How to convert the loft in an old property

Extending your living space into the roof allows you to maximise your home’s footprint without impacting on outdoor areas. This article highlights the key considerations

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Converting the loft can be a cost-effective way to increase your home’s living space, and a good solution where adding an extension would negatively impact the garden. According to the Royal Institution of Chartered Surveyors, it also increases the property’s value by as much as 25 per cent.

An extra bedroom and bathroom tends to be the most financially advantageous option, but if a home office, studio or extra living space would suit you better, you may still find it works out cheaper to gain this space from the loft than to extend outwards.

Project success depends on the structure of the roof, the proposed design and any planning constraints.

Exterior of period Victorian house with a loft conversion, in a project by Econoloft

A rooflight conversion tends to require the least amount of structural work. This project by Econoloft uses Velux rooflights. Prices start from around £30,000

Can I convert my loft?

The first step should be to inspect the roof space. Your loft’s suitability for conversion will depend on:

  • available head height
  • the roof pitch
  • the structure of the roof
  • any awkward obstacles, such as water tanks or chimney breasts

Head height is the most important factor. There should be at least 220cm between the bottom of the ridge timbers and the top of the ceiling joists. Once the floor and roof are insulated, this will leave approximately 190cm of headroom – the minimum practical ceiling height. If there is less available head height than this, there are two rather costly options: raise the roof, which will require planning permission, or lower the ceiling in the rooms below.


A living room and bedroom were created in this loft of an 18th-century farmhouse, and a stud wall installed to make space for a tiny bathroom

How much does a loft conversion cost?

The cost will vary depending on the style of loft conversion, the work involved, and the price of materials and fittings. Expect to pay anything from £15,000 to £40,000.

Get at least two quotes for comparison and check the specifications closely to ensure they are pricing up for the complete job.

Bath under the eaves in loft conversion bathroom

If you’re adding an en suite in the loft, you’ll need to ensure there will be sufficient head height next to the basin, as well as in a shower and above the WC. A bath can sit under the eaves, but if it’s cast iron you’ll need to ensure that the floor structure can take the additional weight – a structural engineer will be able to advise if you need to reinforce the floor

Do I need planning permission?

Most loft conversions don’t need planning permission. You can add up to 40 cubic metres of space to a terraced house and 50 cubic metres to a detached or semi-detached property, including dormers, under permitted development.

However, if the house is located in a Conservation Area, there may be limitations on the type of loft that can be created, and if your home is listed, the work will require listed buildings consent. See Planning Portal for full rules and exceptions.

In addition, if you live in an attached property, it’s likely you’ll need a party wall agreement before you can proceed with the work. It’s a good idea to hire a party wall surveyor to look after this for you.


With the area under the eaves offering very little head height, it’s the ideal location for these made-to-measure drawer units by Barbara Genda. Made from oak veneer with solid oak lipping to all visible edges, prices start from £1,200 per linear metre

Which type of loft conversion?

  • Rooflight conversions require the least amount of structural work to the existing space and are therefore the most cost effective. The only changes made are the addition of windows set into the slope of the roof, the installation of insulation, plastering, and the strengthening of the floor.
  • Dormer conversions are the most popular option as they are the easiest way to add light

Aston Matthews bathroom loft conversion

The loft conversion in this charming seaside cottage has dormer windows  as well as rooflights. Pictured is the Epoca cast-iron bath from Aston Matthews

Do I need an architect?

One option for the design of a loft conversion is to commission an architect, architectural technologist or designer to produce drawings, which can then be put out to tender to local builders. A structural engineer will also be needed to oversee some of the more technical elements, such as specifying the size and grade of the joists required to support the new conversion.

Alternatively, full-service design-and-build contractors can take on the whole project. They will deal with planning permission and building regulations approval – and also often offer the benefit of a fixed-price package.

Loft bedroom with characterful exposed timbers

Leaving original timbers exposed really adds to the character of a loft bedroom

Building regulations for lofts

All loft conversions require building regulations approval in order to ensure that safety measures are in place and targets for thermal efficiency are met.

The new staircase leading to the loft will have to comply with building regulations regarding appropriate head height. These rules are quite complicated, so it is advisable to seek the advice of an architect, unless full-service design-and-build contractors have been engaged.

The roof space should be kept as airtight as possible, as well as being well ventilated to prevent any condensation and to maintain the air quality.

In addition, the conversion will need to meet basic fire regulations, which may just mean fitting a domestic sprinkler system, or could require a fire-resistant escape route with self-closing fire doors.


This double-winder staircase from Econoloft provides a seamless flow up to the loft conversion

Insulating the roof space

Improving insulation in the roof space is a key issue. It is important to maintain the continuity of insulation between the walls and the roof to avoid any cold bridging. There are two main options:

  • insulation can be applied over the rafters, known as a ‘warm roof’
  • or you can use the ‘cold roof’ method to insulate between and beneath the rafters – often with a plasterboard covering – leaving a 50mm gap between the rafters and the roof tiles to promote air flow.

The floor of the loft will also need to be acoustically upgraded for soundproofing, which at the very least involves filling the void between the floor and joists with acoustic insulation. This is usually achieved with mineral-wool insulation.

Neptune bathroom loft conversion

Bringing in light to loft conversions

The most common window solution for loft conversions is to insert rooflights between the rafters that follow the roof pitch. If, however, the home is in a Conservation Area, or the property is listed, standard rooflights are not typically considered acceptable. ‘Conservation’ designs, which are based on the original Victorian metal rooflights and sit more flush with the roofline, are often considered good alternatives.

Another option is to install a dormer window, which not only introduces natural light, but can also increase the space in the loft. There are a number of styles available – from flat-roof construction, to cottage-style pitched-roof dormers, which are more sympathetic for period properties, but provide less usable space.

Where the style of the property permits, full-length glazed doors along a gable wall, with a Juliet balcony, will maximise the sense of space.


Dormer windows in a sloped roof, such as these by Scotts of Thrapston, help to create extra headroom

Fitting a bathroom in a loft conversion

If a bathroom is to be installed, consider the location of the existing services. It should be relatively simple to add hot and cold water by branching this off the existing plumbing from either the boiler or the floor below using flexible plastic plumbing; the same will apply for existing soil pipes. However, it may be necessary to upgrade the existing boiler.


This en suite is part of a loft conversion to a property in a Conservation Area by A1 Lofts. Timber-framed Velux rooflights are sympathetic to the style of the home

50 Degrees North loft conversion bathroom

In this 1920s semi-detached house, the freestanding bath had to be winched up and onto the scaffolding before being carried through to its current position under the rooflight. Designed by 50 Degrees North Architects, the project cost around £64,000Save