The ADU Strategy Matrix

Choosing Your ADU Play

Not all ADU projects are the same. The strategy you choose depends on your capital, your risk tolerance, your timeline, and your target market. This chapter breaks down the five primary ADU investment strategies so you can identify which one fits your situation — and which ones you might graduate into as you scale.

Strategy 1: Garage Conversion

What it is: Converting an existing attached or detached garage into a permitted dwelling unit with its own kitchen, bathroom, entrance, and living space.

Why investors like it: Garage conversions are the fastest and cheapest path to an ADU. The structure already exists. You're not pouring a foundation or framing walls from scratch. You're converting existing square footage into livable, rentable space.

Typical project profile:

What's involved:

• Insulation, drywall, and flooring over the existing slab
• Plumbing for kitchen and bathroom (this is usually the biggest cost driver — running new lines)
• Electrical panel upgrade or sub-panel
• HVAC (mini-split systems are the standard for garage ADUs)
• Window and door installation (egress requirements)
• Fire separation if attached to the main dwelling
• Removing the garage door and framing a wall (or in some jurisdictions, keeping the door as a design element)

Key considerations:

• Parking replacement: some cities require you to replace the lost parking space. Check local code.
• Ceiling height: standard garages have 8-foot ceilings, which is usually adequate. Older garages may be shorter — anything under 7'6" is a problem in most jurisdictions.
• Slab condition: garage slabs are often thinner than residential slabs and may not have a moisture barrier. You may need to pour a new slab or add a vapor barrier and subfloor.
• Setbacks: an existing garage that's legal non-conforming (too close to the property line) may still qualify for conversion in ADU-friendly states. Verify with your planning department.

Best market profile: Suburban areas with older homes that have oversized two-car garages. Markets where the main home is 1,200–1,800 sq ft and the garage represents 400+ sq ft of convertible space.

RISE modeling: Use Fix & Flip mode for conversions where you plan to sell, or DSCR/Rental mode if you're holding. Enter the conversion cost under Rehab Budget. The ARV should reflect comparable sales of properties with legal ADUs in the area.

Strategy 2: Shed / Accessory Structure Conversion

What it is: Converting an existing non-residential structure — a shed, barn, workshop, or detached storage building — into a permitted dwelling unit.

Why investors like it: Similar economics to a garage conversion, but often on larger lots with more flexibility. Rural-suburban markets sometimes have properties with substantial outbuildings that are structurally sound but underutilized.

Typical project profile:

What's involved:

• Structural assessment (can the existing structure support residential use?)
• Foundation work (sheds often sit on pier blocks or gravel — you may need a real foundation)
• Full MEP (mechanical, electrical, plumbing) installation
• Insulation and weatherproofing to residential standards
• Septic considerations in rural areas (does the existing system support an additional unit?)

Key considerations:

• The existing structure may not meet building code for residential occupancy. You may end up demolishing and rebuilding, which changes the economics entirely. Get a structural assessment before you underwrite.
• Utility connections in rural areas can be expensive. Running water and sewer lines 100+ feet from the main house adds cost fast.
• Some jurisdictions don't classify shed conversions under their ADU ordinance — they may treat it as new construction, which triggers different standards.

Best market profile: Rural-suburban areas with large lots (0.25+ acres), properties with existing outbuildings in good structural condition. Markets where land is affordable but rental demand is strong (college towns, tourist areas, military bases).

Strategy 3: Ground-Up Detached ADU

What it is: Building a brand-new, freestanding dwelling unit on an existing residential lot. This is new construction on a small scale.

Why investors like it: Ground-up gives you complete control over design, quality, and unit size. You're not limited by an existing structure's footprint or condition. The finished product is a new-construction unit, which commands premium rents and maximizes ARV.

Typical project profile:

What's involved:

• Site survey and soils report
• Architectural plans (must comply with local ADU development standards)
• Foundation (slab-on-grade is standard; some markets require raised foundations)
• Full stick-built or prefab construction
• Separate utility connections or sub-metering from the main house
• Landscaping, fencing, and separate entrance/pathway

Key considerations:

• Setback requirements will dictate where on the lot you can build and how large the unit can be. This is the single biggest constraint on ground-up ADUs.
• Impact fees and utility connection fees can add $10,000–$30,000+ in some California jurisdictions. Budget for these upfront.
• Design review may be required in certain neighborhoods (historic districts, planned communities). This adds time and cost.
• Permitting timelines for new construction ADUs are longer than conversions. In busy jurisdictions (Los Angeles, Portland, Seattle), plan for 3–6 months just for the permit, before construction begins.

Best market profile: Urban and suburban areas with strong rent-to-price ratios, lots with adequate space for a detached structure (typically 5,000+ sq ft lots), markets where new-construction ADU comps exist.

