Sliding Patio Door Replacement: A California Homeowner’s Guide

Sliding patio doors get more use and more abuse than any window in the house. They also sit at floor level, where water, dirt and foot traffic meet. This guide, part of our California window guide, covers what a replacement involves and which rules apply.

Repair or replace?

Start with what is actually wrong.

If the door is a dual-pane unit in a sound frame and the only complaint is how it rolls, new rollers are a legitimate repair and far cheaper than a door. If it is an original single-pane aluminum slider, parts will not change how it performs. Our article on why glass fogs between the panes explains seal failure, which works the same way in a door.

Frame materials

Patio doors come in the same materials as windows, with the differences magnified by size. Milgard, for example, lists sliding glass doors in vinyl, fiberglass and thermally improved aluminum, in two-, three- and four-panel configurations.

Vinyl

The most common replacement choice in California. Vinyl does not corrode or need painting and insulates well. The frame profiles are wider than aluminum, so you give up a little glass. On very wide or tall doors, check how the panel is reinforced, because vinyl is the least stiff of the options.

Fiberglass

Stiffer and more dimensionally stable than vinyl, with a painted finish and narrower profiles. A good fit for large panels, dark colors, and hot west-facing walls. See our comparison of fiberglass and vinyl.

Aluminum

The narrowest frames and the most glass, which is why mid-century and contemporary houses use it. Old aluminum sliders have no thermal break and are the worst-insulating component in many homes. Current products are thermally improved or thermally broken, meaning an insulating section separates the inside and outside metal. They can meet the Energy Code, but check the NFRC label rather than assuming, since aluminum starts at a disadvantage. More on the material in aluminum windows: advantages and disadvantages.

Wood and wood-clad

Wood interiors with aluminum or fiberglass cladding outside suit traditional houses and match wood windows. They cost more and the interior wood needs finishing and care, particularly at the bottom rail where water and wet shoes land.

Retrofit or full-frame replacement

The same choice as with windows, with higher stakes because the door sits at the floor.

• Retrofit. The old panels and interior track come out, the old frame stays in the wall, and the new door frame is set into it with a fin that covers the old frame outside. There is no stucco or siding work. The opening gets slightly smaller, and the sill gets slightly taller, because the new sill sits on the old one.
• Full-frame. The old frame is removed down to the rough opening. The installer can inspect the framing and subfloor at the sill, install a sill pan and new flashing, and set the new door at the right height. The exterior finish around the opening has to be cut back and patched.

For a door, the sill is the deciding factor. Old sliders that have leaked for years often hide damaged subfloor or framing under the track. If there is staining, soft flooring or swollen baseboard near the door, choose full-frame so the damage can be found and repaired. If the opening is dry and sound, a retrofit is a reasonable way to avoid exterior patching, especially in stucco. Our guide to retrofit versus new construction installation covers the methods in detail.

Rollers and tracks

How a door feels in ten years depends on parts you never see in the showroom.

• Rollers. Tandem rollers, two wheels per assembly, spread the panel's weight and ride over small debris better than single wheels. Milgard describes its AX650 large sliding door as built to glide on tandem rollers. Stainless steel ball-bearing rollers resist corrosion better than plain steel, which matters near the coast and near pools.
• Track. The track takes the whole weight of the panel on a thin raised rail. Aluminum rails wear and dent; a stainless steel cap over the rail lasts longer.
• Adjustment. Rollers adjust up and down through holes in the panel edge. A panel that has settled can usually be squared to the frame in minutes. Ask your installer to show you where the adjusters are.
• Use. Vacuum the track rather than hosing it, and keep the weep holes open. Milgard's warranty asks that operable panels be opened and closed monthly and excludes damage from power washing.

Security

Older sliders earned their poor reputation: a single hook latch, and panels that could be lifted out of the track from outside. Current doors address both.

• Multi-point locks engage the frame at two or more points instead of one.
• Anti-lift features at the head keep the panel from being raised out of the track when closed.
• A secondary lock, such as a foot bolt or a bar in the track, backs up the primary latch and lets you lock the door slightly open for ventilation.
• Laminated glass stays bonded to its interlayer when broken, so it resists entry longer than tempered glass, which crumbles. It can be ordered in many door lines.

Our sibling guide on window and door security in California goes into locks and glass in more detail.

Safety glazing: CRC Section R324

Every pane in a sliding door must be safety glazing. Under the 2025 California Residential Code, Section R324.4.1 (formerly R308.4.1), glazing in fixed and operable panels of swinging, sliding and bifold doors is a hazardous location. The only exceptions are openings too small for a 3-inch sphere to pass through and decorative glazing.

The code also covers glass next to the door. Under R324.4.2, a window panel within 24 inches of either side of a door, with its bottom edge less than 60 inches above the floor, is a hazardous location as well, with listed exceptions. If you are replacing sidelights or adjacent windows along with the door, they need safety glazing too.

