How to build an outdoor cat tunnel

I have never talked in detail about how I actually built the outdoor cat tunnel leading from and to my outdoor cat enclosure in our yard. When we adopted two young cats (meet my cats), I thought it was the perfect time to extend our catio with some more tunnels, and that project gave me the opportunity to finally write a proper step-by-step tutorial. These tunnels have now been in use for years and have held up beautifully. Cat tunnels are such a great way to let your cats safely enjoy the outdoors, even if you don’t have the room for a full cat enclosure.

How to Build a DIY Outdoor Cat Tunnel

There is a big difference between outdoor cat tunnels and indoor cat tunnels. The indoor version is for entertainment and mental stimulation. They mostly crinkle or keep the cats entertained with some attached cat toys which make them play tunnels.
The outdoor cat tunnel’s sole purpose is to keep the kitties safe while enjoying the backyard and fresh air.

How big does a cat tunnel need to be?

Before you start planning and building your outdoor cat tunnel project, you need to make sure that the size of the tunnel will fit your cat. My cats have always big regular size but if you have large cats then you might want to build your tunnels a different size.

Most cat tunnels are about 13 to 14 inches in diameter. My tunnel’s walking surface is 11 inches wide and the mesh part of the tunnel is 14 inches high.

Building instructions

For the tunnels along the top of my fence leading to the cat enclosure, I used cedar fence planks because they are a lot lighter than the pressure-treated deck planks. Those lighter tunnels along the top of our fence were attached with shelf brackets that I made myself out of wood but I’m sure you can buy them as well. Just make sure that they are weatherproof.

Deck planks are cheaper but a lot heavier. The extra weight is better for my floor tunnels since I didn’t want the kids to be able to pick the tunnels up and mess with them. The cheaper price tag was also a bonus.

Step 1: Apply wood stain to all the wood

I stained all the wooden pieces before I even started building anything, and let them all dry. To me, it’s much easier this way. I love using this stain. It’s a great, rich color and really protects the wood. But you can certainly build the tunnel first and stain it before adding the wire fence to it.

Step 2:Measure and sketch out your project on paper

Measure everything before starting the project! This simple step is always the most important part. And every project’s measurements are different.

Step 3:Cut 2x4s into pieces to match the width of two deck planks

Cut the 2×4 lumber in strips to match the width of two deck planks lined up next to each other. These pieces will be the bottom support pieces that keep the cat tunnels together.

Step 4:Cut some deck planks in half

I cut one of the deck planks in half, so I could stagger the pieces, which ensures more stability. It’s not a must, but it certainly helps. Depending on how many tunnels you are building, you might have to cut more in half. For one tunnel, one is enough.

Step 5:Cut smaller pieces of wood if your tunnel is on an incline

For my design, I needed some extra pieces of wood to add to the tunnel surface because our walkway is on a steep incline/hill, and I wanted the cats to have something to hold on to. It’s more like a ladder going up the hill. I did not include this step in our regular tunnels along the fence. It is only necessary on an incline. 

Step 6:Lay your 2x4s on the ground with planks on top

Now it’s time to assemble the bottom part of the cat tunnels. Lay the 2×4 pieces on the ground and add the planks on top.

Step 7:Pre-drill-holes through planks and 2x4s

Then pre-drill the holes where the planks attach to the 2x4s. This is very important because if you don’t pre-drill the holes, the wood will crack. Use a drill bit that is slightly smaller than the screws.

Step 8:Drill screws through pre-drilled holes

Use two to three screws to attach each plank end to the 2x4s through the pre-drilled holes.

Step 9:Lay plank walkway on its side

When you have one large tunnel walkway, it is time to attach the wire fencing. I used 3 planks (2 hole pieces, 1 cut in half) for this tutorial. We made it this big because otherwise, it would have been too heavy to carry, which is another factor to watch out for. Lay the walkway part on its side so you can lay out the wire on top.

(I later attached additional tunnel sections to expand the system.)

Step 10:Trim the wire mesh width

I trimmed the width of the wire fence with a wire cutter since I didn’t want the tunnel to be too tall, but this is optional.

Also, cut the wire fence to the length of the tunnel.

Step 11:Attach wire fence to walkway with fencing staples

Attach the wire fence with the fencing staples and hammer to one side of the plank. I hammered staples into every second rectangle of the wire.

Step 12:Attach wire fence to other side of the tunnel

Now turn the planks and fencing around and bend it over the walkway part, and hammer in the galvanized fence staples on that side as well.

Step 13:Move tunnel to where you want it

To move the tunnel to its final destination. Either connect it to a cat enclosure or add more tunnels to create a tunnel system. You definitely need two people since they are rather heavy and durable.

For this cat tunnel project I chose not to finish the edges of the tunnel with another piece of wood but for the tunnels running along the side of our patio where everything is more visible, I did hide the staples. (see below photos)

The finished outdoor cat tunnels in our yard

Below you can see the wooden shelf brackets that I made to attach the lighter tunnels to the fence.

And here are the kitties using the tunnels and exploring.

And if you are wondering, I temporarily closed the end with a small piece of fence while I planned the next section.

Maya also loves the tunnels. I feel like calling them walkways though because that’s what they really are.

Willy loves it out here. You can see how the wood aged over the years. They are very durable and have held up great over the years. I need to figure out a way to stain it again. Above is our Lilly cat in the same spot as Willy is walking below.

I actually stained the entire outdoor cat run again which is now nicely nestled in between all of our plants.

I didn’t just attach outdoor cat tunnels to my fence, but also outdoor fence art.

Here is my poor skinny old lady Lucy. She just turned 19 and is the last of our old lady crew.

It is so much fun to see them explore and use their outdoor space. The tunnels in my original cat enclosure lasted 12 years before they needed any repairs, and when a section finally rotted, I documented the whole fix. If you are dealing with rotted boards on an existing enclosure, I also wrote about how I repaired a rotted section in my original DIY cat enclosure. Making enclosed tunnels or walkways for your cats is a great way for them to watch birds and butterflies, even if you don’t have room for a full outdoor enclosure. They really are much more fun than just sitting in a cage, don’t you think?

Outdoor Cat Tunnel Ideas

One thing worth mentioning before we get started: you can buy finished mesh cat tunnels online, but those soft, collapsible tunnels are not safe for unsupervised outdoor use. They offer no real protection against raccoons, foxes, or other wildlife that could tear through the fabric. If your cats are going to be outside in their tunnel without you watching, a solid wood and wire mesh construction like this one is the only safe option.

There are so many ways to use outdoor cat tunnels beyond just a straight run along a fence. Here are a few ideas to inspire your own setup.

A tunnel running along the top of a fence is a great space saver if your yard is small. The cats get an elevated walkway with a bird’s-eye view, and you barely notice it from below. A ground-level tunnel winding through garden beds looks beautiful once the plants grow up around it and the whole thing disappears into the greenery. If your cats are indoor only, a tunnel leading directly from a window to a small enclosure is enough to give them fresh air and enrichment without ever touching the ground. And if you have more space, connecting multiple enclosures with catio tunnels creates a whole system your cats can explore for hours.

All of these ideas use the same basic construction method described above. Start with one tunnel section, get comfortable with the process, and expand from there. Once you build your first one you will wonder why you waited so long.

You can also buy finished wooden outdoor cat tunnels, but they are rather expensive, and building your own is definitely a more affordable option.

An online friend of mine with a solid, secure fence used a cat proof fence topper so her cats could enjoy her yard, which is another great idea. It wasn’t doable in our yard though with all the plants and trees that they could climb to get over the fence topper.