Loft conversions

The aim of this page is to provide you with guidance as to when you should submit an application under the building regulations for proposed works involving the conversion of the roof space of a dwelling. It is not intended to provide comprehensive details of the associated regulations but highlights the most important matters that need to be considered. Such works can be more complex than other extensions and it is recommended that you seek professional assistance before submitting a full plans application for us to check, unless you are fully conversant with loft conversion design. This Council does not recommend the use of a building notice for this type of work.

The advice on fire safety is only relevant to conversions providing no more than two habitable rooms or 50 square metres of floor area, not more than 7.5 metres above ground level.

Is an application required?

Building regulation permission is required for conversions that create any type of room in the roof space, even where this is only for storage use. An application is not required where a small proportion of the space is boarded for light storage or access to water tanks as long as this is only served by a portable or retractable loft ladder.

Structural considerations

Most ceiling structures are not strong enough to serve as a floor. Upgrading the structure will involve the installation of new floor joists and in some cases steel or timber beams to carry the floor and roof loads.

The latest version of Approved Document B does not require these doors to be fitted with self-closing devices

Existing walls, lintols and beams may need to be assessed for adequacy to carry additional loads. In some cases foundations may need to be exposed and checked.  The involvement of a Structural Engineer is often needed to calculate the sizes of new structural members.

Fire safety

The formation of a room in the roof of a two-storey house creates a potentially increased risk to occupants of the new floor in the event of a fire. As a result of this, the regulations require that a protected escape route be formed between the new rooms and a final exit such as the front door. The structure forming this enclosure must have 30 minute fire resistance and the doors must be FD20 rated fire doors*. Existing floors separating rooms from landing areas may need to be upgraded to achieve a 30-minute fire rating.

It is usually necessary for the stair enclosure to lead directly to a final exit to external air (ie. via a ground floor hallway) without passing through a room (see diagram 1).  If this cannot be achieved then it is permissible to form two alternative routes to exits that are separated from each other by fire resisting construction and fire doors (see diagram 2).

Achieving the above requirements can be difficult and undesirable to clients in houses with open plan ground floor layouts. Recognising this, the regulations allow an alternative arrangement incorporating a sprinkler system. Using this option, the ground floor is separated from the upper floor by a fire resisting partition and fire door. A residential sprinkler system to BS 9251:2005 is fitted to cover the ground floor only with any cooking facilities being separated from the space by fire resisting construction. This allows a viable alternative emergency escape route from the new loft rooms via suitable escape windows at first floor level.

Smoke alarms should be fitted at every floor level. These should be mains powered with a battery back up supply and conform to BS.5446. Optical type detectors (rather than ionisation type) are less prone to false alarms. They should be fitted in hallways and landings ensuring that manufacturer’s guidance on location and maintenance is followed. They should also be linked so that a single unit activating will set off all the sounders in the dwelling.

Stairs

A retractable ladder is not a permitted means of access to a loft conversion.  The four types that can be considered are:

• a standard staircase
• a spiral staircase
• an alternating tread (‘space saver’) staircase
• a fixed ladder

The last two types are only acceptable where serving a single room (and a bathroom) and where it is not possible to create sufficient space for a standard or spiral stair.

The pitch (steepness) of the stairs and the dimensions of steps and balustrades must comply with the appropriate building regulations contained in Approved Document K. A full 2.0 metre headroom is required to new stairs although slight reductions are allowed where the ceiling slopes over the stair.

Sound insulation

With conversions in attached properties, the sound insulating properties of party walls within the loft space need to be considered. The Council may require parts of walls to be upgraded where they are of a lesser standard than walls at habitable floor levels. Where no party wall exists in the loft, a new wall must be constructed up to the underside of the roof finish with appropriate fire-stopping measures. The specifications of this wall should accord with Approved Document E that deals with sound insulation.

Thermal insulation

A loft conversion creates new ‘thermal elements’ ie. walls and roofs that separate the heated space from an unheated space or outside air. The thermal insulating properties of such elements need to be upgraded to comply with Building Regulations. Technical guidance note 10 gives examples of common specifications that comply.

Electrical installation

This must comply with Part P of the regulations. Design, installation, inspection and testing should be carried out by a contractor who is a member of a competent persons scheme for electrical wiring approved by the Secretary of State. If this is not the case then you should check with your local building control service for advice on their procedure for checking this part of the work.