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Last updated: 12 April 2024

How Much Does a Dormer Loft Conversion Cost in 2024

dormer loft converson cost
  • For a small dormer loft of about 20 square metres, expect to pay £30,000–£35,000. For a medium-sized dormer of about 30 square metres, costs range from £40,000 to £45,000. Larger loft conversions over 40 square metres cost £45,000–£50,000.
  • The choice of a dormer type significantly influences the cost. Shed dormers tend to have a less complex style compared to more elaborate gable dormers.
  • Hidden fees such as structural repairs, scaffolding, waste disposal or VAT may impact the total cost. Keep 10–15% of the total budget on hold to cover surprise overages.

On this page, we will explore in detail the costs associated with dormer loft conversions, factors influencing these costs, and strategies for cost reduction. While reducing costs may be a great way to stay on budget, additional financing may sometimes be necessary.

We’ll discuss different financing sources, such as government and local grants and home improvement loans. Keep reading to uncover more.

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How Much Does a Dormer Loft Conversion Cost?

The cost of a dormer loft conversion in the UK ranges from £30,000 to £50,000 in 2024. The cost varies largely, and depends on many factors, such as the location, the size of your loft, chosen finishes, and more. These factors will be discussed in detail in the following section.

Here we broke down the cost for a small, medium and large conversion:

  • Small (20 square metres) — £30,000 to £35,000
  • Medium (30 square metres) — £40,000 to £45,000
  • Large (over 40 square metres) — £45,000 to £50,000

A two-bedroom ensuite dormer is a premium option, providing ample living space. The typical cost is £45,000 to £55,000. Adding a bathroom costs approximately an extra £5,000 to £7,000.

While more expensive, high-quality two-bedroom dormer maximises loft potential. The investment in enhanced comfort and usability makes it attractive for many homeowners. Careful budgeting allows the creation of an ideal living area in the roof space.

What Factors Affect the Cost of Dormer Loft Conversion?

Several key factors will determine the total cost of your dormer conversion:

What impacts the cost of dormer loft conversion?
  • Size: Larger dormers require more materials and labour, increasing costs over modest conversions.
  • Design: Shed dormers are simpler in style compared to elaborate gables. However, gables maximise space despite higher price tags. This means that more complex designs naturally will occur at higher costs.
  • Timeline: Expedited projects with tight deadlines mean higher fees from extra labour hours and overtime. Most standard conversions take 3-6 months.
  • Location: Construction in London and the South East is typically pricier than other UK regions due to premium rates.
  • Quality: High-end windows, stone, and luxury fittings add expense versus vinyl, laminates and standard items.

By thoroughly evaluating dormer size, building design, project timeline and location, you can establish a reliable budget estimate. Carefully weighing these major influences allows for accurate forecasting of total costs from start to finish.

Cost by Type

The table below shows typical price ranges based on dormer type, along with estimated project timelines:

Dormer typeAverage costAverage time for completion
Rear dormer£25,000–£45,0008–10 weeks
Side dormer£30,000–£50,0008–10 weeks
L-shaped dormer£35,000–£55,00010–12 weeks
Full dormer£40,000–£60,00012–14 weeks

More complex dormer types tend to be more pricey and typically require longer completion. For example, 2 bedroom loft conversion cost UK is on average £45,000–£60,000. Nevertheless, if you aim to fully maximise the size of your new loft, they could be the right choice for you.

dormer loft conversion types

Supply Costs

Purchasing materials make up a large part of the total dormer conversion budget. Key supply expenses include:

  • Windows
  • Floor coverings
  • Stairs
  • Insulation
  • Doors
  • Roofing
  • Bathroom fixtures

Below, we summarised the typical price ranges for standard and high-end fixture options.


