Retrofit vs Full-Frame Windows for Apartment Buildings

Most write-ups of this decision are written for a homeowner replacing eight windows. On an apartment community the same two methods carry different weight, because the cost of disruption is multiplied by the number of households and because the determination has to be made consistently across dozens of openings rather than case by case over coffee.

Here is how the two methods actually differ, and what decides it on a multifamily building.

What each method involves

Retrofit — the frame stays

The sash and glass are removed and a new window is installed into the existing frame. Exterior cladding is not disturbed. Work is largely from inside the unit, and the opening is closed the same day.

This is only available where the existing frame is structurally sound, reasonably square, and not leaking. What you gain is speed and a fraction of the disruption. What you give up is about an inch of glass around the perimeter, and the opportunity to inspect and re-flash what is behind the cladding.

Full-frame — back to the rough opening

The entire window comes out, including the frame. Cladding at the perimeter is removed, the opening is inspected, new flashing and a weather-resistive barrier are installed, the new window goes in, and the cladding is repaired.

This costs more and takes longer per opening. In exchange you get the full opening size back, a fresh flashing detail, and — not incidentally — a look at whether the wall behind the window is dry.

What actually decides it

The condition of the existing frame

This is the first gate and it is not a matter of preference. A frame with rot, corrosion, or significant distortion cannot host a retrofit that will seal. On buildings of mixed age or mixed exposure the answer often varies by elevation — west and weather-facing walls fail first, so a building can genuinely need both methods.

Whether the perimeter is already leaking

If you have staining below sills or damp reported inside, a retrofit puts a new window in front of a flashing detail you already know has failed. The water will keep arriving; you will simply have paid for new windows first. Where perimeter failure is documented, full-frame is the honest answer. Our page on preventing water damage behind siding covers what that damage does if it is left.

Egress in bedrooms

This is the constraint most often discovered late. Bedrooms require a window that provides a minimum clear opening for emergency escape and rescue. A retrofit reduces the clear opening, and on windows that were already close to the minimum, that reduction can put the unit out of compliance. On a building with a consistent original window size, this tends to be all-or-nothing across every bedroom in the community — which makes it a very large discovery to make halfway through.

Any bidder should be measuring bedroom openings before proposing a method. If a bid does not mention egress, that is a question to ask rather than an omission to accept.

How long you can be inside occupied units

On an occupied property this often decides more than price does. A retrofit is a short interior visit. Full-frame means exterior work, longer open-wall time, and a heavier notification and access burden. Neither is unmanageable, but they demand different schedules — our guide to phasing exterior work on occupied properties covers the logistics, and phasing a window replacement across an occupied building covers the window-specific version.

Whether the building is due to be re-clad

If a re-side is coming within a few years, sequencing matters more than method. Windows and cladding share a weather barrier: the flashing at the window head and sill is installed with the siding. Doing full-frame windows and the re-side as one project means that detail is built once and built right. Doing them separately, in the wrong order, means new siding detailed around old flashing.

The compliance floor is the same either way

Whichever method you choose, the windows themselves have to meet California’s energy standards in force when the permit is applied for. That is a property of the window, not the installation method, so it does not favour one approach over the other — but it does mean a retrofit cannot be used to avoid a specification. We cover what currently applies in Title 24 compliance for multifamily window replacement.

What to require from every bid

• Both methods priced, with the count of openings assumed for each.
• The determination rule — what condition moves an opening from retrofit to full-frame, and who decides on site.
• Bedroom egress addressed explicitly, with measured clear openings, not an assurance.
• A stated unit price for an opening that changes method after work starts, so a discovery is a known cost rather than a negotiation.
• What happens to the interior finish — stool, apron, casing and paint are frequently excluded, and residents notice.

The multifamily scope-of-work guide covers the same discipline applied to cladding, and most of it transfers.

Working with Heritage Exteriors

We replace windows on occupied apartment communities across Sacramento, the Bay Area and Northern California, and we do both methods with our own crews — CSLB #1055919. If you want the determination made properly before the budget is set, we will survey the openings, measure bedroom egress, and give you both prices with the assumptions written down. Call (916) 546-2991.