DIY: Insulating Your Cat Flap

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Arthur strives to balance aesthetics, functionality, and quality with costs when planning DIY projects in the home and garden.

The Sufferance of Cat and Dog Owners

If you own a cat or dog and you provide them with their own pet flap, then over the winter months you are going to suffer the discomfort of draughts; which invariably means more expensive fuel bills as you turn up the central heating to compensate.

There’s nothing we can do about it during the day because our cats need access, but in the evening (once our cats are in for the night) we can shut the cat flap. This then helps to reduce the draughts and heat loss a little; albeit it can still be draughty, especially on a cold wintery windy night.

Most cat flaps have a magnetic seal so they’re not so bad, even when in use; although they still let in some draughts, and are a source of some heat loss. However, because we have a Maine Coon cat, he’s too big to fit through a standard cat flap, so we’ve had to install a small dog flap for him. Maine Coons are large cats, typically weighing between 15 lb and 25 lb; ours (Greebo) weighs 17 lb.

Irritatingly, dog flaps don’t usually have the magnetic seals common in cat flaps, so they tend to flap in the wind; and although with ours we can pull down the plastic shutter that comes with it, when we close it for the night, noticeable amounts of cold and draughts still get in.

Cat flap in open position, which offers little protection from cold winds.

Introducing Our Pet Subject

Greebo and Dippy (his sister) are our two adorable and lovable cats. Their father (who Greebo takes after) is a Maine Coon, and their mother (who Dippy takes after) is a Rag Doll; another large breed cat.

Maine Coons are often described as ‘gentle giants’, reflecting their passive nature; and are amongst one of the more intelligent breeds of domestic cats. Not only are they as large as small dogs but they also have many characteristics which are more dog than cat-like.

For example, Greebo depends on human companionship and will sit and interact with me in an evening, and demand my attention during the day when I’m gardening or doing DIY in my workshop. He quickly learnt the command for sit (with little training) and unlike any other cats we’ve owned both Greebo and Dippy come when called; which makes it easy to get them in on an evening. Albeit they sometimes like to play ‘catch me if you can’ or ‘hide and seek’ with us in the back garden; before finally conceding to our demands and come in.

Finding the Right Solution

Something Simple yet Effective

When our cats are in for the night we can close the cat flap, and previously over the cold winter months, we would push a large cushion against it to act as a draught excluder. Although of limited benefit, it wasn’t as effective as I would have hoped in that I could still feel draughts around the edges of the cushion.

Therefore, in the absence of anything suitable and affordable on the market, I decided I would make my own bespoke cat flap insulator that could at least be used overnight; once the cats were in.

What I needed to make was a rigid padded board that I could press tightly against the cat flap, and lock in position, to seal all gaps and prevent draughts; and which would also provide some insulation to keep the warmth in.

The Freedom to Roam


Alternate Use When Not Insulating the Cat Flap

While relaxing over a cup of coffee (my equivalent to a thinking cap) I pondered on what to do with the Insulator board when not in use e.g., during the day and in the summer months. I wouldn’t really want it to clutter up the conservatory, be in the way or take up valuable storage space.

That’s when I had my moment of inspiration that if it was laid flat on the floor, with the padded surface facing upwards it would automatically make a superb cat bed.

The only issue to resolve was how to get it to lay flat without the bolt getting in the way. With a little thought, the answer seemed obvious. Put feet on it that are bigger than the thickness of the bolt; with the feet doubling up as pull handles when pushing the insulator board against the cat flap on a night, or removing it in the morning to let the cats out.

This article is about my solution to what is undoubtedly a common problem for cat and dog owners—with a design that also makes it multifunctional, so when not in use to insulate the cat flap it also doubles up as a cat bed.

Outline Design and Function

Having the concept in mind, I made another cup of coffee and while sipping it sketched a simple design, as follows:

  • A half-inch of foam firmly held in place by carpet upholstered to a sturdy piece of plywood; to act as the padded surface that could be pressed firmly against the cat flap, with
  • Two rail handles and a bolt fitted on the back.

I could have used upholstery material, but opted for carpet because the thickness of the pile would act as a natural draught excluder; especially as I would be using a piece of Axminster carpet off-cut, leftover from when we recently had our livening room re-carpeted. With Axminster being a particularly good choice for this purpose because of the density of its pile, albeit any carpet with a dense pile would be ideal.

