Cost to Build an ADU in Palo Alto, CA: what the permits say

How much does it cost to build an ADU in Palo Alto?

The usual ADU job filed with Palo Alto is $108,045, from 205 priced permits, October 2023 through September 2026. The middle half of firms usually file between $66,111 and $133,896. Half of jobs were filed for less, half for more. A filed value is what the contractor wrote on the permit, not a quote or the final bill.

What the spread looks like

Approximately, from each firm's own spread: every firm's range of filed values, weighted by its 205 priced permits across 157 firms, pooled into one. Half of Palo Alto ADU permits were filed between $67,800 and $166,000.

Busiest firms and what they usually charge

Top 10 by permits in the last 12 months. Usual is each firm's middle filed value; middle half is the range its middle half of jobs were filed in; both are shown for firms with 5 or more priced permits. Busy is not the same as careful: pick what you value to build a list.

Why filed values run low or high

• The 10 busiest firms usually file $140,590; the 157 firms with fewer than 10 permits usually file $115,484.
• One permit type covers small and large jobs: 1 in 10 ADU permits is filed under $26,100 and 1 in 10 over $286,000, 11 times as much.
• 99.5% of the 206 permits carry a value; the 1 without one are left out of every figure here.

When to schedule ADU construction in Palo Alto

Palo Alto files the fewest ADU permits in July (70 against an average month of 100) and the most in March (146). If you can choose, ask for quotes in a quiet month. We have no prices by month, so this is about crews' schedules, not a discount. When each trade is busiest in Palo Alto →

Guides for this trade

• ADU vs home addition: what the permit file shows
• What is an ADU? ADU vs DADU vs JADU, California's rules, and what ADU permits show
• Can an unpermitted ADU be legalized? California's AB 2533 rule, and what it costs and takes
• How to check a contractor's license in California

All guides →

Common questions

• How many quotes should I get for an ADU job in Palo Alto?At least three. In the permit record the middle half of Palo Alto ADU firms usually file between $66,111 and $133,896 a job, so two ordinary firms can sit 2.0 times apart and both be normal for Palo Alto. A third quote shows which one is the outlier. Filed values are what contractors wrote on permits, not quotes, so use them to judge the spread, not to price your own job.
• What range is normal for ADU jobs in Palo Alto?Half of permits were filed between $67,800 and $166,000; 8 in 10 between $26,100 and $286,000. These are approximate, pooled from each firm's own spread.
• How much do ADU builders charge in Palo Alto?The usual ADU job is filed at $108,045; the middle half of firms usually file between $66,111 and $133,896. The 10 firms with the most permits in the last 12 months usually file $140,590, more than the usual. See every firm's usual job →
• Why do prices I see online differ from $108,045?$108,045 is the construction value contractors wrote on Palo Alto permits. Online figures are usually all-in ranges whose scope you can't check (design, fees, site work), and our file mixes small and large jobs of this type in one number. Use the spread above to see where a quote sits.
• How many ADU firms work in Palo Alto?158 firms appear on the file; 39 pulled at least one permit in the last 12 months.
• Where does this data come from?City of Palo Alto Development Center building permits on single-family, duplex and ADU homes, read October 2026. How the records work in Palo Alto →