Free worksheet · ADU Budgeting
Most homeowners see one big number and have no way to know if it's fair. So instead of guessing, break the project into the eight buckets every ADU budget is made of. Once you can see the parts, you can model your own project — and pressure-test any quote you're handed, even one that isn't ours.
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The idea
A single project total is impossible to judge. Is $X fair? You have no idea — until you know what's inside it. Every ADU budget, no matter who builds it, is really the sum of eight buckets. Some are fixed, some are wildly variable, and a few are entirely within your control.
Work through them in order below. Jot your own rough number next to each — a range or a percentage is fine, and honestly better than a false-precision total this early. When you're done, you'll have a budget you actually understand, and a checklist to hold any contractor's quote up against.
The worksheet
Read each bucket, then fill in your own estimate. No signup, no gate — this is yours to use for any project or any quote.
Turning your goals into permittable, buildable plans. Skimping here is the classic false economy — thin drawings lead to expensive change orders and rework once the crew is already on site.
Driver: Detailed plans vs. napkin sketch
The structural work — and sometimes a soil report — required for the city to approve your build. It scales with complexity: a simple flat-lot cottage needs far less than a two-story or hillside unit.
Driver: Structural · soils (if sloped)
Plan-check and permit fees paid to your city. California has capped or eliminated many of the old impact and connection fees, so this bucket is usually smaller than homeowners expect — but never zero.
Driver: Plan check + permit issuance
Grading, foundation, and prep — the single most unpredictable line in the whole budget. A flat, clean lot is cheap; a sloped, tight, or obstructed one can multiply this bucket several times over.
Driver: Flat lot vs. sloped lot
Framing through finishes — the largest share of almost every ADU budget. It's driven mostly by two things you control: total square footage and the level of finish you choose.
Driver: Driven by size + finish level
Connecting water, sewer, and electrical to the new unit. The cost is mostly about distance: the farther your ADU sits from existing lines and panels, the more trenching and upgrades it takes.
Driver: Close to lines = lower cost
Everything you see and touch — flooring, cabinets, counters, fixtures. This is your biggest lever. "Rental-grade" keeps costs lean; "forever-home" premium finishes can add tens of percent.
Driver: Rental-grade vs. forever-home
Money set aside for the unexpected — the surprise under the slab, the mid-project upgrade, the code detail nobody saw coming. Smart budgets reserve 10–15%. Projects without one "discover" costs the hard way.
Driver: Reserve 10–15%
Prefer to fill it in on paper? Download the printable PDF and bring it to every builder meeting.
Read this before you sign anything
You get two bids for what looks like the same ADU. One is far cheaper. It's tempting to assume that builder is just a better deal. Usually, they're not — they're describing a different project. Here's where the gap almost always hides:
One quote is complete. The other isn't.
The lower number often quietly leaves out design, engineering, permits, utilities, or site work. Those costs don't disappear — you simply pay for them later, mid-project, when you have no leverage.
One uses rental-grade finishes. The other uses premium.
Two quotes can describe the same square footage and look identical on paper while assuming completely different flooring, cabinets, and fixtures. Finish level alone can swing a budget by tens of percent.
One builds in contingency. The other 'discovers' costs.
A quote with a 10–15% contingency looks higher today. A quote without one looks cheaper today — right up until the first surprise, when the change orders start and the real number reveals itself.
Compare scope, not just price.
Line up both quotes against the eight buckets above. If one is missing a bucket — or quietly assumes cheaper finishes and no contingency — it isn't actually cheaper. The lowest quote is frequently the most expensive project by the time it's finished.
Put it to work
1. Build your own honest number
Fill in a range for each of the eight buckets. Add them up. You now have a budget grounded in real categories instead of a wish or a headline figure.
2. Interrogate every quote
Ask each builder to map their bid to these eight buckets. Any that are missing, vague, or suspiciously low are the questions to ask before you sign — not after.
3. Get an instant sanity check
Want a fast ballpark to check your work against? Our ADU cost calculator gives you a range in about a minute — a useful gut-check on the total you just built.
Questions
Still have a question? Ask us during your free consultation.
There's no single honest number — it depends on all eight budget buckets, especially size, finish level, and site conditions. Rather than quote a total that won't apply to your lot, this worksheet teaches you to build your own estimate bucket by bucket, then pressure-test any quote against it. For an instant ballpark, our ADU cost calculator gets you a range in about a minute.
Site work. On a flat, unobstructed lot it's a modest line item. On a sloped or tight lot — with grading, retaining, or a deeper foundation — it can multiply several times over and quietly blow up an otherwise reasonable budget. It's also the bucket most often left vague or missing in a low quote, which is exactly why it's worth asking about first.
Almost always because they cover different scope, not because one builder is simply cheaper. The lower quote may exclude design, engineering, permits, utilities, or site work, assume rental-grade finishes, and carry no contingency. Compare the scope line by line before you compare the totals — the cheapest quote is frequently the most expensive project.
Plan for 10–15% of your construction budget set aside for the unexpected. It covers surprises under the slab, code details, and mid-project upgrades. A quote that omits contingency isn't cheaper — it's just quietly moving that risk onto you, to be paid later as change orders.
No. This worksheet is built to help you model your project and evaluate any quote — including ones that aren't ours. Understanding where every dollar goes makes you a sharper buyer no matter who you hire. If you'd like, we're happy to give you a free, fully itemized estimate you can hold every other bid up against.
No pressure, just clarity
We'll break your project down into all eight buckets and give you a fully itemized estimate — the exact document you can hold every other quote up against. Free, no obligation, and yours to keep.
