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Design a catio for your own window, wall or balcony

Catio Designer is a free online catio design tool. Enter your space and it builds the catio in 3D from standard lumber, checks the mesh, gaps, shelf steps and shade, and lists every board, roll of mesh and screw to buy.

What are you building?
The sample design in 3D at golden hour: a cedar window-box catio on a house wall under an open sash window, with mesh walls, a clear roof under shade cloth, two staggered shelves and a ramp. A marmalade tabby sits on the top shelf watching a small blue bird on a branch outside. Sample

Sample window box

4 ft wide, 2 ft deep, 3 ft high at the wall, 2x2 frame, 1 cat

9fit1to check0fail
Sources read on 12 October 2026Worked out in your browser
1Your space
2The window and your cats
3Lumber, mesh and roof
4Sun and the site
The link holds your whole design after the # sign. Nothing is sent to a server.

This is a sample: a window box for one cat under a sash window in New York, facing south. Change any size to make it yours.

The checks, with their sources

Guidance from the sources named in each row, read on 12 October 2026. No official standard for catios exists.

Fits means inside the guide; check means worth a second look; fail means change it before you build.
ResultCheckYoursGuideWhy
Mesh
FitsMesh material1/2 in hardware cloth, 19 gauge, galvanizedWelded wire or hardware clothWelded steel mesh, galvanized or stainless, as the catio guides use. Newegg, 1/2 in hardware cloth, F.H. Brundle, 13 mm welded mesh, Catio Spaces, choosing mesh
FitsMesh opening1/2 in x 1/2 inNo more than 2 in x 3 inInside the largest grid opening the catio guides recommend. Smaller openings also keep out more wildlife. Catio Spaces, predators, BC SPCA catio plan
CheckWire gauge19 gauge16 gauge or heavierLighter than the 16 gauge one guide recommends. 19 gauge welded mesh is sold for pet runs; where coyotes, raccoons or dogs visit, choose the heavier wire. Catio Spaces, predators, Screwfix, 13 x 13 mm mesh
Gaps
FitsLargest gap0 in between the frame and the house wallNo wider than 1/2 inThere should be no openings a cat could squeeze through, even on top. No guide gives a gap size, so the tool holds every gap to the short side of your mesh opening and never more than 1 in (25 mm). Humane World for Animals, catios
Roof
FitsRoofClear polycarbonate panelsMesh or panels over the topA covered top keeps the cat in and climbers and birds of prey out. Humane World for Animals, catios, Catio Spaces, predators
FitsRoof slope for panels7.1 degreesAt least 5 degreesSteep enough for rain to run off the corrugated panels. Palram, corrugated sheet guide
NoteSnow and windClear polycarbonate panelsCheck locallyMake sure the roof is strong enough for any snowfall you get. This tool does not size the frame for snow or wind; ask a local builder or your building department if you get heavy snow. Humane World for Animals, catios
Shelves and steps
NoteFloor to Shelf 1Ramp at 38 degreesA rampA ramp turns this step into a walk. Cover it with outdoor carpet or sisal for grip.
FitsShelf 1 to Shelf 29 in upUp to 24 in for a young, athletic catA step the cat can manage. The Refined Feline, shelf spacing
FitsShelf thickness3/4 in plywoodAt least 3/4 in for cats under 15 lbUse 1 in (25 mm) or thicker for larger cats. The Refined Feline, catwalk guide
Space for the cats
NoteFloor area8.0 sq ftNo published minimum for one catNo official standard exists. Catios range from cat-sized window boxes to rooms; one enclosure maker gives 2 square metres per cat only when cats share, and every cat needs climbing space and places to hide. Humane World for Animals, fact sheet, Catnets, enclosure size, Catnets, enclosure FAQ
NoteHeight3 ft at the wall, 2 ft 9 in at the frontNo published figureNo guide we checked gives a height per cat. All cats need vertical climbing space, which the shelves give. Catnets, enclosure size
Sun and shade
FitsShade on the longest day30% of the floor at 15:00, the least shaded hourAt least 25% shaded every hour, 11:00 to 15:00 sun timeThere is a shaded place to rest at every hour of the summer day. Keep fresh water out and the way indoors open. Catio Spaces, heatwave tips, Catio Spaces, choosing a place, Humane World for Animals, catios
NoteSunSun reaches the floor for part of the dayA sunny place to restCats like a sunny resting spot as well as shade. Catnets, enclosure size, Catio Spaces, choosing a place
Floor
FitsFloorPlywood floorMesh under the base, pavers or a deckNothing can dig under it. Catio Spaces, predators
Materials
NoteLumber2x2, actual 1 1/2 x 1 1/2 inUntreated cedar, redwood or pinePressure-treated lumber is wood impregnated with a pesticide, and older arsenic-treated (CCA) boards turn up second hand. Cats rub and chew, so choose sturdy, nontoxic materials: untreated cedar, or wood with a pet-safe, water-based finish free of heavy metals. Humane World for Animals, catios, US EPA, wood preservatives, BC SPCA catio plan
Before you build
NoteHOA and lease rulesFixed to the buildingCheck before you buildCheck HOA and lease rules before you build. If you rent, check with your landlord or management company. Humane World for Animals, catios

Shopping list

Type the prices from your store to see a total. The tool ships no prices.

