If you are thinking about a loft conversion in West London, the first question on your mind is probably “how much is this going to cost me?” It is a fair question, and one we get asked every single day. The answer is not as straightforward as you might hope, but we can give you a proper breakdown based on 25 years of experience across Ealing, Hammersmith, Richmond, and beyond.
Let us be straight with you: loft conversions in West London are not cheap. But they are also one of the best investments you can make in your property. You are typically looking at £40,000 to £70,000 for a standard conversion, though costs can go higher depending on your choices. The good news is you will likely add 15 to 20 percent to your property value, often more in premium areas like Kew or Chiswick.
We will break down exactly where your money goes, what affects the price, and how to get the best value without cutting corners that will come back to bite you later.
The Basic Cost Breakdown for Different Conversion Types
Not all loft conversions cost the same. The type you choose makes a massive difference to your final bill. Here is what you are looking at in West London for 2026:
Velux (Roof Light) Conversion: £40,000–£50,000
Works within your existing roof structure; adds roof windows and converts the space.
No major structural changes or roof extensions.
Perfect if you have decent head height and want a compact but functional space.
Full building regulations compliance, proper insulation, and high quality finishes.
Examples include Acton and Shepherds Bush, ideal for an extra bedroom or home office.
Dormer Conversion: £45,000–£60,000
Extends the roof outward, creating more usable floor space and better head height.
Most commonly, a flat roof dormer is built across the rear of the property.
Costs vary by size and finishes:
- Basic dormer with standard fittings: £45,000–£50,000
- With ensuite, premium flooring, and custom storage: £55,000–£60,000
Hip to Gable Conversion: £50,000–£65,000
Converts a hipped roof sloping on all sides into a gable, providing extra space.
Popular in Richmond and Ealing on Victorian or Edwardian homes.
Higher cost due to structural work, essentially rebuilding one side of the roof.
Mansard Conversion: £55,000–£70,000
Changes the roof angle to create near vertical walls, maximising usable space.
Creates a loft that feels like a full floor of the house.
Common in Hammersmith and Fulham on period properties.
Usually requires planning permission, adding time and cost.
L Shaped Conversion: £60,000–£90,000
Extends around the side and rear, often doubling loft space.
Works best on detached or semi detached properties with side access.
Perfect for a full master suite with ensuite, walk in wardrobe, and separate study.
What Actually Affects the Cost of Your Loft Conversion?
Property Size and Roof Structure
Bigger property equals bigger loft equals higher cost. Existing roof timbers, head height, and structural condition impact efficiency and expense.
Structural Work and Steelwork
Includes new floor joists, steel beams, and roof reinforcement.
Steel beams typically cost £1,500–£3,000 each.
Essential for safety and building regulations compliance — do not cut corners.
Staircase Design and Location
Compliant staircase is mandatory for pitch, head height, and fire safety.
Costs:
- Basic straight staircase: £2,000–£3,000
- Spiral or space saver: +£1,000–£2,000
- Custom hardwood with glass: £5,000+
Bathroom and Plumbing
Ensuite bathrooms add £8,000–£15,000 depending on fittings and plumbing complexity.
Windows and Natural Light
Velux windows: £800–£1,200 each.
Dormer windows included in basic cost; premium glazing adds extra.
Maximise natural light for a proper room feel.
Insulation and Heating
High performance insulation is required by building regulations.
Heating options:
- Extend central heating: £1,500–£2,500
- Underfloor heating: £2,500–£4,000
Finishes and Fittings
Basic: plasterboard, simple skirting, carpet or laminate.
Premium: hardwood floors, smooth plaster, designer lighting, custom joinery.
Focus on structure and compliance first; finishes can be upgraded later.
Hidden Costs You Need to Budget For
- Planning permission: £500–£800 (not always needed under permitted development rights)
- Building regulations: £800–£1,200 (mandatory)
- Structural engineer fees: £1,500–£2,500
- Architect fees (if planning required): £2,000–£4,000
- Party wall agreements: £700–£1,500
- Scaffolding: £1,500–£3,000
- Furniture and decorating: £3,000–£5,000+ for a bedroom or master suite
Temporary accommodation is not required — work happens above living spaces.
How to Get the Best Value Without Cutting Corners
- Get multiple detailed quotes (at least three)
- Choose a fixed price contract
- Do not skimp on structural work
- Invest in good insulation
- Plan finishes strategically
- Use a specialist loft conversion company
Financing Your Loft Conversion
- Savings: simplest, no interest
- Remortgaging: release equity at lower rates
- Home improvement loans: unsecured, higher rates
- Credit cards or personal loans: for small gaps
Return on Investment
Typically adds 15–20 percent to property value.
Example: £50,000–£60,000 investment on an £800,000 home → £120,000–£160,000 added value.
Regional Cost Variations Across West London
- Premium Areas (Kew, Richmond, Chiswick, Barnes): larger homes, premium finishes, stricter planning
- Mid Market Areas (Ealing, Acton, Hammersmith): best value, generous sizes
- Up and Coming Areas (Shepherd’s Bush, Hanwell): similar costs, strong ROI potential
What You Get for Your Money
A typical dormer loft conversion includes:
- Full structural survey and design
- Planning permission and building regulations applications/fees
- Structural engineer calculations
- Steel beam installation
- New floor joists and flooring
- Dormer construction with windows
- Velux roof windows
- Full insulation
- New staircase installation
- Electrical work including lighting, sockets, and heating
- Plumbing for radiators
- Plastering and decorating
- Flooring throughout
- Project management from start to finish
- Five year insurance backed guarantee (HIG)
Frequently Asked Questions
What is the average cost of a loft conversion in West London?
£45,000–£60,000 for a standard dormer; Velux: £40,000–£50,000; Mansard or L Shaped: £70,000–£90,000. Fixed price quotes ensure no hidden costs.
Do I need to pay for planning permission and building regulations separately?
All fees are included in the fixed price quote.
How much does it cost to add an ensuite bathroom?
£8,000–£15,000 depending on fixtures and fittings.
Can I get a loft conversion for under £40,000 in West London?
Unlikely for quality work. Velux conversions start around £40,000–£50,000.
Is a loft conversion cheaper than moving house?
Almost always yes. A £50,000 loft conversion can add £120,000–£160,000 in value, avoiding moving costs and stamp duty.
What is included in a fixed price loft conversion quote?
All structural work, materials, labour, professional fees, planning and building regulations, project management, and guarantee.
How much value does a loft conversion add?
Typically 15–20 percent of property value, often higher in premium areas.
Can I do a loft conversion in stages to spread the cost?
Not really. Structural work must be completed in one project; finishes or ensuite bathrooms can be added later.
