October 29, 2026

Loft Conversion Cost UK 2026: Prices, Budgets and Quote Checks

A loft conversion typically costs around £30,000 to £160,000, depending on the roof alterations, structural work and specification. A straightforward rooflight conversion sits towards the lower end, while a mansard involving substantial roof rebuilding sits towards the upper end.


Those figures are starting points, not fixed prices. Location, access, bathrooms, finishes and the scope of the builder’s quotation can change the budget considerably. VAT also needs checking: a £175,000 quotation excluding VAT becomes £210,000 when 20% VAT is added.


The most useful way to budget is to identify the conversion type, separate construction costs from other allowances, and compare quotations against the same detailed scope.


Key Takeaways

  • Indicative budgets range from £30,000 to £45,000 for rooflight work to £80,000 to £160,000 for a mansard.
  • Compare quotes on the same scope, floor-area basis and VAT treatment.
  • Allow for access, existing services, hidden structural work and making good.
  • Check planning requirements early; building regulations apply even without planning permission.



Table of Contents

How Much Does a Loft Conversion Cost in 2026?


The following ranges provide a practical early budget for four common approaches. Check whether any estimate includes VAT, professional fees and the complete internal fit-out before comparing it with another price.


These are indicative construction periods, not the total time from initial design to completion. Design work, permission checks and preparation sit outside the on-site programme.


A broad £40,000 to £80,000 headline estimate can be useful for initial research, but it does not cover every project. More involved builder quotations can fall between £60,000 and £150,000, depending on specification and structural detail.

What Should a Loft Conversion Quote Include?


A total price is only useful when you know what it buys. Ask for a breakdown that separates the physical building work, site-running costs, contractor overheads and any exclusions.


Construction and fit-out

  • Structure: steel beams, floor joists, roof alterations and any temporary support.
  • Roofing: coverings, dormer construction, rooflights and associated installation.
  • Internal finishes: insulation, plasterboard, flooring, wall finishes and decoration.
  • Access: the new staircase and work needed around its opening.
  • Services: electrical and plumbing installation, including connections to existing systems.
  • Room specification: bedroom, bathroom or en suite, and storage where included.


Site costs and business overheads

Scaffolding, waste removal, site setup and project management all cost money, even though they do not become part of the finished room. Contractor overheads can also include vehicles and the time spent managing the job.


These allowances are not automatically unnecessary extras. The important question is whether they are clearly described and consistently included across the quotations you compare.


Fees, approvals and contingency

Check allowances for structural engineering, building regulations, planning requirements and any applicable party wall matters. Do not assume that these are included simply because the quotation describes a complete loft conversion.


There should also be a clear approach to contingency and unforeseen work. Opening an existing roof or removing linings can reveal problems that were not visible when the original price was prepared.

Why London Prices Can Be Higher


Indicative regional rates provide another way to check an early loft conversion budget:


  • London: approximately £2,200 to £3,200 per m².
  • Outside London: approximately £1,500 to £2,400 per m².


These figures are broad feasibility guides, not substitutes for measuring and pricing the actual work. A simple rooflight scheme and a structurally complex mansard should not be expected to cost the same per square metre.


Location is also about more than the property’s postcode. A London-based company using its usual workforce outside the capital may still quote at London rates.


Access can matter as much as floor area

Work at the top of an occupied house can involve carrying materials through several flights of stairs, protecting existing finishes and working in narrow spaces. Limited parking and little room for storage can add further difficulty.


Two schemes with similar floor areas may therefore have different costs. A useful quotation should reflect the actual access and working conditions rather than relying solely on a standard rate.

A £210,000 Example: Why Project Scope Matters


A priced London project combining an extension with loft work came to £175,000 excluding VAT, or £210,000 including VAT. It included a 46 m² lower extension component and loft accommodation above, with approximately 92 m² used as the combined floor-area basis.


This was not a standalone loft conversion. Using its total price as an ordinary loft benchmark would be misleading because the budget also covered the extension below.


Selected allowances from the combined project show how a substantial construction budget builds up:


These are selected items, not a complete cost schedule. The electrical allowance covered first and second fix, rather than a full house rewire. Similarly, the plumbing allowance should not be interpreted as covering every possible upgrade to the existing property.


Compare like-for-like floor areas

A cost-per-m² figure is only meaningful when the price and measured area cover the same scope. Dividing the £175,000 combined-project price by the 46 m² lower footprint produces roughly £3,800 per m², but that calculation includes work above the footprint too.


When checking a loft conversion quote, ask which floor area has been measured and which costs are included in the numerator. Otherwise, apparently precise rates can give a false comparison.

Which Conversion Type Fits Your Budget?


Rooflight: the least extensive roof alteration

A rooflight loft conversion generally retains the existing roof shape. The work can include insulation, plasterboard, flooring, a staircase, electrics, decoration and two to four rooflights.


The lower price reflects fewer external alterations. It does not mean the project is merely decorative: the space still needs appropriate structural work and a compliant fit-out. Check bathroom provision carefully rather than assuming every rooflight quotation includes one.


Dormer: more space with a larger structural package

A dormer projects from the roof, commonly as a box-shaped addition at the rear. It is a common option for terraces and semi-detached houses.


The construction package can include steel beams, new floor joists, temporary support, structural engineering, dormer side walls and a flat roof. A typical fit-out may provide a bedroom, en suite and storage.


