I am a homeowner who is fed up with banging his head when he ventures into his basement. I need to dig up the existing floor and excavate about a foot in order to get the clearance to be able to walk upright in my basement. The foundation footings are sitting on bedrock, and the bedrock extends into the basement anywhere from 18 to 24 inches. Then the basement floor slopes downwards, and previous owners poured cement over dirt and rubble. My question is….when I start digging, how close should I go to the footings. And is there any other things I should be aware of before I embark on this adventure. Thanks.
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Consult an engineer. I once was to buy a house, my offer was in and I had my dad look at it. We noticed something strange the south side and basement looked out of sort. It also had a dirt floor. We found some drawing in the basement with an engineers seal on them. So we went to the engineers office, he chuckled when we asked him about the house saying "oh that one". Then he pulled out some drawings and photos it seemed that the former owners wanted a larger basement and were hand digging it out . Then the foundation wall and footing collasped into the new basement as well as the whole south side of the house. Thinking that it may have other hidden problems we skipped on buying it.
In a typical basement wall you have the exterior soil pushing inward s on the foudation wall the floor joists are putting a load on the wall prevent the top of the wall from tipping in that is way you never backfill a foundation untill the first floor system is in place at least. thenyou have the concrete floor holding the bottom in place preventing it from under sliding like a landside into the basement.
Your situation is too specific to remedy on a web site or engineer your self. Needless the house above was a HUD house it was repoed by HUD when the owners gave it up when the foundation failed. This is one area you don't what to try to save money.
Definitely one for an engineer. You should look at two options given your bedrock situation. The cost for digging farther down may turn out to be more than the cost of having a house mover lift the building a foot and build new cripple walls under it. Air is a lot easier to displace than bedrock. But this can only be determined by on-site expertise.
-- J.S.
Pour a foot of concrete over bedrock and build cabinets over the 18-24 inches of bedrock (are you sure?) and just dig out the dirt. Done a couple in plain dirt and pouring 18 in. wide 'berm' up to top of footing and never had any problems. Make sure there is a 'key' or 3/4"pin every foot or so into bedrock to resist side soil forces and you will be ok.
done a few off these for customers & never had a problem. completed last one in feb. all fill was taken out in 5 gal cans because of 18" stairway . cupboards over 18-24" outer edge good idea. we usually form basement like a bathtub bracing sides from ceiling with 2x2's or 1x3 pickets driven into floor & break them off after concrete drys, formed this way you can do it in one pour of concrete 3500 psi' for better looking results we parge walls & new fotting next day and end up with what looks like a fresh poured concrete wall.
My wife and I sell real estate in a small town that was mostly built in the 1900-1929 time frame. This was coal mine country and most of homes were small and were built on laid stone foundations over expansive soils. Great, huh? In homes we see here it is very common for the cellar to be dug out. Almost always it was dug down at least two feet from the outside wall. A lot of the work was done in a less than ideal manner, and yet most of them look pretty good for cellar storage areas.
Saw one resently that was done with concrete block laid on a poured footer. Looked good and straight. All cores had been poured and owner said there was "plenty of rebar".
Good luck!
It doesn't matter how fast you get there, it just matters that you go in the right direction.