# No Footing



## tom in indy (Jan 31, 2010)

Early 1900s home has basement with block walls and no footing. Slab is 3 inches thick. The bottom of the slab is at the same level as the bottom of the lowest block. The idea was to install an interior foundation drain, but with no footing I am all out of ideas. Is raising the slab level my only solution?


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## Heritage (Mar 20, 2007)

tom in indy said:


> Early 1900s home has basement with block walls and no footing. Slab is 3 inches thick. The bottom of the slab is at the same level as the bottom of the lowest block. The idea was to install an interior foundation drain, but with no footing I am all out of ideas. Is raising the slab level my only solution?


No, the most obvious thing to do in such circumstances would be to excavate all the backfill/soil from the outside perimeter of the house, all the way around...down to about 2' below the lowest block.

By doing this, you will eliminate the source of the problem (soil).

GOOD LUCK :thumbup:









_Follow advice at your own risk. Heritage is not responsible for any possible negative outcome. _


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## tom in indy (Jan 31, 2010)

Thanks for your reply

Basically my concern is that if I were to cut and dig a trench for the interior drain tile it would have to be next to and at a lower level than the bottom of the foundation wall (with no footing) to be beneath the slab. Would I be undermining the foundation by digging deeper than and next to but not underneath the wall? Certainly im not the only guy who wanted to put an interior drain on a house that didnt turn out to have a footing. Even so, I can not seem to find any information on this situation.


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## Sisyphus (Nov 1, 2010)

I would, as you say, have concerns about excavating right beside the existing wall. You could excavate in sections and pour concrete until you have a footing ("underpin") and then proceed with your perimeter drainage. Doing this from outside is probably the best and, naturally, most expensive option. Another possibility might be to put in a sump to lower the over all water level which may or may not produce acceptable results depending on drainage, slopes, radon, height of water table, energy requirements etc. 

The old rule of thumb to prevent undermining was, IIRC, to move out laterally 1 foot for ever foot one dug down when digging beside an unsupported wall.


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## greg24k (May 19, 2007)

Are you sure the slab you describing is not a monolithic slab?

In any case, I would suggest telling the HO to have an engineer come out and evaluate the existing condition and come up with the best remedy for the drainage so everyone can sleep good. Last thing you want is to have a foundation collapse on your hands or worst...on top of you.
If perimeter drain is required in or out, most likely he will request underpinning the foundation...or come up with another solution to rectify the water situation which is less costly.

Keep us posted and let us know please what the verdict will be :thumbsup:


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