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How to insulate this foundation wall and in turn help with water

thegiz | Posted in General Questions on

Ok so have a question about this foundation wall in picture.  Before I moved in a drain was installed that prevented basement flooding but I still have dampness.  This is the only foundation wall that is buried in soil and gravel all other walls are exposed.  So my thought is I might be better off with exterior basement insulation.  On this particular wall I have a few questions. 

1. this wall slopes down to a patio with a small retaining wall.  Could I insulate the upper half of foundation wall and then somehow slope water away from wall and down a pipe out to daylight.  I could even reroute my gutters that are shooting straight down into earth.  This would send water away from foundation

2.  Is digging down to bottom and removing all soil my best and only option.  I don’t mind filling entire pit with gravel and concrete.  Don’t really know what kind of drainage was installed.  I also have gas lines and an ac unit on this will so I don’t know how difficult that might be.

3.  If I do insulate from outside what is the easiest way to do this for a diy.  Something that is economical but not impossible.  I live in climate zone 5

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  1. GBA Editor
    Brian Pontolilo | | #1

    Hi Joe.

    A few questions: Where is the drain that was installed? Is it an interior perimeter drain or is it outside? Are you sure that the "dampness? is not a leak? Is the interior finished at this time? Where is this house located?

    While exterior insulation works great on basements and excavating will give you the opportunity to make sure that you have working footing drains and to take some waterproofing measures, it's a lot of work. If the dampness is condensation, you could work from the interior and some combination of insulation and dehumidification may do the trick.

    Also, no matter what you decide to do, you need to make sure the grade is sloped away from the house and get the roof water away from the house.

  2. thegiz | | #2

    Hi Brian, the drain is on the outside in gravel. I have never seen it but I know it solved a flooding problem. The interior is unfinished, a few years I removed everything, it was improperly done everything was mold. The concrete walls feel dry to touch but floor in area around this wall remains damp. Hopefully just need sealing and a dehumidifier, how would I determine what kind of moisture I have? Contractor gave me a reasonable estimate to pour new slab with insulation and vapor barrier and replace support posts. Just trying to see if I could solve moisture problem and just level existing slab before I have this work done. I’m in suburbs of nyc

  3. Jon_R | | #3

    First try the low cost options of directing water away from the house and running a dehumidifier.

  4. walta100 | | #4

    From a photo it is difficult to tell what way the ground is sloped but to my eye that sidewalk and the brick edging seem to be higher than the surface along the wall. The very first things to do are simple low cost fix and get any surface and gutter water to flow away from the house.

    You said before you move in new drains were installed. How long ago was that? Did you get a copy of the invoice? To my eye that ground does not look like it has been disturbed recently. Installing exterior drain is likely to cost ten thousand plus dollars, no one selling a house is likely to spend that much money to sell a house without a lot of kicking and screaming.

    My guess is the sellers agreed to do some minor work to the gutter drains and realtors let you believe major work was done.


  5. thegiz | | #5


    I actually purchased this home from family, it was previously my grandmothers house and I know she paid a good amount to have it done properly, if they did it properly is another question but I know it stopped flooding. Not sure exactly how long ago work was done but prob 20-30 years ago. Could I divert gutters to patio below without major excavation or that would cause major flooding? I’m not sure how else to divert it everything else is surrounded by stone, sidewalk, concrete, or driveway. Thanks, Joe

  6. thegiz | | #6

    Here are some better pictures it slopes down. Also pictures of 2 gutter channels and bottom with retaining wall.

  7. walta100 | | #7

    From here the only thing I can say is you need to get as much water as possible to run away from the house.

    Pour a bucket of water on the sidewalk if the water runs off the house side of the sidewalk you need to fix that.

    Pour a bucket of water by the house if the water does not flow onto the sidewalk and away from the house you need to fix that.

    If the patio, sidewalks and concrete are tilted toward the house you need to fix it even if the only fix is a jack hammer.


  8. Expert Member
    AKOS TOTH | | #8

    99% of wet basement issues can be solved by channeling water away from the house. Walter's suggestions are bang on.

    Looking at the soil by the house, there seems to be a lot of stone in it. The soil near the house needs to be somewhat water impermeable. Any type of gravel/stone will just channel water down and against the foundation instead of away from the house. You want a layer of compacted soil or limestone screeing. The insulated slab on grade type of insulation "wing" just bellow grade also works well.

    Your downspouts MUST dump away from the house. This could mean running underground piping to daylight or re-locating downspouts to the downslope of the house.

