A tunnel course is the cheapest piece of cat furniture that still gets used in week 6. One section is a 30 cm cardboard box with both ends open, 3 to 5 sections join into a 90 to 150 cm run, and the layout gets rebuilt every 2 weeks so the cat has to solve it again. Total cost is a roll of tape and boxes you already have.
The failure mode is not boredom, it is engineering. An unbraced tunnel that a 5 kg cat launches into at speed folds at the joint, and a folded cardboard edge is a cut waiting to happen. Build for the pounce, not for the photo.
One section, three measurements
Length 30 cm, opening 20 to 25 cm, wall 3 to 5 mm. Those are the numbers that decide whether a tunnel gets used. At 30 cm a section is shorter than the cat's body, so the cat can stand inside with head and tail just at the openings, which is what makes it feel like cover rather than a corridor.
The opening matters more than the length. Under 18 cm, an adult cat has to duck and will usually refuse; over 28 cm, the box stops feeling enclosed and the cat treats it as a doorway. A 20 to 25 cm opening fits a 4 to 5 kg cat and still excludes a large dog nose. For a kitten under 6 months, cut to 15 to 18 cm; for a Maine Coon, 28 to 30 cm. If you are unsure which size you are dealing with, start with breed size.
Joining 3 to 5 sections
Three sections give 90 cm, which is about 2 body lengths for an average cat and enough for a straight run with one turn. Five sections give 150 cm, which is where you can build an L or a U and get a genuine ambush loop. More than 5 becomes a maze the cat cannot see the end of, and use drops sharply after about 2 weeks.
Join with a 4 to 6 cm overlap and tape around the full circumference, not just the top. Two strips at 12 o'clock and 6 o'clock let the seam hinge open under a landing. If the boxes are different sizes, cut a collar from a third box and slide it over the joint, then tape the collar, which spreads the load over 10 cm instead of 1.
Five layouts worth building
Each layout changes how the cat has to move: straight is speed, L is a blind corner, U is a loop, and the zigzag forces 2 direction changes in under a metre. Rotate through them rather than inventing something new every time; the same bracing rules carry over to larger play structures.
| Layout | Sections | Total length, cm | Floor space needed, cm | What it trains |
|---|---|---|---|---|
| Straight run | 3 | 90 | 100 by 40 | Sprint and exit timing |
| L corner | 3 | 90 | 70 by 70 | Blind-corner ambush |
| U loop | 4 | 120 | 80 by 110 | Circling, re-entry |
| Zigzag | 4 | 120 | 90 by 90 | Direction changes under speed |
| Long course with side exit | 5 | 150 | 120 by 100 | Choice, pause and scan |
Rebuild every 14 days
Novelty is the whole mechanism. A cat maps a fixed tunnel in about 3 to 7 days, and after that it walks through instead of hunting through it. Rebuilding on a 14-day cycle keeps it just unfamiliar enough: long enough for the cat to settle, short enough that interest has not fully gone.
The rebuild does not have to be a rebuild. Rotating 1 section to a new angle, swapping which end opens into the room, or moving the whole course 1 m to a different wall resets the puzzle in about 3 minutes of work. Add a scent cue: rub the inside of one section with a worn T-shirt, and move that section each time so the cat has to find it.
Collapse and pinch points
Cardboard fails in 3 places: the taped joint, the top panel under a landing cat, and the cut edge at each opening. Test the joint by pressing down with about 10 kg, roughly twice the weight of the cat that will use it. If the top panel bows more than 1 cm, add a cross brace: a folded strip of box, 30 cm long and 5 cm wide, taped across the middle.
For the cut edges, tape the full rim on the inside and outside, 2 layers at the corners. Never use staples, wire or hot glue on any surface the cat's face can reach. Remove handles, shipping labels and any plastic film, and cut 2 hand-holes of 5 cm on the sides of long sections so a startled cat is never trapped by a collapsed end.
Placement matters as much as construction. Put the course against a wall or a sofa so it cannot roll, keep both ends in view of a hiding spot, and never block a litter box, a water bowl or the only route to either. A tunnel that creates a dead end with no escape is the one cats stop using. When cardboard keeps failing at the joints, a sewn nylon tunnel holds a 5 kg cat for years, and tunnel types covers the trade-offs.
Handing off to the chase game
The tunnel alone is a hiding place. It becomes exercise when the toy goes in at one end and out the other. The sequence that works: drag a wand toy past the far opening, let the cat enter, then pull the toy 30 to 50 cm along the outside of the tunnel so the cat has to track it through cardboard, and pause 5 to 10 seconds at the exit before the pounce.
Work in 3 to 5 minute blocks, 2 or 3 times a day, and end each block with a real catch and 3 to 5 pieces of food at the tunnel mouth. That last step is what makes the course worth returning to. Without a catch, most cats disengage after 2 or 3 passes and the tunnel goes back to being furniture.
Build it in 6 steps
- Collect 3 to 5 boxes of similar height, cut both ends to 20 to 25 cm, tape every rim twice.
- Join with a 4 to 6 cm overlap and tape the full circumference, then press 10 kg on the joint to test it.
- Brace the top of each section with a 30 by 5 cm folded strip if it bows; never staple.
- Lay out a straight run first, and only move to L or U once the cat uses it within 24 hours.
- Play 3 to 5 minutes twice a day, always with a catch and food at the exit.
- Mark a rebuild date 14 days out, rotate 1 section, and refresh the scent cue.
Terms mentioned in this article
Frequently asked
How many boxes do I actually need?
Three is the minimum that produces a usable course, giving 90 cm, or about 2 body lengths. Five sections at 150 cm is the practical maximum before the tunnel becomes a maze the cat cannot scan. Most households settle at 4 sections, 120 cm, because that fits a corner of a room and still allows an L or a U.
What stops the tunnel from collapsing when the cat jumps on it?
Overlap the joints by 4 to 6 cm and tape the full circumference, then press about 10 kg on the joint as a test. If the top panel bows more than 1 cm, tape a folded 30 by 5 cm strip across the middle as a brace. Skip staples and wire entirely, and put the course against a wall so it cannot roll.
How often should the layout change?
Every 14 days. A cat learns a fixed layout in about 3 to 7 days and stops hunting through it. Rotating 1 section or moving the whole course 1 m resets the puzzle in about 3 minutes. Changing it every 2 or 3 days usually backfires, because the cat never gets confident enough to sprint.