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Property possibility reportConfirmed report

Your Property's Possibilities, Clearly Mapped

18724 Chase St Northridge 91324

Prepared August 7, 2026

Detached ADU · Detached SB-9 + ADU · Main-house Addition

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Subject property overview
Existing building

3321

Zoning

RS-1

Lot area · sq ft

12520

Backyard depth · ft

21

Rear lot width · ft

80

Backyard area · sq ft

1684

Perimeter · ft

661

Hybrid property map
Hybrid property map
Transportation map
Transportation map
Street view
Street view
ZIMAS property map
ZIMAS property map
Possibility 01 · Extra units

Detached Accessory Dwelling Unit

Conceptually feasible
One-story detached ADU concept

Option A · One-story detached ADU

A compact first-floor concept sized to the usable yard. Construction is estimated at $215–$235 per square foot.

Two-story detached ADU concept

Option B · Two-story detached ADU

A smaller footprint preserves more yard while providing two floors. Construction is estimated at $225–$245 per square foot.

Preliminary project cost estimateDetached ADU
Architectural design + permit drawings$4–$6 / sq ft
Structural design + engineering$1–$2.50 / sq ft
Title 24 energy compliance$300 flat
Survey + site plan$1,800–$2,500
Permit coordination$1,500 / permit
Plan check + permit allowance$2,000–$20,000
Design + permit range$11,600–$34,500
Combined planning range$341,600–$484,500
Completed project exampleHatteras One-Bedroom ADU Conversion
View project →
Possibility 02 · Extra units

Detached SB-9 + ADU

Preliminary fit available
Detached SB-9 and ADU concept map

Stacked two-unit concept

Lower floor: SB-9 unit. Upper floor: ADU. The mapped footprint adapts to the actual open yard instead of forcing one fixed rectangle.

Concept configuration

500–800 sq ft per floor

Two stories · two units · larger building side aligned with the shorter lot dimension where geometry permits.

Two-story construction$225–$245 / sq ft
Completed project exampleSAF Duplex Van Nuys
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Possibility 03 · Main house

Main House Addition

First + second-floor concepts

More space for the main home

The existing home may support a connected addition.

First-floor and upper-floor directions can be compared before the final design is selected.

Maximum estimated rental potential

Existing Property Rental Income

Existing main house0 bedrooms · 3,321 sq ftUp to $3,460/month
Total potential gross rentUp to $3,460/month$41,520/year before expenses

Preliminary market estimate. Final rent depends on the completed design, property condition, and current market.

First-floor house addition concept

Option A · First-floor attached addition

The footprint is shaped around available backyard space and connected directly to the existing main house.

Second-floor house addition concept

Option B · Second-floor addition

A second-floor option uses the existing building footprint and can combine with a smaller connected first-floor remainder.

Preliminary project cost estimateMain house addition
Potential addition area1,615 sq ft
Architectural + permit drawings$4–$6 / sq ft
Structural engineering$1–$2.50 / sq ft
Survey + site plan$1,800–$2,500
Permit coordination$1,500 / permit
Plan check + permit allowance$2,000–$20,000
Planning note

Construction and design totals are preliminary allowances. Survey, zoning, structural capacity, setbacks, and agency review remain required.

Preliminary combined range$341,600–$484,500
Completed project exampleTop of Bel Air · Addition Project
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Client-ready property package

Download the Full Property Possibilities Report

Property facts, mapped concepts, zoning screens, project examples, and preliminary investment ranges in one PDF.

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Next step

Turn a preliminary possibility into a verified design strategy.

Schedule a site review with the 121 Design Build team to confirm the concept, establish the project scope, and prepare the path toward drawings and permits.

info@121designbuild.com(424) 600-110017801 Ventura Blvd, 2nd Floor
Encino, CA 91316121designbuild.com
Schedule a consultation

Bring the report to a design review

We will review the mapped opportunities, identify the required verification, and outline a practical design and permit path.

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