Loft Conversion Regulations

If the building is listed or situated in a conservation area listed building consent and planning permission may be required.

Houses not listed or located in a conservation area can be extended up to a particular volumetric limit without planning permission being required. However, if a dormer is or dormers are being formed whose volume, once the volume of any previous extensions to the property is added, is likely to exceed that permitted, planning permission is required.

If a hip ended roof is to be changed to a gable end roof, planning permission may be required.

If a dormer on the back addition is proposed, planning permission may be required. Where planning permission is required, this should be applied for and granted before works start.

Dormers must not project above the ridge.

If a loft space is to be used for any purpose other than storage, a Building Regulations application is required.

In some instances an application will be required for the use of a loft for storage. There is a separate guidance note on the use of lofts for storage, which should be read if one is considering the storage of materials in a loft, which would significantly increase the loading on existing ceiling joists.

Although loft conversions may be relatively small in size, there are a multitude of problems which can occur which could mean that the conversion fails to satisfy the minimum standards set out in Building Regulations and that it does not satisfy its purpose.

For this reason we advise that applications for loft conversions are submitted. When an application is deposited, the drawings and details submitted are formally checked by a Building Control Surveyor and most deficiencies and potential problems will be resolved before the application is approved.

There are a number of points that need to be considered:

If the proposal assumes that an internal wall is loadbearing, its construction and foundations are to be exposed for assessment and if not adequate further details are to be submitted. Indeed, any existing element of structure likely to be receiving a greater loading than previously should be assessed for suitability and if not adequate replaced or the loads taken safely to ground by alternative means.

Steel beams are often required to support new floor joists. A suitably qualified person should undertake the structural design. Any beams, beam bearings, posts, trimmers and connection details should be justified by calculations, copies of which should be submitted for checking by the Authority.

Beams must not bear into chimneys or the party wall between chimneys.

Rafters are to be doubled up on either side of rooflights. If rooflights are to be provided side by side, it is unlikely that doubling up of the rafters will be sufficient. The appropriate strengthening should be determined by calculation.

A safe means of escape, in the event of fire, is to be provided. This guidance assumes the existing dwelling has at least two stories. The means of escape and fire protection required where a bungalow is to have a loft conversion are less exacting, due to shorter travel distances. However, with any loft conversion, the staircase must discharge close to a door leading to an external safe place and not in a room.

Staircases are to be enclosed by construction (doors and walls or partitions) capable of resisting fire for at least 30 minutes.

The only internal doors opening onto staircases that may have glazing which is not fire resisting and do not need to be fire resisting are doors into bathrooms or toilets.

The condition of existing doors and door frames must be assessed. If they do not provide at least 30 minutes fire resistance, they must be replaced with doors capable of achieving at least 30 minutes fire resistance.

Mains powered interlinked smoke detectors are to be provided, with a minimum of one detector per level. The installation is to comply with BS5939: Part 6: 1995.

Since 1 January 2005, domestic electrical installations have been subject to control under Part P (Electrical safety) of the Building Regulations. Additional information is given in our electrical safety guidance note and in the website of the Department of Communities and Local Government.

If the building has a basement its ceiling is to be underdrawn to achieve at least 30 minutes fire resistance and the basement is to be separated from the ground floor by fire resisting construction.

The first floor ceiling is to achieve at least 30 minutes fire resistance.

Any glazing in, over or adjacent to internal doors opening onto the staircase, other than those serving toilets or bathrooms, is to be fire resisting. This requirement also applies to glazed panels in walls or partitions between rooms and the staircase.

The minimum headroom on staircases and corridors is 2 metres. In circumstances where there is insufficient space to achieve this height, a minimum headroom at the centre of the stair of 1.9 metres may be acceptable.

Loft room external walls are to achieve a U-value of not more than 0.30W/m2oK, and roof areas are to achieve a U-value of not more than 0.20W/m2oK.

Ridge vents equivalent to a continuous 5mm gap and eaves vents equivalent to a continuous 25mm gap are to be provided (front and rear). This is required unless a vapour permeable sarking layer (“breather felt”) is used.

If a dormer is to be built with a “cold deck” roof, eaves vents equivalent to a continuous 25mm gap are required.

Ridge vents must be positioned so that they ventilate the roof space above ceiling level.

Ensure that there is a clear gap of at least 50mm over insulation in sloping and horizontal ceiling areas. This gap must also be maintained at the ridge. A “closed-cell” insulation, such as polyurethane board, should be used to insulate sloping ceiling areas.

If the conversion involves forming a dormer, dormer cheeks within 1 metre of a boundary are to achieve at least 30 minutes fire resistance in both directions. The dormer roof is to be capable of resisting external fire spread, also for at least 30 minutes.

Although this list may cover the most common issues, it is not exhaustive.