How much does a loft conversion cost in the UK

Table of Contents  
  • How much does a loft conversion cost in the UK?  
  • Cost of loft conversion types  
  • Cost breakdown for loft conversion 
  • Hidden loft conversion costs 
  • Factor affecting loft conversion costs  
  • Tips to reduce loft conversion costs  
  • Bottom Line 
  • FAQ 

Loft Conversion Cost UK – Planning to undergo loft conversion to gain more space? Then keep reading this comprehensive guide that’ll address all your concerns related to loft conversion costs. In the urban landscape, loft conversions serve as an ultimate option for extending the home to increase the habitable area. Having a sound knowledge about the prices will help you strike a better deal. Also, knowing cost estimates will keep you rest assured that you’re paying the right money and you’re not cheated. Here we have covered every loft conversion cost aspect in detail along with loft conversion type. So, without further ado, let’s get started. 

How much does a loft conversion cost in the UK

The average cost of loft conversion for a basic 20 m2 will be around £20,000 and for a bigger and more luxurious one, it comes out to be around £50,000. This is just a cost estimate, the actual cost will depend on the type of loft conversion availed and its complexity. Other main factors that may affect loft conversions costs are: 

  • How large is your loft? 
  • The existing roof structure  
  • Labour costs  
  • Quality of finishings  
  • Time taken by the project 
  • Your location and accessibility  
  • Quality and type of finishings (materials) 

It may take around 6 to 8 weeks to complete the loft conversion construction. The construction process kick-starts once all the planning permits or other formalities are completed.  

Size of Loft Conversion (m2)  Average Cost 
20  £20,000 
30  £25,000 
96  £40,000 

The average cost of a Velux loft conversion will be less than that of a dormer and mansard. The reason is that lesser complexity is involved. In some cases, where the space is larger, Velux loft conversion would be like doing the walls, flooring, and insulating only and the area would be ready. The average cost of a Velux loft conversion starts from between £15,000 and for a small dormer loft conversion, the cost will start from £20,000 and upwards. While a hip-to-gable loft conversion that transforms a hip roof to a gable end starts from around £30,000. Mansard loft conversion is the most expensive as it reshapes the entire roof and is more like adding a storey. The average cost of Mansard loft conversion starts from £40,000 and can go up to £70,000 depending on the features you add.  

Type of Conversion   Average Cost per m2   Average Cost 
Velux  £1,000  £15,000 
Dormer  £1,500  £20,000 
Hip-to-gable  £1,200  £30,000 
Mansard  £1,800  £40,000 

The costs stated above are just estimates. 

Cost of loft Conversion by Types

There are multiple types of loft conversions, and each has its own benefits. Indeed, there are cost considerations as well. Adding more windows, luxurious finishes, a new staircase, installing a bathroom etc will certainly increase the cost of the loft conversion. Apart from that, there are certain factors such as the location of the project and weather conditions that also impact the cost. Unfavourable conditions adversely affect the time to completion and cost as well. Let us dig down on each type of loft conversion option and understand the detailed costs. 

(A) Cost of Velux Loft Conversion: Also known as skylight or roof light loft conversion, Velux loft conversion is the simplest and most cost-effective loft conversion. Here skylights or roof light windows are added to the pitched roof. The cost varies depending on the number of windows installed, the size of the attic, flooring, insulating or other features. The average cost for a 20m2 area for Velux loft conversion is estimated to be between £15,000 and £25,000. Here is a breakdown of the expenses and services. The entire process takes around four-six weeks for completion. 

Cost Breakup  Price 
Average Total Cost  £15,000 to £25,000 
Builder cost  £10,000 to £20,000 
Structural Engineer  £500 to £900 
Architect  £1,100 to £1,700 
Plumber/Electrician   £1,000 to £1,800 
Other professionals Fees  £500 to £700 

(B) Cost of Dormer Loft Conversion: Dormer loft conversion is one of the most popular and preferred types of loft conversion in London. Here you get more headroom as the roof is extended vertically and a box structure is added to provide that extra space. There are many types of dormer loft conversion available in the market such as L-shaped, gable-fronted, flat-roof dormers, hipped roofs and more. Each has its own implications. The average cost of a dormer loft conversion starts from £20,000. It keeps on increasing according to size, complexity or if any structural modifications are required.  

