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Replacement Windows and Doors

Since April 2002 Building Regulations have applied to any new or replacement windows and also doors with more than 50% glazed area. They do not normally apply if the work is for replacing broken glass, rotten sashes or rotten sections of the main frame members. However if you are any doubt please contact the Building Control section on 02380 285245

When is an application required?

For replacement windows and glazed doors you do not need to make an application if the work is registered with a Competent Persons Scheme (FENSA, CERTAS, BSI) as they will self-certify the work and issue a certificate.

If the work is not being done by someone registered with a Competent Persons Scheme you will need to make a Building Regulation application and pay a fee. This needs to be submitted before the work is started. The work will then be checked by a Building Control Surveyor for compliance with the Building Regulations who will then, if satisfied, issue a completion certificate.

What standards does a replacement window or door need to meet?

All new and replacement windows must comply with the standards set out below.

Heat Loss

Windows and doors need to comply with the requirements of the Building Regulations in relation to the amount of heat that can pass through the glass and framework, which is measured as a U-Value. This U-value should not be exceeded and is set out in the table below.

U-Values for Replacement Windows and Doors


New Unit

Replacement Unit

Window, roof window or roof light

U-value = 1.6W/m2K

U-value = 1.6W/m2K

Doors with more than 50% glazing

U-value = 1.8W/m2K

U-value = 1.8W/m2K

Other doors

U-value = 1.8W/m2K

U-value = 1.8W/m2K

Safety glazing

Safety glazing should be provided to glass in any of the areas listed below.

  • Any glazed area within a window below 800mm from floor level
  • Any glazed area within a window that is 300mm or less from a door and up to 1500mm from floor level
  • Within any glazed door up to 1500mm from floor level

Fire Safety - Means of escape

Windows are often required to provide a means of escape in case of fire. This applies to all habitable rooms at first floor level, and to rooms that are considered to be inner rooms. An inner room is one where escape within the building is only available by passing through another room. This does not apply to kitchens, en-suites or utility rooms. Nor are escape windows required to bath or shower rooms or WC accommodation.

Where an existing window is being replaced the means of escape should be no worse than the existing arrangements or should achieve the standard referred to below.

The criteria for egress windows are:

The openable space should be at least 0.33 square metres, with neither width nor height being less than 450mm. In effect the smallest window will therefore need to have a space of 450mm X 750mm. The opening should be within 800mm & 1100mm of the floor level.

Fire Safety - Unprotected areas

Where a door or window is close to the boundary there may be a limit on the area that can be allowed in order that potential fire spread between buildings can be controlled. If the wall is within 1m of the boundary, the maximum permitted "unprotected area" is 1 square metre. Sometimes this can be overcome if the glazing is appropriately fire resistant and the window is fixed. Similarly doors close to a boundary could be fitted as fire doors and be self-closing.

Access to buildings

Where altering an access in a dwelling built since 1999 it may be necessary to retain the level threshold originally provided. This is in order to retain the access facility for wheelchair users.

Trickle Vents in Replacement Glazing.

In a recent survey of homes that have had replacement windows installed it was found that fitting modern, draught-sealed windows and doors can have a substantial impact on air leakage, but as a result, can lead to a greater risk of condensation & consequent mould growth. The fitting of trickle ventilators into the window frames can lead to reduction of this risk and is therefore recommended.

For any further clarification please contact Building Control on 02380 285245

Updated: 23 Oct 2014
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