Window, door & siding replacement in Mill Valley, CA

Custom Exteriors replaces windows, entry doors, patio doors, and siding for Mill Valley homeowners, with products chosen for shade, moisture, and wildfire exposure under Mount Tamalpais. We install Infinity from Marvin fiberglass windows, James Hardie fiber cement siding, and ProVia and Therma-Tru entry doors, using our own full-time AAMA Certified Master Installers, not subcontractors.

Why Mill Valley homes are hard on windows and siding

Mill Valley homes sit in redwood canyons and on wooded hillsides, so exteriors stay shaded and damp far longer than in most Bay Area towns. That constant moisture leads to rotting wood window frames, swollen sashes, mildew, and siding that fails first on the shaded side of the house.

The town grew up around a sawmill built in the 1830s on Cascade Creek and incorporated in 1900. After the 1906 earthquake, many San Franciscans settled here permanently, and early summer cabins in the canyons became year-round homes. Today about 14,000 residents live in a mix of downtown Victorian and Craftsman cottages, converted canyon cabins, midcentury ranch and view homes, and modern rebuilds with walls of glass.

With median sale prices above $1.6 million, homeowners here want replacements that respect the character of older homes and hold up in a wet, wooded setting. Custom Exteriors has completed 30,000+ projects over 29 years with Infinity from Marvin, James Hardie, and ProVia and Therma-Tru products, exclusively. We do not install vinyl or builder-grade alternatives.

Moisture and wildfire considerations for Mill Valley homeowners

Mill Valley homeowners deal with two risks that pull in opposite directions: dampness most of the year and wildfire in the dry season. The right exterior materials handle both.

Moisture. Canyon neighborhoods like Old Mill, Cascade, and Blithedale Canyon sit under redwoods and summer fog, so sun rarely dries out siding and window frames. Fiberglass window frames and fiber cement siding do not rot, swell, or attract pests the way wood does.

Wildfire. CAL FIRE's 2025 Fire Hazard Severity Zone maps place parts of Mill Valley in the Very High category, especially along wooded hillsides near open space. Fire code enforcement for the City is handled by the Southern Marin Fire Protection District. You can look up your address on the CAL FIRE Fire Hazard Severity Zone viewer.

That is where product choice matters:

Windows: Infinity from Marvin windows are available with tempered glass options, the same type of glass California requires on new homes in fire hazard zones.
Siding: James Hardie fiber cement siding is noncombustible. Learn more about fire-resistant siding.
Energy: Glass packages that meet Title 24, California's state building energy code, keep shaded, fog-cooled rooms warmer and reduce condensation on the glass.

Replacement windows and patio doors

Infinity from Marvin fiberglass windows are the window line we install in Mill Valley because fiberglass holds up to years of shade and moisture without rotting. Fiberglass expands and contracts at nearly the same rate as glass, so the seal between frame and glass stays tighter over time than vinyl typically does. See our fiberglass versus vinyl comparison for the specifics.

What a Mill Valley project looks like depends on the house:

Downtown cottages and Craftsman homes: Double-hung windows with divided-lite patterns and trim profiles matched to the original construction.
Canyon homes: Casement windows that seal tightly and open fully for airflow in shaded rooms.
Midcentury and Eichler homes: Large-format window replacement matched to original opening sizes and sightlines.
View homes and modern rebuilds: Picture windows, window walls, and sliding, French, or bi-fold patio doors that open onto decks.

We choose retrofit, block frame, or new construction installation based on your existing frames and any rot or water damage we find in the openings. Our window installation methods guide explains each one. For stair-access hillside homes, we plan delivery and installation logistics during the consultation. As an Infinity from Marvin Platinum Partner, Marvin's highest certification tier for Infinity dealers, we carry full-size displays in our Pleasanton showroom.

Entry door replacement

In Mill Valley's damp canyons, original wood entry doors often swell, stick, and lose their finish within a few years. A new fiberglass or steel entry door fixes those problems and updates the look of the house at the same time.

ProVia and Therma-Tru entry doors come in fiberglass and steel, including fiberglass doors with realistic wood-grain finishes that suit a Craftsman cottage or a brown-shingle home. Our design consultants help you choose a style, glass, and hardware that fit the house.

James Hardie fiber cement siding

James Hardie fiber cement siding is the siding we recommend for Mill Valley because it solves the two biggest problems here: rot from constant moisture and exposure to wildfire. Wood siding on shaded walls often shows soft spots, mildew, and peeling paint long before the rest of the house, and wood is combustible.

