4201 Bloomfield Road — Pre-Application Feasibility Brief

Our overriding goal is to design something that lands cleanly — we would rather adjust the concept now than discover a classification problem at plan check. We are glad to bring this to a formal Project Review meeting.

The proposal

On a new building pad at the north edge of the parcel's oak grove: three independent, freestanding structures — the ADU and two detached home offices — none sharing a wall or roof, each separated by open space (we intend ≥ 10 ft between structures). Separately, a detached 3-car garage on the eastern part of the parcel, below the hill near the existing developed area.

North pad · dwelling

Main ADU

~1,185 sqft · 2 bed / 2 bath · single story. A ministerial ADU under Gov. Code §65852.2 (we understand the parcel allows up to two ADUs).

North pad · accessory

Office — West

~257 sqft · home office / workspace. Habitable, with a bathroom. No kitchen, no sleeping room.

North pad · accessory

Office — East

~257 sqft · identical to West. Habitable, with a bathroom. No kitchen, no sleeping room.

East · accessory

Garage (3-car)

~700 sqft · vehicle storage. Proposed straw-bale walls on a slab foundation. No kitchen, no sleeping room.

Construction: timber frame (ADU + offices) and load-bearing straw-bale (garage); wood + metal cladding; low-slope roofs; substantial glazing to the northwest view; pier/post or slab foundations on the sloping ground. WUI Chapter 7A-compliant exteriors; Title 24 solar on the ADU. This brief addresses land-use feasibility and classification; interior layouts, finishes, and landscape elements are not part of the question.

Property & existing conditions

Existing structures (to remain): the 1988 single-family dwelling (~3,456 sqft; VR permit ZPE16-0070 was revoked at transfer and is not relied upon); a 1,152 sqft former goat-dairy structure legalized as a non-dwelling (BLD03-1684); the private well; and a septic system documented for 1 unit / 4 bedrooms (SDS #1342, 1988).

Disclosed history (all files closed): two prior code-enforcement cases cited the former dairy barn as an illegal second dwelling (VBU02-0038, VPL02-0039, VBU05-0538). We are aware of this record and specifically want to design the new accessory structures so there is no ambiguity about their non-dwelling status.

Already confirmed — 2026-05-01 counter visit

A detached ADU is permitted here — ministerial, 60-day review — and the parcel now allows up to two ADUs.
ADU standards: ≤1,200 sqft, no height limit or setbacks beyond the state ADU minimums.
No ADU-related ceiling on accessory structures — "as many as desired" (studios, outbuildings, etc.).
The well is Class 2 — sufficient for multiple dwellings; no extra yield test or storage tank required.
Septic path = a Type III findings report via our septic consultant (BC Engineering engaged).
Permits: BLD + SEP; GRD only if earthwork >50 cy; ENC if work is within 30 ft of the Bloomfield Rd ROW.
ADU government fees ≈ $13K impact + $4–5K review (~$17–18K).
The combining overlays (OAK / RC50/50 / SR) do not push the ADU into discretionary review; siting is a civil-engineering determination.
Closed violations (VBU02 / VPL02 / VBU05) are not a plan-check issue; VR permit ZPE16-0070 was revoked at transfer.

What remains open

AUse & classificationCentral question

Planning confirmed there is no ADU-related ceiling on accessory structures. Building on that: please confirm that two detached home offices — habitable, each with a bathroom, but with no kitchen and no sleeping room — remain by-right accessory structures (building permit only, no use permit). Specifically:
1. a bathroom alone (no kitchen, no sleeping room) does not reclassify them as a guest house, "guest room," or dwelling unit;
2. the guest-house standards (≈640 sqft, one-per-parcel, within 100 ft of the primary dwelling) therefore do not apply; and
3. what specific plan features the County uses to keep such a building unambiguously an office/accessory structure (closets, extent of plumbing, square footage, finishes), so we can design to that line.

Is there a maximum size and/or height for habitable accessory structures in LEA? (The ≤1,200 sqft / state-minimum standards we have are ADU-specific.)

