Whole home remodels in Sonoma County got more complicated this year, and most owners find that out after they have already started. The 2025 California Energy Code took effect for permit applications filed on or after January 1, 2026, with heat pumps as the baseline for space and water heating. Cal Fire’s new hazard maps moved thousands of acres of the county into higher fire-severity zones. Homeowners insurance keeps shifting onto the state’s FAIR Plan. Any one of those can change what your remodel has to include and what it costs. This guide walks through where to start, in the order we actually do it at ZSM Construction Co., from the first walkthrough to the final inspection, with the Sonoma County specifics that a generic remodeling article leaves out.
CSLB #1055901 · B General Building · Own earthwork, foundation, framing and finish crews · One-year workmanship warranty · Santa Rosa, serving Sonoma County and Marin
Key takeaways
- Start with the structure, not the finishes. The walls you want gone, the roof you want raised and the floor plan you want opened decide the budget before a single tile does.
- Budget for what is behind the walls. Houses in Santa Rosa, Petaluma and Sebastopol built before the 1980s hide bad subfloors, undersized headers and old wiring. The written change order is how a good contractor handles that.
- Permits are a schedule item, not an afterthought. Santa Rosa’s published first review for a residential addition or alteration is six to eight weeks once the application is complete; unincorporated Sonoma County runs through Permit Sonoma.
- Three rules changed the game for 2026: the heat-pump baseline in the Energy Code, the new Wildland-Urban Interface Code that replaced Chapter 7A, and the updated fire-hazard maps.
- Check the licence before you sign. California requires the number on every contract and every ad; the CSLB site shows status, bond and workers’ compensation in thirty seconds.
- A whole home remodel runs three to six months of construction once permits are in hand. Plan where you will live before demolition starts.
Not sure where your house stands?
A site visit, a plan review and an honest read of the structure. No charge, no obligation, and you keep the notes either way.
What a whole home remodel covers
A whole home remodel is a renovation that touches most of the house at once: the floor plan, the structure that holds it up, the systems inside the walls, and then the kitchens, baths and exteriors that ride along. It is different from a single-room project in one important way. Instead of working around the house, we open it up and rebuild the parts that no longer fit how you live.
At ZSM that usually means some mix of the following:
- Taking out walls and putting in beams to open a main floor.
- Adding a second story or a side addition, tied into the existing foundation and roof.
- Converting a garage or building a detached unit as an ADU, which we cover under additions.
- Rebuilding a house that lost a wall or a wing to fire or water.
- Bringing 1970s electrical and plumbing up to current code while the walls are open.
- The kitchen, bathrooms and exterior that come with the job.
What it is not: a cosmetic refresh. If you want new counters and paint, you want a kitchen remodel, and we will say so at the first visit. Our residential remodeling page lays out the six kinds of remodel we take and how they differ.
Step one: decide what the house needs to do, not what it needs to look like
Every remodel I have watched go sideways started with a finish decision made before a structural one. Someone falls in love with an island, then discovers the wall between the kitchen and the living room is carrying the second floor. So we start somewhere else.
In the first walkthrough we ask three things. How do you use the house now? What does the house stop you from doing? What has to be true in five years? A couple who both work from home needs two quiet rooms more than a bigger kitchen. A family planning for a parent to move in needs a bedroom and a full bath on the main level, and a door wide enough for a walker. Those answers point at the structure. The finishes come later, and they come easier.
Write the answers down. The list becomes the brief for your architect or designer, and it becomes the test we use when a change order comes up mid-build. If the change does not serve one of those three answers, it probably does not belong in the project.
Step two: find out what the house will allow
Before anyone draws, we look at the bones. In Sonoma County that means a few things specific to this housing stock.
Load paths. Many houses here from the 1960s through the 1980s have interior walls that carry roof or second-floor loads. Opening them is routine, but it means a beam, posts and sometimes new footings under the slab. That is foundation work, and it is where a lot of remodelers stop. We do our own earthwork, foundations and framing in house, so the beam and what holds it up are one conversation.
Foundations and slopes. Hillside lots in Glen Ellen, Bennett Valley and the Mark West corridor often have stepped or post-and-pier foundations. An addition on a slope needs a real foundation designed for it. On the flats in Rohnert Park and Windsor, older slabs can be fine or can be the first surprise.
What is in the walls. A homeowner called us a few years ago mid-flooring job. Pulling carpet to lay vinyl plank, they found the subfloor had been installed wrong 35 years earlier. We fixed the part we could and put them in touch with the right trade for the rest. That call is a fair preview of what a whole home remodel finds. Budget for it, and work with a contractor who tells you the same day with a photo and a written change order, not at the end with an invoice.
