Case Study: The 800 SF Backyard ADU

1. The property. A flat 7,200 SF lot in an East LA-adjacent suburb; 1,400 SF house, wide-open rear lawn, alley at the back.

2. The goal. Maximum durable rental income (Module 1's most common answer), held long-term for retirement.

3. The constraints. A sewer easement along the north line (2.4 — discovered on the title report during feasibility, exactly where it should be discovered), the main panel on the house's far side, and a mature avocado tree the owners refused to lose (correctly — 2.5).

4. Options considered. (a) 1,000 SF 2BR/2BA — the lot could take it. (b) 800 SF with the 2BR fork (4.5). (c) Two-story 800 to preserve more yard (3.5). The owners ran 4.2's math: the extra 200 SF cost ~$70K and moved rent perhaps $200/month; the two-story premium bought yard they didn't need on a 7,200 SF lot. They chose (b) — the efficient 2BR at the top of a rent step (4.7's rule, applied).

5. The final design. The compact 2BR from 4.8's playbook: bedrooms on opposite ends, living core between, bath centered on one wet wall with the kitchen backing it. Placement followed 7.10's logic — shifted 25 feet toward the alley side, clearing the sewer easement, shortening every trench, and keeping the avocado's root zone untouched. Entry faced the alley side; not one window faced the main house directly (8.5).

6. City issues. Essentially none — a coordinated set (9.7) in a city with a functional portal.

7. Permitting. One correction round, 9 items, cleared in one response. Permit in 9 weeks.

8. Construction. 7.5 months. The placement decision proved itself: gravity sewer (no pump), a 60-foot combined utility trench instead of the 110-foot run the original sketch implied — the designer's estimate put the placement savings at ~$28K. One weather delay (a wet February) and a 6-week cabinet lead time handled by ordering at permit issuance (12.7's discipline).

9. The final result. An 805 SF 2BR/1BA with laundry, private patio, and alley-side parking spot. Leased at the top of the local band to a couple who cited "it doesn't feel like a backyard unit" — 8.5's privacy engineering, quoted back verbatim.

10. Cost range. $295,000–$315,000 all-in, including $38K of soft costs and fees, solar (7.9), and landscape restoration.

11. Timeline. First call to lease: just under 13 months.

12. Lessons learned. The two decisions that defined the budget were made before any drawing existed: unit size (top of the 2BR rent step, not past it) and placement (utilities chose the spot). Everything after was execution. Also: the tree stayed, shades the patio, and appears in every listing photo — constraints and amenities are sometimes the same thing.