Understanding how the costs add up enables you to make the most out of your planned investment. In this price guide we will provide you with all the elements and variables to make the best decisions when investing in a loft conversion.
Depending on your location within the UK, the price of a loft conversion will vary. Furthermore, the type of conversion and the legal and technical constraints placed upon it will also play a key role in determining the likely cost. Excluding likely finishes such as windows, flooring, and sanitary ware, the typical cost of a loft conversion will cost between £1,200 and £2,000 per square metre.
The variation in the cost per square meter depends on the type of loft conversion, the size of the alterations to the roof, the access, the type of finishing and the location.
Special projects to develop the roof space in period buildings can require higher investments. In prime locations, they can double the value of a property after they’ve been completed, like this roof development project in Chiswick, London we completed in 2019.
It requires the installation of rooflight windows in the roof to allow sunlight to enter the loft. It usually includes strengthening of the existing floor, flooring, insulation, plasterboarding and installation of rooflights. They are generally allowed under permitted development outside conservation areas and other designated areas.
With a rooflight conversion you keep the alterations to a minimum. This means the result will be basic, without budget for plumbing, extensive electrical work etc.
The average price across the UK can be between £15,000 to £25,000.
This consists of a boxed-shape structure that replaces one of the slopes of a pitched roof. The result is a flat-roofed space that allows the installation of full-sized windows and the use of full-height furniture and other appliances. They are sometimes allowed under permitted development when not in designated areas.
The cost is higher than that of a roof light conversion, as it requires the complete rebuilding of one roof pitch plus the full associated internal works.
The average cost of a standard dormer loft extension is between £25,000 and £50,000. For an L-shaped dormer, it can go from £40,000 to £75,000.
In end-of-terrace or detached properties, the roof slope at the end of the terrace or of the detached house is replaced with a vertical brick wall. It is combined with a dormer conversion to maximise the space. The alterations to the roof are extensive and you need to build a brick gable wall, as opposed to the stud wall needed for the dormer conversion.
The average cost of a hip-to-gable conversion is higher than a dormer extension, and can go between £32,000 and £60,000.
A mansard loft conversion creates a flat roof space, with four or two of the external walls gently sloped. It can extend to create an additional storey on top of an existing building. It is an extensive building alteration and it always requires planning permission.This design is the most expensive option for a loft conversion.
The average cost of a mansard loft extension can go from £40,000 to £70,000, assuming the mansard covers the extension of the loft only.
When discussing the topic of building works, there is no one-size-fits-all. This is reflected in the costs, too. In general, building works are cheaper where the property market prices are lower.
Much of the variation is due to the nature of expensive property areas: generally they are busier, more densely built and inhabited. This translates into higher costs, for multiple reasons. For example:
For a better idea of the most expensive and the cheapest areas in the UK, as an average:
When planning any building works, you will need to consider professional fees in addition to the building costs. Even if planning permission is not required, you will still need drawings of your loft conversion to be produced for the council, the building regulation officers and for the building teams.
Ensuring the drawings are produced by a professional is always a sensible approach as they minimise the likelihood of miscalculation and incorrect information. Producing and submitting unclear or incorrect requirements and measurements can cause both delays and mistakes that can be very expensive to rectify at a later point.
Whilst loft extensions can often be completed without planning permission, you will still need to file for a Certificate of Lawfulness from your council. This will cost approximately £100.
Fees for filing for the planning permission differ amongst the councils and heavily depend on the amount of work the planning authorities need to process the application. Householder applications, required for extensions and garden buildings, are around £210.
For more information on the planning process and fees across the UK, you can visit the Planning Portal.
For a loft conversion, you will need to produce at least building regulation drawings. For a standard loft conversion, the design fees would be between £1,000 to £2,000.
Furthermore, you will need to budget for structural calculations, such as whether a new beam or other structural alterations are required. The fee for the structural design will range from £900 to £1,800 for a standard loft conversion.
Design and the associated drawings produced for a loft conversion planning application, can cost between £1,000 and £3,500.
Keep in mind that design costs can vary substantially, depending on the architects you appoint and the complexity of the design A cheaper alternative is to appoint a consultant, rather than choosing an architectural practice. Alternatively you can choose to hire a design and build company, who will quote for your loft conversion including the design fees. In some cases, the planning fees will also be included in a design and build quotation.
If your loft conversion will need building work to a wall that sits astride a boundary you will need Party Wall agreements with all the neighbours that share that party wall with you.
This is very often the case in terraced or semi detached properties, or if you are extending a flat in a block. The typical cost of a party wall agreement depends on whether your neighbours and you will want or need to appoint a party wall surveyor.
Typically, party wall agreements will cost £700 to £1,500 per neighbour.
Keep in mind it is possible to serve the notices yourself without the need to pay for a surveyor if your neighbour agrees on the proposed work, and they don’t appoint a surveyor themselves.
You will need a Building Control certificate at completion, which certifies that all the work is in compliance of building regulations. The average cost for a loft conversion is approximately £750, depending on the size and the nature of the works.
You can liaise directly with the local authority or engage a government-approved inspection company. Both will check that the work is carried out in compliance and will issue the certificate at completion.
Whenever a loft conversion project is not a standard one, costs can increase accordingly. The most common reasons why the budget can be higher than the average are:
When planning building works to your home, it’s important to consider how much value the alterations will add to the current property. It is recommended to consult local estate agents, to better understand the potential sale price of properties in your area where a loft extension was added.
Once you understand the increase in value that a loft conversion could add to your property value, you can use that figure to support many decisions in the course of the project. Design solutions, finishes, space, lighting etc can be evaluated and selected, according to your understanding of the investment return.
This is an excellent way to stay in control of your budget and be confident that the extension is a worthwhile investment.
If you are planning a loft conversion, get in touch regarding any questions and support you may need; you can also book a free site visit and free quotation from our specialised teams.