Whether a normal or a microchip cat flap, installation is pretty similar and nothing that a decent home DIYer cannot handle. This guide outlines essential steps for installing cat flaps on all kinds of doors.
For DIY installation, wooden doors are the easiest option for cat flaps. But if you want to install your cat flap anywhere else, you should contact a trained professional.
What Cat Flap Size Do I Need?
The cat flap size should be big enough to allow your cat to pass through it comfortably. To select the right cat flap size, you should take two very simple measurements of your cat.
First, measure the width of your cat. This will help you to understand how wide the cat door needs to be. Select and measure the widest part of your cat, which is the chest. Make an adjustment by adding two inches to this measurement. This adjusted width value will be used for selecting the right cat door size.
Now you should measure the height of the cat’s body. This will allow you to determine the height of the cat door. Select the bottom of the cat’s belly and the back. Measure the distance between these two parts. Now choose the bottom of the chest and the shoulders. Measure the distance between these two parts. Select the larger of the two numbers. Make a simple adjustment to this number by adding two inches. This adjusted height value should be utilized for determining the height of the cat door.
You should now refer to the cat door size chart provided by the manufacturer. Here is an example provided by PetSafe.
pet door size
flap width (inches)
flap height (inches)
Compare the adjusted values to the given dimensions. Let’s first look at the small pet door size.
The flap width is 5 ½ inches, while the flap height is 5 1/8 inches. If the adjusted width for your cat is under 5 ½ inches AND if the adjusted height for your cat is under 5 1/8 inches, then this cat flap size is right for your pet. If one or both adjusted values exceed these numbers, then the cat flap may prove to be too small for your cat.
Let’s look at the next size, which is small+. The flap width is 7 1/8 inches, and the flap height is 7 ½ inches. If the adjusted width of your cat is below 7 1/8 inches AND the adjusted height is under 7 ½ inches, then this flap size is suitable for your cat. If one or both adjusted values of your cat exceed these numbers, then this cat flap size may not be big enough.
Using the method explained above, you can select the right sized cat door from any manufacturer. Just obtain data on cat door dimensions for different sizes and compare them with the adjusted values as explained above. This is a straightforward method indeed.
How Big Should a Cat Hole Be?
To cut an opening of the right size for your cat flap, you can make use of the cat flap template. This template is available with the cat flap kit.
Information on how the template should be used is mentioned below in this step-by-step procedure:
Can You Put a Cat Flap in a Wooden Door? How?
Cat flap installation for wooden doors is much easier as compared to walls and glass or composite doors.
To install a cat flap, you must first cut out a hole in the door. It should be sized accurately to hold the cat flap securely in place. You can then screw on the cat flap onto the hole.
Here are the steps you need to take to cut the right sized hole:
Mark the Height of the Cat’s Belly on the Door
Using a ruler, measure the distance between the ground and the lowest point of the cat’s tummy. With a pencil, draw a horizontal straight line on the door at this same exact height from ground.
Making use of a spirit level can ensure that the line is perfectly horizontal. Most cats measure about 4.7 inch from the ground to their stomach.
If you own multiple cats, you should measure the height of the smallest cat. This way, the height will be appropriate for all your cats, regardless of their size. The taller cats should not face any problems with the lower height since they can crouch to go through the cat door. This step is important since it will allow your cats to enter and exit your house easily.
Find the Center Point of the Door’s Width
Use a measuring tape to determine the exact width of your door. Divide this number by two to get the center point of the door’s width. Mark an X at this point. To reach this point, measure the distance starting from one vertical edge of the door. Thereafter, measure the same distance from the adjacent vertical edge. These two measurements must coincide with each other. Measuring the center in this way will ensure accurate results. This point is the center of your cat flap.
