7 Essential Steps to Plan Your ADU Construction Project

Planning to build an Accessory Dwelling Unit (ADU)? Here's a quick guide to get you started:

Set clear goals for your ADU
Assess your property's suitability
Plan your finances and budget
Design your ADU
Select a qualified builder
Obtain necessary permits
Create a construction schedule

Quick facts:

ADUs typically range from 600 to 1,200 square feet
Average costs: $32,000 to $300,000+ depending on type
Permit approval can take 1 to 6 months
Construction timeline: 7 to 18 months on average

Key considerations:

Check local zoning laws and building codes
Factor in 10-15% extra for unexpected costs
Choose contractors with ADU-specific experience
Design for future needs and accessibility

By following these steps and keeping these points in mind, you'll be well-prepared to tackle your ADU project. Remember, thorough planning is crucial for a successful build.

What is an ADU?

An Accessory Dwelling Unit (ADU) is a secondary living space on the same property as a main house. It's like having a mini-home in your backyard or attached to your house.

ADUs are self-contained living spaces. They have their own kitchen, bathroom, and living area. But here's the key: they're always smaller than the main house and on the same lot.

The Los Angeles City Ordinance No. 186481 defines an ADU as:

"An attached or detached residential dwelling unit provides complete independent living facilities for one or more persons and is located on a lot with a proposed or existing primary residence."

ADUs usually range from 600 to 1,200 square feet. That's enough space for comfortable living without overshadowing the main house.

Types of ADUs

ADUs come in different flavors:

Detached New Construction: A standalone structure in your backyard. Think of it as a tiny house behind your main house.
Garage Conversion: Turn that old garage into a cozy living space.
Basement Conversion: Transform your unused basement into an apartment.
Attached ADU: An addition to your existing home, like an in-law suite.

Here's a quick look at these ADU types:

ADU Type	What It Is	Typical Size	Common Use
Detached New Construction	Backyard standalone	500-1,200 sq ft	Rental or guest house
Garage Conversion	Transformed garage	220-500 sq ft	Home office or studio
Basement Conversion	Basement turned apartment	~760 sq ft	Long-term rental
Attached ADU	Addition to main house	Varies	Family living space

Why Build an ADU?

Adding an ADU to your property can be a game-changer. Here's why:

Extra Cash: In hot rental markets like Portland, where apartments go for about $2,000 a month, an ADU can be a nice income boost.
Property Value Boost: A well-designed ADU can make your home more valuable and attractive to future buyers.
Flexible Living: Need space for aging parents or adult kids? Want a home office? An ADU can adapt to your changing needs.
Affordable Housing: In tight housing markets, ADUs offer more budget-friendly rental options compared to regular apartments.
Smart Use of Space: Got an old garage or unused basement? An ADU can turn that wasted space into something useful.

But remember, ADUs aren't all sunshine and rainbows. They come with their own set of challenges and considerations.

Maxable, an ADU consultation company, says:

"After consulting with 4000 homeowners about their ADUs, and seeing 300 of them completed so far, we've pretty much got ADUs down to a science!"

This shows that ADUs are becoming more popular, and there's a lot of expert knowledge out there to help homeowners navigate the process.

Step 1: Set Your Goals

Setting clear goals is key to a successful ADU project. It'll help you make smart choices throughout the process. Here's what to focus on:

Planned Use

Figure out how you'll use your ADU. This decision will shape everything else.

Common ADU uses include:

Rental unit for extra income
Housing for family members
Home office
Guest house

Each use has its own considerations. For a rental, you'll need to check local regulations. For family housing, think about privacy and accessibility.

Money Limits

Set a realistic budget. ADU costs can vary a lot based on size, location, and finishes.

Here's a tip: Add 10-20% to your initial budget for unexpected costs. Trust us, they always pop up.

Project Schedule

Map out your timeline. Here's a rough guide:

Design: 1-2 months
Permitting: 3-4 months
Construction: 4-6 months

But remember, your timeline might be different. Local rules and contractor availability can change things.

Design Needs

Think about both looks and function. Consider:

Size: How big can it be? Check local rules.
Style: Match your main house or go for something different?
Features: What do you NEED in your ADU?

Maxable, an ADU expert, says:

"After consulting with 4000 homeowners about their ADUs, and seeing 300 of them completed so far, we've pretty much got ADUs down to a science!"

