Since 1 April 2002 building regulations have applied to all replacement glazing. The regulations apply to thermal performance and other areas such as safety, air supply, means of escape and ventilation.
An external window or door is a "controlled fitting" under the Building Regulations and as a result of this classification these Regulations set out certain standards to be met when such a window or door is replaced.
General guidance on the performance expected of materials and building work in order to comply with the building regulations and practical examples and solutions on how to achieve compliance for some of the more common building situations can be found in the approved documents section.
You could use an installer registered with the relevant competent person scheme. A registered installer will be approved to carry out the work to comply with building regulations without involving local authority building control. When work is complete you will receive a certificate showing the work was done by a registered installer. More information about Competent Person Schemes can be found on the Gov.uk website.
Alternatively, you could use an unregistered installer or DIY, in which case approval can be sought from the relevant Building Control Body – either at your Local Authority or an Approved Inspector. They will check the replacement window(s) or door(s) for compliance and, if satisfied, issue a certificate of compliance.
Thermal Heat Loss
Dwellings are required to be energy efficient. A method of achieving greater energy efficiency is to take steps to reduce the amount of heat that is lost through the glazing in both windows and doors.
If you are to install windows and doors you should be aware that they 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. For information on the maximum U-Value allowed please refer to Approved Document L-1B, Table 1.
Safety glazing should be provided to any glass in a critical area. Below is a list giving general view as to when safety glazing is required:
- Unobstructed openable area: At least 0.33 square metres and at least 450mm high and 450mm wide
- Within any glazed door up to 1500mm from floor level.
See diagram 5.1 in Approved Document K for more information.
Windows and doors provide ventilation to rooms within a dwelling and rules apply to how much ventilation. The type and extent of ventilation will be dependent on the use and size of the room. For example, rooms where steam will be produced (kitchens, bathrooms, utility rooms etc) should be provided with higher levels of ventilation (normally mechanical fans and windows) than other rooms where suitably sized window openings and background ("trickle") ventilators may suffice.
There are two aspects to be considered:
- Fire spread between properties through "unprotected areas"
- Means of escape in case of fire.
External doors and windows may need to have fire resistance and (in the case of doors) be self-closing or (in the case of windows) be fixed shut to limit the risk of fire spread between adjacent properties. The area of walls, doors and windows permitted to have reduced or undetermined fire resistance (known as “unprotected areas”) will be dependent on how close these elements are to the boundary.
Means of escape
When replacing any window, the opening should be sized to provide at least the same 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 could be reduced down to the minimum as specified in the criteria below.
The means of escape should be considered for any new window installed to an extension or existing dwelling. If an escape window is required then criteria set out 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.
See below for the general criteria 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 - The bottom of the openable area should be no more than 1100mm above the floor area.
Only one window per room is generally required.
Access to buildings
When replacing main entrance doors in a dwelling unit that has been constructed since 1999, it is important to ensure that the threshold remains level otherwise the works will not comply with the Building Regulations as it would be making the threshold worse than it was when constructed. This is to enable people, including those with disabilities, to have continued access to the dwelling.
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