500 SF
500 SF ADU Floor Plan
A compact concept for guest accommodations, smaller rental units, or efficient backyard infill.
CA Licensed · 99% Permit Approval
Your Trusted California Architects & Structural Engineers
Licensed architects and structural engineers for ADU design, home additions, remodeling, wall removal, and permits. Accurate, permit-ready plans with a 99% approval rate across California.
#1 on Thumbtack · 500+ Reviews
20+ Active Projects Monthly
99% Permit Approval Rate
By the Numbers
California Trusted Architectural & Structural Engineering
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Monthly Active Projects
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Projects Delivered
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Permit Approval Rate
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Professional Team Members
Trust & Collaboration
Approved Plans Across California Cities.
Our architectural and structural plans are consistently approved across California — from Northern to Southern cities. With deep familiarity of local building codes, we help homeowners avoid rejections, shorten review cycles, and secure permits with confidence.
All featured projects are real, city-approved plans.
Our Services
Our Range of Services
Comprehensive design and construction solutions for residential and commercial projects, delivered with expertise and attention to detail.
ADU Design
Custom Accessory Dwelling Unit designs that maximize your property value while maintaining aesthetic harmony.
Wall Removal
Remove load-bearing walls to create more space in your home.
Home Addition
Add extra space to your home with a new room or extension.
Home Remodeling
Transform your home with expert kitchen, bathroom, and living room remodeling.
Building Permit Service
Secure your building permits with our 100% approval rate and complete regulatory compliance guidance.
Foundation Inspection
Expert foundation inspection with detailed structural reports to ensure safety and long-term stability.
ADU Floor Plans
See what your ADU could look like.
Three concept floor plans — from a compact 500 SF studio to a 1,200 SF family-ready layout. Each includes a floor plan and 3D renderings so you can picture the space before committing.
700 SF
700 SF ADU Floor Plan
A balanced concept that begins to separate living, cooking, and resting zones more clearly.
800 SF
800 SF ADU Floor Plan
A mid-size concept that feels more complete for long-term use without becoming oversized.
900 SF
900 SF ADU Floor Plan
A comfort-focused concept for owners who want an ADU that feels closer to a small home.
Browse all ADU floor plans
These are concept layouts. We adapt the final plan to your lot, setbacks, and city permit path.
Why Choose Us
Why Homeowners Choose Cecilia Home
We’re not just another design firm — we’re the most-reviewed architecture firm on Thumbtack, completing 2–3 projects every week across California.
#1 RANKED ON THUMBTACK
The highest-rated and most-reviewed architecture firm on Thumbtack in California — 500+ verified reviews and a 4.9★ rating from real homeowners.
FIXED-PRICE, ALWAYS
We give you the complete, all-inclusive price before you commit — no lowball estimates, no change-order surprises. Just one honest number you can plan around.
DEEP SPECIALIZATION
We complete 2–3 projects of the same type every single week. That’s more hands-on experience in one month than most firms accumulate in a year.
TRUSTED CONTRACTOR NETWORK
We connect you with vetted, licensed contractors we work with repeatedly — no vetting required on your end, no coordination gaps between design and construction.
COMPLETE QUOTE UPFRONT
Share your project details and we respond within 1 business day with a complete, all-inclusive quote. No ‘I’ll need to come see it first,’ no hidden fees added later.
CALIFORNIA PERMIT EXPERTS
Licensed architects and structural engineers with deep knowledge of California codes, city-specific requirements, and a 99% permit approval rate across the state.
Our Process
Our Process
Our process is designed to be transparent and efficient, delivering a complete one-stop service from design to final permit approval.
Guidance for your project
- 01Free Consultation & Fixed-Price Quote
Free Consultation & Fixed-Price Quote
Share your project details and get a complete, fixed-price quote — full scope, full cost, no vague estimates.
Step 120% - 02On-Site Assessment
On-Site Assessment
Precise measurements and site evaluation for accurate project planning.
Step 240% - 03Design Development
Design Development
Creating detailed plans and visualizations to bring your vision alive.
Step 360% - 04Permit Acquisition
Permit Acquisition
Navigating complex approval processes to ensure code-compliant construction.
Step 480% - 05Construction Support
Construction Support
Ongoing guidance and contractor coordination throughout the building process.
Step 5100%
Client Testimonials
Trusted by California Homeowners
Ranked #1 on Thumbtack based on verified reviews from homeowners who relied on our architectural and structural engineering services.
We wanted to build an ADU in our backyard but had no idea where to start. Mason walked us through zoning, setbacks, and the permit timeline. The plans were approved on the first submission—way faster than we expected.
JL
Jennifer L.
ADU Design · Fremont, CA
Removing our load-bearing wall seemed risky, but Mason explained the beam options and provided engineering calcs the city approved right away. Our open-concept kitchen is exactly what we dreamed of.
DK
David K.
