Building regulations when installing new windows and doors

Building regulations control the standards for design, construction and alterations of every building in the UK. Building regulations set the appropriate standard for properties and the regulations that must be complied with during construction and development. The association is developed by the UK Government to ensure that all buildings meet a strict criteria and standard so that they are constructed safely and securely.

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Since 2002, the installation of all replacement glazing has come within the scope of the building regulations, meaning that all installers have to comply with specific quality and thermal standards. However you choose to have your windows and doors replaced you will need to get a certificate to prove that the installation has complied with the current regulations. You can either apply to your council directly who will then come and assess the work or use an installer that is registered with a certified Competent person scheme such as FENSA.


FENSA is the government authorised competent person scheme for replacement windows and doors in England and Wales to check that the installation is completed to the relevant building regulations. The scheme ensures that any FENSA registered installer is working to the relevant building regulations. FENSA improved installers are rigorously and routinely assessed for their ability to install replacement windows and doors to the relevant standards.

Using a FENSA approved installer takes the stress and hassle away from your new glazing installation. FENSA provides vetted individuals and firms the ability to self-certify that their work complies with building regulations . You will not need to contact your local council or worry about getting permission as the installer will be able to provide you with the compliance certificate after the installation has been completed. This is often much easier and cheaper for you as you don't have to worry about local authority inspections, waiting times and fees.

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What are the building regulations for double glazing?

The regulations ensure that the windows comply with strict thermal performance and safety standards. A variety of factors relating to the windows and the installation are assessed to ensure:

Fire safety

There must be a means of escape in case of a fire, so the opening should be sized appropriately to provide a potential escape. The width and height cannot be any less than 450mm. The regulations state that where means of escape exist in a habitable room on a first floor, or in an inner room on the ground floor, then this means of escape must be maintained. If no means of escape currently exist in the property then, whilst it isn’t a legal requirement to introduce one, we would highly recommend one in each habitable room upstairs or in an inner room downstairs.

Minimum thermal heat loss

The glazing must be classed as energy efficient and provide protection against thermal heat loss. The minimum energy rating for newly installed windows in the UK is a C grade, at Safestyle we only install A-rated glazing which is recommended by The Energy Savings Trust. The window must also attain the required U-value and the installer must be able to provide calculations to show how the U-value is attained.

Two uPVC windows

Safety glazing

Safety glazing should be provided to any glass that is deemed to be in a critical area. Any glazed area within a window below 800mm from floor level will need safety glazing. Any glazed area within a window that is 300mm or less from a door and up to 1500mm from floor level will need Safety glazing. It will also be required within any glazed door or glazed side panel to the door between floor level and 1500mm above. Any window that is located within 800mm measured from the bottom of the bath or shower is also classed as being in a critical location and will require safety glazing.


There are regulations in place to determine the extent of ventilation each window and door is required to give. If ventilation is required to meet the building regulations the window must provide this and therefore must have an opening. Typically this is dependent on the use and size of the room they are being installed in.

Regulations also ensure that, unless in a historic building, all new glazing must be double glazed at a minimum meaning that single glazed windows are no longer compliant to regulations. Low emissivity glass must be used on the inner pane and the air gap between the panes of glass must be at least 16mm.

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Do you need planning permission for installing new windows and doors?

In some circumstances there can be planning restrictions that you will need to take into consideration before undergoing any major home improvement. Typically you would not need to apply for planning permission for a new window and door installation, as long as they are of a similar appearance and size to the ones used in the construction of the property.

If you live in a listed property then you would need to gain listed building consent for any significant work whether it is internal or external. You may also need to gain permission if you live in a flat or in a conservation area. If you are drastically altering the appearance of the property, such as having a large bay window that will require building work installed, then you may need building control permission before having the work completed. Our surveyor will be able to discuss planning regulation with you but generally we find that it is very rare to need any authority permission for the installation of replacement windows and doors.

Fitter Preparing windows

As a FENSA approved installer we will provide the highest quality installation that is compliant to building regulations. Speak to one of our helpful representatives who will be able to discuss all of the requirements with you and help you find the perfect windows for your home.

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