Dug out crawl space

**Bill Penn** · 03-10-2012, 07:26 AM

I am looking for some guidance. I have run across this situation in older homes. The home was originally built on a crawlspace, footings in our area go down 42". A home owner at some point in time decided to dig out the crawl to make a basement. Typicaly I see approx 24" of soil left on the inside of the existing wall. Sometimes it is finished either poured or block and sometimes left exposed as in the photo.

Does anyone know of any reference material as to what is considered a good or safe dug out?

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**wayne soper** · 03-10-2012, 07:45 AM

Footings should not be exposed or undermined, as they appear to be in that photo, and ANY home that has had modifications to the sub structure needs to be checked and OK'd by a structural engineer.
That foundation would have to be resupported from below to comply with today's standards now that they have bastardized it, and in the midst of trying to save it, the whole wall will end up being replaced.
Why leave a loose stone wall above a nice new foundation

**John Kogel** · 03-10-2012, 09:22 AM

The "Angle of Repose" comes to mind for that. Try a Google search.

**Chris Weekly** · 03-12-2012, 08:53 PM

Sure looks like that foundation has been severely compromised.
Recommend structural engineer for that one

**Michael Derrick** · 03-13-2012, 10:30 AM

rule of thumb is for every foot down below the footing you need 1.5 ft horizontal. so for instance 4 feet below the footing you would need 6 feet away from the footing leaving that much fill to support the weight.
Again this is a rule of thumb and anything that might change structural integrady should be done by qualified engineers.

Mike

Originally Posted by Bill Penn

I am looking for some guidance. I have run across this situation in older homes. The home was originally built on a crawlspace, footings in our area go down 42". A home owner at some point in time decided to dig out the crawl to make a basement. Typicaly I see approx 24" of soil left on the inside of the existing wall. Sometimes it is finished either poured or block and sometimes left exposed as in the photo.

Does anyone know of any reference material as to what is considered a good or safe dug out?

**Matt Fellman** · 03-13-2012, 01:33 PM

Different guidelines for different soil types - 45 degrees of undisturbed soil is the one I've seen most. Some say go laterally 1 foot then apply the 45 degrees. I've seen engineers bless much steeper angles but it's a case by case basis depending on the soil.

Not much of a question for the one pictured - it needs support. Realistically, it's not any big mystery. There just needs to be a foundation poured to retain the soil cut.

**Jerry Peck** · 03-13-2012, 03:49 PM

Originally Posted by Matt Fellman

Different guidelines for different soil types - 45 degrees of undisturbed soil is the one I've seen most. Some say go laterally 1 foot then apply the 45 degrees. I've seen engineers bless much steeper angles but it's a case by case basis depending on the soil.

Not much of a question for the one pictured - it needs support. Realistically, it's not any big mystery. There just needs to be a foundation poured to retain the soil cut.

45 degrees, or 1/1 (one foot down, one foot out from footing) is a good rule of thumb.

However, different soil types have different angles of repose, some are actually greater than 45 degrees (greater than 1/1, some types might be 1 foot down and 1-1/2 feet out, as stated above).

For swimming pools, the typical design is 1/1+1, i.e., one foot out for every foot down, then one more foot out. That means if you go down 5 feet, you go out 6 feet (5 feet + 1 foot).

If the pool is closer than that to the house footing, typically the steel is doubled both ways, i.e., instead of on a 12" x 12" grid, the steel is now on a 6" by 6" grid in the area of the pool which falls within that 1/1+1 area.