Design
for Real Approval.
The GC-ADU-490 has been designed by Guesscreative, approved by California Building Departments | Engineered | Fabricated by Premier SIPs (45+ Years, 10,000+ Projects)
It’s a compact, high-performance detached ADU engineered with Structural Insulated Panels (SIPs) chosen for durability, efficiency, and long-term comfort.
It is permit-tested.
This plan set successfully cleared:
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Municipal planning review
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California Building Code compliance
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Structural engineering
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Title 24 energy requirements
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Very High Fire Hazard Severity Zone standards
Most ADU plans are conceptual.
This one exists in approved form.
Limited Availability: Jurisdiction adaptation slots fill 4-6 weeks in advance. Reserve your spot now.
GC-ADU-490
Permit-Proven SIP Panel Accessory Dwelling Unit
Design Specifications
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Size: 490 SF (≈415 SF conditioned) 13'-5" x 36'-5"
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Layout: 1 Bed / 1 Bath
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Construction: SIP wall + roof system
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Foundation: Stem wall (engineered details included)
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HVAC: Ductless mini-split
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Appliances: Electric
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Code Basis: 2022 California Residential Code / 2021 International Residential Code
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Energy: Title 24 compliant
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Fire: VHFHSZ-compliant
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Approvals: Moorpark, CA (complete) | Chula Vista, CA (complete)
A Home That Just Feels Right
You don’t need more space. You need better space.
This ADU feels calm the moment you walk in.
The bedroom is private. The kitchen flows.
The living area opens without feeling exposed.
Nothing is wasted. Nothing feels tight.
Everything feels intentional.
It’s a complete home.
Designed Around Real Life
No long hallways. No awkward corners. No unused rooms.
Every square foot serves you.
Light enters where you live.
Sound stays soft.
Movement feels natural.
The bedroom is sized for real rest.
The kitchen has counter space that works.
The bathroom feels generous, not squeezed.
This is what happens when 490 square feet is designed with precision instead of compromise.
Cost Transparency
For this design, the factory-engineered SIP panel package (walls, roof, floor, accessories, engineering review, and freight) is approximately $30,500.
This replaces multiple conventional scopes:
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Wall and roof framing
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Insulation
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Air sealing
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Much of the labor variability that causes delays and change orders
Total Build Cost Estimate = $120,000 - $150,000 (all-in, approx dependent on local contractors)
BUILT WITH SIPs, WHY THAT MATTERS.
This ADU is built with Structural Insulated Panels (SIPs), not conventional stick framing.
The walls don’t just enclose space.
They actively support comfort, health, and efficiency.
You feel the difference every day, even if you never think about why.
Learn more about SIPs below.
GC-ADU-490 Floor Plan
36'-5"
13'-5"
Choose Your Climate Version
Select the version engineered for your region’s thermal demands.
Choosing the correct climate version reduces adaptation time, improves performance, and avoids over- or under-building the envelope.
Standard Climate (Moderate Zones)
Best for:
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IECC Zones 3–4
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California, Texas, Arizona, Southern Nevada, Coastal regions
What it prioritizes:
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Balanced heating + cooling loads
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Efficient SIP thickness without excess material
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Proven approval precedent in California
Cold Climate (Northern Zones)
Best for:
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IECC Zones 5–7
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Colorado, Northern California, Utah, Oregon, Washington, Northern states
What it prioritizes:
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Higher R-values
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Condensation control
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Freeze-protected detailing
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Snow and cold-weather performance
Cold Climate plans are engineered differently not just insulated more. Wall thickness, roof assemblies, air sealing, and detailing are modified to perform in heating-dominant environments.
Standard Plan
Moderate Climate | Permit-Proven Reference Design
GC-ADU-490 Standard Plans
Permit-Proven Architectural Plan Set
Instant PDF delivery
$4,995
For builders & homeowners
who want a proven starting point.
Includes:
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Complete architectural plan set (PDF)
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As-approved reference drawings
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Floor plan, elevations, sections
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Foundation & roof plans
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Electrical, mechanical & plumbing layouts
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SIP panel logic & coordination notes
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Single-project license
BONUS: SIP Performance Brief (PDF)
Share this 4-page technical brief with your GC, lender, or building department. Covers cost comparisons, labor efficiency, and financing considerations.
Reference design. Jurisdictional adaptation and engineering required for permit submission.