  • The bolt on the back ensures that when the cushioned board is pressed hard against the cat flap it can be locked in position; ensuring a tight fit to keep out the draughts.
  • The rail handles are used to push or grab hold of and pull when placing the cat flap insulation board in place or removing it, also acts as feet and Keeps the bolt off the floor when the insulator board is alternately used as a cat bed.

This Is What a Cat Flap Should Be Like

Below is a short video of a fully insulated pet flap; and about time too. It’s the only one I’ve been able to find so far that's truly insulated; just like a front door or double glazed window.

However, with its level of sophistication and technology, it’s far too expensive for most pet owners to be able to afford.

PetWALK Fully Insulated Cat Flap


The few bits of materials needed don’t cost much, and as it’s such a simple design, it's easy and quick to make, taking no more than an hour.

As it happened it didn’t cost me anything, apart from the cost of a bolt, as I had all the materials I needed in my workshop; including the carpet, which was an offcut from when we recently had our living room re-carpeted.

The board, on which the foam and carpet are fitted, should ideally be at least half an inch thick. I would normally have used plywood but I had a spare piece of pine board in my workshop (which is just as suitable), so I opted to use that.

The steps required to construct and assemble the insulator board for a pet flap are as follows:

  1. Measure for the size of the required board, for the height from the floor, adding on a few inches above the top of the cat flap; and for the width (space permitting) adding at least a few inches to each side of the cat flap.
  2. Cut a piece of thick plywood slightly smaller than the required size; to take account of the thickness and density of the carpet’s pile. The plywood should be at least half an inch thick; although 3/4 inch plywood will be better as you’ll be able to use slightly longer screws, making the construction stronger.
  3. Cut a piece of 1/4 inch plywood slightly smaller than the other piece. This second piece will cover the edges of the carpet on the back (giving a neat finish) and provide a flat surface for fitting the rail handles and bolt. This piece needs to be slightly smaller especially at the bottom so that it doesn’t scrape along the floor when used for insulating the cat flap.
  4. Round and Smooth the edges of both pieces of plywood with an electric sander.
  5. Cut a piece of half-inch foam to the same size as the first piece of plywood.
  6. Cut the carpet a couple of inches larger all round to the dimensions of the main plywood.
  7. Cut a couple of pieces of timber to size (a few inches shorter than the height of the cat flap insulator), to act as rail handles which you can pull and push when positioning the insulator in place or removing it. For added grip, you may wish to fashion the handrails on a lathe or with a router.
  8. Measure and Pre-cut timber for holding the cat flap insulator in place on one side, and if necessary for somewhere to bolt it in place on the other side—see the illustrations below as an example.

Sheets of plywood used to make cat flap insulator.


Assembly is done in a few simple steps that shouldn’t take long, as follows:

  1. Place the foam on the thicker plywood.
  2. Lay the carpet over the foam.
  3. Turn the whole lot over.
  4. Fold the carpet over on one end, and tack it in place with a few staples.
  5. Pull the carpet taut at the other end, fold it over and tack in place.
  6. Tuck-in one of the carpet corners and tack in place; you may need to trim off some of the carpet at the corners because of its thickness.
  7. Repeat for the other three corners.
  8. Fold over and tack one side of the carpet in place.
  9. Pull the other side taut as you tack it in place.
  10. Finally, tack firmly in place all around, with staples about every half inch.
  11. Screw the thin piece of plywood in place on the back.
  12. Screw the rail handles and bolt in place on the back.

Carpet being stapled in position over foam and plywood to create cat flap insulator.

Snuggly Fits Skirting Boards

The beauty of the design is that because the foam is under more tension (and therefore more compressed) at the edges, it gives the insulator board a natural curve that conveniently fits over the skirting board, giving a nice snug fit over the cat flap.


The cat flap insulator is held firmly in place on one side by slotting into a recess created by screwing two pieces of wood together (one wider than the other); and screwing that to the wall or door.

The cat flap insulator is then bolted in place on the other side; which may require fitting a piece of timber to the wall or door that’s the same thickness as the insulator when it’s in its compressed state e.g., to ensure a tight fit to prevent draughts.

Likewise, to prevent draughts, the insulator should be a tight fit in the groove. If it’s just a loose fit then you’ll still get the draughts (cold airflow) around the edges of the insulator.

