Quick answer: Plain corrugated cardboard is safe for cats, but packing tape, metal staples, glossy printed labels and strong glues are not. Strip all plastic tape and staples, cut away heavily printed or coated panels, join pieces with water-activated paper tape or a little non-toxic PVA glue, and check builds weekly, more often when several cats share them.
Cats love cardboard, and moving boxes are free. That makes cardboard houses, tunnels and scratchers some of the best-value cat projects you can do. But boxes come with things that are not cat-friendly: plastic tape, metal staples, shipping labels, glossy print and sometimes chemical treatments. In a multi-cat home, where several cats chew, scratch and wrestle in the same build, these problems show up faster.
This guide is about materials and checks. For building ideas, see the cardboard castle hub, cardboard projects to do with kids and the our first tape, ink and staple overview.
Is cardboard itself safe?
Plain brown corrugated cardboard is mostly paper fibre and starch-based glue. Cats scratching or chewing a little of it is generally not harmful. The risks come from what is on the cardboard, and from cats that swallow large amounts of it. If a cat eats cardboard, rather than just shredding it, give it a hard plastic toy instead and mention it to your vet; persistent chewing of non-food items can be a sign of a health or behaviour problem.
Kittens are the exception to relaxed rules. They mouth and chew everything while teething, so give them cardboard play only while you are watching, and take it away if they start swallowing pieces.
Choosing boxes worth building with
The best boxes for cat builds are double-wall corrugated moving boxes and appliance boxes. They are thick enough to hold a cat's weight on an upper floor and stand up to scratching. Thin single-wall shipping boxes are fine for tunnels and small hideaways, but sag if a cat jumps on them.
| Box type | Strength | Best use | Watch for |
|---|---|---|---|
| Double-wall moving box | High | Floors, towers, walls | Bottom seam staples |
| Appliance box | Very high | Base of a big build | Foam inserts and plastic ties |
| Single-wall shipping box | Low–medium | Tunnels, hideaways | Plastic tape, labels |
| Printed retail packaging | Medium | Base only, printed side in | Glossy coatings |
| Produce or grocery box | Medium | Avoid | Wax coating, food residue |
Store collected boxes flat in a dry place. Damp cardboard grows mould and loses strength, and a musty smell can put cats off the build. In apartments, flat-packed boxes slide under a bed until you need them; apartment cardboard castles covers compact designs.
Tape: what to remove and what to use
| Tape | Safe for cat builds? | Why |
|---|---|---|
| Plastic packing tape | No – remove it | Sticky, chewable, can be swallowed in strips |
| Duct tape | No | Strong adhesive, fabric threads, sticks to fur |
| Masking/painter's tape | Only outside, temporarily | Easy to peel and chew |
| Water-activated paper tape | Yes | Paper and starch glue, bonds into the cardboard |
| Washi tape | Decoration only, out of reach | Peels easily |
Peel all plastic tape off the box before you start. Warm stubborn tape with a hair dryer on low, then pull slowly. Where tape will not come off, cut away that strip of cardboard. Join pieces with water-activated paper tape, the kind used for shipping cartons; it becomes part of the box surface and gives cats nothing to peel.
Staples: find every one
Many boxes are stapled at the bottom seam with large metal staples. These can cut paws and mouths and are easy to miss once the box is cut up. Before building:
- Check all seams, especially the bottom flaps and corners.
- Pull staples out with pliers, not your fingers.
- Run a magnet over the box and your work area to catch broken pieces.
- Count staples into a jar so you know none ended up in the build.
Never use a staple gun to join cardboard in a cat build. Staples pull out as the cardboard is scratched and can be stepped on or chewed.
Ink, labels and coatings
- Plain brown boxes with a little printed text are usually fine.
- Glossy, heavily printed or plastic-coated boxes (such as some product packaging) are best avoided for scratch and chew surfaces.
- Peel off shipping labels; their adhesive and plastic layer can be chewed.
- Avoid boxes with waxed or water-resistant coatings, often used for produce.
- Avoid boxes that smell of chemicals or have held cleaning products, pesticides or food that spoiled.
If a box has a nice plain side and a printed side, turn the printed side inward or use it only for the base. Turn panels so cats scratch plain brown surfaces.
