Alongside my house is an old coal door that was never properly sealed. Some caulk was added around the metal exterior door, and a piece of plywood nailed over the interior opening (more to keep out critters than water, I believe).

As you can see from this exterior view, there's not much I can do about removing the door itself:

Exterior view of coal door

But on the inside there is a cavity that could be filled in somehow:

Interior view

The framing inside here was metal -- it's mostly rusted out now -- and there is a little bit of daylight making its way through. This is very obviously not watertight.

The house has a brick and mortar foundation. What's the right way to seal this up to keep water and critters out?

  • How do you feel about excavating the exterior through—what is that? Asphalt?—down below the level of the door?
    – wallyk
    Commented Sep 3, 2013 at 18:18
  • I'd rather not at this point... the asphalt driveway was just re-sealed before we bought the house. But if that's the only option, I'd consider it.
    – Joe Shaw
    Commented Sep 3, 2013 at 18:26
  • Personally, I'd fill it with >2lb polyurethane foam. Most 2lb density foam is considered open cell where higher densities are closed cell and will provide a much better long term absolute seal. That also relies on using a 2 part mix cured in the hole, not a foam block cut to size.
    – Jason
    Commented Sep 3, 2013 at 21:55

4 Answers 4


As you already know there is water getting into there, if you only seal up the inside to make it look better you will have water collecting between the door and your seal. You don't want a pool installed in your wall.

To do this properly you really do need to excavate the outside remove the door and metal frame (if there is a steel load bearing piece across the top I'd recommend leaving that in and if there is a rain catch on the outside that could be left, but it doesn't look like there's either from the pictures). Patch the hole with material that functionally matches the foundation wall. Water seal the patched area then once it is dry back fill where you excavated. It would be good to make that area right against the seal a little higher grade when you fill it in than the area around it to help the water drain away and reduce infiltration.


Well, I would suggest excavation down below the opening taking out the coal door, install a small window and make the area that was excavated a window well. I have known some people that have done this very thing and it works great. Does it leak in a heavy rain since they laid the asphalt above the opening or is it graded away from the house?

  • I like the idea, but unfortunately this is right against our driveway (hence the asphalt) and I'm not sure I can spare the space for a window well there. The grading is pretty good and there certainly isn't a rush of water in that way, but there is some daylight and water making it through the top part of the door.
    – Joe Shaw
    Commented Sep 30, 2013 at 15:41

First let's talk about your objective. If your primary objective is to keep out the water and critters, then why don't you just use some silicone over it on the inside? That will make it watertight and anything watertight is also "bugtight" (not a word I know lol).

However, as the other answerers stated, the better solution will be to entirely excavate the site. The problem with this may be:

  • you may not know how to do this
  • it may be more work then you are prepared for
  • you are worried about other unknown variables like screwing up something in the wall during excavation.
  • it looks like it may be built into the concrete wall (or whatever the wall is made of), so in order to remove you'd have to tear apart the wall and you're not prepared to do so

So, given the above, I could see why you might be reluctant to excavate it entirely. If you are unwilling to excavate it, then, as long as your concern is to keep the water and critters out of the INSIDE since sealing up the inside will not affect the wall), my suggestion is just to head to the hardware store and get a bunch of silicone.

If you cannot excavate, here is a quick fix from start to finish:

  1. It looks like the outside opening drops down into the where there is currently plywood at the top on the inside view. If this is the case, then I would suggest removing the plywood (which can rot and mildew) and replacing the plywood with something more permanent - ideally hard plastic, because metal rusts. Try getting a thick sheet (ideally 1/2" to 1" thick - or more if possible) of that clear plastic, which is relatively inexpensive, from the hardware store or nearby plastic shop.

  2. If desired, spraypaint the plastic (black spraypaint is ideal) so it cannot be looked through. Alternatively, you could use it as a sort of window to let in natural light, and remove the door on the outside. You could put a curtain on the inside so you could close it for privacy but open the curtain when you want some extra natural light.

  3. Cut the plastic to size, and install where the wood was located.

  4. Seal up all the edges both at the top (from outside the building), and from the bottom (from inside the building), using waterproof silicone. Be VERY liberal with the silicone.

  5. Consider grinding down the metal on the inside to remove the rust, and using it as a nice shelf. (OPTIONAL)

This should do the trick. Let me know if it works.


I'd fill the hole entirely with low expanding spray foam.

  • I like this answer so I voted up but really the other answers are better as it will be much better to excavate the door entirely.
    – diy
    Commented Sep 22, 2014 at 21:15

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