Who approves the work
You can use the local authority's building control team (Birmingham City Council, or Solihull Council in Solihull) or a registered building control approver, the private-sector route. Either way the standards are the same national ones, set out in the Approved Documents.
For a loft conversion the sensible route is a full plans application: the drawings and structural calculations are checked before work starts, so problems are found on paper rather than on site. A building notice, which lets work start after a short notice period without plans being approved, is legal for houses but leaves more to be agreed during the build.
Structure
The existing ceiling joists of the first-floor rooms were never designed to carry a bedroom. A new floor is built, usually with new joists alongside or above the old ones, often supported by steel beams bearing on the walls. A structural engineer calculates the sizes. Where the roof is made of trussed rafters, the factory-made triangles with diagonal timbers common from the 1960s onwards, the trusses have to be replaced by a new structure before the loft can be opened up.
Fire safety: the escape route
Converting the loft of a two-storey house creates a third storey, and the rules change at that point. The usual approach under Approved Document B is a protected stairway: the stair from the loft down to the front door is enclosed by fire-resisting walls and doors, so people can get out through it even if a room off the stair is on fire.
- Fire-resisting doors (usually to the FD20 or E20 standard) on the habitable rooms that open onto the stair, including on the existing first and ground floors.
- The stair leading to a final exit, or to two escape routes on the ground floor.
- Mains-powered, interlinked smoke alarms on every storey, with a standby power supply.
- Fire-resisting construction to the new floor.
The staircase
Approved Document K asks for 2 metres of clear headroom over a staircase. Loft conversions are the one case where less is allowed if there is no space for it: 1.9 metres at the centre of the stair, reducing to 1.8 metres at the side. The pitch of a private stair can be no steeper than 42 degrees, with handrails and guarding to the sides.
Where there is genuinely no room for a normal stair, an alternating tread stair can be accepted, but only to serve one habitable room, plus a bathroom or toilet as long as it is not the only toilet in the house. Finding space for a proper stair is one of the main things a survey looks at, because it shapes the whole layout.
Insulation, ventilation and light
The roof slopes, dormer walls and dormer roof are insulated to the current Part L standards. In a loft that usually means insulation between and under the rafters, which takes some of the height, so the specification is chosen with the headroom in mind. Ventilation is needed to the rooms (opening windows and extractor fans in bathrooms) and to the roof structure, to stop condensation building up in the timbers.
Electrics, plumbing and the en-suite
New circuits are certified by a registered electrician under Part P. An en-suite brings in drainage (the route of the waste to the existing soil stack is checked early), hot water and water efficiency rules. The cold water tank that sits in many Birmingham lofts usually has to move or go altogether, often with a change of boiler or cylinder, so the heating engineer is involved at design stage.
The completion certificate
Building Control inspects at set stages during the build and issues a completion certificate when the work is finished and complies. Keep it with the house deeds: a buyer's solicitor will ask for it, and a loft room without one can be described as a loft rather than a bedroom when you sell.
Questions people ask
Does every loft conversion need Building Regulations approval?
Every conversion that turns the loft into a room does, whether or not it needs planning permission. Boarding a loft for storage alone usually does not.
Do I need fire doors for a loft conversion?
In a two-storey house, usually yes. The common approach is a protected stairway, with fire-resisting doors on the habitable rooms that open onto the stair on every floor.
What headroom do I need over loft stairs?
Two metres is the normal requirement. In a loft conversion where that is not possible, 1.9 metres at the centre of the stair and 1.8 metres at the side is acceptable.
Can I use a loft ladder or a space-saver stair?
A retractable ladder is not acceptable for a habitable room. An alternating tread stair can be, but only where there is no space for a normal stair and it serves one habitable room, plus a bathroom or toilet if that is not the only toilet in the house.
What happens if a loft conversion has no completion certificate?
It can cause problems when you sell, because the room cannot be shown to meet the regulations. Regularisation is possible through the council, but it may mean opening up finished work.