Fitting a Cat Flap in a UPVC Door

· 5 min read
Fitting a Cat Flap in a UPVC Door

Allowing your cat to go in and out of the house whenever it wants is an excellent way to keep your pet active and mentally stimulated. A flap can help reduce accidents with toilets by making it easier for your cat to leave the home when required.

Measure the Door

A cat flap allows your pet to move around as they please without opening the door for them. This is ideal to keep them in the house the home when you're away, and helps keep unwanted pests out of the house as well!

It is essential to take measurements of the door to ensure you get the right size cat flap. There are various sizes available. This will ensure that you purchase the correct size to fit inside your door made of upvc, otherwise, it might be too small or too large and your cat will struggle to use it.

Use a ruler to measure the width at several points along the edge of the door. Also, you should take measurements of the door's height in a few spots. A door that is too high will make your cat do an exercise routine every time it uses the flap.

Ask a glazier for assistance in case you're not sure how to measure the door. They should be able to assist you in determining whether or your door is suitable for a cat flap and help you decide on the best size of flap to purchase.

Mark out the shape of your hole on the door once you have the measurements. This will help you when you're cutting the hole and save you money!

Make sure to put holes in the right position. For instance, if fitting the cat flap in a patio door, it's important that the hole isn't too close to hinges, as this can cause leakage and problems with the seal.

If you have an opening made of glass, it might be best to leave this task to a professional glazier. It can be difficult to install a cat-flap within an existing pane. You might also discover that it breaks and loses its weatherproof seal.

Measure the Cat

A cat flap lets your pet to go and come as they please without you needing to leave them to themselves. It also helps stop draughts from entering your house, which aren't good for either you or your cat!

However, if you have a uPVC or composite door, it can seem tricky to fit the cat flap. These doors are constructed of different materials and the process of installing them is different. Be sure to check with the manufacturer if it is compatible before installing a cat flap on your uPVC composite or uPVC door. Alterations may cause warranty issues.

Generally speaking, these kinds of doors are designed to be tough and durable with insulation included. This makes them more resistant to the elements of weather than other types of doors, but they may be difficult to fit a cat flap into. If  read article  whether your uPVC or composite door is able to accommodate a cat flap, consult with a professional joiner prior to starting.

To ensure that your cat can get through the door, you'll need to measure their height. It's easier to measure their height when they are at peace or asleep, which means they don't sway around. Once you know their height you can measure the distance from their stomach to the floor to determine the position of the bottom of the flap. You can then mark this location on the door.

If you are using power tools to cut your composite or uPVC door, you need be extra cautious. The act of drilling into metal can cause it to crack, especially if the area is toughened glass. This is why it's highly advisable to hire an experienced glazier when putting your cat flap into a pane of glass. This will stop the glass from breaking and becoming fragile. A glazier will also provide you with a circular hole to use for the flap for your cat. This is less likely to crack and is safer for your kitty to use.

Cut the Hole

A good cat flap comes with a template drawing that you can use to mark the spot on your door where the hole needs to be. If it isn't, you can create one by using an uncoated sheet of paper (tracing paper is ideal). Once the shape has been drawn on the door, you can use your spirit level and make sure that it is horizontal. This will ensure that the cat flap sits properly in the opening, and it won't slide open or close.

Then, you can use your jigsaw, and cut the shape that has been written on the door. Make sure that you're using a blade that is suitable for use on uPVC doors - usually it will be marked accordingly, if not ask the staff at the DIY store for guidance. Once you have the hole made, place the flap section against it and push it open to ensure that the flap's action is smooth. If it is bound at any point, you can use a filer or rasp to fix this.


Check that there aren't any electric or gas pipes within the door you're planning to cut into. Your jigsaw could damage them. Also, be aware of any handles, or other fixtures that are on the door which have to be removed to accommodate the cat flap. Be cautious not to damage these items in the process.

Most people who install a cat flap on their own have the standard solid uPVC front door, meaning they won't have to deal with these issues. If your door is made of wood or has an ornamental panel that can't be removed then this will add to the complexity of the task.

It is always worthwhile seeking professional assistance from a cat flap fitter for these kind of jobs since it is important to get them right to avoid any possible issues in the future. Making the wrong choice could lead to the door being damaged and could cause the warranty to be invalidated.

Install the Flap

Once you've got your hole drilled, put the flap on to see whether it is able to open easily. If you notice any spots that stick or catch, file them down with a hand file or sandpaper until it is a perfect fit and opens without any problems. Make sure that the flap is flush with the door.

Some kits include a template for this however, even if yours does not provide a template, you could make use of a piece of thin paper instead - something similar to tracing paper. Place the paper on the door and draw an area on which you'll need to position the flap (this will serve as your cutting guide). Then using the pencil lines you've drawn on the door, mark out four screw holes in each corner of the flap. These will be the screws that you'll use to secure it in the correct position.

Most uPVC door are solid and easy to cut. If your door is made of composite or GRP, it can be more difficult. If you're not experienced with this, it might be wise to get a professional to do the work for you. They will also be able to inform you if the door is suitable for the installation of a cat flap.

If you're planning to install a cat flap on composite doors, it is important to first check with the manufacturer or a professional joiner. Any changes made to these doors could cause the warranty to be void. If you decide to do the work yourself, bear in mind that this can be messy and even dangerous.

You'll need an instrument like a grinder or a saw to cut through composite doors, rather than only the GRP. Be aware that this can be extremely dangerous work and you'll have to take extreme care not to damage the door or yourself, as it is extremely fragile. It's important to remember that it is much more difficult to cut the door glass than a uPVC door or solid wood door.