Glass in hazardous locations has to pass the impact test in the federal standard CPSC 16 CFR 1201, and each pane must carry a permanent manufacturer's designation, etched or otherwise applied so it cannot be removed without being destroyed. A new factory-built door arrives this way. The rule matters most when someone replaces only the glass. Our page on California tempered glass requirements covers the other hazardous locations.

Title 24: a glazed door is fenestration

The 2025 Energy Code defines a glazed door as an exterior door with a glazed area of 25 percent or more of the door's area, and states that glazed doors shall meet fenestration product requirements. The Energy Commission's compliance manual says it plainly: glazed doors are treated the same as windows and must meet the U-factor and SHGC requirements for windows.

So a replacement sliding door is held to the replacement-fenestration figures for your climate zone:

• Maximum U-factor 0.27 in Climate Zones 1 to 5, 11 to 14 and 16, which covers Sacramento, the Bay Area and Tahoe. Maximum 0.30 in Zones 6 to 10 and 15.
• Maximum SHGC 0.23 in Zones 2, 4 and 6 to 15. No SHGC requirement in Zones 1, 3, 5 and 16.

The small-job exception helps with doors. Replacement of no more than 75 square feet of vertical fenestration may use a U-factor up to 0.40 and, where SHGC applies, an SHGC up to 0.35. A standard six-foot slider is roughly 40 square feet and an eight-foot one roughly 53, so a single door replaced on its own usually fits inside the exception. A door plus several windows in the same project may not.

The NFRC label on the door shows both values. Large doors with narrow aluminum frames are the products most likely to miss 0.27, so check the label for the exact size and glass quoted. The details are on what Title 24 requires of replacement windows, and how to read an NFRC label explains the numbers.

Threshold and water management

Sliding doors are designed to manage water, not exclude it completely. Rain that reaches the track is collected in the sill and drained to the outside through weep holes. That system needs three things from the installation.

• A sill pan or equivalent flashing under the door, sloped or dammed so any water that gets past the sill goes out, not into the subfloor. The Residential Code requires doors to be installed according to the manufacturer's written instructions and openings to be flashed.
• An exterior surface lower than the track. Patios, decks and pavers that have been built up to door level are a leading cause of leaks. The Residential Code also limits how far below the threshold the landing can be: for exterior doors other than the required egress door, the landing or floor must be no more than 7 3/4 inches below the top of the threshold.
• Clear weeps and intact sealant. Both are maintenance items.

A higher sill generally resists more water under wind pressure, and a low or flush sill is easier to step or roll over. If someone in the house uses a walker or wheelchair, ask about low-profile sill options and be realistic about exposure: a low sill on a wall that takes direct weather needs an overhang or a drain outside. Our sibling guide on flashing and waterproofing explains the layers.

Sizing and configuration

Most tract-house sliders are two panels, one fixed and one operating, commonly five, six or eight feet wide and either six feet eight inches or eight feet tall. Replacement doors are built to the measured opening rather than pulled from stock, so an odd size is not a problem.

• Which panel slides. Doors are ordered with the operating panel on the left or right as seen from outside. You can usually change this when you replace.
• Three- and four-panel doors fill wider openings. In a four-panel door the two center panels slide apart.
• Making the opening wider or taller is a structural change. The header above the door carries the wall and roof, so a bigger opening means a new header, a building permit with plans, and exterior and interior finish work. The larger systems are covered in our sibling guide to multi-slide and folding glass doors.
• Switching to hinged doors in the same opening is usually possible. See French versus sliding patio doors.

Screens, blinds between the glass, grids and glass tints are all options at order time and difficult to add later.

Permits

Replacing an exterior door that is fenestration under the Energy Code generally needs a building permit in California, the same as replacement windows, and the permit is where safety glazing and energy compliance get checked. Rules and fees are local. See whether you need a permit for retrofit windows. For budgeting, see our cost page.

Sources

• 2025 Building Energy Efficiency Standards: definition of glazed door (Section 100.1), Section 150.2(b)1B and its exceptions, Table 150.1-A
• 2025 Single-Family Residential Compliance Manual, Chapter 3 (glazed doors) and Chapter 9 (alterations)
• 2025 California Residential Code, Chapter 3: Sections R318.2, R318.3, R324.1, R324.3 and R324.4
• 2025 California Residential Code, Section R609
• Milgard sliding glass doors, Milgard AX650 and the Milgard warranty effective 1 January 2026

Working with Heritage Exteriors

We replace sliding patio doors alongside window projects and will tell you when rollers or a glass unit would solve the problem instead. When we do replace, we look at the sill and the patio height first, because that is where patio doors fail. Licensed in California, CSLB #1055919. Call (916) 546-2991.