Want to transform your attic into a new room? A Velux loft conversion is one of the best ways to do it. It is the most cost-effective type of conversion. Most homeowners do not require planning permission. This complete guide covers the cost of a Velux loft conversion and how to convert your loft in 2026.
How much does a Velux loft conversion cost?
The cost of a Velux loft conversion is between £15,000 and £35,000. This is the average cost for most homeowners. The overall cost depends on three things. First, the size of the loft. Second, where you live. Third, how many Velux windows you need. A Velux loft conversion is one of the most cost-effective conversion types available. It costs far less than a dormer loft conversion or a mansard loft conversion.
| Loft Size | Average Cost (2026) |
|---|---|
| Small (up to 30m²) | £15,000 – £20,000 |
| Medium (30–50m²) | £20,000 – £28,000 |
| Large (50m²+) | £28,000 – £40,000+ |
These prices cover structural work, insulation, flooring, a staircase, and the Velux roof windows. They do not cover furniture or painting.
How much do Velux windows cost?
The number of Velux windows you fit will affect the overall cost. Most homeowners use at least two Velux windows. Two windows are enough to make your loft room bright and airy.
- Fixed Velux window: £300 – £600 each
- Centre-pivot window: £400 – £800 each
- Top-hung roof windows: £700 – £1,500+ each
- Fitting cost: Add £200 – £500 per window
What factors affect the cost of your Velux loft conversion?
Your location
Where you live has a big effect on the overall cost. London and the South East cost 20–40% more than the rest of the UK. Labour costs are higher there. A job costing £22,000 outside London can reach £30,000 in the capital.
Loft size and roof space
The size of the loft and the slope of your roof both matter. They help decide if your loft is suitable for conversion. You need at least 2.2 metres of height for a room you can live in. Most older homes have a steep enough existing roof. Many new build homes do not. A larger loft also costs more to insulate and plaster. Not sure which option suits your roof? Read our guide on which type of loft conversion is right for your home.
The number and types of windows
More windows mean more light. They also raise the overall cost. Installing Velux windows into the slope of your roof is a key advantage of this type of conversion. Top-hung roof windows are great for energy efficiency. Electric windows cost more but are very easy to use.
Planning permission
Most homeowners do not require planning permission for a Velux loft conversion. You can add windows into the slope of your roof without applying to the council. You just need to follow simple rules about the existing roof. Use our Permitted Development checker to find out where you stand.
You will require planning permission if:
- Your home is in a Conservation Area
- Your home is listed
- An Article 4 Direction is in place
- You have already used up your Permitted Development rights use our extension potential checker whether you property requires planning permission
If you do require planning permission, budget an extra £3,000 – £6,000. This covers drawings and the £258 fee. Read our full guide on planning permission for a loft conversion to find out more.
Building regulations and permit costs for Velux conversions
All homeowners must comply with Building Regulations for a Velux loft conversion. This applies even if you do not require planning permission. Building Regulations make sure your new space is safe and warm. We produce building regulation drawings for loft conversions across London. Your application will cover four key areas:
- Part A — the structure of the roof and floor joists
- Part B — fire safety and escape routes
- Part L — insulation and energy efficiency
- Part K — stairs and fall protection
| Route | Typical Cost |
|---|---|
| Full Plans (LA Building Control) | £800 – £1,500 |
| Building Notice | £500 – £1,200 |
| Approved Inspector (private) | £700 – £1,400 |
Party wall fees
Do you share a wall with a neighbour? The Party Wall etc. Act 1996 may apply. You must give your neighbour at least two months notice. If they disagree, you will both need a Party Wall Surveyor. Read our full guide on party wall agreements for loft conversions to find out more.
- One shared surveyor: £800 – £1,500 per neighbour
- Two surveyors: £1,500 – £3,000+ per neighbour
- Notice only: £150 – £350
Use our free party wall cost calculator to get an instant estimate.
Does a Velux loft conversion add value to your home?
Yes. A Velux loft conversion can add 15–25% to your home value. In London, the new loft space can add more than the overall cost of the project. The room must comply with Building Regulations to count as a proper living area. Build quality matters too. Most homeowners find it the best home improvement project they can do.
The Pros and Cons of a Velux Loft Conversion
Pros
- The most cost-effective of all conversion types
- Fast to build — usually just 4–8 weeks
- Most homeowners do not require planning permission
- Very little disruption to your home
- Great natural light from Velux roof windows
- Good energy efficiency with new glazing
Cons
- Only works if the existing roof is steep enough
- Less floor space than a dormer or mansard conversion
- Flat roofs are not suited to this type of conversion
Do building regulations apply to a Velux Loft Conversion?
