The soft-cost categories
| Category | What it covers | Where your real number comes from |
|---|---|---|
| Design & engineering | Architectural plans, structural engineering, and site-specific adaptations — even pre-approved plans need site plans and licensing. | Designer or design-build proposals; see architect vs. design-build and pre-approved plan programs. |
| Plan check & permit fees | What the city charges to review and permit the project. | Your city's published fee schedule — linked from our city guides. |
| Impact fees | Development impact fees — statutorily exempt at 750 sq ft or less of interior livable space. | Our impact-fee guide has the thresholds and an exemption checker. |
| School fees | Separate from impact fees; fully exempt at 500 sq ft or less under SB 543. | Same guide; amounts come from your school district's schedule. |
| Utility connections | Trenching, meters, panel upgrades, sewer connection — heavily distance- and capacity-dependent. | Our utility guide, then your utility providers. |
| Surveys & soils reports | Required case-by-case — sloped lots and some cities' checklists trigger them. | Your city's submittal checklist; ask at the counter before assuming. |
| Title 24 energy documentation | Energy-code compliance docs, including solar for most new-construction ADUs. | Our solar requirements guide; your energy consultant prices the docs. |
| Insurance & financing costs | Course-of-construction coverage, loan origination and interest during the build. | Our insurance guide and loan calculator; your insurer and lender quote the real figures. |
| Post-completion | The property-tax increase from partial reassessment — ongoing, not one-time. | Our tax estimator. |
We deliberately don't publish a single "soft costs are X%" figure — the honest range is wide because fee schedules are local, lots differ, and several categories are triggered case-by-case. What we can tell you: a budget that only contains the construction bid is incomplete, and our cost guide explains which of these the typical construction ranges exclude.
What affects your soft-cost total most
Size — the 750 sq ft impact-fee threshold and 500 sq ft school-fee threshold are hard statutory lines worth designing around when you're close. City — plan check and permit fees vary meaningfully between jurisdictions. Lot conditions — slope and utility distance can move soft costs more than any other factor. Design path — pre-approved plans compress design fees; custom architecture doesn't.
Ask-your-city checklist — one counter visit gets your real numbers
- The ADU submittal checklist — it reveals whether surveys or soils reports apply to you.
- The current fee schedule — plan check, permit, and any city-specific ADU fees.
- Utility connection requirements — separate meter policies and sewer connection rules.
- Whether your size triggers impact or school fees — bring your target square footage.
- Pre-approved plan catalog — compressing the design line is the biggest controllable soft-cost saving.
Frequently asked questions
Any single percentage would be misleading — fee schedules are local, and categories like soils reports or panel upgrades apply to some projects and not others. Build the budget by category using the table above, with the fee items quoted by your actual city and utilities.
Sometimes partially — which is exactly the problem. One bid may include permit fees while another excludes them, making totals incomparable. Our bid-comparison guide shows how to normalize for this.
Construction loans and renovation financing typically can include soft costs in the project budget; HELOC funds are yours to allocate. Confirm with your lender what their appraisal and draw process covers — our financing comparison covers the structural differences.