Navigating ADU Rules in Historic Areas

Want to add an ADU to your historic property? Here's what you need to know:

ADUs are allowed in historic districts, even on historically listed homes
Design must match the historic style and use appropriate materials
Most historic areas only allow converted ADUs or new ones hidden from street view
Size limits are typically 150-1000 sq ft, depending on lot size and local rules
You'll need a Certificate of Appropriateness (COA) and possibly a historic resource assessment

Quick comparison of new vs. converted ADUs in historic areas:

Aspect	New ADUs	Converted ADUs
Allowed	Not visible from street	Yes
Size	150-1000 sq ft	No limits
Setbacks	4 ft from lot lines	None for existing
Distance from main house	6 ft minimum	No minimum

Key tips:

Work with local preservation commissions early in the process
Hire architects and builders experienced with historic properties
Be prepared for a longer approval process (2-6 months)

With careful planning, you can successfully add an ADU to your historic property.

Historic District Rules

Building an ADU in a historic area? You'll need to know the rules. These areas have special standards to keep their unique look while allowing new additions. Let's break it down.

Basic Historic Area Rules

Historic districts have strict rules to protect their character. Here's what you need to know:

You'll need a Certificate of Appropriateness (COA) for any outside changes, including your ADU.
Many districts don't want new buildings visible from the street.
Your ADU usually needs to be smaller than your main house and sit behind it.
The new structure should match the historic look of the area.

The LNA's Exploratory Historic District Committee reports: "In 2016, every ADU proposed in the historic districts of Irvington and Ladd's Addition was approved." So yes, you CAN build an ADU in a historic area if you follow the rules.

Federal Historic Standards

The Secretary of the Interior's Standards guide ADU projects in historic districts. These federal rules make sure new additions fit in. They say you should:

Keep important materials and architectural features.
Make sure new work looks different from old work, but still fits in.
Don't remove historic materials or change key features of the property.

Even in states with tough preservation laws, like California, you can build ADUs on historic properties if you meet certain criteria.

Types of Historic Districts

Different historic districts have different rules for ADUs. Here's a quick look:

District Type	What It Is	How It Affects ADUs
National Register Districts	Recognized by the federal government	Might be more flexible
Local Historic Districts	City-specific rules	Usually need more review
Conservation Districts	Focus on neighborhood character	Might allow modern designs if they fit in
Landmark Districts	Protect specific landmarks	Often have the toughest rules

San Diego County has several historic districts, each with its own style:

Old Town San Diego: Spanish and Mexican influences
Gaslamp Quarter: Victorian-style buildings
Mission Hills: Craftsman and Spanish Colonial Revival homes

Each district might have specific rules about ADU construction, from materials to style.

The Los Angeles City Planning Department says: "Getting an ADU permit in a Historic Preservation Overlay Zone (HPOZ) involves steps like checking the property's historic status and reviewing preservation guidelines."

When planning an ADU in a historic district:

Talk to local preservation experts early on
Work with architects who know historic preservation
Make detailed plans showing how your ADU will fit in
Know both zoning laws and historic preservation rules

Getting Started

Want to build an ADU in a historic area? Here's how to kick things off.

Property Check List

First, make sure your property fits the bill:

Item	What to Check
Historic Status	Is it 45+ years old, historic, or in a historic district?
Lot Size	Does it meet the minimum for an ADU?
Zoning	Does your zone allow ADUs?
Setbacks	Got enough space to meet requirements?
Visibility	Can you build an ADU out of street view?

Historic Status Effects

Your property's history matters:

Designated Historic: Tougher rules. You'll need a Certificate of Appropriateness for exterior changes.
In Historic District: Design must fit district guidelines and federal standards.
45+ Years Old: Might need extra review, even without official historic status.

"In San Diego, ADU permit reviews in historic districts take about 10 business days for simple projects, up to 20 for complex ones." - San Diego City Planning Department

Zoning Rules

Know your local zoning:

Check if ADUs are allowed in your zone.
Size limits depend on your lot and main house size.
Height caps are usually 16-18 feet for detached ADUs.
Side and rear setbacks? Often 4 feet minimum.

Pro Tip: Sacramento offers a choice: Local ADU Ordinance or State ADU Standards. Each has perks, so check both.