This shows how important good planning is. Set clear goals, and you're off to a great start.

Step 2: Check Your Property

Before diving into your ADU project, you need to make sure your property can handle it. Here's what to look at:

Land Review

Take a walk around your property. What do you see?

How much space do you have?
What's already there?
Any trees or slopes to work around?

Remember: Your ADU can be up to 900 square feet or half your main house size, whichever is smaller. So grab that measuring tape!

Zoning Rules

Local laws can make or break your ADU dreams. Check these out:

Are ADUs even allowed where you live?
How big can they be?
Where can you put them?
What about parking?

Take San Mateo County, for example. They've got specific ADU rules for both non-coastal and coastal areas. You'll find them in Chapters 22.5 and 22.5.1 of their ADU Regulations.

"After consulting with 4000 homeowners about their ADUs, and seeing 300 of them completed so far, we've pretty much got ADUs down to a science!" - Maxable

Distance Rules

Setbacks are a big deal. Here's a quick look at typical requirements:

Location	Typical Setback
Side and rear property lines	4 feet
Corner lot (street side)	15 feet
From main house	5 feet
Front of property	4 feet (as of 2023)

But don't take our word for it. Always check your local rules!

Utility Access

Your ADU needs the basics:

Water
Electricity
Sewer or septic

No easy access? Your wallet might feel the pinch.

Site Conditions

Last but not least, look at your actual site:

Is it flat? Sloped?
Where does water go when it rains?
How's the sunlight?

Pro tip: Try tools like Symbium.com for an ADU report on your property. It'll show you what's possible.

Step 3: Plan Your Money

Building an ADU isn't cheap. Let's break down the costs and funding options.

Price Planning

ADU costs vary based on type. Here's a quick overview:

ADU Type	Cost per Sq Ft	Total Cost
Prefab modular	$80 – $160	$32,000 – $192,000
Attached	$125 – $225	$50,000 – $270,000
Detached	$150 – $250	$60,000 – $300,000
Above garage	$200 – $500+	$80,000 – $600,000+
Basement conversion	$50 – $100+	$20,000 – $120,000+
Garage conversion	$50 – $200	$20,000 – $240,000

Keep in mind: These are averages. Your actual costs might be different.

Money Sources

How can you pay for your ADU? Here are some options:

Home Equity Loans/HELOCs: 56% of California ADU builders use these.
Cash-Out Refinancing: You'll need about $200,000 in home equity.
Renovation Loans: RenoFi offers loans up to 90% of future home value.
Unsecured Personal Loans: LightStream provides $5,000 to $100,000 loans.

Justin Goldman, Co-Founder and CEO of RenoFi, puts it bluntly:

"Simply put, recent homebuyers are stuck between a rock and a hard place as it can take a decade or more to build up the equity needed to tackle their renovation wishlist."

Cost Breakdown

Where does all that money go? Here's a typical breakdown:

Cost Category	Price Range
Design and Planning	$6,000 – $14,000
City Fees	$3,000 – $11,000
Construction Labor and Materials	$175 – $350 per sq ft
Finish Materials	$50 – $100 per sq ft

Labor is a big chunk - usually 40% to 60% of your total costs.

Extra Funds

Always plan for surprises. Set aside 10-15% of your budget for unexpected costs. For a $150,000 ADU, that's an extra $15,000 to $22,500.

Building an ADU isn't cheap, but with careful planning and the right financing, it can be a smart investment.

Step 4: Plan Your Design

Designing your ADU is where the rubber meets the road. Let's dive into the key elements:

Room Layout

Think flow when planning your ADU's layout. Open floor plans can make smaller spaces feel bigger and brighter. And don't forget about multi-functional areas - they're a game-changer in tight spaces.

Take this real-world example: A San Diego homeowner built an ADU for her 95-year-old mother-in-law. Their focus? An open layout with wide doorways for easy mobility.

Building Style

Your ADU should look like it belongs with your main house. Match or complement the exterior materials, and carry over key design elements.

Here's a quick guide:

Main House Style	ADU Design Approach
Craftsman	Wood trim and earthy colors
Modern	Clean lines and large windows
Victorian	Decorative elements and gabled roofs

Space Needs

Size matters - and it's often limited by local rules. In Boise, Idaho, ADUs can't exceed 900 square feet or the size of the main house (whichever is smaller). Nampa, Idaho caps them at 500 square feet.

