Are ADUs Under 750 Sq Ft Exempt From Impact Fees in California?

Are ADUs under 750 sq ft exempt from impact fees in California?

Yes. Under California's state ADU law, a city or county cannot charge impact or development fees on an accessory dwelling unit smaller than 750 square feet. This is a statewide floor, not a local courtesy — jurisdictions can't opt out of it, and it applies whether your ADU is detached, attached, a garage conversion, or a Junior ADU carved out of the main house.

An impact fee is a one-time charge a local agency levies on new construction to offset the added demand it places on public systems — parks, roads, traffic, drainage, and other public facilities. On a full new house those fees can run into five figures. The under-750 exemption exists because the state decided a small ADU adds too little demand to justify treating it like a new single-family home. For a lot of Sacramento homeowners that single line is worth thousands, which is why it drives so many size decisions.

The threshold is the ADU's own floor area, measured as conditioned (heated and cooled) living space. Come in under 750 square feet and the impact-fee line on your permit should read zero. Hit 750 square feet or more and the exemption ends — but you still don't pay a full new-home impact fee. Instead, state ADU law requires any impact fee on a 750-plus ADU to be charged proportionally to the square footage of the primary dwelling. More on that math below.

One caution that trips up a lot of homeowners: 'impact fee' is a specific legal category, not a catch-all for every cost on your permit. The exemption does not erase your building-permit and plan-check fees, school-district developer fees, or the water and sewer connection and capacity charges from your utility. Those live outside the exemption and are covered in the next section. For the official statewide framework, HCD publishes the current ADU guidance.

What counts as an impact fee, and what still gets charged

The cleanest way to think about it: the under-750 exemption zeroes out the development-impact fees a city or county collects for public infrastructure. It does nothing to the fees charged by other agencies — the building department for reviewing your plans, the school district under separate school-facilities law, and your water, sewer, and electric providers for physically connecting and reserving capacity for a new dwelling.

That distinction is where most of the confusion (and a few bad sales pitches) comes from. Here is how the common fee types sort out on a Sacramento-region ADU — which the exemption erases and which survive it. Any dollar amounts we cite anywhere on this page are 2026 regional estimates, not quoted government rates; always confirm the current figure with the agency that charges it.

See also:ADU sewer connection fees (SASD, Sacramento County) — the biggest fee the exemption doesn't touch

How the proportional rule works at 750 sq ft and up

Once your ADU reaches 750 square feet, state ADU law switches from 'no impact fee' to 'proportional impact fee.' The fee has to be scaled to the ratio between the ADU and the primary dwelling, so you are never charged the same impact fee a standalone new house would owe.

Here's the shape of it with illustrative numbers (not a quoted rate): say a jurisdiction's impact fees for a comparable new dwelling total roughly $12,000, your main house is 2,000 square feet, and you build a 900-square-foot ADU. A proportional charge based on 900 divided by 2,000 would land near $5,400 rather than the full $12,000. The exact methodology — which fees are included and how the ratio is calculated — varies by jurisdiction, and some agencies bundle different components, so treat this as the concept, not a promise.

It's also worth knowing that not every jurisdiction levies heavy impact fees to begin with, so the proportional bill on a 750-plus ADU can range from modest to meaningful depending on your address. That's a per-parcel question, not a regional constant.

This is why the 750 line matters so much in Sacramento specifically. State ADU law guarantees you the right to build at least an 800-square-foot ADU even where local limits are tighter — and 800 is just over the 750 fee-free threshold. So a homeowner who wants the biggest guaranteed unit sits right on the edge: the last 50 square feet is what flips you from a zero impact-fee bill to a proportional one. For many Midtown and Curtis Park infill lots, keeping the design at 749 square feet or below is both a fee decision and a lot-fit decision.

See also:What an ADU costs in Sacramento — where impact fees fit in the full budget

How Sacramento and the four counties apply it

The exemption is state law, so it holds across the whole region — but the agencies that charge the fees you do still owe change with your address. The City of Sacramento confirms that ADUs under 750 square feet are exempt from its impact fees, and it runs an ADU Resource Center plus a pre-approved plan set that can drop plan check to roughly 30 days. Detached ADUs there use a 4-foot side and rear setback, a 16-foot height limit (taller near major transit), and require no replacement parking. None of that changes your separate sewer, water, and school obligations.

