The corner of my living room (on split level) has drafts coming in via the bottom of the wall and a sump pump well (specifically, a plastic pipe that drains into it). The carpet is damp to the touch, and the carpet tacks are rusty, but there's no liquid water in the sump, even after heavy rain.

inside corner sump with black pipe and dirt outside corner

FWIW, the rain downpipe extends away a few feet from the house onto a slope (nevertheless, I'm thinking about digging a french drain outside in the spring).

What should I do to seal the corner (on a budget)? On the outside, is the air getting in through the brick? the siding? the porch? the ground? On the inside, is the sump actually doing anything useful? If not, would it be good or bad to cap it with airtight insulation?

  • 2
    Can you take a picture of the inside and outside on that corner?
    – DMoore
    Feb 24, 2015 at 15:43
  • How wet is your carpet getting?
    – DMoore
    Feb 26, 2015 at 20:22
  • Carpet isn't dripping, or even wring-able, but definitely feels damp. I think it's coming through the brick & concrete. Maybe use siloxane sealer?
    – Foo Bar
    Mar 3, 2015 at 13:24
  • Can you please edit your question when you try solution suggested by Jeff Meden; because I’m 99% sure that's not the problem? PS: I really don't care for bounty points I’m just curious. Mar 5, 2015 at 8:13

2 Answers 2


Is the seal on the sump cover in good condition? Also, from the look of it the floor in question is the second level (i.e. half-dug next to a deeper, full-dug basement) correct? Only if you are really confident in the (other) sump pump in the lower basement should you consider doing anything at all to modify that pump well or piping. Sumps are not usually installed just for fun, so it is probably needed to keep your basement dry in the event of severe rainfall or snow melt, even if you haven't seen it in use in the past. I would look into better sealing the cover over the well to prevent air from getting in and cooling the surrounding area (causing the condensation you feel).

Do you know if the basement was finished with full insulation all the way to the floor? Sometimes very minimal fiberglass sheets are used for belowground walls, which just don't cut it for full comfort. If air is still getting in from the basement walls, you can try sealing the area around the baseboard with caulk but you will probably need to remove the baseboards and drywall to really stop it, by sealing and then re-insulating the entire wall area. This is where spray-on insulation really shines because it will seal and insulate. Alternately, if you don't want to tear out the walls you can get blown-in insulation via small holes, that are easy to repair and the extra insulation will probably cut down on the cold draft enough to minimize the condensation.


To make long story short from what I see my best guess is that you have condensation issue. Most likely since your pump is in the corner there is somewhere thermal insulation missing and since you said that there is draft that means cold air is coming inside. Where from?.... I cannot be 100% sure. My money would be on the wall because most likely places where pipes are going through the wall aren’t insulated, but since you said that you are feeling draft is coming from the floor maybe something is happening over there. Anyway placing thermal insulation under the pump (best if possible) and on the places where there are pipes should fix your problem.

  • I don't understand "insulation under the pump". Lay it on the bottom of the sump?
    – Foo Bar
    Feb 27, 2015 at 19:54
  • Yes...that would be the best solution Feb 28, 2015 at 18:03

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