Are your new replacement windows breaking the law? It pays to check first...

Live in a period property, and thinking of replacing old windows? It might seem reasonable that as a property owner you have the right to just go ahead and replace old windows, or to install double glazing – but, be careful. Depending on how old your building is, whether it's listed or not, and what materials you're planning on using for your new windows, you may need planning permission or listed building consent to proceed. 

And failing to apply for appropriate permission and just replacing old windows could incur a fine of as much as £2,000 – and an order to replace them again with historically appropriate windows. These are the permission facts you need to know if you're thinking about replacing your windows – before you do. 

1. Replacing single glazed windows with single glazing

It's a 'no'. To conform with building regulations, any windows you replace must be replaced by double glazing as a minimum. Check the government's guidance on this for more information.

2. Replacing windows in a Conservation Area

If you're not sure whether you live in a conservation area, you can type in your postcode on the Gov.uk website. Many buildings in conservation areas retain permitted development rights, which means you shouldn't need permission from the council to replace your windows, so long as they are 'in keeping' with the character of the building. 

However, if your building falls under Article 4 Preservation, this overrides any permitted development rights you may have, and you will need to ask your council for permission. They will always certainly ask for a 'like for like' replacement of your windows. 

Our advice? Always check before you go ahead with your local planning department.

3. Can I replace windows if I live in a listed building?

The answer is pretty much a definite 'no'. If your home is listed, then any work done to it, including replacing windows, will require full planning consent from the council, called listed building consent. They rarely grant permission for work on listed buildings, and if they do, your windows will need to be 'like for like', including the material. You will not be able to replace wooden window frames with UPVC ones, for example, and the council may even request that they keep the old window frames, if they are of historical value. 

4. Can I install double glazing in a listed building?

This very much depends on what grade listing your building is: Grade I will almost certainly not allow any double glazing to be installed; in a Grade II listed building, you may be able to install double glazing that's approved as 'heritage'. Again, contact your local council before making any plans. 

5. Who can I hire to replace my windows?

To replace windows and conform to building regulations you also need to have either building control sign off for an unregistered fitter (you'll need to arrange this and get the paperwork lined up) or if you can, find a FENSA registered window fitter who can self-certify the work for you – and provide the all important paperwork as proof.

Live in a conservation area or listed home? Look for a company that has experience of this kind of work; they'll be able to advise on appropriate materials and designs. Specialist, bespoke heritage window manufacturers or specialist joiners are best. 

Want more advice? Read our guide on choosing windows for period homes.