Replacement Windows

For many years, it was not necessary to apply for Building Regulation consent when replacing windows in existing dwellings unless a structural alteration was involved. This usually occurred when the existing opening was made wider, which made the installation of a new support lintel necessary.

From the 1 April 2002, all owners replacing windows now need to obtain consent, and the new windows themselves have to fully meet the requirements of the Building Regulations. So even if you are replacing only one window with one bought from a local DIY centre you still need to follow the guidance below.

What do I have to do?

There is a choice you can either:

• Use an installer registered under the FENSA scheme run by the Glass and Glazing federation, in which case you do not need to make a Building Regulation application to the Council. Your installer should then ensure your windows comply fully with the Regulations and will supply you with a certificate confirming this when the installation is complete. If you wish to use this option please ensure that your installer is properly registered under the scheme before placing an order. You can check this and find more details of the scheme by visiting the Glass and Glazing federation website at http://www.ggf.co.uk/ (external link)
• Make a Building Regulation application to the Council, and in most cases the simplest way of doing this will be to submit a Building Notice. You should complete a Building Notice form and return it to us together with the appropriate charge, at least two working days before removing the old window(s).

Once we receive the Building Notice, a Building Surveyor will normally visit your property. If all is found satisfactory, a Completion Certificate will then be issued to confirm this. You may well be asked by your solicitor to produce this certificate if you sell your property, so please follow carefully the guidance given to ensure one can be issued to you.

How much will it cost?

If you use a contractor registered under the FENSA scheme the cost should be included in the quotation you are given for the works. In all other cases the Council will make a charge for dealing with your Building Notice application based on the total cost of the work. We will be able to tell you the charge for your scheme.

What regulations do the windows have to comply with?

Owners of listed buildings and buildings in Conservation Areas may not need to satisfy these requirements in all cases. It is still necessary to apply for consent through the Council or the FENSA scheme.

Please remember that separate Planning Permission may be required from the Council for these works. In the first instance you should contact the Conservation team on tel: 01244 402395.

Thermal Insulation

The replacement windows will need to meet the new thermal insulation requirements of the regulations. If the replacement windows have wood or plastic frames, then the glazing needs to achieve a maximum U-value of 2.0W/m² while for metal frames a slightly higher U-value of 2.20W/m² is allowable.

(Please note that these values are very difficult to achieve and many double-glazing units currently on sale will not meet these standards)

Take great care when ordering new windows that your supplier can prove the glazing units used will satisfy this requirement, as the Building Surveyor will need to see this proof before issuing a completion certificate. We would particularly recommend that you leave any labels on the glazing in place until after the Building Surveyor has carried out a satisfactory inspection.

In some cases it may be permissible to use glazing units which do not meet the above specifications, but to do so you (or your supplier) would have to submit calculations to prove that the overall insulation requirements of the regulations would still be met.

This may be possible if other insulation measures are undertaken at the same time as the window replacement for example, installing cavity wall insulation or "topping up" loft insulation. The benefits gained by installing this extra insulation can be used to offset the higher losses through the glazing, but this should not be undertaken lightly.

We would strongly advise you do get such calculations checked by the Building Surveyor well before the replacement windows are installed, so that expensive mistakes can be avoided

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 windows in loft conversions and in any ground floor rooms where exit is only possible through another room.

To meet this requirement all such windows should have openings of a size and position to enable escape. Information on these sizes is available from the Building Consultancy.

If your existing windows do not have opening lights, which meet the above requirements, we would strongly recommend for your own safety that you take the opportunity to provide them in the replacement windows. This is not a however a requirement of the regulations, which simply state that the replacement windows must be no worse than those they replace in this respect. Where the existing windows already have opening lights, which are larger than the above requirements, those in the new windows can be reduced in size provided they are not reduced to less than the minimum dimensions.

Safety Glazing

Low level glazing (glazed areas within 800mm of floor level) and glazing in doors within 1500mm of floor level should generally be of a type so that if broken, it will break safely. In practice this means such glazing should be either laminated or toughened. Manufactures of safety glass will have put a small symbol on the glass. Ordinary glazing can still be used in small pane sizes however, provided the glass is sufficiently strong to resist breakage. The Approved Document to part N of the Building Regulations gives maximum sizes according to the thickness of glass - for example, in a single pane less than 1.1m square - 8mm glass would be satisfactory.

Structural Safety

If the replacement windows are wider than those they replace, or involve the replacement of bay windows, then the Building Surveyor will need to be satisfied that proper structural support is provided above the window. In older buildings, the timber frame of the window was often sufficiently strong to carry the load of a wall or roof above it without a lintel. Obviously in these cases either a lintel needs to be installed when the window is replaced, or the new frame carefully reinforced to carry the load.

Ventilation

The Building Regulations require that adequate ventilation is provided for people in the building and this should be considered when deciding on the size of opening lights in the replacement windows. For most rooms, one or more opening windows totalling 5% of the floor area, with background "trickle" vents totalling 8000mm² will be adequate. For kitchens, utility rooms and bathrooms an extract fan is also normally required.

In some cases the existing windows may contain a permanent vent to supply combustion air to a heating appliance, although this is now rare. If this is the case however 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.

Ask questions now, don't wait until it's too late.

Be Safe - Be Sure - Not Sorry

This information note has been prepared as a guide on meeting the requirements of the Building Regulation L1.
(conservation of fuel and power)

The Authority accepts no responsibility for action taken resulting from the use of this information note.

If you would like to speak to a member of the Building Consultancy Team please contact us, details below.

Contact Details

Building Consultancy

Email - buildingconsultancy@chester.gov.uk

Opening hours - 8.45am - 4.45pm

Phone number - 01244 402224

Fax - 01244 321876

Address - Building Consultancy, Development Directorate, Chester City Council, The Forum, Chester, CH1 2HS