Glue: keep it simple
Most cardboard builds need very little glue. Where you do glue, use a non-toxic PVA glue or a glue stick and let it dry completely, at least 24 hours, before cats use the build. Hot glue holds well but leaves hard strings that cats pick at; if you use it, trim the strings and keep beads inside joints. Avoid construction adhesives, spray adhesives and contact cement, which give off strong fumes.
Many builds can avoid glue entirely with tab-and-slot joints: cut slots in one piece and tabs in another and push them together. See the one-hour castle build for a design that uses mostly slots.
Extra checks for multi-cat homes
With several cats, a cardboard build takes more wear in a week than a single cat gives it in a month. Cats chase each other through it, dig at doors and lean on walls. That brings hidden tape and staples to the surface, and weakens joints.
- Check daily for the first week, then weekly.
- Look for exposed tape, staples or labels revealed by scratching.
- Make sure upper levels have not sagged; a collapsing floor can trap a cat underneath.
- Keep every room with two openings so a cat can escape another cat.
- Remove soiled or wet panels; some cats mark new objects in multi-cat homes.
The International Cat Care guide to multi-cat households explains why exits and space matter so much when cats share resources.
Paint and decorating safely
Kids often want to decorate cat houses. Use water-based, non-toxic paints or washable markers and let them dry fully. Keep paint on the outside walls, away from entrances and inner surfaces cats rub on. Skip glitter, sequins, pom-poms and googly eyes; they are easy to swallow. Do not use spray paint or permanent markers indoors.
A safety checklist before first use
- All plastic tape removed or cut away.
- Every staple pulled and counted; a magnet swept over the area.
- Shipping labels and glossy panels removed or turned inward.
- Glue and paint dry for at least 24 hours with no smell.
- Upper floors tested by pressing with your hand; no sagging.
- Every room has two exits, and no openings are small enough to trap a head.
- No string, ribbon, small decorations or plants attached.
- Build placed away from stairs, heaters and candles.
Tick through it each time you add a new section, too. Most problems appear when a build grows over several weekends and the newest box is added in a hurry. Five minutes of checking is far quicker than a trip to the vet for a cut paw or a swallowed strip of tape.
Plants, toys and add-ons
- Do not decorate with real or dried plants; many, including lilies, are toxic to cats. The FDA warning on lilies and cats explains the risk.
- Hang no toys on strings; put them loose inside.
- Use catnip or silvervine in a small paper bag rather than loose on the floor of the house.
- Avoid bells and small plastic parts that can come off.
When to replace a cardboard build
Cardboard is not meant to last forever. Replace a house or scratcher when it is soggy, soiled, sagging, or when tape or staples keep surfacing. Most multi-cat builds last one to three months. Recycle clean cardboard and throw away soiled pieces. If you find your cats prefer cardboard scratching, a corrugated scratcher in a sturdy frame is a longer-lasting choice; see the corrugated scratcher guide.
Cardboard cat build safety: FAQ
Is packing tape dangerous for cats?
It can be. Cats peel, chew and sometimes swallow strips of plastic packing tape, and the adhesive sticks to fur and paws. Strip all old tape and labels before you build, and if a seam truly needs tape, use water-activated paper tape on the outside only. In multi-cat homes, where play gets rougher, check every seam daily during the first week.
What glue is safe for cardboard cat houses?
Non-toxic PVA glue, a school glue stick or homemade flour-and-water paste are the safest options for cardboard. Let joins dry for at least 24 hours before the cats use the build, because damp glue invites licking. Avoid hot glue strings, spray adhesive, contact cement and construction adhesive, which give off fumes or leave hard, sharp beads.
Is printed cardboard safe for cats?
Plain brown boxes with a little printed text are usually fine. Avoid glossy, heavily printed, waxed or plastic-coated boxes for any surface a cat will scratch or chew, since coatings flake off and inks can transfer to mouths. Build with the plain side facing the cats where possible, and peel off address labels and barcodes first.
How often should I check a cardboard cat house?
Inspect it daily for the first week, then weekly once you know how your cats use it. With several cats, look for chewed corners, loose flaps, damp patches and any tape or staple that has worked its way to the surface. Remove problem pieces straight away, and replace the whole build once it sags, smells or gets soiled.
Can I use staples to build a cardboard cat house?
No, staples work loose as cats scratch and wrestle, and the exposed points can cut paws, gums and tongues. Before building, run your fingers along every flap and seam to find factory staples, and pull them out with pliers. Join pieces with PVA glue and wooden skewers instead, which hold firmly and leave nothing sharp behind.
