All builders and home owners who are replacing windows must make a Building Regulation application, unless the windows are to be replaced by a Fensa registered installer. The new windows will have to meet all building regulations, so even if you are replacing one window you will need to follow the guidance provided below.

Regulations that your windows must comply with.

Where windows are to be fitted into a listed building, or a building in a conservation area, it may not be necessary to comply fully with all the requirements below.

For further details you should contact your local council's planning office.

Thermal insulation: Replacement windows must comply with minimum standards of thermal insulation. For uPVC frames the glazing needs to achieve a maximum U-value of 2.0W/m2K.  Make sure when ordering your new windows that your supplier can provide evidence that the glazing units meet these requirements, as a building control surveyor will need to see proof of this before issuing a completion certificate.

Structural Safety

If the replacement windows are wider than those they replace, or involve the replacement of bay windows, then the Building Control Surveyor will need to be satisfied that proper structural support is provided above the window and in the bays that support corner posts are adequate.

Safety Glazing Low level glazing areas within 800mm of the floor, glazing in doors and within 300mm of door edges less than 1500mm above floor level should generally be of the type so that if broken, it will break safely. This means the glass should be toughened of laminated.

Ventilation Building regulations require that adequate ventilation should be provided for people in buildings, so you must not worsen the existing rooms ventilation provisions. If your original windows have background trickle ventilation, then the replacements should also have them fitted. In addition all habitable rooms and rooms containing a wc should have opening lights of at least 1/20th of the floor area of the room they serve. Kitchens and bathrooms also normally require an extractor fan, so if you are removing window fans these must also be reinstated.

Combustion air to fires and heating appliances In some cases the existing windows may contain a permanent vent to supply combustion air to heating appliances, also you may find the removal of ill fitting windows which previously let air filter into the room could cause problems to your appliances. if this is the case you should ensure that either the replacement window contains a similar permanent vent, or that some other means of providing the required ventilation is installed at the same time. It is advisable to have your appliances checked out by registered installer e.g corgi for gas appliances.

Retention of disabled thresholds

Many newer properties are now provided with level access thresholds and your new doors must not worsen this access, nor reduce the doors clear opening width.

Means of escape All first floor windows in dwellings should ideally have opening lights large enough to allow you to escape through them if you were trapped in the room by a fire. This also applies to ground rooms where they do not open directly into a hall leading to an external door through which you can escape. To meet this requirement all such windows should have an unobstructed openable area of at least 0.33m2 and be not less than 450mm high and 450mm wide (the route through the window may be at an angle rather than straight through).