All plans are licensed for one constructed project. Engineering stamps and energy models are site-specific and provided during adaptation.
Jurisdiction-Adapted
Standard Plan
GC-ADU-490 - Moderate Climate
Jurisdiction-Adapted Plan
$7,495
When you want a real permit submission, not a generic reference set.
Includes:
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LAHJ-specific General Notes (code amendments, local requirements)
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Energy compliance updates (Title 24 or equivalent)
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Custom Site Plan prepared for your property
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Climate, seismic, and fire-zone adjustments
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Structural note revisions (no stamped drawings yet)
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One resubmittal coordination round
Delivered 2–4 weeks from receipt of required site information & 50% initial deposit.
Most jurisdictions require an engineer’s stamp for permit issuance. Some jurisdictions also require an architect’s stamp. This package prepares the plan set for submission but does not include professional stamps. All plans are licensed for one constructed project. Engineering stamps and energy models are site-specific and provided during adaptation.
Turnkey Permit Package
GC-ADU-490
Turnkey Permit Package
$9,995
For clients who want the shortest path to permit.
Includes everything in the Jurisdiction-Adapted Plan plus:
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Structural drawings and calculations
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Licensed structural engineer stamp
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MEP engineering per property location
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Licensed MEP engineer stamps
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SIP manufacturer coordination (Premier SIPs)
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Builder handoff package
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One-hour builder Q&A session
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Priority coordination
Turnkey Permit Packages include professional services for one permitted build only.
Additional builds require:
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An Additional Build License per unit
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New site plans
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New engineering coordination and stamps
Delivered 4–6 weeks from receipt of required site information & 50% initial deposit.
All plans are licensed for one constructed project. Engineering stamps and energy models are site-specific and provided during adaptation.
Cold Climate Plan
High-Performance Envelope | Northern Zone Optimized
GC-ADU-490 Cold Climate Plans
Permit-Proven Architectural Plan Set
Instant PDF delivery
$5,995
For builders & homeowners
who want a proven starting point.
Includes:
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Complete architectural plan set (PDF)
-
As-approved reference drawings
-
Floor plan, elevations, sections
-
Foundation & roof plans
-
Electrical, mechanical & plumbing layouts
-
SIP panel logic & coordination notes
-
Single-project license
BONUS: SIP Performance Brief (PDF)
Share this 4-page technical brief with your GC, lender, or building department. Covers cost comparisons, labor efficiency, and financing considerations.
Reference design. Jurisdictional adaptation and engineering required for permit submission.
All plans are licensed for one constructed project. Engineering stamps and energy models are site-specific and provided during adaptation.
Jurisdiction-Adapted
Cold Climate Plan
GC-ADU-490 - High-Performance Envelope
Jurisdiction-Adapted Plan
$8,495
When you want a real permit submission, not a generic reference set.
Includes:
-
LAHJ-specific General Notes (code amendments, local requirements)
-
Energy compliance updates (Title 24 or equivalent)
-
Custom Site Plan prepared for your property
-
Climate, seismic, and fire-zone adjustments
-
Structural note revisions (no stamped drawings yet)
-
One resubmittal coordination round
Delivered 2–4 weeks from receipt of required site information & 50% initial deposit.
Most jurisdictions require an engineer’s stamp for permit issuance. Some jurisdictions also require an architect’s stamp. This package prepares the plan set for submission but does not include professional stamps. All plans are licensed for one constructed project. Engineering stamps and energy models are site-specific and provided during adaptation.
Turnkey Permit Package
GC-ADU-490
Turnkey Permit Package
$10,995
For clients who want the shortest path to permit.
Includes everything in the Jurisdiction-Adapted Plan plus:
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Structural drawings and calculations
-
Licensed structural engineer stamp
-
MEP engineering per property location
-
Licensed MEP engineer stamps
-
SIP manufacturer coordination (Premier SIPs)
-
Builder handoff package
-
One-hour builder Q&A session
-
Priority coordination
Turnkey Permit Packages include professional services for one permitted build only.
Additional builds require:
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An Additional Build License per unit
-
New site plans
-
New engineering coordination and stamps
Delivered 4–6 weeks from receipt of required site information & 50% initial deposit.
All plans are licensed for one constructed project. Engineering stamps and energy models are site-specific and provided during adaptation.
Add On Services
Choose the level of support that matches how quickly you want to move from plan to permit.