Building Standards

Key ADU standards in historic areas:

New ADUs must be at least 150 square feet.
Max size varies. Some places cap at 850 sq ft (1,000 for 2+ bedrooms).
Design must match the main house's historic look.
Keep 6 feet between your house and a detached ADU.

In most historic districts, you're limited to converted ADUs or new ones hidden from the street.

Design Rules

Adding an ADU to a historic area? You'll need to follow some specific design rules. Let's break them down.

Matching Historic Style

Your ADU should fit in with your main house and the historic neighborhood. It doesn't have to be an exact copy, but it should look like it belongs.

Here's how different levels of integration stack up:

Integration	What It Means	Cost
Complementary	Similar materials, not identical	Most affordable
HOA-Level	Closer match, careful coordination	Mid-range
Seamless	Nearly identical look	15-20% more than standard

In San Antonio's historic districts, ADUs must match the main house's style, look, and character. This includes using similar materials, windows, and roof styles.

Size Rules

Historic areas often have stricter size limits for ADUs. Here's a quick guide:

Smallest allowed: 150 square feet
Largest allowed: Depends on your lot and main house size

For smaller lots (under 10,000 square feet):

Up to 850 square feet (1,000 if it has 2+ bedrooms)

For bigger lots (10,000+ square feet):

Up to 850 square feet (1,200 if it has 2+ bedrooms)

Attached ADUs? They're usually limited to half the size of your main house or 800 square feet, whichever is bigger.

Approved Materials

Using the right materials is key. While rules vary, here are some general tips:

Exterior siding should match or complement your main house
Roofing should fit the historic look
Windows and doors should use materials typical for the time period

In South Pasadena, they follow the Secretary of the Interior's Standards for historic properties when choosing materials.

Window and Door Rules

Windows and doors are crucial for keeping that historic look:

Keep original windows and doors if possible
New windows should match your main house's style
For detached ADUs, main doors must be at least 8 feet from side property lines
Second-story windows close to property lines need to be designed for privacy

Space Between Buildings

Proper spacing keeps your ADU from overwhelming your main house:

At least 6 feet between your house and a detached ADU
Detached ADUs go behind the main house
The ADU shouldn't block too much light from neighbors

"In 2016, every ADU proposed in the historic districts of Irvington and Ladd's Addition was approved", says the LNA's Exploratory Historic District Committee. This shows that with careful planning, you CAN add an ADU to your historic property.

Getting Permits

Getting permits for your ADU in a historic district isn't a walk in the park. But don't worry - it's doable. Here's how to tackle it:

Required Papers

For ADU approval in a historic area, you'll need:

Certificate of Appropriateness (COA)
Detailed architectural plans
Historic resource assessment
Site plan showing ADU location
Materials and finishes list

In San Diego? Heads up: projects in historic districts need extra paperwork. A thorough historic resource report can speed things up.

Historic Board Review

Getting the historic board's thumbs up involves:

1. Pre-application meeting

Chat with the preservation commission about your plans.

2. Design review

Show off your ADU design to the board.

3. Public hearing

Some projects need the community to weigh in.

4. Revisions

Be ready to tweak your plans based on feedback.

Leah Kabli, founder of TheBestADUBuilders.com, says: "Talk to preservation commissions early. It'll save you headaches - and cash - down the road."

Building Permits

Got historic approval? Great. Now for building permits:

Submit your application online through your city's planning department.
Pay the fees.
Wait for plan check review (10-20 business days for historic properties).
Handle any corrections or info requests.
Get your permit.

Common Problems

Watch out for these snags:

Problem	Solution
Design doesn't fit	Team up with an architect who knows historic preservation
Missing paperwork	Use a checklist to cover all your bases
ADU visible from street	Try a different spot or go for a converted ADU
Wrong materials	Stick to historically appropriate stuff

Time Frames

Permits in historic districts take longer:

COA: 15 days for staff review, more if there's a public hearing
Building permit review: 10-20 business days
Total process: 2-6 months, depending on complexity and changes needed

Don't forget: there's a 10-day appeal period after the COA decision before you can grab your building permit.

