My house is built into a slope, with the bottom floor partially underground. See photo 1 - grey wall is a common wall with my neighbor, the white back wall is entirely underground, and the left wall is partially underground, as marked by the red line I drew. To give an idea of dimensions, the wall height is 14', room width left to right is 16'. It's an old house so I would assume no waterproofing was originally applied. Walls are allegedly reinforced concrete, they should never be brick, sandstone, cinder block or anything else where I am. Side wall is about 8", so I'm assuming all walls are. It's in a tropical climate in Asia so we're coming into wet season.

The marks on the white wall, shown in the main photo are patches where water is damaging the paint, so I've removed debonded sections back to the concrete wall. In photos 2 and 3 you can see a bit better. The bubbling around the sides is a result of the rain the last few days.

I can't get to the external wall, excavate, waterproof and backfill properly because the road is built so close to the house, and the house is built right to the border of our plot so I wouldn't get permission anyway. I'm looking at ways to manage it instead. The air-conditioner you see is set to dehumidify 24/7 and seems to keep the wall dry and prevent mold growth on furniture down there so I'm happy to continue doing this, but I want a better looking wall.

My basic approach for a false wall, as I understand it:

  • scrape off as much plaster and membrane as possible, exposing bare concrete wall to help it breathe/dry
  • stainless steel bolts and framework, but using suspended framework not flush with the wall (similar to a false ceiling in a commercial building) so it is one large cavity behind there
  • 3-4" cavity
  • vents at the bottom and top
  • water resistent plasterboard sheets
  • no plans to hang anything heavier than a mirror, so standard thickness plasterboard sheets ought to be strong enough

I want to prevent mold growth in the wall cavity as much as possible, which is why I mention the vents. Would the dehumidifier being on 24/7 in combination with the ventilation holes be enough to keep the wall as dry as it currently is, or do I need forced ventilation? Forced, as in, 2 low-rpm fans in the top of the cavity drawing air up from the bottom and out into the room?

For the left wall I'm considering a stepped false wall roughly along the dashed line I drew also with a vent hole, and continue the same cavity as the back wall. This would hopefully prevent any water ingress coming around the side of the false wall, if it was inclined to do so.

I don't know my neighbours that well but I do know they suffer the same problem, but just let it deteriorate.

I'm aware of things like epoxies, which at best only move the problem elsewhere, as well as the option of digging a hole for a sump and pump but I don't want to go that direction if possible. It seems so far I don't have the volume of water to justify that (compared to others on the internet). That, combined with local contractors having zero skill in this area because basements are rare would mean I'd likely get a poorly executed installation.

Appreciate any guidance or opinions.

photo 1 photo 2 photo 3

Update for clarity: essentially what I'm investigating is if a solution like sub-floor ventilation can be adapted to my situation. They share similarities - one side is an ever present source of moisture, the other side we want to keep dry. If my wall were to actually weep or drip then it's a different story but it so far it's only ever just deteriorated the paint and plaster, and no more. If forced ventilation (or even passive) can prevent mold and moisture problems for raised floors, can't I, in theory achieve the same with a false wall and fans? Apologies for not articulating this clearly in my original post.

I've also been careful not to use the word 'fix' because that can't be achieved from the inside, which is why I chose the word 'management' instead.

  • 2
    Since the damage is a the top a shallow pit with a pump may be your best path forward, if your neighbors are having the same issue and you even have 4” wide along the home you could trench and put a French drain in to eliminate the standing water working with them for mutual advantage sometimes works. An internal false wall will be a place for things to grow it would be best to fix it from the outside.
    – Ed Beal
    Commented Mar 30, 2020 at 15:46
  • I know this is old... I can imagine that building a false wall would do nothing but put a decorative cover over the problem. If the solution you have (AC on 24/7) isn't keeping the walls dry enough to prevent the paint from coming off, all your false wall will do is hide the ugly. If that's all you're after, then sure, go for it. Just know that behind that wall, the paint, and eventually the concrete are deteriorating and you won't know how bad it is until it's too late.
    – FreeMan
    Commented Sep 24, 2021 at 14:41

2 Answers 2


Unfortunately there is no way to fix this issue from the inside. Any product you apply will only temporarily fix the problem of water infiltration through the wall. The only fix that will work is to excavate around the perimeter, install a drain to carry the excess water away, and apply a product to the outside of the wall that will seal it and another to provide a path for any water that reaches the barrier to flow down to the drain.