    There also looks like there is a concrete curb near the bottom that is also channeling water towards the house. You want to either remove this or have some means of drainage to daylight from it.

    Digging up the foundation and waterproofing is the last resort.

  9. thegiz | | #9

    Thanks everyone for your help. Is it possible that the system put in for flooding is already diverting gutter water? I guess I have to dig down to find out. So I have what I think might work based on what you are telling me. So I’m thinking of putting in a channel drain directly next to sidewalk to divert water down from gutters onto patio which is slightly pitched to back yard. I would place a whole in bottom of retaining wall so water would see daylight and exit. I think it would have time to dry in sun. I would remove all those rocks and large gravel and place limestone screening with it sloping an inch down from foundation. Does this sound right or is there a better way? Will I end up with too much water somewhere else. I still don’t know what’s going on under dirt, there may be a French drain. I attached a picture of my idea.


  10. Jon_R | | #10

    I used sheet polyethylene to form a sloped surface and to form a ditch. Both covered with gravel.

  11. thegiz | | #11

    So if I start at foundation wall to create a 2 inch slope away from house into a 2 foot deep trench I could drop a French drain into trench is pitch it to patio. Could I use a drywell at bottom or is that too close to house. I would use 6ml plastic to cover slope and bottom of trench. Cover French drain with 12 inches of gravel put down fabric and throw limestone screening on top of everything. My final layer of screening would still pitch 1 inch from house onto sidewalk. Could I do it this way? Everything I see online is digging all the way down to footing and dropping French drain directly next to house

    1. Expert Member
      AKOS TOTH | | #12

      Not sure I'm following your exact route, but your diagram in post #9 is good. Just make sure that the channel drain dumps out far enough away from the house that water won't find its way back to the foundation.

      Water proofing and french drains by the foundation can only do so much. I commonly see people waterproofing their house this way (dig, dimple map, perimeter drain, back fill with gravel) but failing to fix the downspouts. A year or two down the road, the downspouts are always moved.

      I own place with brick foundation and no water proofing. When I got the place, there was a stream of water flowing through the basement during any rainstorm. Moving the downspout so that it dumps about 3' from the house and re-sloping the dirt along with a sloped membrane about 4" bellow the dirt has completely fixed all issues. The basement went from walls covered in solid layer of mold to bone dry.

  12. thegiz | | #13

    Akos so supposedly my downspouts are directed towards the backyard into a drywell. I will have to check by digging, it’s at least 10 feet away and underground so I will see from where it starts. I didn’t see work done. I’m going to slope water away from foundation into a drain that will shoot out onto concrete patio. I have to make a hole in a concrete wall to disperse water out. Drain will be next to concrete sidewalk. In this case what would make more sense a trench drain near surface or a French drain dug 3-4 feet down. The slope is taking water about 2-3 feet away from wall. When you made your slope how did you backfill it, did you use soil or something else

    1. Expert Member
      AKOS TOTH | | #14

      If you have no waterproofing on the foundation wall, you want to prevent the water from entering the soil in the first place. A french drain 3' to 4' bellow grade still relays on surface water percolating through your soil, which you don't want. You want to channel rain water away from the house and allow it to percolate into the soil only a good distance from the house.

      In my case I had to re-slope most of the backyard, so that was done with the existing soil. Near the house I had the membrane under the soil. I did have a french drain running from near the middle of the backyard out to a laneway, but that was mostly for keeping the backyard dry.

      1. thegiz | | #16

        Akos I just realized you only went 4 inches below and used a membrane I thought 4 feet. I’m an idiot, how thick of a membrane did you use?

        1. Expert Member
          AKOS TOTH | | #17

          I'm not sure, it was left over roof EPDM so pretty thick. Pretty much anything will work, something beefier is less likely to be inadvertently damaged. Pond liner EPDM is easy to get.

          For working around your AC unit, the easiest is to lean a tall ladder against the wall over it and lift it with a couple of ratchet straps attached to a rung. Make sure it is secure and that you don't kink the AC lines when you lift it.

  13. thegiz | | #15

    So in my case I only have 3 feet wide by 30 foot long area next to foundation to work with. I can make whole in concrete on bottom and shoot water out Onto paved patio. Going to slope down soil 2-3 inches away from house into 1 foot deep trench. Cover whole area with 6mil poly sheet, on slope, under and around pipe. Cover whole thing with gravel if I don’t want any water to soak into soil. This way any surface water drops down into pipe and away from soil.

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