Cost Breakup  Price 
Average Total Cost  £20,000 to £38,000 
Builder cost  £12,000 to £24,000 
Structural Engineer  £600 to £1,100 
Architect  £1,500 to £2,500 
Plumber/Electrician   £2,000 to £3,000 
Other professionals Fees  £700 to £1,500 

(C) Cost of Hip-to-Gable Loft Conversion: Hip-to-gable loft conversion involves converting a hipped roof to a gable wall. This provides more internal habitable space. The new space can easily be used to create a bedroom, a kid’s room or even a gym space. Hip to Gable loft conversion is ideal for properties having a hipped roof or terraced houses. The average cost for a 20 metres square hip to Gable loft conversion starts from £30,000. The final price may vary and depends upon various factors such as structural work required, size of the loft, complexity of the project and additional features. 

Cost Breakup  Price 
Average Total Cost  £25,000 to £45,000 
Builder cost  £15,000 to £30,000 
Structural Engineer  £700 to £1,500 
Architect  £1,700 to £3,000 
Plumber/Electrician   £2,200 to £4,000 
Other professionals Fees  £1,000 to £2,000 

(D) Cost of Mansard Loft Conversion: Mansard loft conversion is one of the most expensive ones as it involves altering the entire shape of your roof. A mansard roof provides you with the maximum internal space. As it involves a complex design and extensive structural alterations, the cost touches £40,000 to £70,000 with an average of £50,000 for a normal-looking mansard conversion.

Cost Breakup  Price 
Average Total Cost  £40,000 to £70,000 
Builder cost  £25,000 to £40,000 
Structural Engineer  £600 to £2,000 
Architect  £1,700 to £3,500 
Plumber/Electrician   £2,000 to £3,000 
Other professionals Fees  £700 to £1,500 

(E) Cost of Bungalow Loft Conversion: The best way to expand and add additional space to a bungalow is by converting its loft into a habitable space. You can easily go for any type of Bungalow loft conversion that includes Velux, dormer, or mansard loft conversion. The basic cost of a bungalow loft conversion starts from £25,000 and may go up to £50,000 depending on structural requirements, property design, size of attic and type of conversion.

Cost Breakup  Price 
Average Total Cost  £25,000 to £50,000 
Builder cost  £15,000 to £30,000 
Structural Engineer  £700 to £1,500 
Architect  £1,500 to £3,500 
Plumber/Electrician   £2,000 to £3,000 
Other professionals Fees  £1,000 to £1,500 

Cost breakdown for the loft conversion

Loft conversion involves a lot of trades and building processes as part of construction. To get a perfect cost loft conversion idea, here is an entire cost breakdown for a loft space 30m2 for a dormer loft conversion. The space includes a dormer, and a Velux window over a new staircase. A new bedroom with ensuite is constructed with full plumbing and electrical work. Here’s the estimated cost breakdown.  

Job/ Process for Loft Conversion  Cost (for 30m2 loft) 
Project Management – including building control costs  £9,000 
Internal Preparation  £1,000 
Roof Coverings  £6,200 
Alterations to Roof Structure  £4,200 
Steelwork to support structural changes  £3,400 
Joinery – excluding staircase  £3,600 
Electrics  £1,000 
Plastering  £2,400 
Staircase  £2,200 
Decoration  £1,000 
Total  £40,000 

 As such there is no fixed cost calculator for loft conversion, there are several factors associated with this. Let’s discuss some of the above-mentioned trades in detail. 

  • General Construction Materials: The general building materials include framing lumber, drywall, structural components, beams, and other finishing materials. The cost of these materials depends upon the quality as well as quantity required for the completion of the project. The higher the quality the cost will also be higher. Choosing high-quality building materials will ensure that the loft conversion achieved is timeless and durable. 
  • Insulation: Insulation is a must-have in a loft conversion as it regulates the temperature and makes the space energy efficient. Fibreglass, rigid foam boards and mineral wool are some common insulation materials that are popular in the industry. Depending on the thickness and type of the insulation material, the costs may vary.  
  • Windows: The cost of loft windows depends on their material, size, and glazing options. Double and triple-glazed windows would be more expensive than normal-glazed ones, but these will dramatically improve the thermal efficiency of the loft space.  
  • Fixtures and fittings: The fittings and fixtures include lighting, plumbing and electrical fixtures. Their cost depends on the brand, specifications, and quality. Low-flow plumbing options for the fixtures optimize water consumption. Preferring LED lighting over traditional ones will also result in significant energy savings. 
  • Roofing materials: There are several roofing materials available such as metal roofing, tiles, slates etc. The cost depends on the quality and type of the roofing material. Also, you need to ensure to use the same roofing material for your loft as used in the existing roof. 
  • Stairs: Stairs come in various shapes, sizes, and styles. The cost of the staircase will vary depending on its complexity, size and material used. The common and most popular options available for loft stairs are spiral stairs and paddle stairs or space-saving stairs. 

