How Much Does a Loft Conversion Cost?
Check out this expert guide to find out how much you should budget to extend into your loft and where that money goes
Amanda Pollard
16 August 2021
Senior Editor at Houzz UK and Ireland. Journalist and editor specialising in interiors and architecture.
Senior Editor at Houzz UK and Ireland. Journalist and editor specialising in interiors... More
A loft conversion can add value to your property, both financially and in terms of extra space and functionality, but what is it likely to cost? As part of our Loft Planning guide, we asked three loft specialists to provide an explanation of average costs, how the money is allocated, and what extras you should budget for.
* Prices correct as of February 2024
Professional advice from: JP Lal of Visionary Lofts; Jack Davey of LoftCraft London; Joel Tomlinson of Shore Lofts
Beginning your loft conversion project? Read How Do I Begin a Loft Conversion?
* Prices correct as of February 2024
Professional advice from: JP Lal of Visionary Lofts; Jack Davey of LoftCraft London; Joel Tomlinson of Shore Lofts
Beginning your loft conversion project? Read How Do I Begin a Loft Conversion?
What’s the average overall price of a typical loft conversion?
“You should expect to pay a minimum of £65,000 to £75,000 for a finished rear dormer loft conversion that includes a bedroom and shower room, with two small skylights and two uPVC windows,” Jack Davey says. “This price is based on a standard, 5m wide, 7m deep, mid-terrace property and excludes the cost of sanitaryware and tiles.”
“Typically, loft conversion companies will quote to a shell finish with plastered walls and second-fix carpentry done,” JP Lal says. “The client would supply the bathroom suite and we would fit it.”
“You should expect to pay a minimum of £65,000 to £75,000 for a finished rear dormer loft conversion that includes a bedroom and shower room, with two small skylights and two uPVC windows,” Jack Davey says. “This price is based on a standard, 5m wide, 7m deep, mid-terrace property and excludes the cost of sanitaryware and tiles.”
“Typically, loft conversion companies will quote to a shell finish with plastered walls and second-fix carpentry done,” JP Lal says. “The client would supply the bathroom suite and we would fit it.”
Which type of loft is cheapest?
A single dormer conversion costs the least, followed by a mansard loft. “They are more complex to build and require a greater volume of materials, plus the build duration is longer,” Joel Tomlinson says. “For example, once you’ve constructed your mansard frame, the windows then need their own small dormers within the mansard to put them on the vertical plane.”
An L-shaped dormer (where an additional section is added over an outrigger) is more expensive than a mansard, while the most costly style is a hip-to-gable loft conversion.
To see more from any of the designers whose photos are featured in this article, click on the image, then on Learn More if you’re in the app, and follow the links to the professional’s profile.
A single dormer conversion costs the least, followed by a mansard loft. “They are more complex to build and require a greater volume of materials, plus the build duration is longer,” Joel Tomlinson says. “For example, once you’ve constructed your mansard frame, the windows then need their own small dormers within the mansard to put them on the vertical plane.”
An L-shaped dormer (where an additional section is added over an outrigger) is more expensive than a mansard, while the most costly style is a hip-to-gable loft conversion.
To see more from any of the designers whose photos are featured in this article, click on the image, then on Learn More if you’re in the app, and follow the links to the professional’s profile.
What should I consider when choosing a quote?
Jack recommends you think carefully before taking the cheapest quote. “When companies cut their prices to secure work, that work is typically at the bottom of their priorities, and they’ll often disappear to complete projects that will earn them better money,” he says.
“Generally speaking, it’s pretty difficult to pay too much these days, as the market is very competitive,” he continues. “It does pay to ensure the quote you proceed with is as comprehensive as possible, though, and includes everything necessary to pass all inspections by Building Control.”
Find an architect or building designer in your area.
Jack recommends you think carefully before taking the cheapest quote. “When companies cut their prices to secure work, that work is typically at the bottom of their priorities, and they’ll often disappear to complete projects that will earn them better money,” he says.
