Apartment and Multifamily Window Replacement: How to Plan It

Replacing windows in an apartment or condo building is less about the window and more about access, notices and sequencing. Each unit has to be entered on a schedule residents can live with, the building usually needs a permit with Title 24 energy compliance, buildings built before 1978 need lead-safe work practices, and condo projects need association approval first. The biggest decision is whether to install from inside each unit with retrofit windows or from outside with scaffolding and full-frame windows, because that choice drives cost, disruption and how well the openings stay watertight.

This guide is written for Bay Area owners, property managers and HOA boards planning a building-wide project. If you only need one window replaced in a single unit, the same rules apply on a smaller scale.

Installing from inside vs from outside

If the building has a history of leaks around windows, a retrofit insert hides the problem rather than fixing it. Water that gets past an old frame keeps reaching the sheathing and framing behind it. Our guide to retrofit vs new construction windows goes deeper on that trade-off.

Combine windows with siding work when you can

Windows and siding on older apartment buildings often wear out on a similar timeline. Doing both together means the scaffold goes up once, every window gets new flashing lapped into a new weather barrier, and residents deal with one project instead of two. It is also the point where hidden sheathing damage around old windows can be found and repaired. Our multifamily siding and window renovation page explains how we scope those projects, and our Santa Rosa four-unit James Hardie project shows a building-wide re-side.

Who has to approve the project

Rental buildings

The owner decides, but residents still have rights to notice and privacy (see below). Cities with local rent ordinances, including San Francisco, Oakland and Berkeley, may have their own rules on construction in occupied units and on passing capital improvement costs through to tenants. Check with the local rent program before you finalize the schedule.

Condos and HOAs

Start with the CC&Rs. They decide whether windows belong to the individual owner, the association, or are exclusive-use common area, and that decides who pays and who signs the contract. Where owners need architectural approval, California's Davis-Stirling Act requires the association's decision to be in writing, made in good faith, and not unreasonable, arbitrary or capricious. A disapproval must explain why and describe how to ask the board to reconsider. An approval can't override building codes, so a permit is still needed.

For association-wide projects, boards usually agree on one window product, color and grid pattern for the whole building. Mixed products from unit-by-unit replacements over the years are a common reason buildings look patchy.

Resident notices and access

For rental units, California Civil Code Section 1954 allows a landlord to enter to make necessary or agreed repairs, alterations or improvements, with reasonable written notice. Twenty-four hours is presumed reasonable, and a notice sent by mail is presumed reasonable only if mailed at least six days before entry. Entry is generally limited to normal business hours. Get your own legal advice on notices, especially in rent-controlled cities.

Beyond the legal minimum, a few things make building projects go smoothly:

• Publish a schedule by unit or by stack and update it when weather or deliveries shift.
• Tell residents what to move. Furniture, plants and items on sills need to be cleared from in front of each window, and blinds or curtains usually have to come down.
• Plan for pets, security and weather. An opening should be closed in the same day, and units shouldn't be left open overnight.
• Name one contact for residents to call about access problems or damage.

Lead-safe rules in pre-1978 buildings

Many Bay Area apartment buildings were built before 1978, when lead-based paint was still in use. Under the EPA's Renovation, Repair and Painting (RRP) rule, anyone paid to disturb painted surfaces in pre-1978 housing must be an EPA-certified firm using certified renovators and lead-safe work practices. EPA states that window replacement is always covered, regardless of how much paint is disturbed.

In multi-unit buildings, the firm must give the building owner EPA's Renovate Right pamphlet and get written acknowledgment. When work affects common areas, occupants of the affected units must be told the nature, location and expected completion date of the work, by delivering the information to each unit or by posting signs while the work is going on. You can confirm a contractor's certification with EPA's online firm search.

Permits, Title 24 and code checks

Energy code

Window replacement in apartment buildings falls under the multifamily alteration rules in Section 180.2 of California's 2025 Energy Code, which took effect for permit applications filed on or after January 1, 2026. Replacement windows must meet maximum U-factor and, in many climate zones, solar heat gain and visible light values from a table that varies by window type and climate zone. When 150 square feet or less of the building's windows are replaced, the solar heat gain and visible light requirements don't apply. Replacing only glass or sashes in existing frames is treated as a repair. Our Title 24 guide explains U-factor, SHGC and NFRC labels.

Escape openings

Apartment buildings of three or more units are generally governed by the California Building Code rather than the Residential Code, but sleeping rooms still need compliant emergency escape openings. A replacement window should never shrink a bedroom's clear opening. Our egress window guide explains how clear opening is measured.

Fire-related glazing

Two situations call for special glass or rated assemblies. Windows in walls close to a property line or another building may need fire-protection-rated assemblies under the building code. Buildings in a Fire Hazard Severity Zone fall under the California Wildland-Urban Interface Code, which typically calls for multi-pane glass with at least one tempered pane. The building department will tell you which applies during plan review, so raise it before windows are ordered.

Scheduling and phasing

1. Survey every opening. Windows that look identical across a building often differ in size, condition or framing. Measure each one before ordering.
2. Order by elevation or by stack. Labeling windows by unit and location keeps installation moving and avoids reshuffling deliveries.
3. Phase by side of the building. Scaffold one elevation at a time so most residents have only a few days of disruption.
4. Plan around the rainy season. Bay Area winters bring storms from roughly November through March. Full-frame work and siding tie-ins are easier in dry months; inside retrofits are less weather-sensitive.
5. Inspect as you go. Check flashing and sealant on the first few openings before the crew repeats the detail across the building.

What drives the cost

• Retrofit vs full-frame installation, and whether siding or stucco has to be cut and patched
• Access: scaffolding, lifts, street-use permits and upper-floor work
• Window material and options such as tempered glass, sound-rated glass or custom colors
• Lead-safe work practices in pre-1978 buildings
• Repairs to rotted sills, framing and sheathing found when old windows come out
• Scheduling constraints from occupied units

We don't publish flat prices for multifamily work because every building differs. We give a free written estimate after walking the building.

Frequently asked questions

Do tenants have to move out during window replacement?

Usually not. Window replacement is normally done one unit at a time while residents stay in place, and each opening should be closed in the same day. Residents need written notice before entry and should clear the area in front of each window.

Should apartment windows be replaced all at once or in phases?

Phasing by elevation or by building is common and spreads out cost and disruption. Replacing everything in one project usually gets better pricing and consistent product and color across the building. Either way, choose one product and finish for the whole building.

Who pays for window replacement in a condo?

It depends on the CC&Rs. Windows may be the individual owner's responsibility, the association's, or exclusive-use common area with shared rules. Check the governing documents and get architectural approval before ordering.

Do apartment window replacements need a permit?

In most cases, yes. The permit is how the city checks Title 24 energy compliance, emergency escape openings and any fire-related glazing. Confirm with your local building department.

Is retrofit or full-frame better for apartments?

Retrofit inserts are faster and less disruptive when the existing frames are sound and dry. Full-frame replacement is better when openings leak or the siding or stucco is being replaced, because it lets each window be flashed into the weather barrier.

Sources

• California Energy Commission: 2025 Energy Code, Section 180.2 alterations (PDF)
• U.S. EPA: Renovation, Repair and Painting Program for contractors
• U.S. EPA: Pre-renovation education for common areas in apartment buildings
• California Legislative Information: Civil Code Section 1954
• Davis-Stirling.com: Civil Code Section 4765, architectural review