I learned what a door seal for sliding door looks like when it has failed at 11 PM on a Tuesday in November, when I was sitting on the couch in my Brooklyn rental reading a book and I felt a draft on the back of my neck that was not coming from the window and was not coming from the wall and was coming, I figured out after about fifteen minutes of looking for it, from the bottom of the sliding glass door that opens onto the patio. The seal at the bottom of a sliding glass door is a foam strip, or sometimes a rubber strip, or sometimes a brush strip, that sits in a channel at the bottom of the door panel and that is supposed to fill the gap between the door and the threshold so that air does not come in and heat does not go out. The seal on my door had been replaced by the previous tenant in 2019, according to the tag that was still attached to the foam, and the tag said the foam was rated to last five years. It had lasted seven years and was now letting in a draft that I could feel on the back of my neck from six feet away. The draft was the reason the apartment was 64 degrees at 11 PM in November, which was the reason my gas bill was $187 that month, which was the reason I sat down on the kitchen floor with the seal in my hand and read the back of the package that the new seal had come in, and the back of the package said, in a sentence I am going to quote for the rest of this article, "Sliding door seal replacement takes 20 minutes and a pair of scissors." The package was lying. It took me two hours. I am going to tell you why.
Why the Package Said 20 Minutes and the Job Took 2 Hours
The reason the package was lying is that the package was written by a person who was replacing a seal on a sliding door that was the kind of sliding door that you can buy at Home Depot and that has a channel at the bottom of the door panel that the seal slides into with no tools required. My sliding door was installed in 1962, which means the channel at the bottom of my door panel is not the same channel that is at the bottom of a Home Depot sliding door, and the seal that the previous tenant bought in 2019 was not the seal that was supposed to go into the channel, and the previous tenant had jammed the seal into the channel with a putty knife and a lot of swearing and the seal had held for five years by friction and by the foam being thick enough to fill the gap. The seal that I bought at Home Depot on Atlantic Avenue was the right length and the wrong thickness, and the wrong thickness was the reason the seal was letting in a draft after twenty minutes of installation. The draft was not because the seal was missing. The draft was because the seal was not the right seal for the door.
The Landlord's Reply
I told my landlord, in an email I sent on a Wednesday morning, that the door seal had failed and that I would like either the super to come replace it or for me to replace it myself and deduct the cost from the security deposit. The landlord replied on Friday afternoon, in two sentences, that the super did not replace seals, that I could replace the seal if I wanted, that I should pick something "good for the building," and that the cost would be deducted from the security deposit at the end of my lease. The two sentences were the same two sentences the landlord had sent me about the patio door in October, and the two sentences were, I am beginning to realize, the landlord's standard reply to any request that involves a part that is older than the lease. The reply does not say yes. The reply does not say no. The reply says that the cost is my problem and that the part I pick is my problem and that the part I pick is going to be inspected at move-out by someone who is going to look at the part and see a part.
What Most Articles About Sliding Door Seals Get Wrong
I am telling you this because the question of how to replace a door seal for sliding door is not the question most articles, or most YouTube videos, are going to answer for you. Most articles are going to assume you have a Home Depot sliding door that was installed in the last ten years, not a sliding door that was installed in 1962 by a super who is no longer at the building. Most articles are going to assume the channel at the bottom of the door panel is the right size, not that the channel is the wrong size and that the previous tenant jammed the seal in with a putty knife. Most articles are going to assume the foam seal you buy at the hardware store is the right thickness for the door, not that the foam seal you buy at the hardware store is the wrong thickness and that the wrong thickness is going to let a draft in for the next five years. The question most articles answer is "how do I slide a foam strip into a channel at the bottom of a sliding door," and the question most renters actually have is "how do I find the right foam strip for a 1962 sliding door that has the wrong channel and that the previous tenant fixed with a putty knife."
Three things actually mattered when I was picking the seal: the door brand, the channel width, and the seal type. Cost was the fourth thing, but cost is not a decision so much as a constraint. The door brand is the manufacturer of the sliding door, which is stamped on a metal plate at the top of the door panel and which I had to look at from a step ladder with a flashlight because the metal plate was six feet off the floor and the lighting in the hallway was bad. The channel width is the width of the slot at the bottom of the door panel that the seal slides into, which I measured with a ruler that I borrowed from my upstairs neighbor, and which turned out to be a quarter inch narrower than the seal the previous tenant had jammed in with a putty knife. The seal type is whether the seal is foam, rubber, or brush, and the type you pick is the type that fits the channel without jamming, which is the type that the door brand says to use. The cost is the cost, and the cost is going to come out of your deposit. Pick the $24 foam if you want to spend the least. Pick the $40 rubber if you want it to last ten years. Pick the $60 brush if you have a pet that scratches.
