Fire safety
A loft room on a typical two-storey house creates a new storey more than 4.5m above the ground, which is too high to escape safely from a window. Approved Document B (paragraphs 2.21 to 2.23) says that in this case:
- the whole escape route, from the loft down to an exit, should be addressed;
- doors onto the route should be fire-resisting (minimum E 20) and partitions fire-resisting (minimum REI 30), including upgrading existing doors where necessary;
- in an open-plan layout, new partitions should enclose the escape route, or an alternative approach can be used: sprinklers in the open-plan areas, a fire-resisting partition and door separating the ground floor from the upper floors, and cooking facilities separated off.
Homes should also have mains-operated smoke alarms (with a standby power supply such as a battery), and the Planning Portal notes that interlinked alarms will be needed in the stairway at each level.
Stairs and headroom
Approved Document K sets out the rules for stairs in homes:
- a normal private stair should be no steeper than 42°, with each step rising 150mm to 220mm and a going (tread depth) of 220mm to 300mm;
- headroom should be 2m, but in a loft conversion without space for that, 1.9m at the centre of the stair reducing to 1.8m at the side is acceptable;
- an alternating tread stair can be used only in a loft conversion without space for a normal stair, and only for access to one habitable room (plus, if wanted, a bathroom or WC that is not the home's only WC);
- a fixed ladder with handrails on both sides can be used only for a loft conversion with one habitable room and no space for a stair;
- retractable ladders cannot be used as a means of escape.
Finding room for the stair is often the hardest part of a design, because it usually comes out of an existing bedroom or landing.
Structure
Existing ceiling joists are rarely designed to be a floor, so a loft conversion usually needs new floor joists, and dormers, hip-to-gable and mansard conversions often need steel beams. A structural engineer's calculations are normally part of the building regulations application.
Insulation and energy
The new room's roof, walls and floor need insulating to current standards under Approved Document L, and new windows, heating and lighting have their own requirements. Your designer or building control body will confirm what applies.
Getting approval
You can choose your council's building control team or a private registered building control approver (GOV.UK). There are two main ways to apply (GOV.UK):
- Full plans: the plans are checked before work starts, with a decision within 5 weeks, or 2 months with your consent. This is the usual route for a loft conversion.
- Building notice: work can start 2 days after the notice is submitted, but GOV.UK describes this as only for smaller projects, and the work is checked as it goes.
After the final inspection you get a completion certificate, which you will need when you sell. GOV.UK warns that without approval you may not have the certificates you need to sell, and could be made to pay to fix faulty work.
Berkshire councils publish loft conversion charges of £726 to £1,385 for a full plans application, including VAT, depending on the council and the size. See each council's figures in our planning guide.
Neighbours and party walls
If the work affects a wall you share with a neighbour, for example cutting in steel beams, the Party Wall etc. Act 1996 may apply. Read our party wall guide.
The Approved Documents are the official guidance on meeting the building regulations in England. See all Approved Documents on GOV.UK.