Where you sit in the region decides your sewer path, and the sewer path decides one of your biggest separate line items. Urban Sacramento County parcels — including City neighborhoods and unincorporated Carmichael, Fair Oaks, and Orangevale — connect to SASD / Sacramento Regional Sanitation, which charges a sewer connection and capacity fee the impact-fee exemption does not touch. Deep alley-loaded lots in Land Park and Pocket-Greenhaven can support a larger ADU without the lot-coverage squeeze you feel on a narrow Midtown or Boulevard Park grid lot — though a bigger unit is exactly what pushes you past 750 into proportional-fee territory.

In the foothills — Auburn, Placerville, Cameron Park, Loomis, Granite Bay, and El Dorado Hills — Placer County Building and El Dorado County Planning & Building are the permit authorities, and many of those parcels are on septic rather than a sewer main. On a septic property your 'sewer connection fee' becomes a county Environmental Health review of your septic system's capacity, which can mean a new or upsized system entirely. In West Sacramento and the rest of Yolo County, the City of West Sacramento Community Development and county authorities govern, again with their own utility connection charges. Note that historic-district review in Land Park, East Sacramento, or Boulevard Park can shape your design, but it does not change the impact-fee exemption.

See also:City of Sacramento pre-approved ADU plans — the ~30-day plan-check path · Narrow Midtown lot setbacks & lot coverage — when the lot, not the fee, caps your size

School fees and utility connection fees are a separate bill

This is the part contractors gloss over when they say an ADU under 750 square feet is 'fee-free.' It isn't. Three separate charges commonly survive the impact-fee exemption:

School-district developer fees are levied under California's school-facilities law, not the ADU impact-fee rules, so they sit outside the exemption. Whether a given district assesses them on a small ADU varies, and some districts do not charge them on the smallest units — confirm with the district that covers your parcel before you assume either way.

Water and sewer connection and capacity charges are explicitly treated as separate from the impact-fee exemption. In urban Sacramento that means a SASD / Regional San sewer connection fee plus your water provider's charge; in the foothills it means a septic capacity review through county Environmental Health. These are commonly among the largest 'soft' costs on an ADU and typically run into the several-thousand-dollar range in 2026 — confirm the current amount with the district that serves your lot.

SMUD electric service is its own path too. If your ADU needs its own meter, a heavier service, or a panel upgrade, that's a SMUD charge unrelated to the impact-fee exemption. Budget it separately, because it can be the difference between a clean tie-in and a several-thousand-dollar service upgrade.

• Building permit & plan-check fees (city/county building department)
• School-district developer fees, under separate school-facilities law
• Water connection and capacity charges from your water provider
• Sewer connection and capacity fees (SASD / Regional San, or septic via county Environmental Health)
• SMUD electric service, meter, or panel-upgrade charges

What some contractors get wrong

After pulling these permits across the region, these are the shortcuts and mistakes we see most often — the ones that turn a 'fee-free' promise into a surprise bill:

• Selling 'no fees under 750 square feet' — the exemption only covers impact fees; permit, school, water, sewer, and electric charges still apply
• Confusing the impact-fee exemption with sewer connection fees — the SASD / Regional San connection and capacity charge is separate and survives the exemption
• Measuring the wrong square footage — the 750 threshold is conditioned floor area; a design drawn at 760 to 780 sq ft can trigger proportional impact fees for a handful of feet
• Assuming county rules match City of Sacramento rules — an unincorporated Fair Oaks or Orangevale parcel is governed by Sacramento County, not the City
• Ignoring septic on foothill lots — in Auburn, Cameron Park, or El Dorado Hills there may be no sewer connection at all, but a septic capacity review through county Environmental Health instead
• Pushing to the state-guaranteed 800 sq ft without flagging that it crosses the 750 fee-free line

How Upside handles the fee question

We treat the fee analysis as part of feasibility, not an afterthought at permit submittal. Before you commit to a design, we pull the specific impact-fee schedule, sewer or septic path, water provider, and school district for your exact parcel, and we tell you where the 750-square-foot line lands your build — including whether the last few square feet are worth the proportional fee they'd trigger.

Upside ADU is a licensed California contractor and we keep permits and engineering in-house, so the size decision, the fee math, and the plan-check package are handled by the same team rather than tossed between a designer, an expeditor, and a builder who each blame the others when a fee appears. You get the honest number — the impact fee (usually zero under 750), plus the separate school, utility, and permit costs — before you spend a dollar on design.

ADU fees and codes change as jurisdictions update their ordinances to match state law. This page is orientation, not a fee quote. We confirm the current figures with your named authority as part of a free feasibility check.

See also:Get a free feasibility check — we price the fees for your exact parcel