Why does air come in at the bottom corner of your sliding door?

The symptom

You feel air, or see daylight, at a bottom corner of the closed sliding door. It may be the corner at the side of the frame. It may be the bottom of the meeting point, where the sliding panel and the fixed panel overlap.

This guide covers that one symptom: what it points to, what you can check with the door in place, and when to ask for a repair. It does not ask you to take anything apart.

If the door also drags or sticks, read why a sliding door is hard to open as well.

What the draft points to

A draft at a bottom corner can point to a seal there, or to a panel that no longer presses against its seals.

JELD-WEN's wood patio door guide gives two causes for light or air leaking through the corners of a sliding door: worn weatherstrip, and a pile dust pad that is out of place. Andersen's steps for air coming through a gliding door start with two simpler things: routine cleaning, and keeping the door closed and locked when not in use.

What seals the bottom corners

A sliding door seals with weatherstrip. JELD-WEN says sliding door weatherstrip is usually located around the perimeter of the operating panel, the panel that slides, and in the interlocks. It describes the interlocks as vertical strips down the edges where the two panels meet, which join when the door closes, with weatherstrip in them for a weather-tight seal. It says dust pads and weatherstrip placement are critical to water and air infiltration control.

The bottom corners are where these seals end, and makers put extra parts there:

• At the bottom of the meeting point. Andersen's 400 and 200 Series doors have a black foam sill plug at the bottom of the interlock weatherstrip on the fixed panel. Its 100 Series doors use two foam plugs with the interlock weatherstrip, one at the head and one at the sill. Its A-Series Frenchwood doors use dust plugs above and below the interlock weatherstrip.
• Along the bottom of the sliding panel. On Andersen's 400 and 200 Series doors, a bottom rail filler fills the gap between the bottom of the sliding panel and the sill. It carries a fuzzy pile weatherstrip for a weather-tight seal. On some JELD-WEN wood doors, a seal along the bottom of the sliding panel, or along the sill, blocks air from entering at the sill.
• Around the frame. Andersen's 100 Series has a gray, fuzzy pile weatherstrip on all four sides of the frame.

Which of these your door has depends on its maker and series. The glossary explains the part names.

What else door makers check

Panel height. The rollers under the sliding panel set how high it rides. JELD-WEN warns in both its vinyl and wood guides that adjusting the door too high may allow water and air leakage. It says to set the rollers just high enough to clear the sill track and keep the weatherstrip hidden when the door is closed. Andersen's air leak steps include adjusting the rollers so the weatherstrip lines up with the seal.

The lock. Andersen says its reachout lock pulls the sliding panel into the weatherstripping for a tight seal. Its air leak steps include checking the lock's adjustment. It also says that when the door is left unlocked, the weatherstrip may decompress and push the sliding panel slightly away from the side of the frame.

Weather and installation. Andersen lists damage from severe weather as a cause of air coming through a gliding door. Under similar symptoms in the same article, it also notes that a patio door must be plumb, level, and square to operate smoothly.

What you can check safely

Each check is done with the panel in place.

1. Close and lock the door. Andersen recommends keeping a gliding door closed and locked when not in use. Lock it, then feel the corner again.
2. Clean the track. Andersen calls routine cleaning key to helping prevent air infiltration. Its method is to open the door, clear the sill track with a soft-bristle brush and warm, mild soapy water, rinse with clean water, and let the track dry before closing the door.
3. Look at the weatherstrip. Andersen's next step is to check the weatherstrip for gaps, damage, or permanent compression, which means a flattened strip. JELD-WEN tells owners to check the placement and quality of the weatherstrip. Look along the frame, the meeting edge, and the bottom of the sliding panel, and at any plug or pad at the bottom of the meeting edge. Note any weatherstrip that is torn, flattened, or missing, and any plug or pad that is torn or out of place.
4. Check the gap. Andersen's check for a panel out of adjustment is to open the sliding panel slightly and look at the narrow gap between it and the frame from top to bottom. If the gap is not equal from top to bottom, it says the panel needs adjusting. JELD-WEN's wood door guide says to check by almost closing the door and looking for an even, parallel gap.
5. Note which corner. Is the air at the side of the frame, or at the bottom of the meeting point? Does it come in all the time, or only on windy days? A photo of that corner helps.

Leave the adjustment screws alone. JELD-WEN's guides show that the direction of turn differs between door lines, and they warn that a panel set too high lets in water and air. This site gives no roller or lock adjustment steps.

When to ask for a repair

Ask for help in any of these cases:

• the draft stays with the door closed and locked and the track clean;
• the weatherstrip at the corner is torn, flattened, or missing, or a plug or pad there is torn or out of place;
• the gap between the panel and the frame is uneven;
• the panel sits lower at one end, or the door also drags;
• the door was damaged in a storm.

Several of these seals are replaced with the panel out. Andersen's steps for the sill plugs on its 400 and 200 Series start with removing the operating panel. It says replacing the bottom rail filler requires removing the operating panel, that panels are extremely heavy, and to contact a service provider for help. JELD-WEN's replacement steps for the angle seal on some of its wood doors, and for its interlock weatherstrip, include removing the operating panel. JELD-WEN's vinyl guide marks operating panel removal "For Professionals Only" and says removal and installation require two or more people. Its wood guide warns: "Because panel removal can be awkward and could cause physical injury or product damage, we recommend the help of additional people." This site treats replacing these seals as a technician's job.

What a technician does

A technician confirms which corner the air comes through. Then the weatherstrip, the plugs and pads at that corner, the panel's height at each end, and the lock are checked. Worn or missing seals are replaced, a dust pad that is out of place is put back, and the rollers and lock are set so the panel presses evenly against its seals. Where a seal is fixed to the panel or sits under it, the panel comes out first. If the frame itself is out of plumb, level, or square, that is a separate conversation.

Where to go next

• The alignment page covers a panel that sits crooked or out of adjustment.
• The roller repair page covers worn and badly adjusted rollers.
• If water also comes in at the bottom of the door, read water coming in at the sill.

To ask about a repair in Plano, Allen, McKinney, or Frisco, describe the corner and what you saw on the contact page. The photo guide lists what to photograph first. The operator reviews every inquiry and replies with the next step. Sending the form is not a booking.