Custom Site Plan Design
GC-ADU-490
Site-specific ADU placement prepared
for your property.
$1,500
Includes:
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Property-specific site plan layout
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ADU placement based on provided survey
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Setbacks, access, orientation, and clearances
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Relationship to existing structures
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North arrow, scale, and zoning annotations
Requirements:
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Boundary survey or topographic survey provided by client
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Survey must be prepared by a licensed surveyor
Delivery:
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7–10 business days after receiving complete survey files
Architectural site layout only. Civil engineering, grading, drainage, and utility design not included.
Mirrored Plan Request
(Optional)
GC-ADU-490
Mirrored Plan
$750
Some sites require a flipped orientation due to access, setbacks, or lot constraints.
Available for:
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Standard & Cold Climate Plans
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Jurisdiction-Adapted Plan
This add-on provides a professionally mirrored version of the GC-ADU-490 plan set, reviewed for layout consistency and code alignment.
Note: Mirrored plans are provided as architectural reference drawings. Some jurisdictions may require additional review or engineering adjustments depending on site orientation and local code. If jurisdictional adaptation is required, mirroring will be coordinated as part of that process. All plans are licensed for one constructed project. Engineering stamps and energy models are site-specific and provided during adaptation.
Structural + MEP Engineering
Package
GC-ADU-490
Engineering for Specific Site
$3,500
For builders & homeowners
who want a proven starting point.
Includes:
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Complete architectural plan set (PDF)
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As-approved reference drawings
-
Floor plan, elevations, sections
-
Foundation & roof plans
-
Electrical, mechanical & plumbing layouts
-
SIP panel logic & coordination notes
-
Single-project license
All plans are licensed for one constructed project. Engineering stamps and energy models are site-specific and provided during adaptation.
Additional Build License (Same Plan Set)
GC-ADU-490
Additional Build License
$1,500
Extend your rights to build the same design again.
Each Additional Build License grants permission to construct one additional instance of the GC-ADU-490 design using the same plan set.
Licenses are non-transferable and tied to a single ownership entity.
Important Notes:
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Licenses are non-transferable
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Each build requires its own permit submission
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Jurisdictional adaptation, site plans, engineering, and energy compliance are not included
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Engineering stamps and energy models are site-specific and must be obtained per project
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Additional Build Licenses apply within the same jurisdiction unless otherwise coordinated
Additional Build Licenses do not include:
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Site plan preparation
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Jurisdiction adaptation
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Engineering stamps or calculations
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Energy compliance updates
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Design modifications or mirroring
Stamp Requirements
Important Permitting Notice
Most jurisdictions require at minimum a licensed structural engineer’s stamp for ADU permit submission.
Some jurisdictions additionally require an architect’s stamp depending on local code adoption and enforcement practices.
Guesscreative will confirm stamp requirements for your Local Authority Having Jurisdiction (LAHJ) before proceeding with adaptation or turnkey services.
WHAT OWNERS, BUILDERS & DEVELOPERS CARE ABOUT.
Faster Construction
Factory-cut panels arrive ready to install
55% faster construction compared to stick framing
Walls install at 64 SF per man-hour
Roof panels install at 113 SF per man-hour
11 days saved between snap lines and drywall (2,500 SF benchmark)
Faster dry-in = lower carry costs + tighter schedules.
Predictable Costs
SIP material cost is nearly identical to stick framing
(~$28.88/SF SIP vs. $27.50/SF stick)
Labor savings average $3,440 per unit
HVAC systems can be downsized due to airtight envelope
Net savings: ~$1,900 per unit even before long-term energy savings
The SIP envelope breaks even on materials then pays back through labor and speed.
Long-Term Durability & Value
20-year structural warranty
50-year thermal warranty on insulation core
Proven performance in hurricanes, earthquakes, and high-wind zones
Less settling = fewer drywall cracks and callbacks
Higher resale value due to energy efficiency and durability
This is not short-term construction. It’s long-life building logic.
Why This Design Exists
The GC-ADU-490 was created for clients who want:
Approved precedent, not conceptual drawings
Faster builds, not open-ended timelines
Predictable costs, not labor surprises
Lower operating expenses, year after year
A home that feels right the moment you step inside
Every line survived review. Every panel delivers performance.
This is permit-tested architecture, engineered once and ready to deploy.
If you're curious about other deployable spaces designed by Guesscreative, check out the movable spaces for businesses who go after opportunity.