Quantities for this design, 9 boards cut from 8 ft lengths, with a tenth spare on screws.
ItemQuantityYour unit priceCost
Lumber
2x2 x 8 ftActual size 1 1/2 x 1 1/2 in. Untreated cedar, redwood or pine.9 boards
Sheet goods
4 x 8 ft plywood, 3/4 in (sold as 23/32 in)Floor, shelves, ramp and add-on panels.1 sheet
Mesh
1/2 in hardware cloth, 19 gauge, galvanized, roll 36 in x 50 ft8 ft of strips with 1 in overlaps.1 roll
Roof
Clear corrugated polycarbonate panels, 26 in x 8 ft2 columns; side lap 3 in.1 panel
Fasteners
Roofing screws with sealing washersAn estimate: about five per panel piece at each roof bar. Follow the panel maker's fixing pattern.20 screws
Exterior wood screws, 3 inTwo at each end of every piece, plus a tenth spare.132 screws
Structural screws or lag screws for the wall fixingsOne per stud crossing on the wall battens and ledger. See the attachment detail for your wall.20 fixings
Exterior wood screws for the plywood, 1 1/4 inAbout one every 8 in (200 mm) round each piece.41 screws
Staples, 1/2 in or longer, for a heavy-duty staplerAbout one every 3 in along every member under the mesh.139 staples
Washer-head screws or screws with fender washers, 1 1/4 inOne every 12 in round the edge of each mesh panel, between the staples.33 screws
Total of the prices you entered

The build plan for this exact catio

Pro turns your design into a plan you can build from: every board with its cuts, the mesh cut to your roll, and the steps in order.

  • Optimised cut listEvery board by stock length with its cuts, packed to waste least, a cutting diagram per board and the leftovers
    Pro
  • Mesh cutting layoutEach wall cut into strips for your roll width, with the overlaps and the number of rolls
    Pro
  • Step-by-step build plan (PDF)Dimensioned elevations, an exploded view for each step, the order of assembly and the fixing detail for your wall
    Pro
  • Add-onsA raised tunnel and bridge, a litter-box bench, a window insert panel with a cat flap, a second tier
    Pro
  • Saved designs and both unitsSeveral designs kept in this browser; the plan in inches and millimetres at once
    Pro
  • 3D files and rendersGLB and OBJ for SketchUp or Blender, and a high-resolution picture to show a landlord, an HOA or your household
    Pro
The cut list page from the Pro build plan of the sample window box: each 8 ft 2x2 board drawn to scale with its cuts labelled in inches and the leftover hatched at the end.
A real page from the Pro build plan of the sample design: the cut list, board by board.
Add-ons Pro

$19 once

Buy Pro on Gumroad

Gumroad handles payment and refunds. Your key turns Pro on in this browser.

The plan is guidance for a hobby build, not an engineering guarantee.

Before you build

Cat enclosure plans in metric

In Australia and much of the UK a catio is a cat enclosure or a cat run. Switch the tool to metric and it plans the enclosure in millimetres: the frame in 45 x 45 mm, 38 x 63 mm CLS, 38 x 89 mm CLS or 45 x 90 mm timber, cut from lengths between 2.4 m and 4.8 m, and the walls in 13 mm welded mesh from 900 mm rolls.

Questions

How big should a catio be?

No official standard exists. Catios range from cat-sized window boxes to whole rooms. The one published per-cat figure we found is from Catnets, an enclosure maker: at least 2 square metres (about 21.5 sq ft) for each cat when cats share an enclosure. Every cat also needs climbing space and a place to hide. The figures and their sources

What mesh should I use for a catio?

Galvanized or stainless welded wire or hardware cloth. Catio Spaces recommends 16 gauge fencing wire with openings no larger than 2 by 3 inches; 1/2 inch hardware cloth in 19 gauge is common and sold for pet runs, but it is lighter. Chicken wire and window screen are not strong enough. Mesh compared

Can I build a catio with pressure-treated lumber?

Keep it away from anything the cat can rub or chew. Treated lumber is wood impregnated with a pesticide (US EPA), and old arsenic-treated boards still turn up second hand. Untreated cedar, redwood or pine, with a pet-safe water-based finish if you want one, is the usual choice.

Is anything I enter sent to a server?

No. The design, the checks and the 3D model are worked out in your browser. The share link keeps the design after the # sign, which browsers do not send to servers. The city list for the shade check is a file on this site. If you buy Pro, only the licence key is sent to Gumroad to check it.

Does it work in metric, for a cat enclosure in Australia or the UK?

Yes. Switch to metric and the frame uses 45 x 45 mm, 38 x 63 mm CLS, 38 x 89 mm CLS or 45 x 90 mm timber in lengths from 2.4 m to 4.8 m, with 13 mm welded mesh in 900 mm rolls.

