Foggy or cloudy sliding door glass means the seal on the insulated glass unit has failed and moisture is trapped between the two panes. No cleaner reaches it. The fix is a new tempered insulated glass unit set into your existing panel; the frame, rollers and lock stay. We measure the unit on site, quote it before ordering, and install it when it arrives.
Likely causes
- The perimeter seal on the insulated glass unit has failed and let moist air in
- Years of daily heating and cooling on a south or west facing door, which flexes the seal
- A unit that was never sealed well from the factory or was disturbed during an earlier repair
- Water sitting in the bottom of the frame against the glass edge
- Not dirt: fog you cannot wipe from either side is inside the unit
What you are seeing
A haze, a milky patch, or beads of water on the glass that will not wipe off from inside or outside. It comes and goes with the weather: worse on a cool morning, sometimes almost clear by afternoon. Over time it leaves white mineral streaks or a permanent cloud, usually starting low where water pools.
The door itself slides and locks fine. Only the view has changed.
If the fog is on one surface and wipes off, it is condensation, not a failed seal. Fog you cannot reach is inside the unit.
What usually causes it
Nearly every patio door made in the last few decades has double-pane glass: two sheets of tempered glass with a spacer between them, sealed around the edge, with dry air or gas inside. That seal is the only thing keeping outside air out.
Seals fail with age. Daily heating and cooling flexes the glass against the spacer, the sealant hardens, and one day it lets moist air in. Moisture then condenses on the inside faces where you cannot touch it. A south or west facing door in full San Diego sun works its seal hardest.
Water standing in the bottom of the sash against the glass edge speeds it up, so a door with blocked weep holes often fogs first. Cleaning does not help because the haze is sealed in.
Need foggy glass replaced this week?
Call or text with your address, how many doors and what the door is doing. You get a firm price before we come out.
What you can check yourself in two minutes
- Wipe both sides. If the haze stays, it is between the panes.
- Find the stamp. Look in a corner of the glass for a small etched label. It usually names the manufacturer and says tempered, and sometimes shows a date. Photograph it; it helps us match the unit.
- Measure the visible glass. Width and height of the glass you can see, to the nearest quarter inch. This is for a rough idea only; we take the real measurements on site.
- Check the weep holes. Look along the outside bottom of the frame for small slots and clear them with a toothpick. It will not fix the fog, but it stops water sitting against the next unit.
Do not try to drill or vent the glass, and leave the glazing stops alone; a loose unit can slip and break.
What we do about it
We replace the glass unit, not the door. On the first visit we measure the unit, confirm the thickness and spacer width, note any tint or low-e coating, and quote the job. Glass is never quoted from a website; it is ordered to size and the price depends on the dimensions and the glass spec.
The new unit is tempered safety glass on both panes, which is required in doors, with a new sealed spacer. When it arrives we remove the sliding panel, take out the old unit, clean the glazing channel, set the new unit on fresh setting blocks and glazing, and re-hang the panel. Since the panel is out anyway, it is a good time to replace tired rollers in the same visit.
See glass replacement for the process.
When it is not worth repairing
A glass unit is worth replacing when the rest of the door is sound. It is not when:
- The frame is failing too: cracked vinyl corners, a corroded aluminum sill, or rot in a wood door. New glass in a bad frame is money spent twice.
- The door is a single-pane aluminum slider from the 1960s or 1970s. There is no seal to fail; haze on those is scratching or mineral etching, and a new single pane of tempered glass is the fix.
- The unit is in a multi-slide or oversized panel where the glass alone is a large order; we quote those after a visit.
The repair or replace guide lays out how the numbers compare.
Across San Diego
Fogged glass shows up most in the 1990s and 2000s vinyl doors in Carmel Valley, Rancho Bernardo and San Marcos, where the original double-pane units are now decades old and the afternoon sun is hard on west-facing yards. Milgard and JELD-WEN panels take a standard replacement unit.
Coastal doors in Del Mar and La Jolla fog for a different reason: a sill that no longer drains leaves water against the glass edge all winter. We clear the drainage while we are there. Andersen and Pella wood-core doors use units sized to the sash, so send a photo of the glass stamp when you book.
Foggy or Cloudy Glass: common questions
Can foggy double-pane glass be fixed without replacing it?
Not reliably. Once the edge seal fails, moisture and mineral deposits are inside the unit. Drilling and venting kits may clear the fog for a while but the unit never seals again and the insulation is gone. Replacing the sealed unit, which keeps your frame and door, is the lasting fix.
Do I have to replace the whole sliding door if the glass is foggy?
No. The insulated glass unit lifts out of the sliding panel and a new one goes in. The frame, rollers, track, handle and lock all stay. Whole-door replacement only makes sense when the frame itself is cracked, rotted or corroded.
How much does it cost to replace foggy sliding door glass in San Diego?
It depends on the size of the unit and the glass spec, such as tint or low-e, so we measure on site and quote before ordering. We do not publish glass prices because a quote without a measurement would be a guess. The rollers, track and lock prices are on our pricing page.
Why is my sliding door glass only foggy in the morning?
Because the trapped moisture condenses on the cold inner faces overnight and evaporates back into the air gap as the glass warms. It is still a failed seal. The fog will become permanent as mineral deposits build up on the inside of the panes.
Is the replacement glass tempered?
Yes. Glass in doors must be tempered safety glass, which breaks into small blunt pieces instead of shards. Every replacement unit we fit is tempered on both panes and carries the stamp in the corner. Check the corner of your current glass for the same stamp.
More answers on the FAQ page. Not sure what your door has? Send us a photo and we will tell you.
Where we see this
We cover all of San Diego County, usually within the week. Some of the places we work:
Related guides
- Repair or Replace Your Sliding Glass Door? An Honest Decision Guide – When a $250 to $400 repair brings a 40-year-old aluminum slider back, when the frame, glass or track means replacement, and typical costs for both.
- What Does Sliding Door Roller Replacement Cost in San Diego? – What sliding door roller replacement costs in San Diego, why quotes run from $250 to $600 or more per door, what should be included, and how to compare.
Ready to get the door gliding again?
Call or text for a straight answer and a price before we come out. Mon to Sat 7am to 6pm.