Fire zone. Cal Fire released updated Fire Hazard Severity Zone maps in February 2025. In unincorporated Sonoma County the very-high zone went from 11 acres to roughly 7,555 acres; Santa Rosa’s very-high acreage actually fell, from about 1,644 to 475 acres, as the maps were redrawn. If your parcel is in a high or very-high zone, the Wildland-Urban Interface Code applies to the work you do on exterior walls, roofs, vents, decks and windows. Permit Sonoma publishes the county map; check it before you plan an exterior change.
Step three: understand the three 2026 rules that shape the plan
Three changes landed within a year of each other. Any contractor quoting a whole home remodel in Sonoma County today should be able to explain all three.
The 2025 Energy Code. It applies to building permit applications submitted on or after January 1, 2026. For new residential construction the baseline is heat-pump space and water heating. For a remodel, the altered systems and the new square footage have to meet the code’s prescriptive or performance paths, which means your HVAC and water-heater decisions are now part of the design, not a line item you pick at the end. Santa Rosa suspended its own all-electric reach code in 2024 after a federal court ruling, so for most of the county it is the state code that governs. Marin County runs three compliance pathways of its own.
The Wildland-Urban Interface Code. The fire-resistant construction rules that used to live in Chapter 7A of the California Building Code moved into a new Part 7 of Title 24, effective January 1, 2026. Same intent, new book. Old articles that say “Chapter 7A” are describing a code section that no longer exists.
The new hazard maps and defensible space. The maps feed local ordinances; Sonoma County’s Fire Safety Ordinance applies in the unincorporated area. State law already requires 100 feet of defensible space in state-responsibility areas, with the most intense work inside 30 feet. The five-foot “Zone 0” ember-resistant rule has been adopted by the Board of Forestry but, as of this writing, is not yet operative. We will tell you when it is.
Step four: get real about what it costs and what moves the number
We publish ranges because people deserve a number before they pick up the phone. These are the ranges we quote today. Every project gets a written estimate after the plan review and the site visit.
| Project | Typical range | Typical construction time |
|---|---|---|
| Kitchen remodel | $30,000 to $100,000+ | 6 to 8 weeks |
| Bathroom remodel | $15,000 to $50,000+ | 4 to 6 weeks |
| Whole home remodel | written estimate after plan review | 3 to 6 months |
| Home addition or ADU | written estimate after plan review | ADU construction runs 6 to 9 months |
What moves a whole home number most, in the order we see it:
- Structural changes. Every wall that comes out is a beam, and some beams need a footing.
- Relocating plumbing. Moving a kitchen or a bathroom across the house is slab work, not just pipe.
- Finish level. The same floor plan can be built at two very different price points. Tell us the budget and we will tell you honestly what it buys.
- What is behind the walls. See the subfloor story above.
- Changing your mind after framing. The most expensive item on this list and the easiest to avoid. Decisions on paper cost a fraction of decisions on site.
Payment runs as a deposit to start, progress payments at milestones, and a final payment when the work is complete and inspected. Never full payment up front. California caps the down payment on a home improvement contract at $1,000 or 10 percent of the contract price, whichever is less, and it is against the law for a contractor to collect for work not yet done or materials not yet delivered. If a contract you are handed does not say those things in bold, that is a problem with the contract.
One more cost that is not on the contractor’s invoice: insurance. The California FAIR Plan, the insurer of last resort, had 8,748 policies in force in Sonoma County at the end of September 2025, up 39 percent in a year. If your home is on the FAIR Plan or your carrier has pulled back, talk to your agent before you add square footage. Coverage limits and rebuild costs should match.
Want a written estimate with the cost drivers spelled out?
Tell us the budget and we will tell you honestly what it buys. Every estimate follows a site visit and a plan review.
Step five: permits, and how long they really take
Permits are where most remodel schedules break, usually because nobody planned for them. Here is what is published.
City of Santa Rosa. The city’s plan-check minimum turnaround, once an application is deemed complete, is six to eight weeks for the first review of a residential addition or alteration, and four to five weeks for each subsequent review. New residential under 25 units runs five to six weeks. An ADU or JADU is 60 days. Those are minimums, not promises.
