For most Southern California stucco houses with sound aluminum frames, a retrofit window is the right choice: it fits inside the existing frame, goes in without cutting the stucco, and costs the least per opening. A full-frame (new construction, nail-fin) window is the right choice when the old frame is rotted, rusted or leaking, when you want to change the size or shape of the opening, or when the walls are already open for a remodel or a re-stucco. Retrofit trades a little glass area for speed and price; full-frame trades stucco work and a longer schedule for a properly flashed opening and full-size glass. The best answer is often decided window by window, not for the whole house.
Green Design and Build is a licensed residential general contractor (CSLB #1110975) based in Van Nuys, serving Los Angeles, Orange and Ventura counties plus western Riverside and western San Bernardino counties. We install windows both ways, often on the same house, so this guide is written to help you pick the method each opening actually needs rather than the one a showroom happens to sell. Any price mentioned below is a budgeting range from our published cost guide, not a quote.
Quick answer: which install fits which window
| What you see at the window | Usually the better method | Why |
|---|---|---|
| Single-pane aluminum slider, frame straight and solid, no stains below it | Retrofit (flush-fin) | The old frame is a sound base, and the stucco can stay untouched |
| Water stains, bubbling paint, white mineral deposits or soft stucco under the window | Full-frame | The flashing behind the stucco has likely failed; a retrofit would seal over the problem |
| Wood frame with rot at the sill, or a steel frame rusting through | Full-frame | A new window is only as good as what it is fastened to |
| You want a bigger window, a door where a window was, or a different shape | Full-frame | The opening itself changes, so the frame, header and stucco all have to be reworked |
| Walls already open for a remodel, an addition or a full re-stucco | Full-frame | The stucco cost that normally makes full-frame expensive is already being spent |
| Wood-trimmed opening with no stucco return, or a historic look you want to keep | Block-frame | Fits inside the existing opening without a fin, so exterior trim can stay |
| Bedroom window that is already small | Check before choosing | A retrofit frame takes glass and clear opening from every edge |
What “replacement” and “new construction” windows actually mean
The terms describe how a window is attached to the house, not how new or good the window is. Many window lines are sold in both retrofit and new-construction versions. What changes is the edge of the frame and what happens to your wall.
Retrofit (replacement, insert) windows with a flush fin
This is the standard Southern California stucco retrofit. The old sashes and glass come out, the old frame stays in the wall, and the new window slides into it. The new unit has a flat exterior flange, called a flush fin or Z-bar depending on the profile, that laps over the old frame and sits against the stucco. That flange is sealed to the wall all the way around. Nothing is cut, and the stucco is not touched.
Block-frame windows
A block-frame window has no fin at all. It is a box that sets into an existing opening and is fastened through its sides, with trim covering the gap. It suits openings with exterior wood casing, brick or siding. It is usually not the first choice on a stucco tract house, because there is often no trim to finish against.
Full-frame, new construction or nail-fin windows
The new window has a flange (the nail fin) around its perimeter that is fastened to the wall framing and woven into the building paper and flashing behind the stucco. To install one in an existing house, the stucco around the opening is cut back, the whole old frame comes out down to the studs, and the wall is rebuilt around the new unit. This is the standard method for new houses and additions in stucco construction, and it is the only way to replace the flashing that keeps water out of the wall.
Terms vary by region, so if a bid says “full-frame,” ask whether it means the nail-fin method with stucco cutback and whether the stucco repair is included.
How a retrofit install works in a stucco wall
- Measure inside the old frame and order the new unit to fit it, with clearance for shims and sealant.
- Remove the sashes, glass and tracks. The old frame stays fastened in the wall.
- Check and prepare the frame so it is solid, level, square and clean.
- Set, shim and fasten the new window through its frame into the old one.
- Seal the fin to the stucco with a continuous bead. On a retrofit, that joint is the primary weather seal, so sealant grade and surface prep matter.
- Insulate the gaps and trim the inside. There is usually no drywall or exterior painting.
A retrofit disturbs almost nothing, but it relies on what is already in the wall. The original flashing and paper stay in place, and if water was already getting past them, a retrofit covers the evidence rather than fixing it.
How a full-frame (nail-fin) install works in a stucco wall
- Cut the stucco back around the opening, far enough to lap new paper over the new fin. Our window and door replacement page describes the cutback we normally use.
- Remove the whole old window, fin included, down to the framed rough opening.