  • Vinyl or composite window frames cost less than wood but withstand weather and wear. Opt for energy-saving double or triple-glazed panes.
  • Smaller window dimensions are cheaper to produce and install. Adding more modestly sized windows spreads natural light at a lower overall expense than fewer large panels. 
  • Consider four 600×600 mm windows rather than two 1200×1200 mm to maximise views without major premiums.
  • Strategic window placement also prevents heat loss in winter yet allows airflow in summer. An experienced architectural designer can advise cost-effective window solutions tailored to your dormer’s dimensions and exposure.
Window typeQualityAverage cost per 1 window
Small, vinyl, double glazedStandard£800
Large, wooden, double glazedPremium£2,400
dormer loft conversion windows


  • Laminate flooring is budget-friendly to install, however, it requires more regular upkeep versus wood over time. Scratches and fading arise under heavy use.
  • Carpet offers a more affordable alternative to refitting the entire loft space with hard flooring. It is softer on the feet than tile or laminate and provides additional insulation.
  • Carefully weigh durability versus cost when selecting loft floors. Considering lifespan prevents repeated future investments.
TypeQualityAverage cost for a 30 m2 dormer
Laminate throughoutStandard£1,000
Engineered woodPremium £3,000


  • If you already have a good staircase, you may not need to install a new one.
  • If your conversion requires a new staircase, opt for straight or L-shaped staircases to save on labour and materials. More elaborate spiral or curved designs severely increase project price and complexity.
  • Pinewood provides an economical option for attractive stairs. It stains well, complementing most aesthetics. Oak or exotic woods add expense mainly for decorative appeal.
TypeQualityAverage cost
Straight, pineStandard£1,000
Spiral, oakPremium£3,000
Dormer loft conversion stairs cost


  • Loft roll insulation meets minimum building requirements at the lowest material price. Supplement with rigid insulation boards for better energy efficiency at moderate extra expense.
  • Prioritise insulating roof rafters, which have the most heat loss. Insulate exterior walls if the budget allows for additional comfort and reduced energy bills. Floor insulation is optional to save costs, relying instead on carpets for underfoot warmth.
  • Install a vapour barrier to prevent dampness and condensation ruining insulation over time. Seek professional guidance to balance thermal performance with realistic dormer renovation budgets.
TypeQualityAverage cost
100m2 rigid boardsStandard£500
100m2 loft rollPremium (High efficiency)£1,500
Dormer loft conversion insulation cost

Internal Doors

  • Hollow core wooden doors made of affordable softwood provide a minimalist look that accepts paint or stain finishes.
  • Opt for simple 4-panel or 6-panel slab door styles, which minimise production costs compared to intricate decorative designs or pricey glass elements.
  • Lighter-weight hollow doors also reduce installation labour and hardware versus solid wood. If desired, upgrade lever handle sets over basic knobs to elevate aesthetics without breaking the budget.
TypeQualityAverage cost per door
Internal hollow coreStandard£100
Internal oak panelledPremium £500
loft conversion doors


  • Explore recycled polymer roof tiles or reclaimed slate shingles to save money while benefiting the environment. Repurposed materials cost less and prevent usable construction supplies from entering landfills.
  • For more affordable options, you can check local salvage yards and used building suppliers before purchasing new materials.
TypeQualityAverage cost for a 30 m2 dormer
Concrete tilesStandard£3,000
Natural slatePremium £6,000


  • Ceramic wall tiles and acrylic shower units provide affordable waterproof finishes. For more affordable options, you can avoid premium materials like heated floors or real stone surfaces, which hike project costs.
  • Modestly sized showers make the best use of small dormer bathroom spaces while consuming fewer tiling supplies and water during use. Limit unnecessary luxury walk-in showers for budget savings.
TypeQualityAverage cost
Basic suite, ceramic tilingStandard£2,000
Luxury suite, stone tilingPremium £5,000
Dormer loft conversion bathroom

Tradesman Costs

Hiring accredited specialists is crucial to constructing the dormer correctly and compliantly. Legally registered builders, plumbers and electricians come at the following typical labour rates:

ContractorPayment per day

Complex projects also require an architect for planning. The architects in the UK usually charge £800–£1,000 for overall planning and drawings.