“Generally speaking, it’s pretty difficult to pay too much these days, as the market is very competitive,” he continues. “It does pay to ensure the quote you proceed with is as comprehensive as possible, though, and includes everything necessary to pass all inspections by Building Control.”
Find an architect or building designer in your area.
Will I need to pay extra for design and planning?
Some loft specialists will provide their own architect, while others will recommend ones for you to choose yourself.
“Many loft specialists can also provide an architectural and planning service and this usually works out to be around 10% to 15% of the total budget,” Jack says.
For more complex projects, Visionary Lofts recommends outside architectural and planning companies to clients and potential clients. “The majority of homeowners will use an architectural technician, who will charge £1,000 to £1,500, while a more complex project might need an architect, which could cost around £3,000,” JP says.
“Approval costs from your local council’s Building Control department will cost £500 to £1,250,” he adds. “A private Building Control service will charge around £900.”
The decision of whether to apply for Planning Permission or stick to Permitted Development will also affect the cost. If your loft conversion is going to be below a certain size, you’ll be able to stay within Permitted Development rules.
“Planning Permission costs around £300 and takes eight weeks,” JP says. “If you’re going for Permitted Development, we recommend a Certificate of Lawfulness, which would require more detailed drawings. It takes eight weeks and costs £250.”
You might also enjoy Can I Extend My House or Loft Without Planning Permission?
Some loft specialists will provide their own architect, while others will recommend ones for you to choose yourself.
“Many loft specialists can also provide an architectural and planning service and this usually works out to be around 10% to 15% of the total budget,” Jack says.
For more complex projects, Visionary Lofts recommends outside architectural and planning companies to clients and potential clients. “The majority of homeowners will use an architectural technician, who will charge £1,000 to £1,500, while a more complex project might need an architect, which could cost around £3,000,” JP says.
“Approval costs from your local council’s Building Control department will cost £500 to £1,250,” he adds. “A private Building Control service will charge around £900.”
The decision of whether to apply for Planning Permission or stick to Permitted Development will also affect the cost. If your loft conversion is going to be below a certain size, you’ll be able to stay within Permitted Development rules.
“Planning Permission costs around £300 and takes eight weeks,” JP says. “If you’re going for Permitted Development, we recommend a Certificate of Lawfulness, which would require more detailed drawings. It takes eight weeks and costs £250.”
You might also enjoy Can I Extend My House or Loft Without Planning Permission?
How much of the budget is allocated to the first stage?
JP explains that the preliminary part involves the site set-up, which includes the scaffolding, waste removal and cleaning. “This is usually 15% to 20% of the cost,” he says.
“In our site set-up costs, we have a specific allowance for project management,” he continues. “At least £2,000 of management time is included in this. We’re appointed at least two to three months before the work starts, so we can project manage right from the beginning.”
JP explains that the preliminary part involves the site set-up, which includes the scaffolding, waste removal and cleaning. “This is usually 15% to 20% of the cost,” he says.
“In our site set-up costs, we have a specific allowance for project management,” he continues. “At least £2,000 of management time is included in this. We’re appointed at least two to three months before the work starts, so we can project manage right from the beginning.”
How much of my money goes towards the second phase?
“The next stage – the core part – is the carpentry work, which includes the beams, frames, plasterboard and glazing,” JP says. “This cost will usually vary from 40% to 50% of total costs.”
“Generally speaking, the division of labour and materials works out to be around 50:50 on a typical build,” Jack says. “Options such as aluminium-framed glazing or large pieces of glass sway the bias towards the materials.”
JP explains that plastic glazing could be upwards of £1,500, while aluminium sliding doors could bring the price up to £5,000 or more.
“The next stage – the core part – is the carpentry work, which includes the beams, frames, plasterboard and glazing,” JP says. “This cost will usually vary from 40% to 50% of total costs.”
“Generally speaking, the division of labour and materials works out to be around 50:50 on a typical build,” Jack says. “Options such as aluminium-framed glazing or large pieces of glass sway the bias towards the materials.”
