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The Old House Basements

Rubble Foundation Questions

2 months ago

Our house (circa 1880) has a rubble foundation, mostly in solid condition though the summer plans were to repoint anything needing attention. Clearing our first corner (inside) we noticed dirt and some water seepage in a couple spots at the base of the foundation where the slab had been poured. We figure this may have been a dirt floor with a slab poured later at the level of the bottom of the foundation, but no matter, our question is what we should do with the gaps were the stones don't dip below slab level to fill these voids where there is nothing but dirt?

In our preliminary research (we're noobs here) we've discovered some discussions about hydraulic cement, mortar, and concrete. Does anyone have experience with this scenario and advice for us?

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Comments (3)

Sigrid
2 months ago
We have a stone foundation, with a basement floor that may or may not have been poured much later. We've had water seepage through the stones (not the mortar). The solution was to get the water away from the foundation. My (amateur) advice is:

1) Pay a lot of attention to when and where the water comes in. Go out and look on rainy days. We discovered our problem after crawling under cobwebby porch in a downpour --- a miserable task, but very informative. If you understand where the water is coming from, dealing with it is much easier.

2) Make sure you are keeping water away from your foundations. That all your gutters and downspouts are in working order and the water discharges far enough from the foundation.

You may find an easy and cheap solution to your problem.
worthy
2 months ago
Here's the full treatment from one of the leading building scientists in North America.
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3onthetree
2 months ago
It sounds like you are trying to fill some gaps (mortar joints) where there is no mortar. If any new mortar were to be combined with old mortar, then the type of mortar would need to be closer in it's lime content to be equivalent in moisture transmission qualities. If however you are removing dirt to fill in gaps, you can just use a hydraulic cement or 'N' type mortar. Concrete has larger aggregate and is not a good gap fill material.

You will still get water leakage, but maybe not free-flowing.

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