An Evening of Cat Balcony R&D
Got tasked with designing and building a bespoke cat balcony — a wall-mounted steel enclosure that spans two second-floor windows on rendered brickwork. Indoor cats get safe outdoor roam space, owners get fresh air into the house. Simple concept, proper engineering challenge.
This is the start of a bespoke service — measure, design, build, install. One-man operation. Every job made to measure.
The Design
The core structure is a steel welded platform shelf that spans both windows, secured to the brickwork with structural through-bolts. Not screws, not basic rawlplugs — proper masonry anchors with 80mm+ embedment into solid brick behind the render.
On top of the platform: a bolt-together steel mesh enclosure with an angled clear polycarbonate roof. The roof slopes away from the wall for rainwater drainage and lets light through so the cats aren't sitting in a dark box.
Removable tray liners on the platform floor for easy cleaning. That detail sounds small but it's one of the biggest selling points — every cat owner knows the pain of trying to clean a fixed-floor enclosure.
Steel Mesh vs Poly Netting
Early on I weighed up two approaches for the enclosure walls:
Poly netting on a lightweight steel frame — cheaper upfront, lighter to handle solo at height. But UV degrades the netting in 2-3 years in UK weather, cats claw at it constantly, and it starts looking tatty fast. That means maintenance callbacks, replacement costs, and a product that doesn't hold up to what you promised.
Galvanised weld mesh bolt-together panels — 25mm aperture, pre-galvanised steel wire. Cat-proof, weather-proof, zero maintenance. Bolt together on site, flat-pack to the job. Looks professional from day one and still looks professional in fifteen years.
The mesh costs slightly more per build. But it eliminates every problem the netting creates. No callbacks, no replacements, no apologising for a product that's falling apart after two summers. The mesh pays for itself on the first job just in time saved.
What's Already Out There
Before committing to a design, I dug into the global catio market. The landscape splits into clear tiers:
Kit Makers
Wooden garden catios, mostly ground-level, self-assembly. Budget-friendly but limited — no wall mounting, no steel, no installation. You're buying flat-pack furniture for your cat. Fine for a garden, not an option for a second-floor window.
Premium Kit Systems
Steel-framed modular systems with patented connectors. Better build quality, powder-coated finishes, expandable designs. But they're still kits — you buy the parts and either fit them yourself or pay for professional installation on top. A mid-size steel catio with professional installation from one of the major UK brands easily runs into the thousands.
Full Bespoke
Custom-designed, custom-built, professionally installed. Cedar frames with corrugated roofing, or full steel fabrication. High-end market — you're paying for design time, materials, fabrication, and installation as separate line items.
Window Box Catios
Small single-window enclosures — more of a viewing perch than a living space. Plywood or basic metal frame, window-mounted. Good for giving a cat a place to sit, but not really "outdoor access" in any meaningful sense.
The Gap
There's a clear space in the market that nobody's filling.
Kit makers sell ground-level, self-install, mostly wooden structures. Full bespoke installers charge premium prices. Window boxes cover a single window and give cats a shelf, not a space.
Nobody is offering a bespoke steel, wall-mounted, multi-window catio at a mid-range price point with installation included.
That's where this sits. A properly engineered steel enclosure, designed to measure, built in the workshop, installed at height — at a price that reflects the work without pricing out the average cat owner.
What Makes This Design Different
After looking at everything on the market, there are genuine points of differentiation:
Two-window spanning design. Every window catio on the market covers a single window. This creates actual roaming space — not just a perch, but a place cats can move around, climb, and lounge.
Removable cleaning trays. Most catios have fixed mesh floors that are a nightmare to clean. Pull-out tray liners that you can hose down and slide back in. Simple, practical, and every cat owner will appreciate it.
Steel at height. Not timber. Steel weathers better, lasts longer, and looks more engineered when it's mounted on the side of a building at second floor. Timber catios make sense in a garden. Steel makes sense on a wall.
Reversible mounting. Structural through-bolts, not chemical anchors or permanent fixings. Remove the bolts, patch the render holes, no trace. This matters for planning considerations and for anyone who might move house.
Built-in enrichment points. Shelf brackets, hammock hooks, and scratching post sockets designed into the frame from day one. Not bolted on as an afterthought — integrated into the structure so accessories slot in cleanly.
Colour matching. The steel frame can be powder coated to match window frames or building render. A small detail that makes a big difference to how the finished product looks on the building.
Planning Permission
This needs to be said honestly: a wall-mounted enclosure at second-floor height will likely need planning permission.
There are no catio-specific building regulations in the UK. Local councils apply the rules for conservatories, balconies, and outbuildings. Wall-mounted and suspended structures are generally treated like balconies, which means approval is likely required.
Other things to be aware of:
- Conservation areas and listed buildings have extra restrictions
- Leaseholders may need permission from the freeholder
- A bedroom window that's the only fire escape cannot be blocked
- Cases exist of homeowners being required to dismantle catios built without approval
Before any work starts, the customer checks with their local council. That's non-negotiable. The reversible mounting design helps — it strengthens the case for a temporary or removable structure — but it's not a guarantee of approval.
Safety at Height
Second floor means the engineering has to be right. No shortcuts.
- Structural-grade masonry anchors with verified embedment into solid brick, not just render
- 25mm maximum mesh aperture — prevents cats getting heads or paws trapped
- All steel edges de-burred and smooth, bolt heads on the outside of the cat space
- Non-toxic finishes only
- Solid tray option on the floor — prolonged contact with open mesh can irritate paw pads
- Closed roof — mesh or solid panel, no open tops
- Load rated for frame weight, multiple cats, wind load, and snow accumulation on the roof
Accessories
The base enclosure is the product. But accessories are where the value grows for the customer and the margin grows for the business:
- Shelving — cedar or steel shelves at different heights for climbing and lounging
- Sisal scratching posts — vertical posts integrated into the frame
- Hammock points — hooks for hanging cat beds and nets
- Cat flap integration — so cats can come and go through the window independently
- LED strip lighting — low-voltage waterproof strips for evening use
- Tunnel connections — link the catio to a second window or external enclosure
- Winter weather covers — removable panels for cold months
- Spare tray liners — replacement pull-out trays
These are all add-ons that can be included at build time or fitted later. The frame is designed with mounting points built in, so nothing needs to be retrofitted or bodged.
What's Next
- Finalise the design — depth, panel layout, shelf positions
- First proper measured survey on site
- Prototype build in the workshop
- Parametric 3D model (already started — all dimensions adjustable for different window configurations)
- Photography for portfolio
- Planning permission guidance template for customers
The Bigger Picture
This fits the pattern. Find a gap in the market, design something proper, build it yourself, sell the skill not just the product. The market is full of wooden garden boxes at one end and expensive bespoke installs at the other. A steel, engineered, second-floor catio at a fair price with proper installation — that gap is wide open, and nobody's standing in it.