JP explains that plastic glazing could be upwards of £1,500, while aluminium sliding doors could bring the price up to £5,000 or more.
What happens next?
The next two stages are roofing and brickwork. “Roofing covers around 20% of costs typically,” JP says. “That’s assuming you’re just covering the new structure and not replacing the existing roof.”
He adds that the majority of projects don’t need brickwork, but if it’s necessary to build a brick party wall, it could add at least £5,000 to the project.
The next two stages are roofing and brickwork. “Roofing covers around 20% of costs typically,” JP says. “That’s assuming you’re just covering the new structure and not replacing the existing roof.”
He adds that the majority of projects don’t need brickwork, but if it’s necessary to build a brick party wall, it could add at least £5,000 to the project.
How is the rest of the budget allocated?
According to JP, the next four stages each account for 5% of the budget.
These stages include plastering, electrics, plumbing and second-fix carpentry. The plumbing would consist of fitting the bathroom suite and radiators, while the carpentry work would focus on aspects such as the skirting boards, architraves, doors and handles, window sills, spindles and handrails.
According to JP, the next four stages each account for 5% of the budget.
These stages include plastering, electrics, plumbing and second-fix carpentry. The plumbing would consist of fitting the bathroom suite and radiators, while the carpentry work would focus on aspects such as the skirting boards, architraves, doors and handles, window sills, spindles and handrails.
Are there any additional costs?
“A client should generally budget at least £5,000 to £12,000 on top of the conversion to cover the cost of their bathroom suite, tiles, finished flooring, such as carpet or wooden boards, and decorating,” Jack says.
JP also advises you think about whether you’ll need parking permits, skips and portable toilets, as these costs can add up.
“A client should generally budget at least £5,000 to £12,000 on top of the conversion to cover the cost of their bathroom suite, tiles, finished flooring, such as carpet or wooden boards, and decorating,” Jack says.
JP also advises you think about whether you’ll need parking permits, skips and portable toilets, as these costs can add up.
How about fire protection?
Our experts highlight the cost of fire regulation work in the rest of the house, which people often forget to factor in. “Fire doors and smoke detectors on each landing will cost on average around £1,500 to £2,000 extra,” JP says.
Another option would be a sprinkler system, which JP says would set you back at least £5,000.
Our experts highlight the cost of fire regulation work in the rest of the house, which people often forget to factor in. “Fire doors and smoke detectors on each landing will cost on average around £1,500 to £2,000 extra,” JP says.
Another option would be a sprinkler system, which JP says would set you back at least £5,000.
Should I keep some budget aside?
“I’d recommend the client has a 5% to 10% contingency budget,” JP says. Some firms build this into the quote. “We allow some leeway in the quote for things that might come up,” he explains. “The more information the client can give, the lower that contingency can be.”
Tell us…
Are you planning a loft conversion? Did you find this budgeting advice helpful? Share your thoughts in the Comments.
“I’d recommend the client has a 5% to 10% contingency budget,” JP says. Some firms build this into the quote. “We allow some leeway in the quote for things that might come up,” he explains. “The more information the client can give, the lower that contingency can be.”
Tell us…
Are you planning a loft conversion? Did you find this budgeting advice helpful? Share your thoughts in the Comments.
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This helps me with my decision to add a bathroom and possibly a dressing room to my existing bonus room which was part of the original house built 22 years ago. Thank you
The stairs had to be moved more into one of the bedrooms due to structural issues. The builders only noticed after the work had started. I had no meeting with the onsite manager before work started. I ended up with two single rooms and the new double bedroom in the converserion rather than two double and one single.
Our experience: 1930s semi with hip to gable and full width rear dormer completed dec 21. 2 bedrooms and a shower bathroom, front bedroom has 2 velux. Cost 60k. The new stairs fitted above the existing with no changes required on 1st floor. We didn’t need to replace any existing doors as we fitted interlinked smokes in every room. We were also able to move our boiler into a cupboard in the new bathroom. We are still decorating, and finally getting the carpets done next week :)