I see that you are concerned about excavating your driveway but there is no other choice.

  • Trenches are great, but if there's no actual dripping going on, wouldn't a couple coats of moisture-seal paint on the (properly prepared) concrete solve the problem? Commented Mar 30, 2020 at 19:08
  • 1
    In my experience, no. If that were all it took why would anyone ever install a foundation perimeter drain, apply expensive exterior foundation sealants, and install drainage mats? The answer is that the interior coating will fail, sooner or later where the correctly done job will last for 30-50 years or longer.
    – jwh20
    Commented Mar 30, 2020 at 19:12
  • What your photo appear to be showing is the water pressure literally pushing the paint and drywall compound off the wall.
    – jwh20
    Commented Mar 30, 2020 at 19:16
  • Fair enough. Thanks for the info Commented Mar 30, 2020 at 19:18
  • @jwh20 in my case it's not my driveway I'm excavating, it's a government road so I simply wouldn't give permission if only out of inconvenience to traffic or risk of damaging public drainage works. So a 'fix' doesn't appear possible here, rather 'management' is what I'm looking into. I've updated my OP to express similarities to sub-floor ventilation.
    – chopper24
    Commented Mar 31, 2020 at 0:47

Moisture seal paint will work, for a while. Maybe 10 years, and then it will fail. Water has a way of getting in. This stuff doesn't last forever, and you'll have another problem sooner than you think.

There's 3 approaches I'd try. You can combine them if necessary.

  1. Break up your concrete next to the wall and dig a trench down the the footing and put in drain tile+rock. Drill holes in the wall below where the concrete would go. If you have hollow concrete block, you'll need to drill a hole in each section so it'll drain. Put in a sump. You may not need the sump as it sounds like you don't get much water, but if you're doing all this work anyway, you might as well. Then cover it back up with cement, and obviously make sure you don't plug up your freshly drilled holes with new cement. You could also try putting dimple board over the drilled holes (More on dimple board below).

  2. Put in dimple board on the inside of the walls, and drain it into your trench. Dimple board is a plastic, waterproof membrane with dimples on it that sits slightly above he surface of the wall so the water has somewhere to flow. Normally this goes on the outside of the house, but you can also put it on the inside as well. This is a supported install method by some manufacturers of dimple board. The idea is that the water will eventually seep through whatever you put in front of it, stopped by the membrane, and flow down the wall, into your trench.

  3. Clean off whatever is on the wall now, down the the concrete. Seal the wall with hydraulic cement. Then coat with waterproof paint to prevent any remaining dampness from getting through. Hydraulic cement will hold up much better than waterproof paint will.

IMO the best options are #1 & #2. Obviously to put in the dimple board, you need a place for the water to go, so you have to do #1 to do #2. If you're really ambitious, do #3 as well.

#3 alone is obviously the cheapest option, and it might work perfectly for decades, or it might fail quickly. Your problem doesn't sound terribly severe, so #3 alone might be a good solution for you. YMMV

I had a similar, but more severe seepage problem in my house that likely went on for the last 60+ years. The wall itself was structurally sound, but the surface was in poor condition from years of seepage. It had tree roots growing through holes in the wall where mortar had worn away. I did all 3 of these solutions on the worst part of the wall, and only #3 on the driest section with the smallest problem. My basement is completely dry now.

None of these options are going to be easy. There's a reason why waterproofing companies charge $30,000+ for this kind of work. It's hard, long grueling work, and even DIYing will cost you maybe $1000-$2000 in materials. You'll be digging literally a ton of earth out of your basement.

It took me the better part of a year of after work and weekends to complete al three steps on my own. I'm happy with the results. Good luck.

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