Hiring Help

Building an ADU in a historic area? You'll need the right team. Here's how to find the best pros for your project:

Historic Expert Help

A preservation expert can be a game-changer for your historic district ADU. Why? They:

Know historic building materials and techniques inside out
Can guide you through the approval maze
Make sure you're following all the preservation rules

"Good craftsmen and contractors are key to protecting your historic building during a project." - Preservation Expert

When to hire: Right at the start. They can help with:

Making a preservation plan
Writing grant applications
Setting up maintenance schedules

Finding ADU Builders

Not all builders can handle historic properties. Look for:

What to Check	Why It's Important
Historic district experience	They know the unique challenges
Traditional trade knowledge	They can use historic methods
Modern code understanding	They balance old and new
Historic project portfolio	They've done similar work before

Pro Tip: Ask builders about their experience with the Certificate of Appropriateness (COA) process in your area.

Working with Architects

For historic district ADUs, an architect isn't just helpful - they're a must. Here's why:

1. They Know Their Stuff

Architects with historic preservation experience can:

Design ADUs that fit with your historic property
Navigate tricky zoning and preservation laws
Get creative within historic guidelines

2. They Manage the Project

A good architect will:

Oversee the whole construction process
Make sure you're following all the rules
Keep your project on time and on budget

3. They Can Save You Money

Hiring an architect might seem pricey at first, but they can save you money by:

Avoiding expensive mistakes
Suggesting smart design solutions
Helping you get permits faster

"Talk to preservation commissions early. It'll save you headaches - and cash - down the road." - Leah Kabli, TheBestADUBuilders.com founder

Finding Builders Online

These days, you can find qualified ADU builders online. Sites like TheBestADUBuilders.com can help. Here's how:

Use filters to find builders with historic district experience
Check that builders are licensed and insured
Read reviews from other historic area homeowners
Look at portfolios for historic ADU examples

Online directories are a good start, but don't stop there. Meet with potential builders to talk about your specific project needs and challenges.

Quick Reference Charts

Adding an ADU to a historic property? These charts break down the key rules and requirements.

New vs. Converted ADU Rules

Aspect	New ADUs	Converted ADUs
Allowed in historic properties	Usually not	Yes
Size	150-1000 sq ft	No limits
Setbacks	4 ft from lot lines	None for existing structures
Distance from main house	6 ft minimum	No minimum
Exterior access	Separate, not on main façade	Separate, flexible placement
Windows and doors	Match historic style	Keep original when possible

Historic District Checklist

Requirement	Timeframe	Notes
Certificate of Appropriateness (COA)	15 days (staff review)	Longer if public hearing needed
Historic resource assessment	Before applying	For 45+ year old properties
Architectural plans	With COA application	Show ADU in historic context
Materials and finishes list	With COA application	Should complement main house
HPOZ Board review (if needed)	Varies	Check local meeting schedule
Building permit review	10-20 business days	Longer for complex projects
Appeal period	10 days after COA decision	Wait before getting building permit

The LNA's Exploratory Historic District Committee reports: "In 2016, every ADU proposed in the historic districts of Irvington and Ladd's Addition was approved." So, with good planning, you CAN add an ADU to your historic property.

These charts give you a quick overview, but remember: each project is unique. Always check with your local planning department for the most up-to-date rules and requirements.

Summary

Building ADUs in historic areas? It's doable, but tricky. Here's what you need to know:

ADUs are allowed in historic districts, even on lots with historically listed homes. But there's a catch: design is key. Your ADU must fit in with the historic vibe. Think matching materials and style.

Location matters too. In most historic areas, you're looking at converted ADUs or new ones that can't be seen from the street.

Size? It's usually more limited in historic districts. Expect between 150 to 1,000 square feet, depending on your lot and local rules.

And heads up: the approval process is more involved. You'll need a Certificate of Appropriateness (COA) and maybe a historic resource assessment.

Here's a quick comparison of new vs. converted ADUs in historic areas:

Aspect	New ADUs	Converted ADUs
Allowed in historic properties	Usually not visible from street	Yes
Size	150-1000 sq ft	No limits
Setbacks	4 ft from lot lines	None for existing structures
Distance from main house	6 ft minimum	No minimum

Good news: it's not impossible. The LNA's Exploratory Historic District Committee reports:

"In 2016, every ADU proposed in the historic districts of Irvington and Ladd's Addition was approved."

But don't go it alone. Leah Kabli from TheBestADUBuilders.com says:

"Talk to preservation commissions early. It'll save you headaches - and cash - down the road."

Smart advice. Planning ahead and working with local preservation commissions can make your historic ADU dream a reality.

Navigating ADU Rules in Historic Areas