Quick answer: Cost per year of use is the purchase or build price plus upkeep, divided by the years the tower lasts outdoors. In our worked example, a $235 DIY cedar tower with $20 a year of upkeep comes to about $49 a year over eight years, while a $90 indoor tower that lasts 18 months outdoors costs $60 a year.
A catio tower lives a harder life than an indoor cat tree. Sun, rain, frost and humidity attack carpet, glue and untreated wood, so the cheapest tower on day one can be the most expensive per year. Comparing cost per year of use gives a fairer picture than comparing price tags.
This guide shows the formula, a worked example with clearly stated assumptions, and the materials that make an outdoor tower last. For indoor towers, see our comparison of a DIY cat tree against store-bought by cost per year, and for build ideas, the DIY cat tree hub.
The Cost-Per-Year Formula
Cost per year of use = (build or purchase price + total upkeep over its life) ÷ years it stays safe and usable.
Upkeep covers re-oiling or re-sealing, replacing sisal rope, swapping worn platform mats and replacing any rusted fixings. Lifespan ends when the tower is no longer safe, for example when wood softens, joints loosen or platforms crack, not just when it looks tired.
A Worked Example (Assumptions, Not Quotes)
The figures below are illustrative assumptions for a mid-size tower, around 150 cm tall with three platforms. Your local prices and climate will differ, so plug in your own numbers.
| Option | Upfront cost | Upkeep per year | Assumed outdoor lifespan | Total cost | Cost per year |
|---|---|---|---|---|---|
| DIY cedar tower, sealed, stainless fixings | $235 ($180 materials + $30 finish + $25 hardware) | $20 | 8 years | $235 + $160 = $395 | $49.38 |
| Store-bought outdoor-rated tower | $160 | $5 | 3 years | $160 + $15 = $175 | $58.33 |
| Indoor carpeted tower used outdoors | $90 | $0 | 1.5 years | $90 | $60.00 |
In this example the DIY tower costs the most upfront but the least per year, because it lasts much longer and its worn parts can be replaced. The store-bought outdoor tower sits in the middle. The indoor tower is cheapest to buy but wears out fastest outdoors, as its carpet traps water and its pressed board swells.
If your DIY tower lasted only five years instead of eight, its total would be $235 + $100 = $335, or $67 a year, which is more than the others. Lifespan is the number that matters most, so build for it.
Materials That Last Outdoors
| Part | Good outdoor choice | Avoid |
|---|---|---|
| Frame and platforms | Cedar, larch or exterior-grade plywood, sealed | Pressed board, MDF, indoor plywood |
| Treated timber | Modern treated timber labelled for residential use, sealed | Old reclaimed wood that may be CCA-treated |
| Fixings | Stainless steel or coated exterior screws | Plain steel screws that rust |
| Scratching surface | Sisal rope, replaced as it wears | Carpet, which holds water |
| Platform tops | Removable outdoor mats or bare sealed wood | Glued-on carpet |
| Finish | Water-based exterior sealer, fully cured | Oil-based stains with strong solvents |
Be careful with old timber. The EPA on chromated arsenical (CCA) treated wood explains that CCA-treated wood was phased out for most residential uses, but old decking and fence posts may still contain it, so do not reuse unknown timber for anything a cat will chew or scratch.
Exterior finishes need time to cure fully before a cat uses the tower. Follow the drying and curing times on the tin, and let the tower air outdoors for a few days so any smell has gone before the cat moves in.
What Shortens a Tower's Life Outdoors
Most outdoor towers fail in the same few places, and each one shortens the lifespan in the cost-per-year sum.
- End grain left unsealed at the foot of posts, which soaks up water from wet paving.
- Platforms that hold puddles because they are perfectly flat; a very slight slope or a few drainage gaps help.
- Carpet or fabric glued to platforms, which stays damp and rots the wood beneath.
- Plain steel screws that rust and stain, then loosen.
- Constant full sun on dark finishes, which dries and cracks the surface faster.
