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Building Regulations

Building Regulations for Doors

An external window or door is considered a “controlled fitting” under the current set of Building Regulations. The Regulations for this classification state that certain standards must be met when a window or door is replaced.

By choosing to use an installer registered with a competent person scheme (BSI, CERTASS or FENSA), you can save time and money. A registered installer is approved to self-certify that their work complies with the stated building regulations without involving local authority building control. When the work is complete, you will receive a certificate that acknowledges that a registered installer did the work.

Using an unregistered installer or DIY, will mean that you have to seek approval from your Local Authority or an Approved Inspector. This will mean applying for approval and then them inspecting the replacement window(s) or door(s) for compliance. If satisfied, a certificate of compliance will be issued. This is a much longer and more drawn out process.

Thermal Heat Loss

A method of achieving greater energy efficiency, as is now required for all dwellings, is to take steps to reduce the amount of heat that is lost through the glazing in both windows and doors.
When you install windows and doors you should be aware that they must comply with the requirements of the Building Regulations in relation to the amount of heat that can pass through the glass and framework (measured as a U-Value). Details on the maximum U-Value allowed can be found in the Approved Document L-1B, Table 2. The stated value that is relevant to you should not be exceeded. Windows that are provided as part of an extension/loft conversion as well as replacement windows for an existing dwelling, must also comply. You can refer to lists ‘a’ and ‘b’ in the document for further details on this.

Safety glazing

Safety glazing should be provided to any glass in a critical area. The following list explains the scenarios in which safety glazing is required:
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!


Windows and doors provide ventilation to rooms within a dwelling. Rules that relate to how much ventilation is needed have been introduced. The type and extent of ventilation required depends on the use and size of the room. For example, rooms where steam will be produced (kitchen’s, bathrooms, utility rooms etc) should be have higher levels of ventilation (normally mechanical fans and windows) than other rooms where suitably sized window openings and background (“trickle”) ventilators may suffice.

Fire Safety

There are two aspects to be considered:

  • Fires spreading between properties through “unprotected areas”
  • Means of escape in case of fire

Unprotected Areas

External windows and doors may need to be fire resistant and in the case of doors, be self-closing or in the case of windows, be fixed shut to limit the risk of fire spreading between adjacent properties. The area of walls, doors and windows permitted to have reduced or undetermined fire resistance (known as “unprotected areas”) will be dependant on how close they are to the boundary.

Means of escape

When any window is replaced, the opening should be sized to provide equal, if not improved potential for escape as the window it replaces. If the original window that is being replaced was larger than necessary for the purpose of escape, then the new window opening can be reduced down to the minimum as specified in the following criteria.

The means of escape should be considered for any new window installed to an existing dwelling or extension. If an escape window is required, then the criteria outlined below should be followed. It is also generally good practice to replace any window on the first floor that is not used as an escape window with an escape window.

The following criteria is applicable for egress windows:

  • Width and Height – Either of these are not to be any less than 450mm
  • Clear Openable Area – No less than 0.33m²
  • Cill height – No less than 800mm and no more than 1100mm from floor level.
  • In general, only one window per room is required.

Access to buildings

When replacing main entrance doors in a dwelling that has been constructed since 1999, it is important to ensure that the threshold remains level. If they aren’t, the works will not comply with the Building Regulations, as they would be making the threshold worst than it was when constructed. This is to enable a wheelchair user to have continued access to the dwelling.

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