Urban Design Learning reposted this
A few months ago I had a hunch I couldn't let go of. Dwellings-per-hectare (the metric in almost every Local Plan density policy) tells you almost nothing useful. The same number is achievable by suburban semis, perimeter blocks, or towers. It says nothing about built form, massing, or character. And it's gameable: hit the dph target with sub-standard micro-units and you've technically complied. So I asked a question: could a combined metric envelope — dph alongside Floor Area Ratio, building height parameters (both minimum and maximum), and site coverage limits — be constructed so that it's mathematically only satisfiable by missing-middle typologies? Perimeter blocks. Mansion blocks. Stacked townhouses. To test it I used Claude (Anthropic's AI) as a structured thinking partner, stress-testing the logic, identifying the gaps, drafting policy text. What I didn't expect was that the experiment would produce something as substantial as it did: a full draft Local Plan policy, a supporting Examination in Public Topic Paper, and a Site Capacity Statement mechanism that makes density genuinely an output of design decisions rather than an imposed target. The framework uses six accessibility tiers derived from proximity to public transport, layered with character modifiers derived from a real settlement evidence base. Two things I learned along the way: 1. Parking strategy is the single biggest density variable. On a representative T4 site, the difference between structured and surface parking (combined with a height constraint) costs you 17 homes per hectare. The policy makes that trade-off visible and auditable. 2. The best question came after the policy was finished. Esther Kurland at Urban Design Learning asked whether capping the percentage of a site accessible to motor vehicles might be a simpler, more intuitive proxy metric than FAR; a 'hero metric' that captures parking, access roads, and turning circles in one measurable figure. I don't know the answer. That's an open question for the room. I presented this at a UDL session on density last month. It's not commissioned work, Stockport MBC haven't seen it, and my honest confidence in it as a complete workable policy is about 6.5 out of 10 (I happen to think it's a bit too long, for instance). But the logic survived scrutiny, and I think the question it asks is the right one. The key on making something work in similar areas is having the evidence base (like the Stockport Character & Urban Density Study produced by Planit and similar work produced for London Boroughs). Without such background evidence, you are effectively plucking numbers out of thin air. Should liveability metrics and the density controls sit in the same policy clause, or are they better kept separate? Happy to share the documents with anyone working in this space. And very happy to be told where I've got it wrong. #planning #urbandesign #housingpolicy #localplan #missingmiddle #densitypolicy #AI