Building Regulations for Windows & Doors

On upper floors, every habitable room — bedrooms, living rooms and studies — must have at least one window that can be used as a means of escape. Kitchens and bathrooms are exempt.

• Minimum openable area of 0.33m² (e.g. 600mm wide × 550mm tall)
• Maximum sill height from floor: 1,100mm
• Minimum 450mm high or 450mm wide (at least one dimension must meet this)
• If the dimensions are at the minimum, the other dimension must be at least 734mm to achieve 0.33m²
• Opening must be unobstructed to at least 0.33m² clear
• Ground floor windows in rooms with direct exit to outside are exempt from fire escape requirements

All rooms must be adequately ventilated to prevent the build-up of condensation and pollutants. Good indoor air quality is important for both health and the fabric of the building.

• Replacement windows must match or exceed the trickle vent provision of the windows they replace
• If the original window had no trickle vents, fit as much Equivalent Area as technically feasible
• Trickle vents should be positioned at least 1.7m above finished floor level to minimise draughts
• Open-plan kitchens need the same vent provision as other rooms
• Purge ventilation: all openable windows and doors must open to at least 1/20th of the room’s floor area

Toughened or laminated safety glass is required in locations that are subject to accidental human impact. Safety glass is mandatory in the following critical zones:

• Any glazing where the bottom of the pane is within 800mm of the floor
• Glazing in doors: any glass in doors where the bottom of the pane starts below 1,500mm from the floor
• Glazing adjacent to doors: windows and side panels within 300mm of a door edge, starting within 1,500mm of the floor

Glass in these zones must be marked with a British Standard kitemark confirming it is toughened or laminated.

Part L covers the conservation of fuel and power in buildings. Key rules for windows and doors include:

• Glazed area must not exceed 25% of the floor area
• No worse energy efficiency than previous windows or doors
• New dwellings: windows and doors must be sealed with air-sealing tape

Part M ensures that replacement and new doors are accessible. The main rules are:

• Replacement doors must be no less accessible than the doors they replace — the threshold step height must not be made worse
• New build homes: external doors should have a threshold no higher than 35mm (or up to 50mm in high weather-exposure areas)
• The clear opening width of principal entrance doors must be at least 775mm, measured from the door edge to the face of the door leaf open at 90°

Part Q applies to accessible windows and doors in new-build homes and extensions — essentially any opening a burglar could reasonably reach. Requirements include:

• Comply with British Standards PAS 24:2012 (also covered by Secured by Design accreditation)
• Main entrance doors must include a spyhole or clear glass, a door chain, and a letterplate that complies with TS008
• Any window without key-locking mechanisms must have laminated glass on all openers
• Door glazing and glazing adjacent to near-door panels or windows must be laminated