- Repair the opening. Rotted sills, damaged sheathing or a sagging header are fixed while they can be seen.
- Flash the sill with a sill pan or self-adhered flashing so water that gets past the window drains out, not into the wall.
- Set the window and flash the fin at the jambs and head in shingle fashion, each upper layer lapping over the one below.
- Rebuild the wall: building paper lapped over the head flashing, lath, then scratch, brown and finish coats with cure time between them, textured to match.
- Paint the patch and repair the inside returns.
The flashing sequence is not a matter of taste. The California Residential Code (Section R703.4.1) requires flashing at exterior window and door openings, installed to the window manufacturer’s instructions (or the flashing or water-resistive barrier manufacturer’s instructions where the window maker’s do not cover it), and calls for a sill pan where no instructions are provided. The industry’s reference installation practice is ASTM E2112, Standard Practice for Installation of Exterior Windows, Doors and Skylights.
Matching an old stucco texture is the hardest part, and a patched band around every window can show unless the wall is finished or painted as a whole. Our guide to stucco repair, re-coating and full re-stucco explains why texture and color matching is difficult and when a full wall finish is the honest fix, and our exterior house painting cost guide covers what repainting adds.
Retrofit vs. full-frame, side by side
| Retrofit (flush-fin or block-frame) | Full-frame (nail-fin) | |
|---|---|---|
| What happens to the stucco | Untouched | Cut back around each opening and rebuilt |
| Old frame | Stays in the wall | Removed completely |
| Weather seal | Sealant between the new fin and the stucco, plus whatever flashing is already in the wall | New sill pan, fin flashing and building paper, then stucco |
| Hidden rot or water damage | Stays hidden | Exposed and repaired |
| Glass area | Smaller, because the new frame sits inside the old one | Full size of the opening |
| Changing size or shape | Not possible | Possible, with header and permit review |
| Interior disturbance | Minimal | Returns or casing usually repaired |
| Schedule for a whole house (from our window page) | About 1 to 3 days of installation | About 1 to 2 weeks, including cure time between stucco coats |
| Cost | Lowest per opening | Our cost guide adds +$300 – $800 per opening for the full-frame method, before any opening is enlarged |
Frame material, glass and size drive price more than the method. For per-window ranges, see our window replacement cost guide for Los Angeles. The +$300 – $800 per-opening figure is a budgeting range from that guide, not a quote, and it does not include repairing rot found once the old frame is out.
Waterproofing: where each method can fail
Most window leaks in stucco homes are not through the glass. Water gets behind the stucco at the corners of the opening and comes out at the sill or inside the wall.
- Retrofit failure points: a skimped or unmaintained sealant joint, drainage paths sealed shut against the manufacturer’s instructions, and old flashing that was already leaking.
- Full-frame failure points: flashing lapped in the wrong order, a missing sill pan, or new paper not tied into the old paper around the patch. Done right, full-frame is the more durable method; done wrong, it can create a new leak.
Before choosing, look at the wall under each window. Brown streaks, white powdery deposits, bubbling paint, cracks from the lower corners or hollow-sounding stucco mean water has been getting in. Those openings should be full-frame. Sealing a retrofit over a known leak is the mistake to avoid.
How much glass you lose with a retrofit
Because the new frame sits inside the old one, every edge of the glass moves inward by roughly the new frame’s thickness. The loss depends on the product, so ask for the visible glass size of the actual unit.
As an example only: if a 36 by 48 inch opening lost one inch of glass on every edge, the glass would go from 36 by 48 inches (1,728 square inches) to 34 by 46 inches (1,564 square inches), about 9.5 percent less. The smaller the window, the bigger the percentage.
Bedroom windows deserve a check. The 2025 California Residential Code moved the emergency escape opening rules from Section R310 to Section R319. A new escape opening needs at least 5.7 square feet of net clear opening (5 square feet at grade floor), at least 24 inches high and 20 inches wide, with the bottom of the opening no more than 44 inches above the floor. Section R319.5 lets a replacement window skip those size and sill-height requirements if it is the manufacturer’s largest standard size that fits the existing frame or rough opening, is the same operating style or a style with equal or greater opening area, and is not part of a change of occupancy. So a qualifying retrofit is allowed even if it shrinks the opening slightly, but a smaller opening is still a smaller way out in a fire. If a bedroom window is already marginal, consider a casement or a full-frame install that restores or enlarges it.