Here we listed a few tips on getting budget-friendly tradesman costs for a dormer loft conversion:

  • Supply mundane materials yourself to avoid markups and compare prices.
  • Schedule your loft conversion during slower seasons for better pricing and take advantage of discounts. 
  • Think about offering 1–2 weeks of your own DIY work in return for a reduced rate from the builders.
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Hidden and Other Costs

Hidden expenses can sneak up during loft conversions. You can familiarise yourself with them to prepare for any unexpected costs. These include:

  • Structural repairs: Unnoticed rot or damage may require urgent structural reinforcement costing £2,000–£5,000. This will need to be addressed before you carry out any work.
  • Access equipment: External scaffolding for safe roof access and window work typically runs £500–£1,500. You can expect to pay around £22.50 per m2 per day for scaffolding.
  • Rubbish removal: Assume at least £500 to hire a waste removal company, more for higher volumes.
  • Building compliance: Meeting glazing, insulation, and fireproofing regulations often entails surprise expenses of £1,000–£3,000.
  • VAT at 20%: Don’t forget Value Added Tax on all labour and building materials. This gets overseen but adds up.
  • Contingency fund: We recommend saving 10–15% of the total budget for unforeseen additions or changes during the project. This provides flexibility to handle last-minute tweaks.

Careful dormer planning reduces shock expenses, but extra buffers pay for inevitable unknowns. Adding just 10–15% contingency can cover most surprise costs.

Rules and Regulations for Dormer Loft Conversion

Converting a loft into a living space requires adhering to building regulations and getting proper permissions. Understanding these requirements ahead of time helps avoid costly delays down the road.

dormer loft conversion regulations

Planning permission is usually needed if the dormer roof extends more than 0.3 metres above the existing roof ridge or if its width is over 50% of the original roof width. It is also required if you are located in a conservation area. 

Always check with your local council to confirm if planning permission is needed. Typical fees range from £150 to £500.

Party wall agreements come into play if the loft conversion extends onto or affects any walls shared with neighbours. Notifying and getting consent from adjacent property owners is critical to avoid disputes. Mid-terraced homes will need a party wall agreement on both sides. Hiring party wall surveyors usually costs £600–£1000.

Building regulations relate to important structural and system issues. Registered builders from Competent Person schemes can self-certify the work, saving for you building control approval fees of £500–£1000.

Here are some tips to potentially reduce costs:

  • Keep the dormer modest in size and matched to the existing house style. This may waive the need for planning permission.
  • Ensure the dormer stays within the property’s existing walls and footprint. This prevents party wall concerns.
  • Hire self-certifying builders to avoid building control fees.

Skipping critical approvals risks fines or rework. It’s best to plan for compliance costs upfront for a smooth loft conversion project.

Planning Permission

Planning permission for loft conversions usually depends on dormer size and how well it matches the existing home style. Planning permission is required for these dormer conversions:

  • Dormers extend more than 150mm beyond the roof slope
  • Dormers raise roof height by over 150mm
  • Dormers occupy over 50% of the total roof space
  • Dormers extend beyond the sides of the main roof

Additionally, consent may be needed if the new dormer does not blend with the architectural style of the house or neighbourhood. This is applicable to homes located in conservation areas. Approval is more likely if the dormer matches the property seamlessly.

Always consult with the council planning office to confirm if your specific dormer requires permission, even if it is below normal size limits. Some areas or properties may need approval regardless.

The permission process involves submitting drawings, plans and fees to the council for review. Decisions usually take 8–12 weeks. Approval depends on the dormer’s suitability for the home and surroundings.

Planning permission fees range from £150 to £500, depending on the local council. Extra charges may apply if resubmission is needed. Securing consent upfront prevents potential violations or removal orders later on.

Building Regulations

Loft conversions in the United Kingdom must meet Building Regulations in the key areas we describe below. Getting familiar with the regulations can help you understand whether additional work will be necessary, thus helping you identify potential extra costs.