Unincorporated Sonoma County. Permit Sonoma handles Glen Ellen, Kenwood, the Mark West corridor, Penngrove, Graton, Occidental and the rest of the county outside city limits. Its ADU Ready program with pre-reviewed plans runs about 30 days against about 60 for a standard ADU permit. Note two things for 2026: the counter stopped taking walk-ins on Fridays from October 2 for a six-month pilot, and the county’s fire-rebuild perks, including the guaranteed five-day plan review for rebuilds, end on December 31, 2026, with the reduced fees already gone as of July 1.
State timelines you can hold them to. Under Government Code section 65913.3, a local agency has to tell you whether a post-entitlement permit application is complete within 15 business days, and for projects of 25 units or fewer it has to finish review within 30 business days of calling it complete. Most remodels are not “post-entitlement” projects in that sense, but the completeness clock is a useful thing to know exists.
Marin County. Planning permits in the unincorporated county generally take three to six months with a 30-day completeness review; hillside lots at six percent slope or more and anything near a ridgeline go through design review. San Rafael moved its permit portal to OpenGov in February 2026.
We file the permits, track them and schedule the inspections. You do not have to learn any of this. But you should know the clock exists, because it is the difference between a remodel that starts in spring and one that starts in fall.
Step six: the build, in the order it happens
Once the permit is issued, a whole home remodel at ZSM runs in six phases. Weekly updates by phone or email the whole way, and you can visit the site any day during work hours, Monday through Friday, 7:00 AM to 5:00 PM.
- Protection and demolition. Dust walls and floor protection on the paths we use, then the tear-out. This is the discovery phase. Anything we find gets a same-day call, a photo and a written change order before it moves.
- Structure. Beams, posts, footings, new framing, roof tie-ins for additions. On a hillside this is where our in-house earthwork and foundation crew earns its keep.
- Rough-in. Plumbing, electrical and HVAC inside the open walls. This is when the Energy Code decisions get built: heat pump, ducts, water heater, panel capacity.
- Inspections, then close-up. The county or city inspects the rough work. Then insulation, drywall, and the house starts to look like a house again.
- Finish. Cabinets, counters, tile, flooring, doors, trim, paint, fixtures. The part everyone pictures when they say “remodel,” and the shortest part of a whole home job.
- Final walkthrough and inspection. We do not call it done until the inspector does and you have walked every room with us. One-year workmanship warranty from there; material warranties vary by manufacturer and we help you register them.
Interior work runs year-round. Concrete and outdoor framing wait out heavy rain, which in Sonoma County means a foundation poured in January is a schedule risk and one poured in May usually is not. We build buffer time into the schedule for exactly that.
Step seven: pick the contractor before you pick the tile
Three checks, all free, all under five minutes.
Check the licence on the state’s website. The Contractors State License Board’s Check a License page shows the licence status, the classification, the bond and the workers’ compensation policy. California requires a contractor to put the licence number on every contract and every form of advertising, websites included. Ours is #1055901, classification B General Building. If a number is missing from a contractor’s site, or the record says “inactive,” keep looking.
Read the contract for the notices the law requires. A California home improvement contract over $500 has to carry the contractor’s name, business address and licence number; the down-payment cap; the statement that it is against the law to collect for work not yet done; a mechanics lien warning; and the insurance disclosures. Those are not boilerplate. They are how you know the contractor has done this before.
Ask who will be on site. The honest answer for a company our size is a named crew and the owner. I walk every ZSM job. When you call, you reach the person who can answer.
Six questions to ask at the first visit
Bring these to every contractor you meet, including us. The answers tell you more than the brochure.
- Which walls are carrying load, and what does it take to open each one?
- Who files the permit, and which office issues it for this address?
- Does this parcel sit in a high or very-high fire-hazard zone, and what does that change on the exterior?
- What does the 2025 Energy Code require for the heating, cooling and water heating in this plan?
- How are surprises behind the walls handled, and what does a change order look like in writing?
- Who is on site every day, and who do I call when something comes up?
A contractor who answers all six without looking anything up has done this in Sonoma County before. A contractor who waves off the third or fourth question has not read the 2026 rules yet.
What this means for a Sonoma County house specifically
Local relevance is not a paragraph of city names. It is the five things that make a remodel here different from one in Sacramento.
- Fire. Exterior work on a parcel in a high or very-high zone follows the WUI Code: vents, siding, decks, windows. That changes material choices and sometimes cost. The maps changed in 2025; check your parcel.
- Insurance. FAIR Plan growth of 39 percent in a year in this county means more owners with coverage limits that may not match a bigger house. Involve your agent early.
- Housing stock. A lot of 1960s to 1980s construction, plus Victorian and Craftsman homes in the older neighborhoods of Santa Rosa, Petaluma and Healdsburg. Matching trim and siding profiles on those is sample-first, order-second work.
