Why “Get Three Bids” Doesn’t Work for ADUs (and What to Do Instead)

Getting three bids sounds like the responsible thing to do. But when it comes to accessory dwelling units (ADUs), chasing bids can cost you more than it saves.

Most homeowners think they’re doing the smart thing: “I’ll get three bids. Then I’ll pick the best price.” And that approach used to make sense, especially for straightforward remodels or home improvements. But ADUs are a different animal.

You’re not just comparing labor and materials; you’re comparing how each builder defines the ADU project itself.

You need builders who are willing to invest time upfront and show their work. Otherwise, you’re not comparing bids. You’re comparing guesses.

The Real Origin of “Get Three Bids”

The idea that homeowners should always get three bids didn’t come from building codes, a consumer protection agency, or any contractor best-practice guide.

It came from… the Yellow Pages.

In the 1960s and ’70s, the Yellow Pages were the place to find service providers. But they had a problem: People would look up a single plumber, electrician, or contractor—and then stop. So they started running print ads and literally included this tagline:

“Always get at least three estimates.”
…and then conveniently listed three companies right next to each other.

It was brilliant marketing for the Yellow Pages—not necessarily for homeowners. Over time, the phrase became conventional wisdom, even though it had nothing to do with better construction outcomes.

Why “Get Three Bids” Fails for ADUs

We totally understand where the instinct comes from. Getting multiple quotes feels like due diligence. But that only works if everyone is bidding on the exact same scope. When it comes to ADUs, that almost never happens.

1. You can’t get three people to price the same thing

In a kitchen remodel, everyone’s quoting the same cabinets, countertop, and layout. Easy comparison.

With an ADU, there are hundreds of variables before you ever break ground—grading, utility tie-ins, setbacks, easements, fire access, solar requirements, what kind of retaining wall you’ll need. It’s a mind blowing list of considerations before even getting to the interior layout of the ADU.

So unless all three builders are working from the same detailed site study and a build-ready plan set, you’re not comparing prices on the same project. You’re comparing three different guesses. And even that plan set doesn’t tell the full story.

Most architects draw what’s required for permits, not what’s required to actually build the project. The plans usually don’t include utility trenching routes or power upgrade requirements, topographical maps & full foundation plans, driveway or flatwork restoration, finish selections or fixture costs. Those details are the difference between a “$300K” bid and a $450K final price.

So when builders price from incomplete information, each one is making their own assumptions.

One might assume flat lot conditions, another assumes trenching through rock, another leaves it out entirely.

The only way to get a truly comparable number is to start with a complete scope of work, grounded in a feasibility study that captures both what’s on the plans and what’s still below the surface.

2. The cheapest bid is often the most expensive outcome

Builders know when they’re being price-shopped. To stay in the game, some intentionally exclude high-cost items (like trenching, power upgrades, or retaining walls) or list allowances that are way too low.

It makes their number look good. Until change orders start rolling in. If a builder isn’t investing time to understand your site and document their assumptions in writing, their number isn’t a bid—it’s a marketing tactic.

Learn more about how to compare ADU builder quotes the right way.

3. Even finding three legitimate design-build bidders is unrealistic

In San Diego, there are only a handful of firms that do true design-build ADUs—meaning they handle zoning, design, engineering, permitting, and construction under one roof.

When homeowners try to “get three bids,” they usually end up comparing three very different kinds of companies:

General contractors who need your plans before they can quote.

Most general contractors aren’t equipped to design, permit, or estimate an all-in ADU project price upfront. They can only price work once a full set of construction drawings exists—which means they’re bidding off someone else’s design, not guiding it. That can create finger-pointing later when costs go up (“we just built what was drawn”). These GCs might give you a quick number to stay in the conversation, but it’s rarely grounded in site realities or permitting constraints.

Designers who don’t build and can’t price today’s real costs

Architects or designers can produce beautiful plans, but unless they’re deeply involved in construction, they don’t have current all-in build costs. They may draw features, sizes, or layouts that blow the budget, or miss practical issues like trenching distance, construction access, or grading challenges. When you later take those plans to a builder, you’ll often discover the design can’t be built within your target budget.

Online ADU brokers who send your info to whoever answers the phone first

These middlemen act as lead generators, not builders. They’ll collect your information and “match” you with contractors, often with little to no vetting or local expertise. You might get calls from random GCs who have never even built a standalone ADU, or who don’t understand your city’s rules. It can feel like progress at first, but it’s really just noise that burns time and creates confusion.

Only a true design-build partner can tie all the moving parts together, understanding design intent, local code, site conditions, and cost implications in real time. That’s how you end up with a number that means something, not three that don’t.

Learn more about different kinds of ADU companies in San Diego. Also read more about the design-build approach.

