How we decide what to tell you

Methodology

Checks are versioned rules

Each check is a rule with an id, a version, a severity, the inputs it reads, a plain-language explanation and remediation, and the sources behind it. Rules record their evidence state — an authoritative requirement, professional guidance, a manufacturer constraint, or product best practice — so you can see how firm each one is. A project records which rule versions produced its findings, so an old design can be reproduced.

Severities

• Blocker — no build package until the design changes or a professional reviews it.
• Warning — a material safety or buildability concern; some may be acknowledged with a note.
• Advisory — better practice for welfare, comfort or upkeep.
• Info — assumptions and notes recorded in the package.

Materials lists come from the same model as the drawing

Framing, mesh and hardware are generated from the design’s parameters; there is no separate decorative model. Stock lengths, kerf, overlap and waste are visible settings. Prices are ranges with a date. Before launch, reference catios are built from generated lists and the differences in materials, cuts and time are reconciled into the formulas.

Plant statuses

Plants are labelled known hazard, no known issue found, conflicting evidence or insufficient data, each with sources and a review date. We never turn incomplete public information into a blanket claim that a plant is safe.

Current catalog oc-catalog@0.1: 51 rules, 106 plants, 15 sources; latest review 2026-10-12.

Limitations

• Guidance, not certification. “No issue detected by the current rules” is the strongest thing a check will say. It is not “safe” and not “approved”.
• Not engineering. Drawings are planning and construction guidance within supported limits, not stamped engineering documents. Elevated, roof-mounted, structurally attached upper-storey, large, high-wind, heavy-snow and guardrail-altering designs require professional review.
• Not code or permit approval. Building codes, HOA covenants and leases vary by place; the planner does not know yours.
• Not veterinary advice. Welfare rules follow published feline-welfare guidance in general terms. Your veterinarian knows your cat.
• Measurements are yours. The planner can only check the dimensions you give it, which is why build packages need confirmed dimensions.
• Cats are inventive. Inspect the finished catio and supervise early use.

Corrections

If a rule, a plant status, a source or a guide looks wrong, email a correction with the page and your evidence. We review every report, record the change and its date in the catalog, and update affected rule or plant versions. Safety-relevant corrections are prioritised.

Sponsorship, partnerships and affiliate relationships never change a finding or a plant status.