- Permits by jurisdiction. Santa Rosa, Petaluma, Healdsburg and Sebastopol each run their own building department; everything outside city limits is Permit Sonoma. The timelines differ, and so do the fees.
- Who bids. Out-of-area outfits come into Sonoma County, bid low, and leave. We live here, our subcontractors live here, and we price for crews that are not stuck in traffic.
If you are in Marin County, the same steps apply with Marin’s own permitting and design-review rules, and we take remodels, additions and ADUs throughout San Rafael, Novato and Mill Valley. See the Marin County page.
What to do next
- Write the three answers from step one and keep them.
- Look up your parcel on Permit Sonoma’s fire-hazard map and note which jurisdiction issues your permits.
- Call your insurance agent and ask what a larger or rebuilt house does to your policy.
- Have the structure looked at before anyone draws finishes. Our consultation is a site visit, a plan review and an honest read, with no charge and no obligation.
- Get a written estimate after that visit, with the cost drivers above spelled out.
- Decide where you will live during construction. For a whole home remodel the answer is usually “not here,” and it is better to know that in month one.
What you get right when you start here, and what goes wrong when you don’t
Start with the structure and the rules, and the remodel comes in close to the estimate, the permit clock runs in parallel with design instead of after it, and the surprises behind the walls are handled by change order instead of argument. Start with the finishes, and you buy an island you cannot have, lose a season to a permit you filed late, and find out about the fire-zone rules from an inspector.
The difference is not the contractor’s skill. It is the order of the decisions.
The remodeling series
This is the root of our remodeling guides. The deeper posts in this series, each one built on the same Sonoma County facts:
- Whole House Remodel Cost in Sonoma and Marin County (December 2026)
- Home Addition Cost in Sonoma County: Second Story vs. Building Out (January 2027)
- Can You Live in Your House During a Remodel? (February 2027)
- Permits for Remodeling in Marin County: What the County Requires (March 2027)
- ADU Cost in Sonoma County, and What the County Waives (March 2027)
- Kitchen Remodel Cost in Sonoma County (May 2027)
The service pages this guide supports: residential remodeling, whole home remodel, home additions and second stories, kitchen remodeling, bathroom remodeling, exterior remodeling and outdoor living, and ADUs.
Frequently asked questions
Where do we start with a whole home remodel?
With what the house needs to do, then with what the structure allows. Finishes come last. The first ZSM visit is a walkthrough of the house with those two questions, and it costs nothing.
How long does a whole home remodel take in Sonoma County?
Three to six months of construction once the permit is issued, plus the permit time, which in Santa Rosa starts at six to eight weeks for the first plan-check review of an alteration.
Do I need a permit for a whole home remodel?
Yes. Structural changes, additions, electrical, plumbing and mechanical work all require permits, and the 2025 Energy Code applies to permit applications filed on or after January 1, 2026. We handle the applications and inspections.
Does the 2025 Energy Code mean I have to go all-electric?
Not necessarily. The state baseline for new construction is heat-pump space and water heating, and altered systems in a remodel have to comply. Santa Rosa's own all-electric mandate is suspended; Marin County offers three compliance pathways. We design the mechanical system to the code that applies to your parcel.
How do I know if my house is in a fire-hazard zone?
Permit Sonoma publishes the Cal Fire Fire Hazard Severity Zone map for the county. Parcels in high and very-high zones follow the Wildland-Urban Interface Code for exterior work.
How much should I set aside for surprises?
Enough that a bad subfloor or an undersized header does not stop the job. We put a contingency in every estimate and handle each surprise with a same-day photo and a written change order.
Can I live in the house during a whole home remodel?
Usually not comfortably. Kitchen and bathroom remodels can be phased around a temporary setup; a whole home remodel is hard to live through. We will tell you the truth about that before demolition.
How do I check a contractor's licence?
The CSLB Check a License page. Confirm the status says current and active, the classification matches the work, and the bond and workers' compensation are in force. ZSM Construction Co. is CSLB #1055901, B General Building.
About ZSM Construction Co.
ZSM Construction Co. is a licensed general contractor based in Santa Rosa, CSLB #1055901, B General Building, owned and run by Zack S. Murphy. We build custom homes, whole home remodels, additions, ADUs and light commercial projects across Sonoma County and Marin County, foundation to finish, with our own earthwork, foundation, framing and finish crews. Zack walks every job.
Planning a whole home remodel in Sonoma or Marin County?
Site visit, plan review, honest assessment. No charge, no obligation.
