Case Study: The Difficult Hillside ADU

1. The property. An LA hillside lot, house at street level, rear yard falling away at roughly 28% — a slope the owners had written off as "unbuildable" for twenty years.

2. The goal. A rental unit — and, candidly, capturing the canyon view that the main house itself barely enjoyed.

3. The constraints. Everything Module 2.5 promised: hillside grading rules, a mandatory soils report (9.6), fire-zone construction requirements (VHFSZ), difficult construction access (no rear alley — everything down the slope by conveyor or crane), and a budget conversation that had to happen before the dream got detailed.

4. Options considered. (a) A small unit near the top of the slope, minimal foundation adventure. (b) A mid-slope unit on a stepped foundation — bigger, better view, real foundation money. (c) The full view play: a 750 SF unit partially cantilevered on drilled caissons. The soils report — commissioned first, before design dollars (9.6's exact advice) — found competent bedrock at workable depth, which made (c) engineerable at a knowable price. The owners, shown all three with honest foundation numbers attached, chose (c) with a contingency to match.

5. The final design. A 750 SF 1BR, living room and deck aimed dead at the canyon (this project was its view — every other decision served it), bedroom tucked into the slope side, fire-zone detailing throughout (ember-resistant vents, tempered glazing, ignition-resistant cladding — 2.5's checklist as a materials list). Utilities ran down the slope alongside the new access stair — one trench, everything in it (7.5's rule, on an incline).

6. City issues. Hillside review added a grading plan cycle and Fire wanted the access stair's details upgraded (10.6's desks, both showing up as predicted). No fights — just more reviewers, more sheets, more weeks.

7. Permitting. Three rounds (the grading and caisson packages drew specialist reviewers), 22 weeks. The team's response pace kept a heavy review from becoming a long one (10.4's chorus).

8. Construction. 10 months. Caisson drilling was the spectacle week — and the invoice to match. The conveyor moved concrete and materials down-slope; the crew's access stair later became the unit's permanent one (planned double duty). Contingency was set at 20% (6.9's hillside band) and finished 60% consumed — a drilling refusal on one caisson (relocated per the engineer) and extra erosion control through a wet month.

9. The final result. The best-renting unit relative to size we've delivered in that zip code — the view does the marketing. The "unbuildable" slope now carries the property's most valuable square footage.

10. Cost range. $430,000–$470,000 all-in — of which roughly $120K was foundation, grading, and access (2.5's warning, itemized). Per-square-foot, far above Module 6's benchmark; per-month-of-rent, it competes.

11. Timeline. About 20 months — the soils report first, and everything else in its proper order.

12. Lessons learned. Hillsides invert the budget: the ground gets the money and the building gets what's left — so the ground gets investigated first, always. Options priced with honest foundation numbers let owners choose with open eyes (this one chose the expensive dream deliberately — 7.10's closing principle at maximum stakes). And "unbuildable" usually means "unexamined": the slope was never the problem; the unknowns were.