Will the catio hold up to snow and wind?

The tool does not size the frame for snow or wind. Make sure the roof is strong enough for the snowfall you get, and check locally with a builder or your building department if you get heavy snow.

Sources

Every figure the tool uses, with the page it comes from. Each was read on 12 October 2026. Lumber sizes are facts from the standard and from merchants' listings; mesh specs are from retailers' listings, without prices; the rules of thumb are cited, not copied. No official standard for catios exists.

  1. American Softwood Lumber Standard, Voluntary Product Standard PS 20-25 (NIST, January 2025), Table 3, nominal and minimum-dressed sizes of boards, dimension and timbers (read 12 October 2026)
  2. American Softwood Lumber Standard PS 20-25, section 5.3.1: standard lengths are multiples of 1 ft or 2 ft, as the grading rules specify (read 12 October 2026)
  3. Structural Plywood, Voluntary Product Standard PS 1-19 (NIST, December 2019), section 5.4: grade requirements stated for 1220 mm by 2440 mm (48 x 96 in) panels (read 12 October 2026)
  4. Travis Perkins: 38mm x 63mm x 3.0m CLS Profile Kiln Dried Studwork and Framing Timber (read 12 October 2026)
  5. Beesley & Fildes: CLS Kiln Dried 50x75mm C16 Graded, finish size 38 x 63mm, lengths 2.4, 3.0 and 4.8 m (read 12 October 2026)
  6. Chandlers Building Supplies: 38x63mm (Nom 50x75mm) CLS Studding 2.4m Length (read 12 October 2026)
  7. Travis Perkins: 38mm x 89mm x 4.8m CLS Profile Kiln Dried Studwork Timber (also sold at 2.4 m) (read 12 October 2026)
  8. MKM: DAR Redpine 45mm x 45mm, dressed all round, 4.2 m (read 12 October 2026)
  9. Mitre 10 (Australia): Timber Treated Pine F7/MGP10 H3 90 x 45mm, available from 2.4 m to 6.0 m in 0.3 m steps (the same section is sold untreated) (read 12 October 2026)
  10. Travis Perkins search: 18mm x 2440mm x 1220mm plywood sheets (read 12 October 2026)
  11. Newegg: Hardware Cloth, 1/2 inch, 36in x 50 ft, 19 Gauge, Hot Dipped Galvanized (also 24in x 100 ft); mesh size 0.5 x 0.5 in (12.7 x 12.7 mm) (read 12 October 2026)
  12. F.H. Brundle: 6m Roll, 36" x 1/2" x 1/2" x 19g Galvanised Welded Mesh; roll width 900 mm, mesh 13 x 13 mm, 19 g (1.00 mm); also 30 m rolls, 1/2" x 1" 19g and 1/4" x 1/4" 23g (read 12 October 2026)
  13. Screwfix: Apollo 13 x 13mm Galvanised Welded Mesh 0.9m x 6m, "ideal for the construction of pet runs and cages" (read 12 October 2026)
  14. Screwfix: Apollo 13 x 25mm Galvanised Welded Mesh 0.9m x 6m (read 12 October 2026)
  15. Catio Spaces: How to Pick the Right Cat Enclosure Mesh for Your Catio (read 12 October 2026)
  16. Catio Spaces: Are Catios Coyote-Safe? (read 12 October 2026)
  17. Catio Spaces: Cooling-Off Kitty, 3 Things to Add to Your Catio During a Heatwave (read 12 October 2026)
  18. Catio Spaces: Where Can You Build a Catio? (read 12 October 2026)
  19. BC SPCA: DIY Stand Alone Catio (PDF plan) (read 12 October 2026)
  20. Humane World for Animals: Catios, Safe Outdoor Enclosures for Happy, Healthy Cats (read 12 October 2026)
  21. Humane World for Animals: Catios fact sheet (PDF) (read 12 October 2026)
  22. Catnets: Cat Enclosure FAQ, "How many cats can I put in my enclosure?" (read 12 October 2026)
  23. Catnets: How many cats can I put in my cat run? (read 12 October 2026)
  24. Catnets: How big should a cat enclosure be? (read 12 October 2026)
  25. The Refined Feline: Cat Shelves Wall, Mistakes to Avoid (read 12 October 2026)
  26. The Refined Feline: How to Build a Cat Wall Catwalk (read 12 October 2026)
  27. US EPA: Overview of Wood Preservative Chemicals (read 12 October 2026)
  28. Palram Australia: SUNTUF Roofing Installation Guide (pitch, purlin spacing, side lap) (read 12 October 2026)
  29. SunCalc 1.9.0 by Vladimir Agafonkin (BSD-2-Clause), sun position from date, time and latitude (read 12 October 2026)
  30. GeoNames cities15000 (CC BY 4.0), trimmed when the site is built (read 12 October 2026)

City latitudes: GeoNames, CC BY 4.0. Not affiliated with any maker, retailer or group named here.