Adding a primary bathroom to your house
Add a primary bathroom to a Simi Valley home, inside the footprint or as an addition. Why it needs City plan check, how long review takes, and what to prepare.
Plenty of Simi Valley houses from the 1960s and 1970s were built with one full bathroom in the hall and, at most, a half bath off the main bedroom. Adding a real primary bathroom is one of the projects that changes how a house lives day to day.
There are two ways to get the space: carve it out of rooms you already have, like a closet or part of a bedroom, or build onto the house. Either way it is new plumbing, new drains and usually new framing, so it goes through the City's full plan check rather than the quick remodel review.
Inside the footprint or an addition
Converting existing space is faster and avoids a new foundation and roof. It usually means giving up a closet, a small bedroom or part of the main bedroom, and moving or adding interior walls. Building onto the house keeps every room you have, but adds a foundation, an exterior wall and roofline, setbacks to respect and, in many Wood Ranch and Big Sky tracts, approval from the homeowners association before the City sees it.
- Inside the footprint: shorter build, no exterior change, lose some closet or bedroom space
- Addition: more space, longer review, foundation and roof work, possible HOA review
Why an addition takes longer at the City
The City's one-week review applies to bathroom remodels without a structural component. A new bathroom with new walls, a new opening or added square footage needs plans, and the City posts a separate timeline for projects that require plan review.
| Stage | Posted time |
|---|---|
| Initial review by counter staff | Up to 5 to 10 business days |
| Plan check after fees are paid | 20 to 25 working days, same for each resubmittal |
| Permit issued after the final invoice is paid | Up to 3 business days |
Getting water in and waste out
A new bathroom has to drain downhill to the main line and vent through the roof. Where the new room sits relative to the existing drain decides much of the cost, and a slab foundation makes long drain runs harder than a raised floor does. We also look at whether the water heater can keep up with a second full shower in the house.
The City asks for one PDF of the full plan set when a project needs plan review, so drawings come first. We will tell you what the drawings need to show and help you line up the work before anything is submitted.
Questions homeowners ask
Do I need plans drawn for a new bathroom?
If the project needs plan review, yes. The City wants the full set as a single PDF with separate files for other construction documents. A bathroom built entirely inside existing space with no structural change may need less, which we can sort out at the estimate.
How long before work can start?
For an addition, the City's posted steps alone run from about five business days to more than a month, plus any resubmittals. Drawings and HOA approval, if your tract has one, come before that. Inside-the-footprint conversions are usually quicker.
My neighborhood has an HOA. Who handles that?
Approval from the association is the homeowner's request, but we provide the drawings and material details the architectural committee asks for. Plan on it before the City submittal for any change you can see from outside.
What does plan check cost?
It depends on the project's valuation. The City's FY 2024-25 schedule also lists an hourly plan check rate of $268.41 for extra review time, and fees are adjusted with inflation each year. We include the City's fees in the estimate as a separate line.
Sources
Facts on this page last verified: .
- City of Simi Valley Building and Safety, Online Permit Submittal Instructions: https://www.simivalley.org/departments/environmental-services/building-safety-division/online-permit-submittal-instructions (2026-10-05)
- City of Simi Valley Summary of Service Charges, effective July 1, 2024 (Building and Safety appendices): https://simivalleylibrary.org/wp-content/uploads/2025/02/CityofSimiValley_FeeSchedule2025.pdf (2026-10-05)
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