4. You’re not buying a number… you’re choosing a partner & a process

Most homeowners start by asking, “What will it cost?” But the real question is, “How will we figure out what it costs… and who will help me get there?”

A legitimate ADU bid isn’t a fixed quote; it’s a living roadmap that evolves as your design, site data, and decisions come into focus. Every property has unknowns—utilities, grading, access, soil, fire requirements—and every choice you make changes the outcome.

That’s why serious builders treat pricing as a process, not a one-time number. The most accurate ADU budgets are built in stages.

When you skip diligence or rush to compare quick quotes, you’re really comparing assumptions, not reality.

ADUs take months of design, permitting, and collaboration. You want someone who communicates clearly, flags risks early, and explains the “why” behind every decision… not someone who started the relationship by tossing out a guess in a recycled Word document.

The right partner helps you feel informed and confident through the process, not confused or pressured by numbers that keep changing.

In the end, one comprehensive, transparent estimate—built with you, not for you—is worth far more than three incomplete ones that only tell part of the story.

Why Cost-Per-Square-Foot Pricing Tells You Nothing Without Context

While we’re dismantling myths, let’s tackle another one that comes up all the time:

“So, what’s your cost per square foot?”

It sounds like a logical way to compare builders. But when it comes to ADUs, cost per square foot is one of the most misleading metrics out there. Here’s why.

1. ADUs have heavy fixed costs

Whether your ADU is 400 square feet or 1,200, you still need the same major infrastructure… sewer and water tie-ins, power upgrades, trenching, mobilizing dozens of trades, site protection & dumpsters, project management, and city fees. Those fixed items make up a big portion of the total cost.

A smaller ADU doesn’t mean it’s cheaper per square foot—it just means those fixed costs are spread over fewer square feet. So your 400 SF ADU will be eye-wateringly expensive on a cost-per-square-foot basis.

Read more about cost per square foot ranges for different ADU sizes — and just the unit itself so we know what we are comparing.

2. Site conditions can swing costs by six figures

Flat, accessible lot with short utility runs? Easy day. Hilly property with retaining walls, long trenching, or fire access requirements? That’s a completely different animal.

If a builder throws out a $/SF number without asking about your slope, driveway, or utility distance, they’re not actually pricing your project..

Read about the many hidden utility and sitework costs that go into an ADU.

3. What’s included (or excluded) changes everything

Some builders quote $/SF numbers that cover just the structure itself—no design, no permitting, no grading, no solar, no utility hookups. Others include everything from concept to keys.

Without a clear list of inclusions and exclusions, a low $/SF number tells you absolutely nothing about what you’ll really pay.

4. Finishes make a big difference

Cabinets, flooring, windows, roofing—these all vary wildly. A builder might assume $10K for an entry-level kitchen where another allocates $25K with higher level finishes and including appliances. The $/SF number doesn’t show those assumptions, and many builders will leave them out entirely when ballparking costs.

5. $/SF is useful after the fact, not before it

Once you’ve completed a few dozen ADUs, $/SF can be a useful benchmarking tool for analyzing trends and setting pricing bands with subcontractors. But using it without context of how big the unit is and myriad other factors is like guessing your restaurant bill based on calories.

So if a GC, architect, or ADU consultant leans on cost per square foot without context, it’s a red flag. They’re either guessing, or they don’t truly understand what goes into an ADU build.  A serious builder will want to talk about your lot, utilities, design goals, and finishes before throwing out a number.

The Smart Way to “Get Bids”

You don’t need more bids. You need better ones.

That starts with understanding what information goes into a bid—and how the best builders arrive at their numbers.

You can’t compare ADU bids meaningfully until everyone’s working from the same level of information. That’s why the smartest builders (and homeowners) follow a phased approach that builds accuracy over time, instead of chasing quick numbers upfront.

The best builders don’t toss out a single number; they build accuracy in stages:

• Proposal: A first look at costs based on your site, access, and basic goals—clearly showing assumptions that will be refined later.
• Feasibility Study & Preliminary Budget: Early design concepts and property data (like surveys, utilities, and setbacks) reveal real-world constraints and start to firm up pricing.
• Construction Drawings & Plan Check: Structural and city requirements come into focus, refining the budget as new details and conditions emerge.

That’s how you make sure the bids you compare are based on the same information, not a stack of incomplete guesses. Read more about our approach to ADU pricing.

Moving Forward: Let’s Talk About Your Project

As for SnapADU? We aim to be the most accurate and predictable. After completing 100 ADUs, we know what pitfalls to avoid.

If you want to see what transparent & thoughtful ADU pricing looks like, we’d love to meet you on a complimentary Discovery Call. If your project’s a fit, we’ll invite you to move forward with a Feasibility SnapShot—a data-backed foundation for everything that follows.