Loft Conversions

Building into your roof is one of the cheapest ways to maximise useful living space and add value to your home.


A dramatic conversion by Access Loft Conversions.

Loft conversions often cost less than half the price per square metre of adding a new extension because the basic structure is already in place, and planning permission is not usually required.

Some lofts can prove expensive to adapt, though, and space will also be taken up by the new staircase, so make sure that you are actually gaining more living space overall.

Not all loft spaces can be successfully converted, and just because you can stand up in the middle doesn’t necessarily mean that enough of the loft area has sufficient headroom.

As a general rule the steeper the roof pitch the greater the potential living space, with low space in the eaves suitable for cupboards.

Although regulations don’t stipulate minimum ceiling heights, look for a useful area that is at least two metres high, some of this being at the head of the planned access stair.

Take a measurement from the bottom of the ridge timber to the top of the ceiling joist; the usable part of the roof should ideally be greater than 2.2m to allow for joists, flooring and insulation. If space is tight then consider extending the area by altering the shape of the roof, adding some generous dormer windows or replacing part of the pitched roof with a raised flat section. These options require substantial modifications to the roof structure, so you will need expert help.



Another more drastic option is to lower the floor of the loft, reducing the ceiling height of the rooms below – a big structural undertaking!


Many specialist companies such as Econoloft ( offer complete design and build services for loft conversions. Alternatively, you can approach an architect or other designer to produce drawings which can then be used for tendering to builders.

Planning permission

Planning permission is not normally required for loft conversions or the insertion of roof lights, unless the house is listed or is located in a designated area such as a national park, an Area of Outstanding Natural Beauty or a conservation area. No extension can be higher than the highest part of the roof, and additions up to 50 m3 (40 m3 for terraces) to the side or rear of the roof – including dormers – are classed as permitted development.

See Guide to Permitted Development »

Bear in mind that any previous roof space additions must be included within this volume allowance.

Side-facing windows must be obscure glazed and non-opening, unless the parts which can be opened are more than 1.7m above the floor of the room in which it is installed.

Planning permission is required where you extend or alter the roof space and it exceeds specified limits and conditions. For more detailed information visit the Planning Portal - the UK government’s online planning and building regulations resource (

Work on a loft or a roof may affect bats, and you need to consider protected species when planning work of this type. A survey may be needed, and a licence may be required if bats are using the building.

Building Regulations

Building Regulations approval is always necessary when creating habitable areas, to ensure the loft is converted to an appropriate standard.

Where an open-plan stairway currently exists, Approved Document B allows a conversion from a two-storey to a three-storey house to have an open-plan layout on the ground floor (where the staircase passes through the open-plan area) as long as certain conditions are met:

  • The open-plan area must be protected by a suppression system – historically, this was normally a sprinkler system.
  • There must be escape windows at first floor. ∙ The first floor must be separated from ground level by a fire-resisting screen and fire door so that the escape windows remain viable.
  • The kitchen needs to be separated from the open-plan area by a ‘fire resisting construction’ - either a fire door or a wall.

These four conditions are not the law – but they are national guidance, so a project that follows them will pass through Building Control more straightforwardly than one that doesn’t.

You may be able to depart from the guidance if either you or your building control officer are armed with suitable fire engineering advice. Fire detection systems such as a panel alarm or sprinkler/mist system can also serve as part of the package.

The structure


There are four main types of loft conversion. Installing roof lights is a popular option that doesn’t involve structural alterations, providing there is sufficient height in the original loft space. Adding dormers easily creates extra height and floor space. Changing the roof structure to form a mansard (a flat roof, with four sloping sides, becoming more steeply sloping hakfway down, and windows usually housed within dormers) is a costlier option which may require planning permission.

Extending from the sloped roof out to the external wall forms a hip to gable conversion. This extends the side roof area so that the hipped roof, which formerly sloped inwards, becomes a vertical wall – creating extra usable space inside the loft.

Modern truss rafters produce a forest of supports within the roof space, making conversion difficult. One solution is to support existing rafters on structural beams such as those developed by TeleBeam (

It is unlikely that the existing ceiling joists will be adequate, and new floor joists will probably need to be installed between them, which may be supported on walls if these prove suitable. Otherwise additional support – such as steel or timber beams – should be introduced.

Some houses have through-lounges on the ground floor, with a steel or timber beam installed over the opening, and this beam would need to be strong enough to carry any new loads from the loft conversion. A structural engineer or building control officer will be able to offer advice.

Other considerations

When converting a roof space into living accommodation the provisions for escape need to be considered. This often means that additional fire protection will be necessary in existing parts of the house, and to ensure adequate fire safety a stair serving the new room will be needed.


Where there is not enough room for a full traditional stair, it may be possible to use a space-saving version, but retractable ladders are not normally acceptable. The new storey must be isolated from the house by half an hour’s worth of fire resistance, which almost certainly means installing fire doors to FD20 rating as a minimum.

Other products include a coating system such as Envirograf ( that allows existing plasterboard ceilings and walls to be upgraded to a 30- or 60-minute fire rating, removing the need to use extra plasterboard to upgrade to fire rating requirements.

Traditionally, attic spaces are well ventilated and often draughty, to allow the building to breathe and avoid condensation forming on cold surfaces which could damage the structure.

Building Regulations require well-insulated walls and ceilings, with construction methods designed to prevent condensation.

Make sure that the new storey is well soundproofed to avoid noise transferring to neighbours or the rooms below, and consider how the new space will be heated. If you intend to extend your existing central heating system then check that the boiler will be powerful enough to cope.

Lofts in new build homes

  • For a new house it makes sense to consider the loft space early on – allowing enough headroom whether you intend to build into the roof space now or later.
  • If possible, build into the loft area when constructing the whole house. Not only will build costs be cheaper, but you will also be able to claim back the VAT if it is part of a self build, whereas converting a roof space is not eligible for a VAT refund.


  • Budget to incorporate attic roof trusses - it is always money well spent because, even if you can’t afford to fit out this level initially, they will enable an easy conversion at a later date for very little outlay. Remember to leave enough room for an additional staircase, though, as this will take up valuable space from the floor below if not carefully designed.powerful enough to cope.

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