When planning your space, you'll typically need a living area, kitchen, bedroom, and bathroom. Get creative with storage - built-in shelving and under-bed storage can be lifesavers.

Main House Match

Your ADU should look like it belongs. Use similar or complementary colors to the main house. Extend this to your landscaping too - use similar plants and hardscaping for a cohesive look.

Here's a fun fact: The National Association of Realtors says homes with ADUs are priced 35% higher on average than those without. Not too shabby!

"No one knows how best to design a desirable and accommodating ADU than the occupant themself!" - Maxable

This quote nails it. Whether you're building for family or future renters, getting their input can make all the difference.

Step 5: Pick Your Builder

Finding the right builder for your ADU is crucial. Here's how to do it:

Find Builders

Start with THE BEST ADU BUILDERS. It's a platform that connects you with ADU pros across the US. Just submit your project details and get matched.

Other options? Try GreatBuildz, Houzz, or BuildZoom. They offer contractor ratings and reviews to help you choose.

Check Skills

Look for builders with ADU-specific experience. Here's what matters:

Skill	Why It's Important
ADU regulation know-how	Keeps your project legal and on budget
ADU project history	Shows they've done this before
Local involvement	Indicates they're in it for the long haul

Paul Dashevsky from GreatBuildz says it best:

"I had a lot of good experiences, and I had a lot of bad experiences."

Compare Prices

Get at least three bids. But don't just go for the cheapest option. David Lang, an LA builder, warns:

"Always get at least three bids, because in this industry... there's a lot of thievery."

When reviewing quotes, look for:

Detailed cost breakdowns
Construction phase timelines
How they handle surprises

Past Work

Talk to previous clients. Ask about:

How the builder communicates
If they stuck to the timeline
The quality of their work
How they dealt with problems

If you can, check out some finished ADUs in person.

Legal Papers

Make sure your builder has the right paperwork:

Document	Why You Need It
Contractor's license	Check it with the Licensing Board
Liability insurance	Covers potential claims
Worker's comp	For on-site accidents

Danny Shuster from Construction & Consulting Services nails it:

"You don't shop around for a price... You literally shop around for the right rep from the right company."

In California, any job over $500 needs a licensed contractor. Use the Licensing Board's search tool to check credentials.

Step 6: Get Permits

Getting permits for your ADU is a key step. Here's how to tackle it:

Building Rules

Cities have different ADU rules. You need to know about:

Zoning laws: Where and how big you can build
Building codes: Safety and quality standards

In San Diego, for instance, you can build ADUs up to 1,200 square feet on most residential lots. But always check your local rules!

Required Papers

Get these ready:

Document	Why You Need It
Permit application	To officially ask for approval
Property ownership proof	To show you can build there
Site plans	To show where the ADU will go
Construction plans	To detail your ADU specs
CalGreen checklist	To meet green building rules

Pro tip: Put the CalGreen checklist in your plans. California requires it for new buildings.

Filing Steps

1. Talk to experts

Local ADU builders or architects know the process well.

2. Get your papers ready

Make sure everything's correct.

3. Submit your application

File it with the local building department.

4. Pay the fees

Expect to pay at least $1,500 for permits and checks.

"You might spend $10,000 before you even start building!" - ADU Expert

Wait Times

In California:

Agencies must respond within 60 days
First review: 10 business days to a month
Total approval: 1 to 6 months

But here's some good news: San Jose offers same-day approval for pre-approved ADUs!

Step 7: Make a Schedule

A solid schedule is key for your ADU project. Here's how to break it down:

Building Steps

Here's what a typical ADU construction timeline looks like:

Phase	Duration	Key Tasks
Pre-construction	1-4 weeks	Site prep, final permitting
Foundation	2-3 weeks	Excavation, footings, foundation walls
Framing	3-4 weeks	Wall and roof framing, rough plumbing/electrical
Exterior	2-3 weeks	Roofing, siding, windows, doors
Interior	4-6 weeks	Insulation, drywall, finishes
Mechanical	2-3 weeks	HVAC, plumbing, electrical systems
Finishing	3-4 weeks	Trim, painting, flooring, fixtures

Keep in mind: This is just a guide. Your project might be different.

Critical Moments

Don't forget to mark these in your schedule:

Permit approval
Foundation pour
Framing inspection
Utility connections
Final inspection

These often need sign-offs before you can move forward. Plan for them.