  • Structural integrity: Existing roof structure and new beams must support the dormer’s weight and stresses. Structural calculations should validate load capacity.
  • Fire safety: Fire separation between floors and escape routes must be provided. Fire-rated doors, walls, ceilings and stairs may be required.
  • Electrical systems: New wiring, circuits and consumer units must meet standards. Additional lighting and power are needed.
  • Insulation: Wall, roof, and floor insulation must achieve minimum thermal efficiency. New elements require insulation.
  • Ventilation: Bathrooms and kitchens need extractor fans and humidity control to prevent moisture issues.
  • Plumbing: Water supply, waste pipes, and drainage must suit the new layout and fixtures. Overflow protection is required.

A building control surveyor typically inspects and signs off on compliance. Their fees range from £500–£1000.

You can waive building control approval if your builder is registered under the Competent Person self-certification scheme.

Ways You Can Reduce the Cost of Your Dormer Loft Conversion

Dormer loft conversions require significant investment. However, if you have a limited budget, there are cost-reduction strategies.

Tips to cut dormer loft conversion expenses:

  • Consult an architect: They will recommend ways to keep your renovation budget-friendly, preventing future overruns. Architects’ consulting and planning costs are around £1000. However, this investment will be worthwhile in the long run.
  • Use reclaimed materials: Salvaged bricks, wood, and doors are cheaper than new ones. Check reuse stores.
  • Choose budget finishes: Affordable flooring, windows, and insulation cut massive supply expenses.
  • Do tidying yourself: Doing your own removal work eliminates labour fees.
  • Compare builder bids: Get quotes from various professionals to find the best rate.
  • Phase sections over time: Tackle structural first. Leave finishes for later budget freeing.

Careful planning and strategic decisions make loft conversion work feasible even with limited money. Focus first on structural necessities and discover creative ways to allot funds.

Financing Your Dormer Loft Conversion Costs

If you need assistance financing a dormer conversion, there are several funding options you can explore:

Financing Your Dormer Loft Conversion Costs
  • Home improvement loans: Banks offer specific loans for home renovations, with extended 5–15 year repayment terms. Interest rates are typically 5–10%.
  • Remortgaging: You may be able to release home equity and roll the project costs into your existing mortgage by refinancing.
  • Secured loans: Use your home as collateral to get a lump sum for renovations at a lower interest rate. Understanding the risks associated with this option is vital. Your property could be subjected to repossession if you do not adhere to the repayment conditions.
  • 0% credit cards: Some cards offer 12–18 months of 0% interest financing, allowing short-term borrowing if balances are repaid promptly.
  • Government grants: Certain local authorities provide grants to support vital home upgrades for low-income families, with amounts ranging between £5,000 and £15,000. These funds can cover expenses for insulation, heating, and structural modifications.
  • Disabled facilities grants: These fund home modifications like stairlifts, ramps and adaptations to help disabled residents live independently. Grants cover £5,000 to £30,000 based on income.
  • VAT Relief: Disability home adaptation VAT relief in the UK is zero-rated without a monetary limit.
  • Charitable Grants: Organisations like Turn2Us, Charis Grants, and Age UK provide small renovation grants of £2,000–£5,000 for disadvantaged groups.

With careful planning and financing, a dormer conversion can work even on a limited budget. Consider exploring these options to find the one that best suits your specific situation for financing your dormer loft conversion.

Compare Dormer Loft Conversion Quotes

Now that you have a sense of potential loft conversion costs, the next important step is getting custom quotes for loft conversion tailored to your property. While this article provides rough figures, nothing compares to price estimates from builders familiar with homes in your area.

Obtaining multiple quotes can offer you several benefits, such as:

  • Accurate pricing reflecting your home’s layout, roof design, access points and other unique factors
  • Ability to compare bids for the same project scope
  • Leverage to potentially negotiate pricing and inclusions
  • Custom options for materials, windows, and finishes to suit your taste
  • Expert advice on best practices for your situation

To simplify getting estimates, use our free quote service. We provide free access to detailed bids from 4 qualified local loft conversion pros.

With GreenMatch, you can easily compare quotes side-by-side with no obligation to accept any offer.

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Tania Zhydkova
Written by Tania Zhydkova, External Writer

Tania is an experienced writer who is passionate about addressing environmental issues through her work. Her writing aims to shed light on critical environmental challenges and advocate for sustainable solutions.

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