When you’re planning your loft conversion you need to make sure your project stays inside the law and keeps you and your family safe from risks like fire. It’s always a good idea to seek the advice of a professional if you’re going DIY with your loft conversion.
What does the Building Regulations guidance allow?
Approved Document B allows a three storey house to have an open plan layout on the ground floor (where the staircase passes through the open plan area) as long as four conditions are met:
- The open plan area must be protected by a suppression system – historically, this was normally a sprinkler system
- There must be escape windows at first floor
- The first floor must be separated from ground level by a fire door so that the escape windows remain viable
- The kitchen needs to be separated from the open plan area by a “fire resisting construction” – either a fire door or a wall.
These four conditions are not the law – but they are national guidance, so a project that follows them will pass through Building Control more straightforwardly than one that doesn’t. You may be able to depart from the guidance if either you or your building control officer are armed with suitable fire engineering advice.
Plasterboard ceilings in the upper rooms will delay the spread of fire to the roof space in an unconverted house. However, when an opening is introduced for the staircase the risk is shared with the conversion — therefore, safeguards must be in place to reduce the risk.
All habitable rooms in the upper storeys served by a single staircase should have an escape window with an obstructed openable area of at least 0.33m², a minimum 450mm high x 450mm wide, and not more than 1.1m above the floor level. For loft conversions to existing two storey houses, more stringent provisions apply, due to the greater risk associated with escape via high-level windows. These require a new 30- minute fire-resistant floor to the loft conversion, and a protected 30- minute fire-resistant stair enclosure discharging to its own final exit, with fire doors to all rooms (except bathrooms and WC). The fire doors do not need to be self-closing.
At least one mains-operated smoke alarm with battery backup must be installed in the circulation space of each storey. All alarms are to be interconnected.