Use Masking Tape to Attach the Cat Flap Template to the Door
Check out the instructions that came with your cat flap. They explain how the template should be attached to your house door. The bottom edge of the template should coincide with the horizontal straight line that you have just drawn. Also, the midpoint of the template should be at the center of your door. You can also use the spirit level to ensure that the bottom edge of the template is perfectly horizontal.
Tape the Template Securely in Place Using Masking Tape at This Position
With the template securely attached to the door in the correct position, use a pencil to draw an outline of the template. This is the opening which you must cut through the door.
You should now drill holes at all corners of your template. These four points will be visible on the template. The holes should be bigger than the width of the jigsaw blade that will be used to cut the opening.
A flat bit measuring 3/8 in or about 10 mm is sufficient for drilling these corner holes.
For rectangular or square cat flaps, you must drill 4 corner holes. But for circular flaps, you just need to drill one hole located on the top of the template.
Remove the Template and Draw Lines between Holes
You may remove the template by peeling off the masking tape. Connect the four holes with two horizontal and two vertical lines. Draw lines using a pencil and a scale. You will get a rectangle or square shape with holes at their corners. This outline will serve as a guideline for cutting a well-formed opening for the cat flap.
Use a Jigsaw to Cut the Opening
Use a jigsaw to cut the cat flap opening. You can begin cutting by placing the blade in one of the corner holes. Cut along the lines carefully. Don’t rush it. Make sure that the cut does not deviate from the lines. If you don’t have enough experience working with hardware, then you should cut as slowly as possible to ensure an accurate opening. If you cut beyond the line, then the damage cannot be undone. So you must get it right the first time by cutting slowly.
Be careful with the jigsaw. Don’t try to press it hard so that it cuts faster. This can wear out the blade quickly and lead to an inaccurately cut opening as well.
Here is how you should use the jigsaw.
Safety always comes first. Wear a dust mask and eye protection googles to ensure your safety. Dust inhalation is hazardous and can lead to several serious medical conditions. So make sure to use a dust mask whenever you are working with wood. Eye protection is also necessary. Small bits of wood can fly into your eyes while cutting wood with a jigsaw. Eye protection can prevent this from happening.
First, connect the power cord of the jigsaw to the socket. Switch on the socket. Squeezing the trigger on the handle will start the jigsaw. Using a jigsaw is not too hard, but you should be careful while using it to prevent accidents and injuries.
Several jigsaw models have a lock switch. If there is one on your jigsaw, you should press it when the jigsaw is running. The jigsaw will continue to operate even if you release the trigger. This way, you will not have to press down the trigger continuously while cutting.
You can also adjust the blade speed by turning the speed dial located at the front of the jigsaw. Setting the dial to a higher number will increase the speed of the blade. On the other hand, a lower number will reduce the speed of the blade.
Always make sure that you keep your fingers away from the blade while cutting wood.
You should also pay attention to the safety of your cat. Prior to drilling, ensure that your cat is not present outside. Some cats have a habit of nudging the door to come inside.
It is best to keep your cat inside while you are drilling holes and cutting the opening. The entire exercise should not take too long.
If you are cutting PVC or metal, use low speed to ensure that the material is not overheated.
For laminate or wood, you should use a faster setting. This will reduce vibrations while you are cutting. The end result is greater control and higher accuracy for the cut.
Here is a pro tip for foolproof cutting. Always cut WITHIN the line. The point here is to keep a small margin for error. If you cut beyond the line, then you cannot undo the mistake because the material cannot be replaced. But even if you leave out a thin margin within the line, you can always remove this unwanted material by sanding or filing. Make sure that this margin is small. Otherwise, you will have to do a lot of filing or sanding.
In short, undercutting is better than overcutting. Keep this in mind when cutting anything.
Use a sandpaper to smooth out the edges that you have just cut. If some extra material remains, you should use coarse sandpaper. Coarse sandpaper is meant for material removal. It will allow you to remove the unnecessary material quickly. Keep a close eye on the lines so that you don’t remove too much.