Energy code: what the new windows must meet either way
The installation method does not change the energy rules. Since 1 January 2026, permit applications in California fall under the 2025 Building Energy Efficiency Standards (Title 24, Part 6). For an existing single-family home, Section 150.2(b)1B says new manufactured windows that replace existing windows of the same total area must meet the prescriptive U-factor and solar heat gain coefficient (SHGC) in Table 150.1-A for your climate zone.
| Situation (2025 Energy Code) | Maximum U-factor | Maximum SHGC |
|---|---|---|
| Replacement windows, Climate Zones 6, 7, 8, 9 and 10 | 0.30 | 0.23 |
| Replacement windows, Climate Zones 11 through 14 | 0.27 | 0.23 |
| Replacement windows, Climate Zone 16 | 0.27 | No requirement |
| Exception: total replaced vertical glass of 75 square feet or less | 0.40 | 0.35 (in Climate Zones 2, 4 and 6 through 15) |
Your climate zone is set by location; the California Energy Commission’s climate zone search tool looks it up by address. The ratings come from the National Fenestration Rating Council (NFRC) label on each window, which lists the U-factor (heat loss, lower is better), SHGC (solar heat let in, lower blocks more), and visible transmittance. Check the label numbers for every product on the order, including large glass doors and specialty units, against the table before anything is ordered.
The same section notes that replacing glass in an existing sash and frame, or replacing sashes in an existing frame, is treated as a repair, provided the replacement is at least equivalent to the original in performance. A retrofit window is not that: it is a complete new manufactured unit, so it has to meet the replacement requirements, just as a full-frame window does.
Permits for window replacement in Los Angeles and nearby cities
Both methods need a permit in the City of Los Angeles. LADBS Information Bulletin P/GI 2020-003 (Express Permits) lists “window and door change-out (same size & type) for residential buildings” as express-permit work with no plan check, and states that dual glazing labeled and certified by NFRC is required for doors and windows replaced in residential buildings of three stories or less, per Title 24, Part 6, Section 150.2(b)1B. The same bulletin lists re-stucco for residential buildings as express-permit work.
- Same size, same type: a retrofit and a like-for-like full-frame replacement both fit the express-permit entry.
- Bigger, smaller, moved or converted openings: a change in size or type falls outside that entry, so it is not an over-the-counter express permit. Enlarging one also means a new header.
- Other cities: Burbank, Glendale, Pasadena and Santa Monica issue their own building permits, and unincorporated areas go through the county, each with its own forms and fees. We file with whichever agency governs your parcel.
Our breakdown of LADBS permit costs explains how city fees are calculated. Two other code sections come up on window jobs regardless of method:
- Safety glazing (CRC Section R324.4, formerly R308.4): glass in swinging, sliding and bifold doors needs safety glazing (tempered or laminated), as does glass within 24 inches of a door edge with its bottom under 60 inches above the floor, large low panes over 9 square feet beside a walking surface, and glass near tubs, showers, pools and stairs, with exceptions listed in the code.
- Window fall protection (CRC Section R321.2): where an operable window’s clear opening starts less than 24 inches above the floor and more than 72 inches above the ground outside, it must not pass a 4-inch sphere or must have an opening control device complying with ASTM F2090.
Older articles cite these rules as R308, R310 or R312, their 2022 numbers. The current text is in the 2025 California Residential Code, Chapter 3.
Pre-1978 homes: lead paint around the frames
Under the EPA’s Renovation, Repair and Painting (RRP) Program, anyone paid to do work that disturbs painted surfaces in homes built before 1978 must be trained and certified and follow lead-safe practices. A full-frame install disturbs far more painted surface (trim, stucco, interior returns) than a retrofit does, so it carries more containment and cleanup.
How to decide, window by window
Walk the house with a notepad and answer these for each opening. If any answer in steps 1 to 4 is yes, that window is a full-frame candidate.
- Is there water damage below or inside the window?
- Is the frame failing: soft wood, rusted steel, or bent or racked aluminum?
- Do you want the opening to change size, shape or type?
- Is that wall being opened anyway for a re-stucco, addition or remodel?
- Is it a bedroom window, a small window or a sidelight? Check the clear opening and glass loss before choosing retrofit.
- Does it need tempered glass? This affects the order, not the method.
- What does the label say? Confirm the NFRC U-factor and SHGC meet your climate zone before the order goes in.
