A gap, a draft or a water leak at a sliding glass door usually means the panel has dropped on worn rollers and no longer meets its weatherstrip, or the pile weatherstrip and sweep have worn flat. Water on the floor is often a sill that cannot drain because the weep holes are blocked. New rollers, an adjustment and fresh weatherstrip fix most of them.
Likely causes
- A dropped panel leaving a wedge of daylight at the top or the lock side
- Pile weatherstrip worn flat, torn or missing from the meeting stile and jamb
- A missing or hardened bottom sweep
- Weep holes in the sill blocked with dirt, so rain backs up over the threshold
- A sill or threshold that has settled, cracked or lost its seal to the floor
What you are seeing
With the door closed and locked you can see a sliver of daylight along the lock side or across the top. Curtains stir on a windy evening. In winter the room by the slider is colder than the rest of the house, and after a Pacific storm there is a puddle inside the track or a damp line on the floor.
The clue is where the gap is. A wedge that is wider at the top than the bottom, or at one end than the other, is a panel that has dropped. An even gap all the way round is weatherstrip. Water alone, with no draft, is usually drainage.
What usually causes it
A dropped panel. The weatherstrip only seals when the panel sits where the factory put it. Worn rollers let it drop, so the pile at the top and the lock side no longer touches, and light and air come through. This is the most common cause, and the door usually drags too.
Worn pile weatherstrip. The fuzzy strip in the meeting stile and the jamb wears flat, tears, or falls out of its channel. The bottom sweep hardens and curls.
A sill that cannot drain. Patio door sills shed rain through small weep holes to the outside. Dirt, paint or a new deck board blocks them, water fills the track, and the next gust pushes it over the threshold.
A settled or cracked sill lets water in under the frame rather than through it.
Need a leak or draft fixed 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
- Find the daylight. Close and lock the door, turn off the lights, and look along every edge. Note where the light is and whether the gap is even or wedge-shaped.
- Look at the weatherstrip. Pile that is flat, bald or missing is done. A sweep that has hardened or is missing shows as a gap at the floor.
- Find the weep holes. Along the outside bottom of the frame, look for small slots. Clear them with a toothpick or a gentle rinse from a hose, from outside. If water drains, the sill was simply blocked.
- Try a quarter turn. If the gap is wedge-shaped, a quarter turn on the roller adjustment screw at the low corner may close it. If nothing changes, the rollers are worn.
Do not caulk the gap closed. Sealant on a sliding panel stops it sliding and traps water inside the sill.
What we do about it
We fix the panel height first. New tandem rollers and an adjustment put the panel back where the weatherstrip can seal, and on a lot of doors that closes the gap on its own.
Then we replace the weatherstrip: new pile in the meeting stile and jamb channels, sized to the door, and a new sweep at the bottom. We clear the weep holes so the sill drains. If the sill has lost its seal to the floor or the frame, we re-seal it from outside so water sheds instead of soaking in.
A leak that comes from above the door, through the wall or the header, is not a slider problem and we will tell you so rather than sell you weatherstrip. See weatherstripping and leak repair and roller replacement.
When it is not worth repairing
Drafts and small leaks are almost always hardware: rollers, weatherstrip, drainage. Stop and reconsider when:
- Water is coming in under the frame and the subfloor is soft. That is a flashing or sill-pan failure behind the door and it needs a contractor, not new weatherstrip. We stay inside the minor-repair line and will say so.
- A vinyl or aluminum frame has bowed so the panel cannot meet the jamb evenly along its full height.
- A wood door is rotted at the bottom rail or sill.
Short of that, a door that leaks air is a door that needs rollers and pile, and both are standard parts. The repair or replace guide covers the judgment call.
Across San Diego
Drafts are a coastal complaint. In Point Loma, Coronado and Encinitas the afternoon onshore wind finds every gap in a west-facing slider, and salt air shortens the life of the rollers that keep the panel sealed. Fleetwood and Andersen doors there seal well once the panel is back at the right height.
Inland, in Escondido and Poway, the call is usually about a cold room in January or a puddle after the first real storm, on Milgard and JELD-WEN doors whose sweeps have hardened and whose weep holes have never been cleared. See door brands for what we carry for each.
Gap, Drafts and Water Leaks: common questions
Why can I see light around my sliding glass door?
Because the sliding panel no longer sits where its weatherstrip can seal. Usually the rollers have worn and the panel has dropped, leaving a wedge of light at the top or the lock side. Sometimes the pile weatherstrip itself has worn flat. New rollers, an adjustment and fresh pile close the gap.
Why does water come in under my sliding door when it rains?
Most often the sill cannot drain. Patio door sills have small weep holes that let rain out to the patio; when they clog, water fills the track and spills inside. Clearing the weeps fixes most of them. If the subfloor is wet or soft, the leak is behind the door and needs a contractor.
Can you replace the weatherstripping on a sliding glass door?
Yes. The pile weatherstrip slides into a channel in the meeting stile and the jamb and comes in standard widths and heights. We measure yours, fit new pile and a new bottom sweep, and set the panel height so the pile actually touches. Most doors are done in one visit.
Will new weatherstrip fix a drafty sliding door?
Only if the panel is at the right height. New pile on a door that has dropped a quarter inch still leaves a gap at the top. We check the rollers first, then the weatherstrip, so the repair holds. Often the draft is rollers alone.
Should I caulk the gap around my sliding door?
Caulk the fixed panel and the outside frame to the wall if those joints are open, but never the sliding panel or the track. Sealant on a moving panel stops it sliding and blocks the weep holes, which turns a draft into a leak. Fix the panel height and weatherstrip instead.
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
- Signs Your Sliding Door Needs New Rollers (And Two-Minute Checks) – Symptoms of worn sliding door rollers in order of certainty, the two-minute checks you can do safely, and how to tell when the track is the real problem.
- 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.
- Stainless vs Standard Sliding Door Rollers in Coastal San Diego – Steel, nylon or stainless rollers: which your sliding door needs, why salt air within a mile of the coast matters, and where the upgrade pays off.
Ready to get the door gliding again?
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