If you are thinking about converting your loft to create an additional room then you will need to apply for Building Regulation approval.
You may also need planning permission if you live in a Conservation Area or a Listed Building and/or are installing a dormer window. The Party Wall Act may also apply, the LABC Best Practice note provides further information.
The upper storeys must by served by a fire protected stairway (protected at all levels). If you have an open plan staircase it will therefore need to be enclosed.
Provision of compliant escape windows removes the need to have a protected escape stair to loft conversions with floors less than 4.5m above ground level. For loft conversions to existing 2 storey dwellings - you now cannot rely on an escape windows to make safe escape, as it is considered that you will be able to reach the ground floor internally via the fire protected stairway.
No Inner Rooms
Rooms within the loft should be designed so that there are no inner rooms i.e. where escape can only be made by passing through another room.
Any new door forming the protected escape route protection will have to be a FD20 / E20 fire-resistant door fitted in an appropriate frame as recommended by the fire door manufacturer. Intumescent seals may also have to be fitted to the frame or door edges as recommended by the door manufacturer to ensure it achieves the FD20 / E20 rating.
For loft conversions to existing 2 storey dwellings, the new floor must be of 30-minute fire-resistant construction. If you are retaining your existing ceilings, which are usually suspended from the new floor construction, you will have to upgrade any sub-standard ceiling construction to ensure the new floor achieves this required rating.
The existing ceiling joists in the roof will almost certainly be inadequate for use as floor joists. In most cases it is possible to install new floor joists and support beams between the existing ceiling joists to maximise the headroom available. You are advised to seek professional guidance and provide calculations for any support beams you intend to provide to support the floor.
You need 30-minute fire protection to the escape routes and the walls forming the protected routes need to be carefully checked to see if they will achieve the required fire rating. Mains powered and battery backed up smoke detectors must be installed on each storey.
The new rooms will need to be fully insulated to prevent excessive heat loss and sound transmission. While there are many ways of achieving this, we would recommend that you check your chosen method with your Building Control Surveyor before any insulation is installed. Be advised that the provision of this insulation will often reduce the headroom to the existing loft space.
There are many other areas where the Building Regulations impose requirements relating to loft conversions and you are strongly advised due to the complex nature of these types of application that you make a full plans application - where the majority of the problems can be resolved before you start the works.