Read the Metal Plate at the Top of the Door Panel
The door brand is the answer to the question of which seal you need, and the answer is on a metal plate at the top of the door panel. The plate is going to say something like "Arcadia" or "Anaconda" or "Pittsburgh" or "Kawneer" or one of about a dozen other brands that were making sliding glass doors in 1962. The brand is going to tell you, on the plate or on the company's website or on the phone if you call the company, what the channel width is and what the seal type is and what the part number is for the replacement seal. The reason this matters is that the seal at the bottom of a sliding glass door is not a generic foam strip, it is a specific foam strip that fits a specific channel in a specific door, and the wrong foam strip is going to let in a draft no matter how hard you jam it in. I called the company on a Thursday afternoon. The company had been in business since 1947. The woman who answered the phone knew the door brand by memory and knew what seal I needed by memory, and she shipped me two of them for $24 total with the note that the seal was going to last ten years if I did not drag the door across the seal when I opened it.
Measure the Channel with a Ruler, Not a Tape Measure
The channel width is the measurement you take with a ruler, not with a tape measure, because the channel is too narrow for a tape measure to fit into. The ruler goes into the channel at the bottom of the door panel and you read the width off the ruler at the top of the channel. The measurement is in fractions of an inch, and the fraction is going to be either an eighth of an inch or a sixteenth of an inch, and the fraction is going to determine whether the seal you buy at the hardware store is going to fit the channel without jamming. A seal that is one sixteenth of an inch too thick is going to compress in the channel and lose its spring in about three years. A seal that is one sixteenth of an inch too thin is going to let in a draft no matter how much you compress it. The right seal is going to fit the channel with the kind of friction that is firm but not forced, and the right seal is the seal that the door brand says to use, and the door brand is the company that has been in business since 1947.
Foam, Rubber, or Brush, and Which One Lasts 10 Years
The seal type is the decision you make once you have the right seal in your hand, and the decision you make once you have the right seal in your hand is the decision about whether you are going to drag the door across the seal when you open it. Foam seals are what most sliding doors came with in 1962, and foam seals are what most sliding doors come with now, and foam seals are the seals that last five years and that let in a draft for the second half of those five years. Rubber seals are what you upgrade to if you have $40 and if you do not drag the door across the seal, and rubber seals last ten years and do not let in a draft. Brush seals are what you upgrade to if you have $60 and if you have a dog or a cat that is going to scratch the seal, and brush seals last fifteen years and do not let in a draft. The reason most renters pick foam is that most renters do not know there is a rubber seal or a brush seal until they have already replaced the foam with foam three times. The reason most landlords do not care which seal you pick is that most landlords do not know there is a rubber seal or a brush seal.
Pick the $24 Foam, Then Install It in 2 Hours Not 20
The cost is the last decision and the most important, and the cost is going to come out of your deposit. The seal I picked was a $24 foam seal from the company that has been in business since 1947, because the $24 was the most I was willing to lose on the seal if the landlord decided at the end of my lease that the seal was not good for the building. The seal that the hardware store clerk tried to sell me was a $20 foam seal that was the wrong thickness and that would have lasted five years and that would have let a draft in for the second half of those five years. The seal that the landlord would have had the super install, if the super installed seals, would have been a $20 foam seal from the hardware store that was the wrong thickness, because the super would not have called the company that has been in business since 1947. The $24 seal I bought is going to last the four years I have left on my lease and the four years the next tenant has on the next lease, and the next tenant is going to feel no draft on the back of their neck at 11 PM in November, and the next tenant is going to have a $187 gas bill instead of a $300 gas bill, and the next tenant is going to look at the door and see a door that does not let in a draft.
The installation is straightforward once you have the right seal. Take the door panel off the track. Lay it flat on the kitchen table. Pull the old seal out of the channel with a pair of pliers. Slide the new seal into the channel. If the seal is too thick, cut about an eighth of an inch off the bottom with scissors. Put the door panel back on the track. The package said twenty minutes because it was written for a door that was not my door. My door was installed in 1962, and the seal it needs is the one the company that made the door still sells.
If your sliding glass door is letting in a draft at 11 PM in November and you do not want to call the super, here is the short version. Read the metal plate at the top of the door panel. Call the company that made the door. Order the seal the company says to use. Measure the channel width with a ruler. Pick the foam seal if you want to spend $24. Pick the rubber seal if you want it to last ten years. Pick the brush seal if you have a pet. Take the door panel off the track. Lay it flat. Pull the old seal out with pliers. Slide the new seal in. Cut a quarter inch off the bottom if it is too thick. Put the door panel back on the track. Open and close it ten times to make sure the seal is not catching. The total cost is $24 to $60. The total time is two hours, not twenty minutes. The result is a door that does not let in a draft on the back of your neck at 11 PM in November.
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