Inspect the dimensions of the opening. If the opening size is just right, you should use fine sandpaper. Fine sandpaper is designed to provide a smooth finish to wooden surfaces. Keep sanding the edges of the opening until they are smooth.
Try out the Opening
You should now test the opening to see if it will allow the cat flap to function properly. Press the cat flap against this opening and align it correctly with the cutout.
With the cat flap in the correct position, push the cat flap open and allow it to swing back to its original position. Let the cat flap close by itself. The closing and opening of the cat flap should be completely unobstructed. It should not touch anything along the way as it swings.
In case the cat flap hits a part of the opening along the way, then take a close look at it. Observe the cutout carefully and see which edge is out of shape. Use a file to shape the imperfect edge to the right dimension.
Before moving on to cat flap installation, you should add finishing touches to the edges of the cutout.
Cat Flap Installation
Now that the cutout is ready, you can proceed with installing the cat flap over this opening.
First, mark the cat flap screw holes on your door. Press your cat flap against the opening. Align it properly with the cutout. The corresponding edges of both cat flap and cutout should be perfectly parallel. The distance between the corresponding edges should also be uniform. With the cat flap in this position, mark the points for screw holes. You can do this by passing a pencil through each of the screw holes on the cat flap. The points you have marked so far will be drilled to make screw holes.
While positioning the cat flap, make sure that it faces the right way up. In the correct orientation, the cat flap will open towards the outside while the lock will be positioned inside.
First, remove the cat flap away from the cutout. Drill holes into the 4 points that you just marked for the screw holes. Keep drilling till the bit comes out through the door on the other side.
Press the front part of the cat flap against the cutout. Push a screw through all the 4 holes. Holding the rear part of the cat flap, press it against the other side of the cutout so that the screws pass through the screw holes. Tighten the screws with the help of a screwdriver. Secure the screws by fastening them with nuts.
The part with the flap should be installed outside. It will offer the best protection against elements like rain and wind. The insides of the door should not be exposed, otherwise wood may start rotting. This safeguard should be mentioned in the manufacturer’s instruction manual.
An added level of protection for your door can be provided with sealant. Use it to seal the spaces between the door and cat flap to make them watertight.
If you have a timber door, paint the edges that you have cut out. This should be done after ensuring that the cutout dimensions are perfect and that the edges have been properly sanded. Paint can help protect the edges from water and wood rot damage.
To ensure that the cat flap is tightly secured, touch it to see if it moves from its position. If it is perfectly still and rigid, then the installation is complete.
Can I Put a Cat Flap in Double Glazing/Glass? How?
Since cutting glass requires a high level of skill, you should contact an experienced glazier. The manufacturer will also provide a mounting adaptor to ensure proper installation of the cat flap on the glass door.
Can You Put a Cat Flap in a Wall? How?
It is possible to install the cat flap on a brick wall. Keep in mind that each cat door may have a slightly different method of installation. Installation may differ, according to model within the same brand. But the basics are the same for all.
The marking methods for making lines and the drill hole points described above can be applied here as well.
You should be cognizant of the fact that drilling an opening through a wall requires experience and skill to prevent damage to the structure. If you do not have much practice in this regard, then it is better for you to consult a qualified and experienced professional. It is better to seek professional help rather than face the risk of property damage, which may be quite expensive to repair.
First of all, clearly mark lines for the cat flap, according to the method described previously. You will need to use the cat flap template.
You should then mark the spots for drill holes, through which the screws will pass. This method has also been explained above.
You must now break through the wall to make an accurately-sized cutout. But prior to cutting out any hole in a wall, you must first install a lintel. This steel lintel should be located above the hole. The purpose of this structure is to provide support to the wall where it will be cut. It prevents the wall from collapsing under its own weight
Here is how the lintel can be installed.
You should first determine a safe point for making the hole. A structural engineer or a qualified builder can ascertain this location. You must provide your house plans to the professional. After studying all the construction details, they will show you where you can safely install the lintel.
