Bay Area Siding Company installs replacement and new-construction windows for Belmont homeowners — from the ranch and mid-century houses around Carlmont down to the flatter streets of East Belmont, and up into the custom hillside homes near Water Dog Lake. We're a Larkspur-based siding and window contractor, and we run the whole job: measuring, glass and energy selection, permitting, removal, flashing and air-sealing, and a final walkthrough.

Ready to move forward? Request an estimate or call (415) 619-5167.

Signs it's time to replace

Plenty of Belmont's mid-century and ranch homes are still running their original single-pane windows, and they usually tell on themselves:

• A draft or a cold zone near the glass even with the sash shut and locked
• Fog or moisture trapped between the panes — a blown seal on a dual-pane unit, which can't be fixed, only replaced
• Sashes that bind, drop, or won't latch — swollen wood, paint-sealed frames, or worn balances
• Heating bills that climb behind single-pane glass with no Low-E coating
• Soft frames, rot, or staining at the sill or the surround

When two or more of these show up together, replacement is usually the better long-term call than another round of patching.

What to look for in a replacement window

Three decisions carry most of the weight:

• Energy performance. Go for dual-pane insulated glass with a Low-E coating. Belmont sits in California's Title 24 Climate Zone 3, and the energy code sets maximum U-factor and SHGC values for replacement windows — the units you choose have to meet the code in force at permit time, so your installer should confirm the current numbers rather than quote a figure from memory.
• Frame material. Vinyl, fiberglass, aluminum-clad wood, and aluminum each balance cost, thermal performance, and looks differently. A mid-century or custom Belmont home with defined trim often reads best with clad-wood or a profile chosen to respect the original opening.
• Retrofit vs. new-construction. A retrofit (insert) install keeps the existing frame and is less invasive; a new-construction install takes the window back to the framing so flashing can be fully renewed — often the right move where there's rot or past water intrusion. We do both and recommend based on what we find.

Comparing brands? Start at our window hub, /bay-area-window-replacement/, then read the specifics for Anlin, Milgard, Andersen, Marvin, and Pella. We install aluminum windows as well.

What to expect: our process

1. Consultation — we look at your existing windows, openings, and goals.
2. Measure — precise field measurements for each opening.
3. Product and energy selection — glass package, frame, and finish chosen to meet Title 24 for Climate Zone 3.
4. Permit — Belmont's Building Department reviews window-replacement work; we submit it.
5. Removal and prep — old units out, openings inspected for rot or damage.
6. Install, flashing, and air-seal — set level and plumb, then flashed and sealed against water and air.
7. Finish and walkthrough — trim, caulk, an operation check, and cleanup with you.

Belmont-specific things to know

Permits. The City of Belmont's Building Department (Permit Center) reviews window replacement, and it publishes separate guidance for openings under and over 75 square feet. Because a window swap is an alteration under the Energy Code, Title 24 energy documentation is part of the submittal. We handle the permitting.

Fire-zone glazing on the west side. Belmont's wooded western slopes — the neighborhoods around the Water Dog Lake open space and above it — fall within fire hazard zones on Cal Fire's 2025 Local Responsibility Area maps, and Belmont is served by San Mateo Consolidated Fire. Where an opening in a fire-hazard area is altered, California Building Code Chapter 7A pushes toward multi-pane glazing with a tempered component, among other requirements. Exactly what applies depends on your parcel and on whether the work is classed as a repair or an alteration, so it's worth pinning down early — we confirm it with the City as part of scoping. Homes in flatter East Belmont typically don't carry this glazing concern.

Older housing stock. Belmont's ranch, mid-century, and bungalow homes frequently still hold their original single-pane sashes, which is why the jump to a modern dual-pane, Low-E unit is so noticeable in both comfort and quiet — a real difference on the busier corridors near El Camino Real and the highway.

Already thinking about the exterior envelope? We also do James Hardie siding and siding replacement in Belmont, and we serve the wider Peninsula. See finished work in our project gallery.

What affects the cost

We don't quote prices online because every job is different. The drivers are the number and size of openings; frame material and brand; retrofit versus new-construction; whether fire-zone tempered or multi-pane glazing is required on an uphill parcel; the condition of the existing framing (rot repair adds scope); and access — upper-story and hillside openings take more setup.

Frequently asked questions

Do I need a permit to replace windows in Belmont? Yes. Belmont's Building Department reviews window replacement, and Title 24 energy documentation is part of the submittal. We take care of the permitting.

I'm up in the Belmont Hills fire zone — do my windows need to be tempered? Quite possibly, if the work is an alteration. In mapped fire-hazard areas, altered openings generally call for multi-pane glazing with at least one tempered pane under Chapter 7A. The exact requirement depends on your parcel and scope, which we confirm before ordering.

Can I keep the look of my mid-century or hillside home? Yes. Frame material and profile can be matched to the original openings — clad-wood and specific vinyl or aluminum profiles all work depending on the house.

Retrofit or new-construction — which do I need? Retrofit is less invasive and keeps the existing frame; new-construction is the better path where there's rot or water damage and you want the flashing fully renewed. We assess and recommend.

Get started

Get replacement windows sized, specced, and installed right the first time. Request an estimate or call Bay Area Siding Company at (415) 619-5167.