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I have a 140-year-old house of heavy masonry (bluestone/basalt) construction. It is built into the side of a hill with about 25% of the "basement" actually below ground level:

excellent drawing

You can probably guess where this is going - the basement has been plagued with salty damp, specifically where it lies under the grade of the hill. It seems to be a combination of rising damp and penetrating damp soaking through the pores of the masonry, with the usual symptoms of bubbling paint, failing plaster, powdery white salt emerging from damaged wall areas, etc...

Up till now we have used a series of relatively cheap measures to hide the problem rather than deal with it properly.

I am seeking advice from anyone who has used, or knowledgeable about injectable chemicals to damp-proof walls -- did you find it effective in solving the issue? Is this something a homeowner could do themselves or does it require a professional? Is it a permanent fix?

I am also wondering, for the walls below ground level, if it is feasible to systematically inject the entire length and height of the wall with chemical solution rather than just a low band of wall to create a DPC. I realise this would be more expensive but I really want a solution, no pun intended...

(We're looking at other approaches as well, such as trenching and waterproofing the exterior walls, but this has been made difficult by the nature of the surrounding terrain and expense of excavation. So, this enquiry is specifically about injectable chemical treatments.) Thanks in advance...

Telescope2334
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    I will only leave this as a comment since it will not answer your question. Injectable waterproofing is always a "hit and miss" proposition. Injectable materials always seek the path of least resistance and it is not always in the direction you need it. The best way to solve the problem is to dig and waterproof on the outside. Still that may not solve a "rising damp" issue. The second best, or perhaps the best way is to cover the walls with an impervious membrane, after the floor is broken out in strategic places so the wall does not cave in under the pressure, set drain tile, tie the (cont) – Jack Jan 24 '22 at 15:43
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    (Cont) membrane in so if there is any moisture coming in under the footing, that creates the rising damp, will be corrected. This is an oversimplification, but if you want a remedy and not a band-aid, it is what it takes. – Jack Jan 24 '22 at 15:44
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    "if you want a remedy and not a band-aid, it is what it takes." - @Jack. +100! – FreeMan Jan 24 '22 at 18:10
  • Back in the day when these homes were built, I am certain, it was never meant to be a living space, a root cellar maybe with no concrete floor, but a dirt floor. Then later somebody thinks they will make a living space out of it, without considering ALL of the implications, and this is what happens. It almost needs to start back at the beginning as if the concrete floor is not there. If not the water will always find a way in. – Jack Jan 24 '22 at 18:19
  • Thanks @Jack for your comprehensive comment -- and I can confirm on the original plan the basement was almost certainly an unfinished cellar space with a dirt floor as you say! – Telescope2334 Jan 25 '22 at 05:53
  • Just how bad does the water intrusion get? Does the water ever puddle in places? Have you been there long enough to see any worst case scenarios? I mean mounds of snow melting and droves of rain coming down over a long period of time... I had dealings with this stuff directly when I was a supervisor in large home construction. – Jack Jan 25 '22 at 06:41
  • There are all sorts of things that can be injected to stem leakage in masonry, but as Jack has pointed out already, these tend to be a crapshoot if you are going from the opposite direction of the leakage. This is because, well, you are going against fluid pressure. It is trivially easy to put a rubber stopper in a bathtub, because the water pressure pushes it against the edge of the drain; you can plug a bathtub and the water will stay for days or even weeks. However, if you tried to plug that same hole with that same stopper from the other side, you would find it difficult if not impossible. – Tungsten Wizard Jan 25 '22 at 09:30
  • @Jack - the worst I see now is a) Plaster bubbling off wall in patches with white, powdery salt crystal deposits underneath; and b) Carpet sometimes feels damp (with mould) where it meets the wall; and c) Musty smells. No puddles visible. When we moved in we ripped out some rotten interior framing timber, which was untreated, and just replaced it without dealing with the underlying damp issue. Interestingly, the dampness does not seem to get that much worse in bad weather, or better in good weather - it is kind of a constant seepage. – Telescope2334 Jan 26 '22 at 07:40
  • @Tungsten-wizard that's a good analogy – Telescope2334 Jan 26 '22 at 07:50
  • I could give an answer below on what to do, but it will have nothing to do with the question. With your info you have given, you have 2 possible ways to have a redone living space. They are pretty much what I have mentioned in the comments. There is a "milder" version, but it would still mean sheet material on the wall(s), tied into a sheet membrane on the floor with a Dri-Core or compatible subfloor system on top of that, new frame walls along the foundation and all that goes with that. Is this something you would be willing to do? – Jack Jan 26 '22 at 14:30
  • @Jack based on the use of "damp" and "mould", I'd suspect the OP is in the UK and has, if he's been there for 3-4 days or more, seen a fair bit of rain. `` – FreeMan Jan 26 '22 at 16:18
  • @FreeMan, I was thinking the New England area of the USA, but his profile is NZ – Jack Jan 26 '22 at 17:23
  • I am in Dunedin, a coastal city in southern New Zealand which gets fairly regular rain all year round. They say we have very "Scottish" weather here! As to what I am prepared to do, at the moment the answer comes down to budget. I am really considering all options at the moment and will then figure out how I will pay for what needs to be done... !! – Telescope2334 Jan 28 '22 at 02:32
  • My apologies, @Telescope2334, for casting you as British. I understand that probably doesn't sit well. My bad. – FreeMan Jan 04 '23 at 12:47

2 Answers2

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Injectables are not particularly suitable for this situation.

As commented above, they are never a 100% solution and work best as a narrow band, i.e. a DPC.

I highly doubt you'd be able to successfully 'waterproof' an entire wall. Water will find a way through somewhere, usually via voids in the wall (and there are always some).

I appreciate the difficult terrain, but if you can find some young guys who want to earn some money, you could supervise the heavy digging and bring in the skilled guys to install the drainage, insulation, membrane and granular backfill. Best in the long run.

handyman
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I really would avoid injecting the walls in your situation. It can be a hard pill to swallow sometimes but your situation really needs a long term solution to fix properly.

It might be worth investigating the installation of a drained cavity as a possible mitigation technique which leads into a floor drain. This won't be cheap (but may be cheaper than the landscaping work depending on the volume and strength of material that needs to be removed).

Good luck!

BMitch
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AWGIS
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