Converting a loft into a habitable space has become a hugely popular way to add more room(s) to a home, whether you’re dreaming of adding a master suite, a guest bedroom or a home cinema. A loft conversion can also add value to your property! 

So what are you waiting for? Our beginner’s guide should help you avoid common conversion pitfalls and make the most of your loft.

How much does a loft conversion cost?

A loft conversion can vary in costs depending on the location, the design, the type of roof and the legal constraints. Excluding finishes like windows, flooring, sanitaryware, the average cost of a standard loft conversion can be between £1,200 and £2,000 per sqm. 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.

Planning and professional fees

Loft extensions can usually be completed under permitted development rights, but it is worth obtaining a Certificate of Lawfulness (approx. £86 as well as your architect’s and building control fees) from your local council for the work. 

Should planning be required, expect planning permission fees (approx. £172 as well as your architect’s and building control fees); these may be included in your agreed contract with the loft company, but do check. 

If you live in a terraced or semi-detached house, you will need a party wall agreement with your neighbour(s). These can vary and typically costs can range from £350 to £1,000 per neighbour.

Building control fees

You will need a building control certificate at completion, this certifies that all the work is in compliance with current building regulations. The average building control fee for a loft conversion is £850 approx, 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 known as approved inspectors. Both will check that the work is done in compliance and will issue the certificate at completion.


Apart from obvious obstacles, such as a water tank or chimney stack, the features that will determine whether your roof space is suitable for a loft conversion are: 

  • Head height: Take a measurement from the bottom of the ridge timber to the top of the ceiling joist; the usable part of the roof should be greater than 2.2 m.
  • Pitch angle: The higher the pitch angle, the higher the central head height is likely to be. If dormers are used or the roof is redesigned, then the floor area can be increased.

Room in roof

Basic ‘room in roof’ conversions are the simplest form of loft conversion and for all in, you can expect:

  • Electrics, lighting and heating
  • Fire safety measures (smoke alarms and fire door)
  • Floor reinforcements
  • Insulation
  • Skylights
  • Staircase

Dormer extension

To add more head height, the least invasive option is to use dormer windows. Doing so gives you more usable floor space and provides more options as to where to place the staircase. For large dormer extensions, you can also consider the benefits of en suite living.

Raising the roof

This is the most expensive option as it’s necessary to remove and rebuild the roof. It’s also harder to acquire planning permission because the property silhouette will be changed. An additional cost to consider is the architectural design work. Overall, the conversions will be a considerable investment but you will be getting a loft conversion with the maximum potential for living space and en suite extras.

Looking to do a loft conversion or alterations to your property but think you may have a Party Wall agreement dispute? Are you keen to avoid costly surveying fees? Not sure what Party Wall Act compensation is? Want to know more about Party Wall Act dispute? 

Find out more about the Party Wall Act and get some free advice from the Surveyors at Seven One Associates.

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.