Yes — always. Every homeowner must comply with Building Regulations when they convert your loft. The four key rules are:
- Structure of the roof — old joists are often too weak. A structural engineer will size new ones alongside them
- Fire safety — you need fire doors, smoke alarms, and an escape window in each bedroom
- Energy efficiency — the existing roof must hit a U-value of 0.18 W/m²K
- Stairs — at least 1.9m of headroom and steps no higher than 220mm
Tips for maximising space in your Velux Loft Conversion
- Fit storage under the eaves — do not waste that space
- Use a compact staircase — it saves space below
- Use light colours and mirrors — they open up the loft room
- Put your desk under the low part of the slope
- Pick Velux windows with built-in blinds for a bedroom
Is a Velux Loft Conversion Right for You?
A Velux loft conversion is the best loft conversion for most homeowners. It works when the existing roof has a good slope. The condition of the existing roof matters too. Most homes built before 1970 are a great fit. Not sure if your loft is suitable for conversion? Our structural drawings and calculations service can confirm exactly what your roof needs. This costs around £300–£500.
Attic with possibilities — light and space for a growing family
Do you need more space? Do not want to move? A Velux loft conversion can transform your attic into a bedroom, office, or playroom. It will not eat into your garden. It will not change your street view. It is faster to build than a rear extension. See our guide on how long a loft conversion takes for a full timeline.
How to realise the potential of your attic space with roof windows
Installing Velux windows unlocks the potential of your loft. A dark storage space becomes a bright living area. South-facing roofs get lots of sun. North-facing roofs give soft, steady light. This is ideal for a home office or studio.
Velux loft conversion ideas
Velux loft conversion ideas for every home
A Velux loft conversion is one of the most flexible types of loft conversions. Here are some popular Velux loft conversion ideas to make your loft work harder:
- Master bedroom with en-suite — two Velux windows on the rear slope give light and privacy
- Home office — north-facing top-hung roof windows give soft, steady light all day
- Children’s room — built-in storage under the slope makes it feel purpose-built
- Guest bedroom — two Velux windows make a bright, airy room
- Studio — great light with no need for a costly dormer
Benefits of a Velux loft conversion
- Transform your loft into a proper living space without touching the roofline
- The most cost-effective way to convert your loft
- Better energy efficiency with new Velux roof windows
- Incorporating Velux windows brings more natural light into your home
- Add value — it is one of the best home improvement projects a homeowner can make
Loft space and conversion process: what to expect
- Check — is your loft suitable for conversion? Look at the size of the loft and the condition of the existing roof
- Design — loft conversion drawings are made for the new space and stairs
- Planning — confirm you do not require planning permission or apply if you do
- Building regs — comply with Building Regulations before work starts
- Party wall — serve a party wall notice if you share a wall with a neighbour
- Build — 4–8 weeks: structure of the roof, installing Velux windows, insulation, plastering, and finishing
- Sign-off — Building Control issue your completion certificate
10 tips to help you get the most out of your loft conversion project
- Get three quotes — the overall cost varies a lot between builders
- Hire architectural design services early — good drawings save money on site
- Use a Full Plans submission — fix problems before work starts
- Check the condition of the existing roof before you commit to any conversion types
- Serve party wall notices early — you need two months before work can begin
- Plan your stairs early — they affect both the loft and the room below
- Plan your electrics early — lights, sockets, and alarms all need approval
- Design for how you will use the room — a bedroom needs an escape window
- Insulate well — good energy efficiency costs far less now than fixing it later
- Keep all your paperwork — you will need it when you sell your home
Get the right amount of daylight in your space
Velux roof windows should cover at least 10–15% of the floor area. This keeps your loft room light and airy. Installing Velux windows into the slope of the existing roof often lets you go beyond this with no extra cost.
- Two Velux windows spread light more evenly than one large window
- Top-hung roof windows placed high on the slope cut glare near beds and desks
- Mix fixed and opening windows — fixed ones cost less; opening ones give fresh air
- Sun tunnels work well in bathrooms where installing Velux windows is not practical
AC Design Solution provides loft conversion services across London and the South East. We cover structural engineering and party wall surveying alongside architecture and building regulations — all in one place. Contact us to talk about your Velux loft conversion project.