So the initial fit, to get the correct width for the wooden groove and correct position for the bolt may be a trial. Therefore I would recommend initially trial fitting the groove assembly to the wall or door with just a couple of screws. Then slotting the insulator in place and pressing hard on it to see how well it fits. This should give you some idea of what adjustments you may need to make to the groove assembly.

Once you’re happy with the groove assembly (with the bolt fitted to the back of the insulator), press the insulator firmly in place over the cat flap and either mark or measure where it’s going to bolt so that you can fit it into place.

Insulator board bolted in position over the cat flap.

Arthur Russ (author) from England on July 16, 2020:

There are now a number of manufacturers who produce ‘draught proof’ cat flaps; they are operated by using the cat’s microchip. If you haven’t had your cat chipped, then most do also support RFID tags (Radio-frequency identification); assuming your cat is happy to wear a collar.

This website gives more information:

Helen on July 16, 2020:

We are getting very high heating bills as I took the metal draught excluder from the cat flap. Our cat seemed to have trouble opening it.

What do you think I should do please?

Cat Door Idea #3: The 4-Way Locking Cat Door

This lockable Cat Mate has a tamper proof slide lock, along with a tough polymer flap to ensure your cat only leaves the home at appropriate times. The transparent flap is preferred by most cats and features a magnetic enclosure and a weatherproof seal to guarantee that no drafts come through. This cat door gets rave reviews. Purchase the Ani Mate 4-Way Locking Cat Door for screen doors here and regular doors here.

If you want to be a bit more decorative and fun, you can add a pretty border of paint. Lowe's has details on painting this DIY Pet Door including this great downloadable stencil pdf for the design.

DIY Cat Tunnel: The Benefits, Proper Usage, and Design Ideas

Does your cat often appear scared? Does he prefer to hide in the closet? Is he always lying around, seemingly lacking in energy? If you answered these questions with an affirmative, then perhaps you should exert effort to increase his confidence and activity levels. One of the best ways to do so is to use a DIY cat tunnel.

Cats love narrow places like boxes, and tunnels are perfect because they can serve as a sanctuary for your cat where he can feel more comfortable and build more confidence while playing. You don’t need to spend money at all on a cat tunnel. You can make your own DIY cat tunnel using simple materials you likely have in your place.

In this post, we’ll share with you some tricks on how to make a DIY cat tunnel for your cat to play with. We’ll also discuss how a simple tunnel can do wonders for your cat’s mental health.

How to make your own cat flap

Pet cats don’t keep regular hours, but you don’t have to be at the beck and call of yours — if you install a cat flap. A specialized pet door for your feline to come and go at will means that they can let themselves in and out without you having to wake up at odd hours, or even when you are not at home. Weatherproofing the entrance and being sure it is the right size are important factors, as well as placement of the entry.

Remove the door the cat flap will be built in. You will need a wooden door to install a cat flap. You can find pre-fabricated pet doors designed to fit metal frames.

Measure the inside dimension of the opening. Cut four pieces of the 1/2 inch board to fit the inside of the square. Cut the two top and bottom pieces to match the dimension of the inside of the square, and cut the two side pieces one inch smaller, to make room for the top and bottom pieces.

Cut eight pieces of 1-by-1-inch trim, to the size of the outside dimension of the opening. Glue and screw them in place on both sides of the door to conceal the seams around the cat flap opening, and cover the hinges where they are hung on the door.

Doors with cat flaps for South East homeowners

At Newview, we install a range of entrance doors with pre-installed cat flaps. Whether you’re interested in a uPVC entrance door or a composite door, we can install the perfect entrance door for you with a pre-installed cat flap. We can even provide a variety of patio doors including bi-fold and sliding doors with pre-installed cat flaps. Our bi-fold doors are available in uPVC, aluminium or timber, all of which can be pre-installed with a pet-friendly cat flap.

Doors with pre-installed cat flaps offer pet loving homeowners a wealth of benefits. With a cat flap door from Newview you get:

  • Excellent access for cats and small dogs
  • Compatibility with a choice of door types and styles
  • Pre-installed cat flap during manufacture
  • No negative impact on your home’s energy efficiency
  • No unnecessary and potentially negative effects from DIY

If you’d like to find out more about our range of replacement doors with pre-installed cat flaps, contact Newview today. Give us a call on 01903 244 449 or send us a message online.

Watch the video: Simple DIY Cat Door

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