Hip-to-gable: changing the sloping roof end

A hip-to-gable loft conversion replaces a sloping end of the roof with a vertical gable to increase usable space. It can suit semi-detached and end-of-terrace properties with the relevant roof form, and is often combined with a rear dormer.


That additional roof restructuring helps explain its higher budget compared with a straightforward rooflight scheme.


Mansard: substantial roof rebuilding

A mansard creates a much steeper roof profile and involves extensive rebuilding. It can provide substantial usable space, but its structural scope, roof work and longer programme place it towards the top of the price range.


For this type of loft conversion, permission checks and a detailed specification are particularly important before treating a preliminary budget as a reliable quotation.

Hidden Costs and Budget Risks to Check


Connecting new services to old systems

New electrical and plumbing work must connect to the existing house. Additional work may become necessary if those connections are more involved than allowed for.


Ask what the services price includes, what existing installations have been assessed, and how further work would be priced.


Opening up the existing structure

Removing linings or opening the roof may expose the need for additional floor or roof joists. A contingency can help accommodate this uncertainty, but it should not replace a clearly defined base scope.


The £5,750 contingency in the combined-project example was specific to that job. It is not a universal allowance for every loft conversion.


Damage and making good

Moving trades and materials through the house can affect walls and finishes below the loft. Check whether protection, repairs, decoration and final defect correction are included.


Supply-only allowances

A product allowance may not include fitting. The example rooflights were priced at £1,150 each, with installation accounted for elsewhere. Check the same distinction for other quoted items.


VAT and exclusions

Never compare a VAT-inclusive price with an excluding-VAT price without adjusting it. Also check whether scaffolding, skips, fees, bathroom work and final decoration are inside or outside the headline total.

Planning Permission and Building Regulations


Some loft work can fall under permitted development, but this is not automatic. Check the applicable rules before committing to a design or relying on a budget that excludes a planning application.


For qualifying houses in England, the commonly cited permitted development roof-volume limits are:

  • Terraced houses: up to 40 m³ of additional roof space.
  • Semi-detached and detached houses: up to 50 m³ of additional roof space.


These are cubic metres of volume, not square metres of floor area. They are not the only conditions that matter, and existing roof additions must be considered when checking the allowance.


Flats, listed buildings, conservation areas, National Landscapes and proposals involving the front roof slope need particular care. Mansard schemes and designs exceeding permitted development limits also require early permission checks. Rules differ across the UK, so confirm the position with the relevant local authority.


Building regulations still apply even when planning permission is not required. A loft conversion must address matters including structure, insulation, fire safety and escape, stairs and ventilation.

How to Compare Loft Conversion Quotes Properly


  1. Set the scope. Identify the conversion type, rooms, bathroom provision, rooflights, storage and finishes.
  2. Confirm the measured area. Make sure each builder is pricing the same scheme.
  3. Request an itemised breakdown. Separate structure, roofing, services, fit-out, site costs and overheads.
  4. Check allowances and exclusions. Identify supply-only prices, provisional amounts and work outside the total.
  5. Confirm VAT and fees. Put all quotations on the same basis before comparing them.
  6. Review uncertainty. Ask how hidden structural problems and additional service connections will be handled.
  7. Check the programme. Understand the assumed duration and allowances for project management and site setup.


For an early decision, a feasibility estimate can establish whether the project is affordable. Once the scope is developed, a detailed bill of quantities can separate labour and materials by trade, supported by a materials schedule and programme.


This is more useful than choosing solely on the lowest headline price. It makes omissions easier to spot and provides a clearer basis for checking costs as work proceeds.

Does a Loft Conversion Add Enough Value to Be Worth It?


Adding a bedroom and bathroom can increase a property’s value. An indicative uplift of around 15% to 20% is sometimes used for this kind of improvement, but it should not be treated as a guaranteed return.


The relevant comparison is the complete project cost against the likely value and usefulness of the finished home. Local property values and the resulting room arrangement matter more than a percentage applied in isolation.


It is also worth comparing the project with moving. Stamp duty, estate agent fees and other moving expenses can make staying and improving attractive. That does not mean every loft conversion is cheaper than relocating, but those costs belong in the decision.

Setting a Realistic Budget


Start with the range for your proposed conversion type, then refine it around the property, location and specification. Before agreeing a contract, make sure VAT, fees, access costs, fit-out and contingency are clearly addressed.


The best budget is a priced scope of work, not a national average. An itemised quotation explains why the project costs what it does and gives you a firmer basis for deciding whether to proceed.

Frequently Asked Questions

What is the cheapest type of loft conversion?

A rooflight or Velux conversion generally has the lowest indicative budget, at £30,000 to £45,000, because it largely retains the existing roof shape. The final price still depends on structural requirements and the internal specification.

How much does a dormer loft conversion cost?

An indicative 2026 budget is £50,000 to £90,000. Steelwork, new floor joists, roofing, bathroom provision, finishes and location can all affect the quotation.

How long does a loft conversion take?

Indicative on-site programmes are 4 to 6 weeks for rooflight work, 8 to 12 weeks for a dormer, 10 to 14 weeks for hip-to-gable work and 14 to 20 weeks for a mansard. Allow additional time for design, approvals and preparation.

Do loft conversion prices include VAT?

Not necessarily. Ask for the VAT treatment in writing. In the combined extension-and-loft example, £175,000 excluding VAT became £210,000 including VAT at 20%.

Can a loft conversion be built without planning permission?

Some qualifying schemes can proceed under permitted development, subject to the applicable conditions. Property type, location, roof-volume additions and design all need checking. Building regulations still apply.

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