Raising the base a centimetre or two off the ground on rubber or composite feet keeps the post ends dry and can add years to the frame. Sealing all cut ends, including screw holes, before assembly is another small step that pays back.
Run Your Own Numbers
Use this short checklist to fill in the formula for your catio.
- Price every material, finish and fixing from your local store, and add them up for the DIY build.
- Find the price of a comparable outdoor-rated tower, and note any stated warranty or care advice.
- Estimate upkeep per year: sealer, sisal and any replacement mats.
- Be honest about lifespan in your climate. Wet, frosty winters shorten it; covered catios lengthen it.
- Divide the total cost of each option by its years of use and compare.
If the numbers are close, choose the option that is easier to maintain, because the one you look after will last longer.
Upkeep Schedule for an Outdoor Tower
- Monthly: push each platform hard, check screws and look for soft or split wood.
- Every spring: clean, let the wood dry fully and re-apply the exterior sealer.
- As needed: re-wrap sisal when it frays, usually once or twice a year for a keen scratcher.
- Every autumn: lift mats, check for damp underneath and replace any rusted fixings.
Upkeep is what makes the DIY figure work. Skip it and the lifespan shrinks, which raises the cost per year. Our guide to replacing worn surfaces without a rebuild shows how to refresh parts rather than start again.
Stability Matters More Outdoors
Wind, uneven paving and excited cats all push on a catio tower. Anchor it to the catio frame or a wall with brackets, and set the base on a level pad. Our stability test for a DIY cat tree and the anchoring safety checklist both apply outdoors.
Shade is important too. Put at least one platform under cover so the cat can rest out of direct sun and rain, and make sure water is always available in the catio.
Cases Where a Store-Bought Tower Wins
A store-bought outdoor-rated tower can be the better choice if you rent, need it this week, or do not have tools and space to build. It is also sensible if you only use the catio in the warmer months and can store the tower indoors over winter, which extends its life and lowers its cost per year.
Some store-bought outdoor towers are designed with replaceable parts. If the one you are considering lets you swap posts or platforms, add those part costs to the upkeep line and give it a longer lifespan in your sum.
Whichever you choose, avoid moving an indoor carpeted tree outside. As the example shows, it is cheap at first but rarely good value once weather gets to it.
Making the Catio Worth It
A tower is only one part of a good catio. Add hiding spots, a scratching post, cat-safe plants and a shaded resting area. Ohio State's Indoor Pet Initiative has ideas for enriching indoor and enclosed spaces, and our news guide on taking an indoor cat outside safely covers the first visits.
Work out your own cost per year before you buy or build. It turns a confusing choice into one clear number.
Catio Tower Cost Questions
Is it cheaper to build or buy an outdoor catio tower?
Building usually costs more upfront but can cost less per year if you use weather-resistant wood, stainless fixings and keep up with sealing. In our illustrative example, a $235 DIY tower lasting eight years works out at about $49 a year, compared with $58 to $60 for the other options.
How do I calculate cost per year of use?
Add the purchase or build price to the total upkeep you expect over the tower's life, then divide by the number of years it stays safe outdoors. For example, a $235 build plus $160 of upkeep over eight years is $395 in total, or about $49.38 a year of use.
Can I put an indoor cat tree in a catio?
You can, but it usually wears out fast. Carpet holds water, pressed board swells and glue joints weaken in damp weather. In our example an indoor tower costing $90 that lasts 18 months outdoors works out at $60 a year, more than a well-built outdoor tower.
What wood is best for an outdoor cat tower?
Cedar, larch or exterior-grade plywood, sealed with a water-based exterior finish that is fully cured before use. Use stainless or coated exterior screws, and seal every cut end before assembly. Avoid reusing old timber of unknown origin, because older treated wood may contain chromated arsenicals.
How often should I maintain a catio tower?
Check screws and platforms monthly, re-seal the wood each spring, re-wrap sisal when it frays and replace rusted fixings in autumn. Regular upkeep is what lets a DIY tower last many years, which is what keeps its cost per year of use low.
