux windows, Juliet balcony and all internal joinery. Excludes painting and tiling.


Total priceSouth East2023
Loft conversion

48sqm mansard 2 bedrooms and ensuite


Total priceLondon2023
Loft conversion

35m2 loft conversion with bathroom (bath). Dormer back, 2 velux front.


Total priceSouth East2023
Loft conversion

ripping out old building work. Dormer extension, 4 radiators, bathroom suite, electrics, plumbing, plastering.


Total priceSouth East2023
Loft conversion

Loft conversion to add a bedroom. About 5m x 3m. All wiring, plumbing for radiator,two velux windows, insulation, plastering and staircase


Total priceEast Midlands2023
Loft conversion

Loft conversion include bathroom installation, include painting, plastering etc.


Total priceLondon2023
Loft conversion

9x4m Flat roof Dormer conversion to create 2 beds & bathroom. Included everything bar floor finish, Bathroom fittings & decorating. Finished to a extremely high standard & would recommend builder.


Total priceEast Midlands2023
Loft conversion

Bungalow loft conversion, front/back dormer windows, new roof, creating one single 1 double bedrooms and storage space. Stairs, 5 plug sockets, all lighting, two rads finished job.


Total priceNorth West2023
Loft conversion

New floor putting in, incl. floor joists and floor boards, removal of chimney breast, full rear dormer with steel beams, installation of staircase, two skylight velux to front, electric points in each room, incl extractor fan in bathroom and all tiling/plumbing (5 radiators), connection to main sewers, change mains fuse board, plastering.


Total priceNorth East2023
Loft conversion

Stairs, 2 large rooms and landing. 4 velux windows, 2 radiators, loft access points, electrics, plastering, smoke alarms and move existing water tank, etc.


Total priceSouth East2023
Loft conversion

3 bedrooms and a bathroom in a loft roughly 50m2 Open plan stair made, 5.5 m x 4 m dormer, huge window in bedroom 4 velux and a bathroom window all fittings and plastered. Only thing not included was the plumbing.


Total priceScotland2023
Loft conversion

extended existing attic room to two bedrooms and ensuite bathroom (fittings not included) with 5 velux windows, raising height of existing ceiling, upgrading insulation, electrics, heating and plastering. Already had a staircase to the attic room


Total priceEast Midlands2023
Loft conversion

loft space size 7m x16 three velux windows two dormer windows 1200×1200 three rads two rooms,bath standard elecs plaster finish


Total priceWest Midlands2023
Loft conversion

Bedroom loft extension, with shower room, toilet and sink en suite bathroom. 3 radiators, 13 double sockets, 2 Velux windows, patio doors, juliette balcony, replace roof tiles, re-point chimneys, replace chimney pots, new guttering and replace cast iron rain water waste. Fitted new ensuite bathroom with all tiling, granite floor, electrics and steam shower. Mains linked fire alarms x 2, oak fire doors x 2. Cupboard built into eaves. New staircase. Lay oak flooring to 1st floor landing, laminate flooring to bedroom and all decorating to and including 1st floor landing. Cost includes all materials, fittings, labour, building control and architect.


Total priceLondon2023
Loft conversion

loft conversion creating 2 x double bedrooms and a shower room. Job inc planning permission, central heating, staircases, 6 x velux windows, doors, all materials inc sanitary/shower ware & all labour – joinery, roofing, plumbing, electrical, design etc


Total priceScotland2023
Loft conversion

New stairs, fitted bathroom, bedroom. 2 cupboards 2 radiators, 2 dormer windows


Total priceSouth West2023
Loft conversion

Very high standard with 2 dormers and shower, WC and basin


Per m²North East2023
Loft conversion

Basic but fully finished with plastering and roofline windows


Per m²Cymru Wales2023
Loft conversion

7x4m loft space, easy stair access from landing, separate bathroom (shower, toilet and hand basin) and single bedroom with the bedroom having a small dormer on it. price includes everything.


Total priceSouth West2023
Loft conversion

Crated two new bedrooms plus a bathroom with two dormer. Took 12 weeks.


Total priceWest Midlands2023
Loft conversion

Simple conversion with no dormers to a one bedroom, three double sockets straight staircase, 7x6m


Total priceEast of England2023
Loft conversion

Fairly straightforward conversion as no plumbing in loft. 8×6 area plus addition of two dormers. price includes everything to the point of decorating.


Total priceEast of England2023
Loft conversion

Hip to gable 1 room and a bathroom


Total priceLondon2023

How much did you pay?

1 – Price submit form – Home & Garden

Please tell us your own prices

To make WhatPrice possible we need your input! We rely on people like you telling us how much was paid (or been quoted) for many jobs and services across the UK, our goal is to help prevent others being ripped off and get the best deal.
Typical level of kitchens, tiling, sanitary ware, switches and other fittings included in the price
Includes VAT?
Please do not include any personally identifiable information. Price information is held anonymously and used to inform and power our pricing guides and calculators.

What is Rising Damp?


What is Polished Plaster?


What is Lime Plaster?


Replacement uPVC Guttering