Sebastopol Multifamily Exterior Siding & Windows Renovation

When an apartment building, condo association, or mixed-use property needs a new exterior, the wall assembly is only part of the job. You also have residents who still need to live there, a board or ownership group that needs defensible numbers, and a reserve study or capital plan that has to hold up. In Sebastopol, the work also has to handle west Sonoma County's weather. The town gets around 36 inches of rain a year, most of it concentrated in winter, and coastal fog and tree cover keep many walls damp and shaded for long stretches.

Bay Area Siding Company is a siding and window contractor based in Larkspur. We take on exterior renovation for multifamily and commercial properties alongside our residential work: full re-siding, window replacement, and combined envelope projects.

Planning a building-wide exterior project? Request a bid or call (415) 619-5167 to schedule a site walk with your manager or board.

Who this page is for

• Property managers handling a building whose siding or windows have become a recurring maintenance line item.
• HOA boards weighing a community-wide re-side against continued spot repairs, and trying to keep the whole association consistent in appearance.
• Apartment and small-portfolio owners planning a capital project, prepping a building for sale or refinance, or responding to an inspection report.
• Mixed-use owners whose ground-floor tenants need storefront access to stay open while work happens overhead.

Whatever the building type, the questions are the same: what is actually wrong with the envelope, what it costs to fix it properly, and how to get it done without turning residents' lives upside down.

Start with what's behind the cladding

Multifamily exteriors in a damp climate tend to fail in patterns rather than in isolated spots. Common examples:

• The same elevation on every building staining first.
• Sills rotting at the same window type across the property.
• Hardboard or T1-11 swelling along the bottom courses wherever landscaping and sprinklers sit close to the wall.

Older cladding on many properties predates modern drainage detailing. In a town where walls can stay wet for months, that gap shows up over time.

So we scope the building before we price it. We walk every elevation and note where damage clusters. Where it makes sense, we recommend opening a few representative test areas so the bid reflects what is really in the wall, not a guess.

On a full tear-off, the old cladding comes off down to the sheathing and substrate. That exposes the water-resistive barrier (WRB) and the flashing at windows, doors, decks, and penetrations for inspection. Framing is only exposed if the sheathing itself has deteriorated enough to need replacement. That is a larger scope we document and price separately, so a board is never surprised by a change order it didn't understand.

The rebuild is a water-shedding system:

• New WRB.
• Corrected flashing and drainage details.
• Proper clearances at grade and at roof-wall intersections.
• Cladding installed to the manufacturer's specifications.

On a property with dozens of openings and long runs of wall, consistent detailing is what keeps the next capital cycle from arriving early.

Keeping residents housed, informed, and safe

Exterior work on an occupied building is mostly a logistics problem. We plan it that way:

• Phasing by building, elevation, or stack. Only a defined section is under construction at a time. Scaffolding, debris, and noise stay contained, and finished areas return to normal quickly.
• Weather-aware sequencing. Sebastopol's rain is concentrated in winter, so tear-off is planned so that no wall is left open to the weather. On larger properties that can mean scheduling the heaviest exposure work for drier months and saving interior-side window finishing for later.
• Resident communication support. We give management a schedule by unit or area so you can send notices under your own obligations. Residents know when crews will be outside their windows, when balconies or patios are off-limits, and which entries and walkways stay open.
• Access and safety. Walkways, parking, trash enclosures, and storefront entrances are kept usable or clearly rerouted, and the site is cleaned daily.

For HOA projects, we can meet with the board and, if helpful, present at an owners' meeting so questions get answered before work starts.

Material choices at portfolio scale

For a multifamily building, the right material balances first cost against long-term maintenance, fire exposure, and how uniform the finished property needs to look. The options we install most often on larger properties:

• Fiber cement, including James Hardie. It is noncombustible, rot- and pest-resistant, and holds paint well. Hardie's factory ColorPlus finish carries a 15-year finish warranty, and the substrate carries a transferable 30-year non-prorated limited warranty when installed to spec. Both help when a board is planning repaint intervals. See the Sebastopol James Hardie page for product details.
• LP SmartSide engineered wood. It offers a wood look that suits Sebastopol's farmhouse and Craftsman character, is lighter than fiber cement, and needs periodic paint.
• Vinyl, including CertainTeed lines. It is the budget-conscious option with no repainting, where the building, the fire exposure, and the association's design standards allow it.

We also work with wood and aluminum. For HOAs, we can match an approved color and profile palette so phased buildings finish looking like one community rather than several projects.

Windows in the same mobilization

If the windows are original single-pane units or early dual-pane units with failed seals, replacing them during the re-side usually makes sense. Scaffolding is already up, the openings are already exposed, and new flashing can tie properly into the new WRB.

We install both retrofit (insert) units, where existing frames are sound, and new-construction (full-frame) units, where the sill or surround shows water damage. Window replacement is an alteration under California's Title 24 Energy Code. We confirm the required performance values for the current code cycle at permit time and prepare the fenestration compliance documentation. For brand comparisons, see the window replacement hub and the Sebastopol window replacement page.

Permits: city or county, and fire designation by parcel

Properties inside city limits are permitted through the City of Sebastopol Building & Safety Division, using the city's online permit portal. Properties on unincorporated land outside town fall under Sonoma County (Permit Sonoma). We confirm the correct authority for each address. That matters for owners whose portfolio spans both.

Fire exposure varies by parcel. The town itself sits low, roughly 65 to 250 feet in elevation, but some wooded and hillside parcels toward the coast carry higher designations under the 2025 Cal Fire Fire Hazard Severity Zone maps that Sonoma County adopted for its unincorporated areas.

Where a property falls in a designated zone, California Building Code Chapter 7A can govern specific assemblies, such as exterior wall coverings and glazing. Whether and how it applies depends on the designation, the product, and the scope of work, so we verify it with the authority having jurisdiction rather than assume. For a multi-building property, that review happens building by building.

What drives a multifamily budget

We don't publish prices. Multifamily costs depend on:

• Total wall area and number of stories.
• Scaffolding and access requirements.
• How much substrate repair the test openings reveal.
• The material and finish chosen.
• Whether windows are included.
• Phasing complexity for occupied units.
• Any fire-zone assembly requirements.

We provide an itemized bid tied to the scope, so a board can compare options, such as fiber cement versus engineered wood, or siding now and windows next cycle, on the same basis. You can look through completed work on our projects page. For other properties in the area, see our Wine Country service area or the Sebastopol siding replacement page.

FAQ

Can residents stay in their units during a re-side? In most cases, yes. We phase the work so only one section of the property is active at a time, and we keep entries and walkways usable. Balconies or patios next to active work may be closed briefly, and we give management a schedule so residents know in advance.

Our property is just outside Sebastopol city limits. Who issues the permit? If the parcel is unincorporated, permitting typically goes through Sonoma County's Permit Sonoma rather than the City of Sebastopol. We confirm the correct authority for each address before scoping the permit set.

Do we have to use noncombustible siding? Only if a parcel's fire-hazard designation and the project scope trigger Chapter 7A requirements, and that differs by property. We check each building with the AHJ. Many boards choose fiber cement anyway because it is noncombustible and holds up in damp conditions.

Can you work from our reserve study or a consultant's specification? Yes. We can bid against an existing specification or reserve study line items, and we'll flag anything the site walk suggests should be adjusted before you commit.

Ready to scope your building? Request a bid or call Bay Area Siding Company at (415) 619-5167 to set up a site walk.