There is a small gap in between my apartment's front door and the door frame. I was told by an exterminator that small roaches may be able to fit through the gap to get inside, and it seems that may be the case given the fact that I sometimes find roaches close to the door. Part of what may be causing the gap is that the metal door isn't fully touching the door frame when it is closed. The advanced age of the door may be a contributing factor.

With respect to possible solutions, I was considering placing an adhesive rubber door gap filler strip around the edges of the door (inside the apartment), but it seemed that that might be unsightly and may not actually prevent roaches from coming through. I was also, thinking about putting some kind of substance (like silicone) in the gap on the outside of the apartment, but was thinking that adding something like that may be a little messy and might not hold up with the constant opening and closing of the door.

What would be the best way to fill the gap? Note: The door frame is metal and the surrounding wall is concrete.

Outside of the door:

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Inside of the door:

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  • Are you concerned only about gaps at the head (top) and sides of the door, or about a gap at the bottom of the door as well? Aug 29, 2021 at 1:18
  • @ThreePhaseEel Just the top and the sides, not the bottom. Aug 29, 2021 at 4:16
  • Can you measure the gap for us (at the various corners, as well as the midpoint of each side?) Aug 29, 2021 at 5:28
  • The gap on the outside is about 3/16 of an inch while the gap on the inside is about 2/16 Aug 29, 2021 at 20:42

2 Answers 2


Baby roaches are the least of your worries

The problem you're not seeing here is that this isn't just any old door. Due to the fact it's the entrance to your apartment from the corridor, it's a fire door, and that means its proper functioning is critical to keeping you and your neighbors safe should the unthinkable happen.

As a result, I'd do everything in my power to find and have removed or repaired whatever is preventing the door from closing fully into its frame, as if a baby roach can slip through a gap at the head or jamb of that door, so can a gout of flame or cloud of smoke. If maintenance says "that's nothing to be worried about", measure it. If it's more than a 3/16" gap, then it's out-of-tolerance as per NFPA 80 and you have every right to call the fire marshal and tell them to bring an inspector over.

If repairing it is absolutely an impossible order, say due to skew in the masonry rough opening, I'd get a fire-rated weatherstripping product (UL1784 and UL10B/10C rated) and apply it to the head and jamb so that the door seals tightly against the weatherstripping when closed. That way, the door will at least seal out the smoke, flames, and baby roaches in the future.

  • Thanks for the information. Given the 3/16'' gap on the outside of the door, and based on your recommendations, I'll probably go ahead and have the building maintenance take a look at the door. I think weather stripping is along the lines of what I was looking for so I'll consider that as well. It's a fireproof building so you're right about ensuring that the air seal on the door is tight. Aug 29, 2021 at 20:52

Roach spray.

Which you need anyway because roaches are coming in. Keep the can by the door and add spray around the frame and at the bottom when you think of roaches. Roaches on their way in probably rest in the tight space while they decide what to do. Those that do will soak up the poison.

  • 1
    However, roaches aren't the only reason to be concerned about what we're seeing with the OP's door... Aug 29, 2021 at 17:28

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