5 Essential Steps to Changing a Window Into Patio Doors

Changing a window into patio doors is an excellent way to open up your house and let in more natural light. Not only does it make your space brighter and more attractive, but it can also increase its functionality, giving you easy access to your garden or patio. 

We often get enquiries about exactly this, and as a window company, not a building company, there are things that need considering before getting in touch.

1. You need Building Regulation approval before you change your window into patio doors.

Changing a window to patio doors doesn’t come under the remit of FENSA; it means altering the structure of your home and it’s therefore crucial to get the necessary building regulation approval.

Want to know what FENSA means?  Read this post to find out.

Building Regulation approval ensures that in doing the building works, your house remains structurally sound and complies with all safety regulations.

After deciding you want to change your window to a patio door, this really is the first step.

2. Here’s how to go through the process of getting Building Regulation approval.

In most cases, the Building Regulation approval process involves applying via a private approved inspector, or directly with your local council before you start any work.

There are two types of application: a building notice and a full plan application.  

There is an option to apply retrospectively, but we don’t recommend this – it’s a gamble and you could be told to reverse all the work you’ve had done.

A building notice is suitable if the work is small-scale and involves only minor changes…such as changing a window to a door.

The application can be completed online and you’ll need to submit approved plans, including detailed construction specifications.  It’s worth noting that there’s also a fee involved.

Once approved, you have five years to complete the work, but we hope you’ll get in touch with us [LINK] sooner than that!

3. Get builders in to do the building work – changing a window into patio doors is best left to the professionals.

Unless you have decent experience, this is something best left to the builders.

If you don’t already know a builder, ask for recommendations, check reviews, get estimates and site visits, book them in and get the job done!

Doors are made to order, so there may be a period where you need to board the aperture up whilst your new door is being made.

4. Decide on the window & door company you want to use.

We’ve written a whole blog post on how to do this in the correct, I’ve done all my homework and trust the company, kind of way.

Somewhere in-between steps 2 and 3, you’d want to be getting in touch with window companies.  

When you’ve narrowed it down, get in touch with photos of where you want your doors to go, sizes of the proposed aperture and details of what you’re looking for (aluminium, PVCu, a brand you like the look of, etc…)

We can’t speak for everyone, but this should be enough to go on for a preliminary estimate, after which, your site survey can be booked.  

Remember, estimates or preliminary quotes are always subject to survey.

5. Choose the right patio doors for you!

You can have a bit of fun at this stage…

Depending on the size of your new aperture, you get to choose between bi-fold doors, french doors and sliding doors.  You’ll always be advised what will be most appropriate at the time of survey, so don’t set your heart on something until this is done.

There are some super, high quality PVCu designs to choose from, especially if you want your new patio doors to compliment your existing windows.

But if you do go with aluminium, there are over 500 RAL colours to choose from (remember when we said about having fun!)  Your patio doors really don\’t need to match your windows, in fact, we think it’s pretty great when they make a bit of a statement!

colour chart from milford window
RAL colour chart – these colours are available when changing your window to a patio door (aluminium only)


Converting an existing window to patio doors is a fantastic way to enhance your home\’s appeal and increase its functionality. 

The decision, however, requires planning, building regulation approvals, a reliable builder and of course a stellar window and door company who install top-notch products, *cough!

You can do this!

If you follow the steps outlined above, you’ll have an excellent chance of undertaking a successful window-to-patio-door installation that meets your needs and budget. 

Always prioritise quality workmanship and pay attention to details when it comes to home renovation projects.  

If you live in Guildford, Godalming or the surrounding Surrey villages, we’re always here to help, so get in touch!

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