Hidden Loft Conversion costs

Many other costs may be omitted by the contractor or builder such as the cost of supplying the fixtures/materials, VAT charges, decorations, Juliet balconies etc. Just be open with your loft conversion contractor about these charges. Stay vigilant before making any final decision. Apart from these, there may be certain hidden or unknown charges that may apply. These include: 

  • Planning Permission Fees: Most likely you will not be required to pay any fees for planning permissions as loft conversion falls under the category of permitted developments. But, in a few cases such as if your property belongs to AONBs, listed buildings, world heritage sites, National Parks etc, you may need to apply for planning permissions. It may cost around £250. 
  • Lawful Development Certificate: While this certificate is not necessary, it is advisable if you’re availing permitted development rights. It will cost around £100-£150 and you can easily sell your property in future without any dispute. 
  • Party Wall Agreement: If you are living in a terraced building or a semi-detached property, getting a loft conversion will mean altering the shared wall. You need to get the consent of your neighbours. The party wall surveyor fees would be around £1,250. So, be ready to bear this fee.  

Factor affecting loft conversion costs

Certain other factors impact the cost of the loft conversion. Have a look at them: 

  • Roof type: If you have a traditional roof, i.e. a roof that was built before the 1960s, loft conversion would be easy as these roofs have ample space beneath them. On the contrary, modern roofs are made of trusses which makes loft conversion a tedious process. This is because it involves the removal of the trusses and other floor supports. This significantly increases the time and money involved.  
  • Type and method of conversion: As Velux loft conversion requires minimum disruption, it is the cheapest. While all others require altering the roof to add a new structure, they are costly. 
  • Presence of chimneys and water tanks: In case your attic space has boilers, water tanks or chimneys placed, you need to remove them and relocate to a new place. This will add to your costs.  
  • Space Intended:  It also depends on the purpose of the space you need. If you want a bedroom along with a bathroom, the costs will obviously increase.  
  • New Foundations: If the old foundations are not able to bear the weight of the newly constructed loft space, you need to go for new foundations. This would mean either underpinning the foundations or constructing new beams to balance the load.  

Tips to reduce loft conversion costs

Let’s discuss some tips and strategies to reduce the loft conversion costs.  

  • Choose the right builder: It is important to select an experienced and reliable contractor for your loft conversion. Get at least three quotes from different professionals. Also, check their past works and portfolios. Ensure that the costs that are mentioned are transparent and do not include any hidden charges. Reach out to your friends and families who have already converted their home lofts, and take their recommendations as well. 
  • Optimise Space: Make sure that you use the available space most efficiently. Try to opt for space saving strategies such as multifunctional furniture, space saving stairs, built-in storage and other smart layouts.  
  • Set Clear Budget: Before starting the loft conversion make sure that you have a clear budget in your mind. This will ensure that you do not overspend and certainly keeps you in control of your finances. Make sure that you have some extra savings or contingency funds to cover some expected costs or issues. 
  • Consider Velux loft conversion:  Velux or roof light loft conversion is the most cost-effective option if you’re on a tighter budget and looking for low-cost options. Though they offer less additional space, they’re very simple to construct and easy on the pocket. 
  • Negotiate: It is always advised to get a minimum of three quotes before finalising your loft contractor. You can always negotiate with your favourite contractor. You never know that you may get your dream loft conversion in your set budget. 
  • Plan carefully: Plan properly and carefully. Take your time. Proper planning will reduce costly mistakes. You may also get 3D renders done, as this will not only help you see your space beforehand but will also ensure flawless construction.  
  • Source your own materials: Shop around and look for various materials. Get the price list from multiple suppliers and compare them. Try to use recycled or reclaimed materials that will save you more on costs.  

The Bottom Line  

Loft conversion is one of the best investments of your life that will not only add habitable space but also increase the value of your property. As it is a big project you need to hire a reliable and trustworthy contractor that has a rich and diverse experience in loft conversion. TEL Constructions is one of the leading loft conversion companies in London that has converted countless lofts to multiple types of houses. Be it detached, semi-detached or terraced, speak to us regarding your choices, tastes, and concerns. Our team will happily assist and guide you through our loft conversion journey. 

Frequently Asked Questions  

  • How much value is added by a loft conversion in London? 

A professionally built loft conversion will add approximately 20% – 25% value to your existing property. Other factors that may impact property value are location, current market condition and quality of construction. 

  •  What is the cheapest way to do a loft conversion? 

Velux loft conversion involves minimum structural changes to the loft, and you just need to perform the basic works such as installing windows, staircase, insulation, heating, decoration and plastering. This way Velux loft conversion offers the cheapest way.  

Drop Your Query Here


Recent Posts

Loft Conversion

Drop Your Query Here

Want to build a new home or renovate your property? Oh!! You are on the right platform. Just submit your details here and schedule a free visit of our experts today.