Many houses end up mixed: retrofit for the sound sliders, full-frame for the stained or resized openings. A proposal should state the method for each opening.
When full-frame makes sense as part of a bigger project
Full-frame’s extra cost is mostly stucco, paint and patching. When those are already in the budget, retrofit loses its main advantage.
- Re-stucco or exterior refinish: set new-construction windows first so every opening is flashed under one continuous finish.
- Whole-house renovation: when walls are open inside, interior returns cost little extra. Our whole-home renovation cost guide shows how windows fit into a full scope, and our whole-home renovation service in Los Angeles covers how we sequence it.
- Rewiring an older house: if a house with knob-and-tube wiring is being rewired, coordinate the windows so walls are patched once.
- Additions: new walls get nail-fin windows. On our Montebello room addition, the new windows were in and their openings taped before the stucco finish coat, the same sequence shown in the photo at the top of this page. See our room additions page if you are planning one.
Still choosing colors, grids and styles? See our window and door design ideas.
Questions to ask before you sign a window contract
- Which method is proposed for each opening, and why?
- For full-frame openings, is the stucco patch, texture match and paint included, and to what edge (the patch only, or the whole wall)?
- How is the sill flashed on full-frame openings, and whose installation instructions will be followed?
- What are the NFRC U-factor and SHGC of each product, and which units are tempered?
- Who pulls the permit, and is the final inspection included?
- How is rot found after removal priced, and is the firm lead-safe certified for a pre-1978 house?
Check any contractor’s license before signing; our guide on how to verify a contractor’s license in California takes a few minutes. Our articles on hiring a contractor without getting scammed and on the California contractor payment schedule explain what a fair deposit and progress payments look like.
Retrofit vs. new construction windows FAQs
What is the difference between replacement and new construction windows?
Replacement (retrofit) windows fit inside the existing frame and seal to the outside of the wall, while new construction windows have a nail fin fastened to the framing and flashed behind the stucco, which means removing the whole old window and rebuilding the stucco around the new one.
Are retrofit windows a bad idea in a stucco house?
No. Retrofit is the right choice for most stucco homes whose existing aluminum frames are straight, solid and not leaking, because it avoids stucco work entirely; it becomes the wrong choice where water damage, a failing frame or a planned size change means the opening itself needs work.
How much more does full-frame window replacement cost?
Our Los Angeles cost guide budgets +$300 – $800 per opening for the full-frame method on top of the window itself, before any enlarged opening or hidden rot repair; it is a budgeting range, not a quote, and the stucco texture and paint scope drive where a job lands.
Do retrofit windows reduce the glass area?
Yes, because the new frame sits inside the old one, every edge of the glass moves inward by about the frame’s thickness, which is most noticeable on small windows; ask for the visible glass size of the actual product before ordering.
Can a flush-fin retrofit window leak?
It can if the fin-to-stucco sealant is poorly applied or not maintained, or if the original flashing behind the old frame was already failing, which is why openings with water damage should be done full-frame.
Do I need a permit to replace windows in Los Angeles?
Yes; in the City of Los Angeles a same-size, same-type window and door change-out on a home is an LADBS express permit with no plan check, and the new units must be NFRC-labeled dual glazing meeting Title 24, Part 6, while changing an opening’s size or type falls outside the express list.
Can a replacement window make a bedroom window too small for egress?
Under CRC Section R319.5, a replacement window is exempt from the escape-opening size and sill-height rules if it is the manufacturer’s largest standard size that fits the existing frame or rough opening and keeps the same operating style or one with equal or greater opening area, but a smaller opening is still harder to escape through, so marginal bedroom windows are worth upgrading to a casement or full-frame install.
Which is better for energy efficiency, retrofit or new construction windows?
Both must meet the same Title 24 U-factor and SHGC limits, so the product sets most of the performance; full-frame adds the chance to air-seal the rough opening, while a retrofit depends on how well the old frame was sealed.
Get a window-by-window recommendation for your house
We will look at every frame and the stucco under it, tell you which openings can be retrofitted and which need full-frame, check egress, tempered glass and Title 24 ratings, and send one written proposal, usually within 48 hours of the site visit. Learn more about our window and door replacement service, read our customer reviews, or see how financing for home improvement projects works. Call (800) 348-3050, 8am to 6pm daily, or contact our team to schedule a visit.