James Hardie fiber cement does not rot, resists moisture and pests, and is noncombustible. HardieShingle siding offers a shingle look that suits many of Mill Valley's older homes. ColorPlus Technology, James Hardie's factory-applied finish, is baked on under controlled conditions, so it holds color longer than siding painted on site. The siding is backed by a 30-year non-prorated product warranty and a 15-year ColorPlus finish warranty. We install James Hardie exclusively because after 29 years of evaluating siding, it is what we would put on our own homes.

If you are replacing siding, it is also the right time to replace windows with new construction installation, so each opening can be fully flashed and sealed against moisture.

Why Mill Valley homeowners choose Custom Exteriors

Mill Valley homeowners hire Custom Exteriors for accountability they can verify before they sign:

Full-time installers, not subcontractors. Our installation team are Custom Exteriors employees, many with more than a decade on our crew.
AAMA Certified Master Installers (American Architectural Manufacturers Association), trained to the installation standards manufacturers require to honor their warranties.
Moisture-focused installation. We inspect every opening for rot and water damage before installing, and we flash and seal to keep water out.
Older-home experience. We are EPA Lead-Safe Renovation, Repair, and Painting (RRP) Certified, which matters for the many Mill Valley homes built before 1978.
Third-party recognition and warranty coverage. Diamond Certified and BBB Accredited. See our awards, reviews, and product and labor warranty.

Frequently asked questions

Q: Do I need a permit to replace windows in Mill Valley?A: Most window replacement projects need a building permit, especially when the work changes an opening's size or removes the existing frame. Requirements depend on where you live: homes inside the City of Mill Valley go through the City's building department, while Tam Valley, Almonte, Homestead Valley, and Strawberry are unincorporated and go through Marin County. Custom Exteriors confirms what your project needs and handles the permit and inspections for you.

Q: What windows hold up best in a shaded, damp redwood setting?A: Fiberglass frames are one of the most durable choices for a damp climate because they do not rot, swell, or warp. Infinity from Marvin fiberglass windows paired with a Title 24 glass package also reduce condensation and keep shaded rooms warmer.

Q: My home is in a Very High Fire Hazard Severity Zone. Do my replacement windows have to be tempered?A: California's wildfire building standards, including multipane glass with at least one tempered pane, apply to new homes in fire hazard zones. Requirements for replacements on existing homes can differ, and we confirm what applies to your property during the consultation. Many homeowners choose tempered glass either way because it meets the same standard new homes must meet.

Q: How much does window replacement cost in Mill Valley, CA?A: Cost depends on the number and size of your windows, the products and glass package you choose, the installation method, and site access. Stair-access hillside homes and large view windows typically cost more than standard installations. Review our window pricing factors and window cost guide before your consultation. We provide free, itemized estimates so you know what you are paying for before you decide.

Q: My Mill Valley home was built before 1978. Does that change the project?A: It can. Homes built before 1978 may contain lead-based paint, and federal law requires lead-safe work practices on renovations that disturb painted surfaces in those homes. Custom Exteriors is EPA Lead-Safe Renovation, Repair, and Painting (RRP) Certified, and we confirm whether lead-safe procedures apply before installation begins.

Q: Do I have to visit the Pleasanton showroom to get an estimate?A: No. We offer free, no-pressure in-home consultations in Mill Valley. The showroom is there if you want to see and handle full-size window, door, and siding displays first.

Ready to upgrade your Mill Valley home's windows, siding, or doors?

Schedule a free, no-pressure consultation and we will walk through your home, your options, and an itemized estimate, with no obligation. Prefer to see the products first? Our Pleasanton showroom has full-size displays of every window, door, and siding product we install.

Schedule a no-pressure consultation | Visit our Pleasanton showroom (2142 Rheem Drive, Suite E, Pleasanton, CA 94588) Phone: (925) 249-2280 local, (888) 957-7800 toll free

Convenient financing options

We offer 18 months zero payments and zero interest, or 4.99% financing on approved credit. Financing is a tool to make a project more accessible, not the reason to choose us. Bring it up during your consultation if you would like to discuss options.

Explore Financing Options

Nearby areas we also serve

Custom Exteriors also serves Sausalito, Tiburon, San Francisco, and Richmond, along with Pleasanton, Dublin, Livermore, San Ramon, Danville, and the greater East Bay. See the full service area list for every city we cover.