Replacement windows

Building Regulations require that work involving replacement windows, doors, and rooflights, etc. is checked to establish if requirements are being met. This does not apply to repair work to frames or broken glass.

There are two main methods you can use to show compliance with the Regulations these being the FENSA scheme or Local Authority Building Control Services. You can choose which way is best for you.

Whichever method you choose you will need to ensure that the work complies with the requirements of the Building Regulations. Replacement windows must comply with the following:

Regulation 4, Schedule 1

  • Requirement A1:Loading - that the element is properly fixed in the structural opening
  • Requirement L1: Conservation of fuel and power- that the required U values for windows, doors and rooflights is achieved. Average U values must not exceed 1.8 for glazing. Alternatively you can use the centre pane method to calculate the U value, however the U value must not exceed 1.2.
  • Requirement N1: Glazing- that safety glazing, of the appropriate rating, is installed in critical locations. Locations are within 1.5m of the floor in doors or side panels within 300mm of the door and within 800mm of the floor in other situations.

Regulation 7, Materials

  • The selection and installation of appropriate products. Sealed double glazed units for instance should avoid the risk of condensation forming between panes as per BRE Report 262.

In addition to the above, replacement windows must not make the existing building worse in terms of ...

  • structural stability

  • opening parts that allow escape in the event of fire

  • ventilation of rooms

  • air supply to combustion appliances

  • protection from falling

  • access for people with disabilities

... and good practice would be to provide:

  • adequate lintel support above the opening

  • structural support for two storey bays

  • opening parts that are suitable for fire escape purposes to all first floor habitable rooms or ground floor habitable rooms where escape is available only by passing through another room. Size when open to be not less than 0.33m2 with no dimension less than 450mm and sited so that the bottom of the opening is between 800mm and 1,100mm above floor level

  • opening parts, that are at least 1/20th of the floor area they serve, for ventilation purposes

  • trickle ventilation, sized at 8,000mm2 for habitable rooms and 4,000mm2 for other rooms, if the room is not provided with other means of background ventilation such as airbricks with hit and miss grilles

  • an air supply that ensures combustion, proper operation of flues, dispersal of products of combustion to the outside air and the cooling of combustion appliances. Advice on this can be found in Approved Document J: Combustion appliances and fuel storage systemsand will depend on the type of appliance. Please note that some appliances require permanently open air vents

  • guarding to prevent falling from upper floor windows where the cill height is less than 800mm from floor level and

  • a clear width when open of 775mm for principal entrance doors to allow access by wheelchair users.

Please note that these guidance notes are for advice only and may not cover all situations. It is your responsibility to ensure that they are appropriate for use in your particular circumstance.