BDetached garage & straw-bale construction

Confirm a detached 3-car garage (~700 sqft, vehicle storage, no kitchen / no sleeping room) is a by-right accessory structure at the proposed eastern location (below the hill, near the existing developed area).
1. We intend load-bearing straw-bale walls on a conventional slab foundation. Confirm straw-bale is acceptable and the path: the prescriptive CRC Appendix AS (Strawbale Construction) per Permit Sonoma Technical Bulletin B-31, vs. an engineered design (architect/engineer stamp + special inspections), and how the required plaster skin and WUI Chapter 7A ignition-resistance requirements apply to straw-bale in this Moderate FHSZ / SRA.

CADU — items not yet addressed

Title 24 solar PV requirement for the new ADU and acceptable compliance paths (grid-tied / battery / roof-ready conduit).
Fire sprinklers (CRC R313): confirm for the dwelling, and whether the offices or garage require them.
We have the ADU fee picture (~$17–18K). Do the accessory offices and garage carry separate impact or permit fees?

DSetbacks & separation between structures

The ADU follows state setback minimums. For the non-ADU accessory structures (offices, garage), confirm the LEA base setbacks (front 55 ft from road centerline / side 10 ft / rear 20 ft) and that none are binding given interior siting.
Confirm the minimum separation that keeps each building "detached" (we understand a ≥6 ft open-to-sky yard; we intend ≥10 ft on the north pad).
At our proposed spacing, confirm the building-code fire-separation requirements (CRC R302.1) for exterior-wall rating and window-opening area on facing walls, and that ≥10 ft between buildings permits unprotected glazing.

ECombining-district specifics

OAK: we know the overlays don't make the ADU discretionary. We still need the specifics: the drip-line standard for building near the grove (the ADU pad is at its north edge), and whether an arborist report, tree survey, or mitigation is required. May we also obtain the GIS overlay layers for OAK and RC50/50 (not provided at the counter)?
RC50/50: confirm the location of any designated watercourse near the pad and that our structures and access clear the 50-ft riparian setback.
SR: the Bloomfield Rd scenic corridor wasn't addressed at the counter — what height, materials, or visibility standards apply under ministerial review? Do low-slope, non-reflective, earth-toned structures satisfy them?

FSeptic — open specifics

Our septic path is a Type III findings report (BC Engineering engaged). Specifically: how do the two office bathrooms, plus the 2-BR ADU, count toward OWTS design flow / bedroom-equivalent on top of the documented 1-unit / 4-BR baseline?
The counter noted the dwelling-to-leach-field / tank / well setbacks weren't specifically confirmed (our engineer will map them). For planning purposes, please confirm the governing distances (well-to-leach-field 100 ft, tank-to-well, structure-to-components) or point us to the OWTS Manual table.

GBuilding · fire · WUI

Confirm the Chapter 7A WUI specifics (ignition-resistant exterior, ember-resistant vents, Class A roof) for all four structures — not detailed at the counter.
The ADU pad is adjacent to the protected oak grove. How do we reconcile defensible space (PRC 4291, 100 ft) with the OAK overlay's tree protection — is a vegetation-management plan (limbing + understory reduction, retaining mature oaks) the accepted approach?
What fire-apparatus access / turnaround and any fire-flow or water-storage requirements apply in the SRA (Bloomfield VFC / Cal Fire)?

HGrading & access

We understand grading triggers at >50 cy. Given the building pad, garage pad, and pier/post foundations on the sloping site, what geotechnical investigation do you expect (expansive LoE/SnD2/SnE2 soils, Seismic Design Category D), and is a soils report required at submittal?
The recorded 50-ft Pullin shared right-of-way wasn't covered at the counter. If our access interacts with it, does Planning need anything beyond the ENC (within 30 ft of the Bloomfield Rd ROW)?

IProcess, submittal & sequencing

Sequencing: we'd permit the ADU first (ministerial). May the two offices and the garage be submitted concurrently, or should they follow? Critically — does adding the offices/garage introduce any discretionary review (e.g., a use permit), or do they remain by-right building permits?
Required electronic submittal format and file-naming convention (not addressed at the counter).
Realistic application-to-permit timeline for the ADU and for the accessory structures.
Do you recommend a formal Project Review (pre-application) meeting for this multi-structure plan, and how do we schedule it?

JPrior record

The closed violations and revoked VR are understood to be non-issues for plan check. Given that history, what should we proactively document so the new offices read clearly as accessory structures, not dwelling conversions?

The proposal

Property & existing conditions

Already confirmed — 2026-05-01 counter visit

What remains open

Reference materials we can provide