Expect the Unexpected

Delays happen. Here's how to deal:

1. Weather buffer

If you're starting in spring, add extra time. Rain might slow things down.

2. Order early

Some items, like windows and custom cabinets, can take a while to arrive. Order them ASAP.

3. Flexible inspections

When you schedule inspections, give yourself a few days of wiggle room.

Pro tip: Add a 2-3 week buffer to your overall timeline. You'll thank yourself later.

Timing is Everything

Coordinating different trades is crucial. Here's how:

1. Get the order right

Make sure electricians and plumbers finish their rough-ins before the drywall goes up.

2. Multitask when possible

While the exterior work is happening, start on interior tasks.

3. Keep everyone in the loop

Use a shared calendar or project management tool. It'll save you headaches later.

"The average ADU construction timeline is around 7 to 18 months, from signing an agreement to the final inspection." - Maxable

That's a big range, right? Your timeline depends on your project's complexity, local rules, and how efficient your contractor is.

Helpful Tools

Building an ADU isn't a walk in the park. But don't worry - we've got your back with some handy tools to keep you on track.

Project Checklist

First things first: you need a game plan. Here's a quick checklist to get you started:

Check local zoning laws
Assess your property
Decide on ADU type and size
Set your budget
Hire an architect or designer
Get those construction plans rolling
Submit permit applications
Pick your contractor
Nail down the construction schedule
Break ground and start building

Cost Sheet

Money talks, so let's keep it in check. Use a cost sheet like this:

Category	Estimated Cost	Actual Cost	Difference
Design fees	$	$	$
Permits	$	$	$
Site preparation	$	$	$
Foundation	$	$	$
Framing	$	$	$
Roofing	$	$	$
Electrical	$	$	$
Plumbing	$	$	$
HVAC	$	$	$
Finishes	$	$	$
Total	$	$	$

Pro tip: Stash away 10-15% extra for those "oops" moments. Trust us, they happen.

Builder Chart

Choosing a contractor? Compare apples to apples with this chart:

Criteria	Builder A	Builder B	Builder C
Years of experience
ADU-specific projects
License & insurance
References
Estimated timeline
Cost estimate
Communication style
Warranty offered

Schedule Form

Time is money, folks. Keep tabs on your timeline:

Phase	Start Date	End Date	Duration	Status
Design
Permitting
Site prep
Foundation
Framing
Rough-ins
Insulation
Drywall
Finishes
Final inspection

Permit List

Permits: can't live with 'em, can't build without 'em. Keep track:

Permit Type	Required	Submitted	Approved
Building permit	☐	☐	☐
Electrical permit	☐	☐	☐
Plumbing permit	☐	☐	☐
HVAC permit	☐	☐	☐
Zoning approval	☐	☐	☐
Site plan review	☐	☐	☐

Want to go high-tech? Check out project management software like Buildertrend. It's like having a personal assistant for your ADU project - tracking budgets, storing docs, and keeping everyone in the loop.

And here's a nugget from Leila Banijamali, CEO of Symbium:

"Our primary focus is streamlining the regulatory aspects of residential construction."

Speaking of Symbium, their "Build" tool is pretty nifty. It helps you visualize your ADU on your property and checks if you're playing by the local rules. Pretty cool, right?

Wrap-up

Building an ADU isn't a walk in the park, but it can be a game-changer for your property. Let's break down the must-knows:

Do your homework Don't jump in blind. Check local laws first. Greg Popovich from Maxable puts it bluntly: "Change orders are the death of getting an economical ADU." Know what's allowed before you start.

Plan like a pro Take time to design and plan. Look at your property, set clear goals, and make a realistic budget. And here's a pro tip: add 10-15% extra for surprises.

Pick your team carefully Work with ADU experts. They know the rules and can save you from costly mistakes. One expert warns: "Not having a cost change clause could cost you dearly."

Think ahead Design for the future. Consider features that make your ADU accessible and adaptable. Your needs might change, and your ADU should be ready for it.

Budget smart ADUs can cost anywhere from $80,000 to $400,000. Don't forget extras like utility meters - electricity alone can set you back $2,000 to $5,000.

Navigate the red tape Permits and approvals can take 1 to 6 months. Factor this into your timeline.

Stay in the loop Even with pros on the job, keep an eye on things. Regular check-ins can catch issues early and keep your project on track.