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It is a relatively common question that people ask us – Can I replace my windows myself, or do I have to get a FENSA approved tradesman to do it?

The answer is very simple – Yes, you can do it yourself!

The thing is that you must follow the building regulations and get a certificate on completion from them when replacing or upgrading your windows – this includes all roof lights, roof windows and doors which are more than 50% glazed.

DIY window fitting

DIY Window fitting – Image courtesy of DIY Network

Now that we know what is covered the next question is how to go about it.

How to Get Building Control Approval for DIY Replacement Windows

Installers that are part of a competent persons scheme, such as FENSA, can self-certify their work and inform the local authority when the job is done. You will not be part of one of these schemes, or if you are using a tradesman who is not, you then need to inform your local building control office before you start.

Typically you will need to give them at least 48 hours notice and pay a fee when you submit your application.

They will confirm with you when they will want to inspect the work, however it will generally be once and at the end, when you have completed all the work.

There are two things that they are looking for;

  1. the work has been carried out according to the building regulations
  2. the windows conform to the current required standard, particularly thermal performance (ie, are the suitably insulating)

What does this mean is practice?

Save money by fitting wondows yourself

Save Money by fitting replacement windows yourself – Image courtesy of Finesse Windows

We will not go into the detailed building regulations which are affected by windows here, as we cover these in much more detail in our project about replacement window regulations. We are going to assume that if you are planning on doing this work you are relatively familiar with them. Although a quick refresher will do you no harm!

Here are a few tips to help you ensure you can meet the regulations easily (and almost as importantly, demonstrate that you have):

  • Take pictures or better still, keep the old windows, so that the inspector can see the previous levels of ventilation, which need to be maintained
  • Ensure that you leave the stickers on the new windows as this will show exactly what the thermal performance is and so the inspector can see it easily. There are also rules about toughening glass which is fitted nearer ground level which you need to prove you have complied with too
  • Ensure that the replacement is structurally sound; this is particularly important if you are increasing the size of the window or it is a bay window
  • Ground and first floor windows have to allow escape in the case of fire

It all sounds daunting, but the manufacturer who sells your windows will know these rules very well, so will be able to advise you.

For more details about the rules we have much more information on which rules are relevant to replacement windows here.

Can You Use a Tradesman that Isn’t Registered to Replace Windows?

You might find it easier to get a tradesman to help you.

You do not have to use a tradesman that is registered to a competent persons scheme, such as FENSA, it just means that they cannot self-certify the work. If you go this route (and there is nothing wrong with it at all) you must ensure that you get the certificate from the building inspector, or the job is not finished! Exactly like you would if you did the work yourself.

It is your home so you are ultimately responsible for ensuring you have the correct certification. If you don’t it could cause problems when you come to sell.

That said, it is not difficult and in our experience of working with local authority building control officers is that they are very helpful and will explain exactly what they need to see to give you the sign off you need.

DIY window replacement is a great way to save money, and is 100% allowed – make sure that you do it right!


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