RISE modeling: Use Ground-Up mode. Enter your total construction cost (including soft costs like architecture, permits, and fees) and model the full timeline including the permitting phase in your Hold Period. This is critical — underestimating the hold period is the most common mistake in ground-up ADU projects.

Strategy 4: Junior ADU (JADU)

What it is: Converting existing space within the main home — a bedroom, a portion of the house, or an attached space — into a small independent dwelling unit. JADUs are typically limited to 500 sq ft and are currently a California-specific designation, though similar concepts exist in other states under different names.

Why investors like it: JADUs are the lowest-cost, fastest ADU strategy. You're working within the existing building envelope, which means no foundation, no new roof, no exterior framing. And in California, you're allowed to build both a JADU and a standard ADU on the same lot — so this can be an add-on to a larger project.

Typical project profile:

What's involved:

• Interior partition walls to separate the JADU from the main living area
• Adding or converting a bathroom
• Kitchen or kitchenette installation (efficiency kitchen is permitted in most JADU ordinances)
• Separate exterior entrance
• Fire separation between the JADU and the main dwelling (fire-rated wall assembly, interconnected smoke alarms)

Key considerations:

• California's JADU law requires owner-occupancy in either the main home or the JADU. This affects investor strategy — it works well for house hackers but complicates a pure investment play unless you have a tenant willing to occupy the main unit while you rent the JADU (or vice versa). Note that owner-occupancy requirements are not enforced at sale in most jurisdictions, so a property with a JADU can still be sold to a non-owner-occupant buyer.
• JADUs can share a bathroom with the main dwelling in some configurations, but units with their own bathroom command higher rents and are more attractive at resale.
• Because JADUs are within the main structure, tenant privacy and noise are bigger factors. Design the layout to minimize shared walls with living areas.

Best market profile: California markets (where the JADU designation exists), properties with underutilized bedrooms or attached spaces, investors using a house-hack strategy.

Strategy 5: Lot Split + ADU

What it is: Splitting a single-family lot into two separate parcels and building on the new parcel, or splitting and placing ADUs on both parcels. This strategy was enabled by California's SB 9 (effective January 2022) and similar legislation emerging in other states.

Why investors like it: This is the highest-upside ADU strategy. Instead of adding a unit to a single-family lot, you're creating entirely new parcels — each of which can be sold, developed, or held independently. In high-value markets, the land value alone can justify the investment.

Typical project profile:

What's involved:

• Tentative parcel map application with the city
• Survey and legal description of the new parcels
• Meeting minimum lot size requirements for both resulting parcels
• Infrastructure: each parcel may need independent utility connections
• Construction of new unit(s) on one or both parcels
• Potentially relocating or modifying existing structures to meet setbacks on the new lot lines

Key considerations:

• SB 9 lot splits have specific requirements: both resulting parcels must be at least 1,200 sq ft (in California), the property can't be in certain protected areas, and there are restrictions on how quickly you can sell (owner-occupancy requirement for 3 years post-split in some cases).
• This strategy requires more capital, more time, and more expertise than a simple ADU addition. It's a small-scale development play.
• Financing is more complex. You may need acquisition financing, a lot split/entitlement phase, and then construction financing. Work with a lender who understands the full lifecycle.
• The upside can be substantial. In markets like Los Angeles, San Jose, or Portland, creating a new buildable parcel in an established neighborhood can generate six-figure returns.

Best market profile: High-value urban markets with large lots (6,000+ sq ft), states with lot-split enabling legislation, areas where land value per parcel is high relative to construction cost.

RISE modeling: Model this in stages. First, use RISE to underwrite the acquisition. Then model each unit's construction and projected income separately. The combined return is your true project return. For the exit, model the sale of individual parcels/units or the stabilized rental income from the full project.

Strategy Comparison Matrix

Choosing Your Strategy

Ask yourself these questions:

1. How much capital do I have available? If under $50K cash, start with a garage conversion or JADU. If $100K+, ground-up or lot split becomes viable.

2. What's my timeline tolerance? If you need to recycle capital in under 6 months, conversions are your play. If you can hold for 12–18 months, ground-up and lot splits offer higher returns.

3. Am I holding or selling? Conversions and JADUs are great for quick equity creation and sale. Ground-up ADUs are ideal for long-term rental holds. Lot splits work best when you sell at least one parcel.

4. What does my market support? The strategy has to match the market. A ground-up ADU in a market where construction costs are $300/sq ft and rents are $1.50/sq ft doesn't work. A garage conversion in a market with strong rental demand and $80K conversion costs might return 25%+ cash-on-cash.

5. What's my experience level? If this is your first ADU project, start with a conversion. Learn the permitting process, the contractor management, and the timeline realities on a smaller, lower-risk project. Graduate to ground-up and lot splits after you've built the muscle.