The area where the lintel will be seated must first be marked. This line should exceed the width of the hole by at least 300 mm. That’s because the lintel ends will be placed above bricks for support.
An angle grinder must be used to cut out the mortar, which can create space for the lintel. Some of the bricks may also need to be trimmed, depending on the mortar thickness.
To remove the remaining mortar, you can utilize a mash hammer and masonry chisel. Clear away as much of the building material as you can from this cut area. To clear up the gap, use a 10 mm masonry bit fitted to a hammer drill. Once the gap is ready, you can then place the steel lintel. If you have a problem forcing it inside, you can use the mash hammer to nudge it in gently.
For the next step, prepare ready mix mortar. Using a trowel, mortar the lintel ends carefully. Glide a finger along the wet mortar so that its profile matches that of the existing mortar line.
After the lintel is ready, you can then draw vertical lines using a spirit level. With the help of an angle grinder, make cuts in the wall along these vertical lines. The angle grinder will throw off plenty of dust during operation. Hence, make sure to wear your safety glasses and a dust mask. Earmuffs should also be worn to protect against the high noise level. Don’t try to push too hard on the grinder. The cut will be cleaner if you allow the angle grinder to work away at the wall gradually.
To remove the bricks easily, you will need to punch holes through them to loosen them up. Load a hammer drill with a masonry bit. Use it to drill holes through mortar between bricks that need to be removed. After you have drilled a sufficient number of holes, you can remove bricks without using too much force.
To take out bricks from the opening, use a brick bolster and mash hammer. Be careful when you strike near the opening’s edges. With proper care, the edges of the opening will remain smooth and neat. The bricks adjacent to the lintel should be removed carefully. The lintel will then not be disturbed.
Now that the hole has been cut out from the brick wall, you can continue to install the cat flap. To drill holes for the screws, make sure that you make use of a hammer drill with a masonry bit.
In order to mount the cat flap onto a wall, you will also need the appropriate mounting adaptor and the tunnel extender.
The tunnel should be horizontal. But you should give it a small downward slope so that rainwater flows outside the house. The slope should be inclined downwards from the interior of the house to the outside wall surface.
Assemble the tunnel extenders together with the help of super glue. After the super glue dries up, cover the tunnel with weatherproof tape.
The rest of the installation technique is basically the same as previously described.
Can You Put a Cat Flap in a UPVC/Composite Door? How?
To fit a cat flap into a uPVC door, follow the instructions provided above for installation on timber doors. For cutting PVC, you need to use the right blade for your jigsaw. Contact your hardware store for more information on the right blade for PVC.
However, for installation on composite doors, talk to an experienced professional so that the integrity of the door is not affected.
Installing a cat flap on a wooden door is easier as compared to doors made from composite materials or glass. Installing a cat flap on a wall is also very challenging and carries the risk of property damage.
Besides wooden door, you should seek professional help for other types of doors and wall installation as well.
- 1 What Cat Flap Size Do I Need?
- 2 How Big Should a Cat Hole Be?
- 2.1 Can You Put a Cat Flap in a Wooden Door? How?
- 2.2 Mark the Height of the Cat’s Belly on the Door
- 2.3 Find the Center Point of the Door’s Width
- 2.4 Use Masking Tape to Attach the Cat Flap Template to the Door
- 2.5 Tape the Template Securely in Place Using Masking Tape at This Position
- 2.6 Drilling Holes
- 2.7 Remove the Template and Draw Lines between Holes
- 2.8 Use a Jigsaw to Cut the Opening
- 2.9 Sanding
- 2.10 Try out the Opening
- 3 Cat Flap Installation
- 4 Can I Put a Cat Flap in Double Glazing/Glass? How?
- 5 Can You Put a Cat Flap in a Wall? How?
- 6 Can You Put a Cat Flap in a UPVC/Composite Door? How?
- 7 Conclusion