A loft room under a trussed roof

Some house roofs are held up by trussed rafters. In England, a loft room under that kind of roof starts with professional advice and with building control. The Planning Portal's rules below are written for England, and it adds that Welsh policy can be different. Scotland and Northern Ireland have their own building rules, and GOV.UK links to them.

Getting advice on the roof first

The Trussed Rafter Association (TRA) says anyone wanting to change an existing roof structure, inside or out, needs professional advice from an architect or structural engineer before making any changes. Without it, the TRA warns, the work can cause weathering problems, or move roof loads onto parts of the house that were not designed to carry them.

Some new roofs are built with the room already in them. The TRA calls these room in roof or attic trusses. They are designed by computer and made in a factory, and one component forms both the structural roof and the floor.

Building regulations approval

Turning a loft or attic into a liveable space needs building regulations approval, according to the Planning Portal. Its guidance is written for a house no more than two storeys high. The rules make sure, for example, that:

The Planning Portal adds that the existing ceiling joists are unlikely to carry a habitable room. So new floor joists would need to be installed. It recommends talking to a building control body, usually your local council, about the plans.

Fire safety

For a typical loft conversion in a two-storey house, the Planning Portal says new fire-resisting doors, and sometimes partitions, are needed to protect the stairway. It explains that escaping through a window from a floor above the first floor is too dangerous. Mains-powered, interlinked smoke alarms are also needed in the stairway at each level.

Planning permission

In England, a loft conversion is permitted development, needing no planning permission, if it meets a set of limits and conditions. The Planning Portal lists them. Among them:

The list has further conditions, including ones on materials, the eaves and how earlier changes to the house were made. Where the limits are not met, or permitted development rights have been removed in the area, a planning application is needed.

Bats

GOV.UK's bat guidance for England says all bat species, and their breeding sites and resting places, are fully protected by law. Wales, Scotland and Northern Ireland have their own guidance. Insulating or converting a loft, and repairing or replacing a roof, are among the activities it says can affect bats.

Damaging or destroying a breeding or resting place breaks the law. So does disturbing a bat while it is in a structure where it shelters. GOV.UK says you will need an expert to carry out a bat survey. Natural England may grant a licence if disturbing bats or damaging their habitat cannot be avoided.

For small works, the National Bat Helpline offers free advice. Its advisers cannot help with works for which planning permission is needed.

Telling the neighbours

Building work near or on a shared boundary, or party wall, has to be notified to the neighbours, GOV.UK says. That applies in England and Wales. Scotland has different rules. The Planning Portal also says you must find out whether your work falls within the Party Wall etc. Act 1996.

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