What drives the cost of an addition or a remodel
What moves the budget for a Simi Valley room addition or whole-home remodel, the City permit fees from the 2024 schedule, and how payments must follow the work.
We do not publish Aguila price ranges yet, and we would rather tell you that than invent a number. Every honest addition or remodel price depends on the scope, the structure of your house and what the City requires for your lot, so it comes after a site visit.
What we can give you now is the list of things that move a budget up or down, the City fees you can verify yourself, and the payment rules California applies to every home improvement contract. Use them to compare any bids you collect, ours included.
The factors that move a budget most
Structure is the largest swing. Anything that changes how loads travel to the ground, such as a removed wall, a new opening, a second story or a hillside foundation, adds engineering, plan check time and materials. Square footage matters, but a small addition with a complex roof tie-in can cost more per foot than a larger, simpler one.
Systems come next. If the panel, water heater or main lines cannot carry the new rooms, upgrading them belongs in the budget from the start. Finishes are the factor you control most directly: cabinets, counters, flooring and fixtures can vary widely for the same layout.
- Structural changes and engineering
- Site conditions: slope, access, soil, drainage
- Utility capacity: electrical service, plumbing, heating and cooling
- Finish level for cabinets, counters, flooring and fixtures
- Concealed conditions found after walls open
City fees you can check yourself
Permit fees are a small part of a large project, but they are public, so they are a good test of whether a bid was built carefully. The figures below come from the City of Simi Valley schedule effective July 1, 2024. They are adjusted over time and leave out plan check, school fees and other agency charges, so treat them as a floor and confirm current amounts with Building & Safety.
| Item | Fee |
|---|---|
| Room addition, single-family, first 500 sq ft | $2,160.68 |
| Room addition, each additional 500 sq ft | $1,014.10 |
| Interior non-structural renovation with plumbing, mechanical and electrical | $171.24 |
| General inspection, per inspection | $75.78 |
| Expedited single-cycle plan check | Double the plan check fee |
How payments must follow the work
California requires the schedule of progress payments in a home improvement contract to describe each phase of work and the amount due for it. The CSLB contract guide quotes the required notice: it is against the law for a contractor to collect payment for work not yet completed, or for materials not yet delivered.
Payments also carry lien risk. Subcontractors and suppliers who are not paid can record a mechanics lien on your property even if you paid the prime contractor. CSLB suggests getting a list of everyone working on the job, watching for 20-day Preliminary Notices, and paying with joint checks where a notice has been served.
Comparing bids fairly
CSLB recommends at least three written bids based on identical plans, specifications and scope, and warns about any bid substantially lower than the rest. A low bid that leaves out engineering, permit fees or a panel upgrade is not cheaper; it moves the cost to a change order later.
Questions homeowners ask
Why will you not give a price per square foot?
Because the number would mislead you. Per-foot figures hide the structural and system work that actually drives an addition or remodel, and two projects of the same size can differ widely. A written estimate after a site visit is the only figure worth comparing.
Are permit fees included in a contractor's estimate?
They should be listed, either as included or as a separate line you pay the City directly. If a bid does not mention permits at all, ask.
What is a reasonable reserve for an older house?
Many owners set money aside for concealed conditions in homes from the 1960s to the 1980s. The size depends on how many walls and systems the project opens. Ask the contractor what they expect to find and how unknowns will be priced.
Does paying for expedited plan check save money?
It saves time, not money. The City charges double the plan check fee for a single-cycle expedited review. It can be worth it when carrying costs or a deadline make waiting expensive.
Sources
Facts on this page last verified: .
- City of Simi Valley, Summary of Service Charges effective July 1, 2024 (FY2024-25): https://simivalleylibrary.org/wp-content/uploads/2025/02/CityofSimiValley_FeeSchedule2025.pdf (2026-10-05)
- CSLB, Contracting for Success: A Contractor's Guide to Home Improvement Contracts: https://www.cslb.ca.gov/Resources/GuidesAndPublications/ContractingForSuccess.pdf (2026-10-05)
- CSLB, How Do I Find the Right Licensed Contractor?: https://www.cslb.ca.gov/Consumers/Hire_A_Contractor/Finding_The_Right_Contractor.aspx (2026-10-05)
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