San Jose ADU timeline: what to prepare before you build

Many people start with this question: “How much will my ADU cost?” That is a fair question. But it is not the first question.

The first question is this: “What am I building, and what does my lot allow?” If you answer that early, every call gets easier.

Step 1: Know your reason

Start with the use. Will the ADU be for family, rent, work, or guests?

This choice changes the plan. A rental ADU may need more privacy. A parent unit may need fewer steps. A work studio may need less kitchen space.

Step 2: Check your lot

Before you pick a design, check the lot. Look at setbacks, trees, slope, fire access, sewer, power, and the path from the street.

San Jose says homeowners should start with the ADU Universal Checklist. The city says this checklist helps show if your property may qualify.

Step 3: Set a real budget

Do not only budget for the building. That is where many ADU plans go wrong.

Your budget may need room for design, engineering, permits, utility work, trenching, panel upgrades, finish items, appliances, and landscaping repairs.

If you already have a number from a builder, read the ADU quote checklist before you sign.

Step 4: Gather your property info

Get these items ready before you talk to builders or designers:

• Your address.
• Your lot size.
• The size of your main house.
• A survey, if you have one.
• Your main electrical panel size.
• Where the sewer line may run.
• Your rough ADU size.
• Your reason for the ADU.
• Your budget range.

You do not need every answer on day one. But the more you have, the better the quote will be.

Step 5: Talk to a designer or ADU pro

A builder can give a rough price. But a rough price is not the same as a real scope.

A simple site plan and floor plan can make the quote much clearer. It also helps you compare builders fairly.

Step 6: Get city feedback if your lot is tricky

Some lots are simple. Some are not. A corner lot, slope, creek, large tree, or tight yard can change the plan.

San Jose says homeowners can contact ADU Ally or ask for basic planner feedback. This is useful before you spend too much on drawings.

Step 7: Prepare plans for permit

San Jose says ADU plans involve many technical codes. The city recommends working with an experienced professional.

The plan set may include a site plan, floor plan, elevations, sections, structural details, energy forms, and utility details.

Step 8: Submit through the city process

San Jose uses SJPermits and SJePlans for many plan review steps. SJePlans lets applicants upload plans, answer city comments, and track the project.

The city says review starts after fees are paid and complete plans are uploaded. If the city sends comments, your team must answer and resubmit.

Step 9: Compare builder quotes before construction

Do not compare only the total price. Compare site work, utilities, foundation, framing, finishes, exclusions, and change order rules.

Use this guide next: how to compare ADU builder quotes.

Step 10: Build, inspect, and keep records

After the permit is issued, construction can start. Inspections happen during the job. Keep the approved plans, permit card, and final sign-off.

Those records matter later. You may need them for insurance, rent, refinance, or sale.

A simple timeline

1. Week 1: Decide your goal, size, and budget range.
2. Week 1 to 2: Check your lot and gather property info.
3. Week 2 to 4: Talk to a designer, ADU pro, or builder.
4. Month 1 to 2: Make a site plan and floor plan.
5. Month 2 to 3: Prepare permit plans.
6. Month 3+: Submit plans and answer city comments.
7. After permit: Build and pass inspections.

This is only a rough order. A preapproved ADU may move faster. A hard lot may take longer. The best way to save time is to submit clean plans.

Can preapproved ADU plans help?

Yes, they can help in some cases. San Jose says preapproved ADUs use standard plans that have already been reviewed for code compliance.

But preapproved does not mean “no work.” You still need a site-specific plan. Your lot still has to work.

Best next step

If you are just starting, do not rush into a contract. Make a simple folder with your property info, goals, budget, and any builder quote you get.

Then ask one clear question: “What is missing before this quote can be trusted?”