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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...

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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
    Commented Jan 24, 2022 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
    Commented Jan 24, 2022 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
    Commented Jan 24, 2022 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
    Commented Jan 24, 2022 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
    Commented Jan 25, 2022 at 5:53

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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.

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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!

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