Wall Removal · San Jose, CA
We remodeled our entire first floor—kitchen, living room, and bathrooms. Cecilia Home handled all the structural drawings and coordinated with our contractor. The permit process was surprisingly smooth.
PM
Patricia M.
Home Remodeling · Oakland, CA
We wanted to build an ADU in our backyard but had no idea where to start. Mason walked us through zoning, setbacks, and the permit timeline. The plans were approved on the first submission—way faster than we expected.
JL
Jennifer L.
ADU Design · Fremont, CA
Removing our load-bearing wall seemed risky, but Mason explained the beam options and provided engineering calcs the city approved right away. Our open-concept kitchen is exactly what we dreamed of.
DK
David K.
Wall Removal · San Jose, CA
We remodeled our entire first floor—kitchen, living room, and bathrooms. Cecilia Home handled all the structural drawings and coordinated with our contractor. The permit process was surprisingly smooth.
PM
Patricia M.
Home Remodeling · Oakland, CA
Adding 800 sq ft to our home felt overwhelming, but Mason's team made it manageable. From foundation plans to the final permit stamp, every detail was covered. We couldn't be happier with the result.
RH
Robert H.
Home Addition · Sunnyvale, CA
After noticing cracks in our foundation, we called Cecilia Home for an inspection. Mason was honest—he explained which cracks were normal for older Bay Area homes and which needed attention. No pressure, just solid advice.
AS
Angela S.
Foundation Inspection · Berkeley, CA
As a general contractor, getting permits approved quickly is critical. Mason's team delivers accurate plans and handles city comments fast. Our projects run smoother when Cecilia Home is involved.
KV
Kevin V.
Building Permit Service · Concord, CA
Adding 800 sq ft to our home felt overwhelming, but Mason's team made it manageable. From foundation plans to the final permit stamp, every detail was covered. We couldn't be happier with the result.
RH
Robert H.
Home Addition · Sunnyvale, CA
After noticing cracks in our foundation, we called Cecilia Home for an inspection. Mason was honest—he explained which cracks were normal for older Bay Area homes and which needed attention. No pressure, just solid advice.
AS
Angela S.
Foundation Inspection · Berkeley, CA
As a general contractor, getting permits approved quickly is critical. Mason's team delivers accurate plans and handles city comments fast. Our projects run smoother when Cecilia Home is involved.
KV
Kevin V.
Building Permit Service · Concord, CA
Converting our garage into an ADU for my mother-in-law was the perfect solution. The design maximized every square foot, and the city approved the plans with no corrections. Now she has her own private space.
MT
Michelle T.
Garage Conversion ADU · Milpitas, CA
Our 1920s bungalow needed seismic retrofitting before we could refinance. Mason provided the engineering report and retrofit plans the city required. The whole process was faster than our bank deadline.
TW
Thomas W.
Seismic Retrofit · Alameda, CA
We hired Cecilia Home for our kitchen remodel permit drawings. Mason's team was responsive and fixed minor city comments within days. Compared to other engineers we've used, their turnaround time is exceptional.
LC
Laura C.
Kitchen Remodeling · Palo Alto, CA
Converting our garage into an ADU for my mother-in-law was the perfect solution. The design maximized every square foot, and the city approved the plans with no corrections. Now she has her own private space.
MT
Michelle T.
Garage Conversion ADU · Milpitas, CA
Our 1920s bungalow needed seismic retrofitting before we could refinance. Mason provided the engineering report and retrofit plans the city required. The whole process was faster than our bank deadline.
TW
Thomas W.
Seismic Retrofit · Alameda, CA
We hired Cecilia Home for our kitchen remodel permit drawings. Mason's team was responsive and fixed minor city comments within days. Compared to other engineers we've used, their turnaround time is exceptional.
LC
Laura C.
Kitchen Remodeling · Palo Alto, CA
FAQ
Frequently Asked Questions
Find clear answers about our services, timelines, process, and how we help you move from design to permit approval smoothly.
Haven't found what you're looking for?
We provide architectural and structural design for ADUs, home additions, interior remodeling, wall removals, foundations, seismic retrofits, and permit-ready plans. We also handle all building permit submissions and revisions until approval.
We start with a free consultation, then complete your preliminary plans within one week. Final stamped plans typically take 2–3 weeks. Throughout the process, we provide clear communication, 3D visualization when needed, and full support through city review.
Our pricing is based on project scope and complexity. We offer transparent, fixed-price packages for common services such as ADUs and additions, and provide detailed quotes during your free consultation with no hidden fees.
Preliminary plans are completed in 1 week, and final plans take 2–3 weeks. City review timelines vary by city, but ADU permits typically take 2–3 months. We keep you updated throughout each stage.
Yes. We help you optimize your design based on your budget and provide cost-conscious recommendations while maintaining structural safety and code compliance.
Simply contact us to schedule a free consultation. We’ll review your project goals, timeline, and budget, then prepare a customized proposal. Virtual meetings are available.