[FL Michael]

I am currently in the design process of my new home for a side sloping lot. My original plan was to have a basement style garage and then fill along the back side of the wall followed by a slab on grade at the same height of the garage ceiling. I have been told that footers must be in "undisturbed soil." I understand this would be the ideal process, but this will cause me to have to build an entire basement below the finished level of the home which I really don't need.

Is there a way to fill and compact to the equivalent of "undisturbed soil?"

Thanks.
-Michael

 

[Bob Mariani]

yes if the soil is compacted this will be accepted. Best to talk with your inspector, since he will have an approved method to be assured he is comfortable with your compaction values. A soil engineer may be required in some areas if your soil conditions dictate this. Another reason why planning is so important.

 

[NJ Brickie]

Sure buildings are built on fill all the time. A good site contractor will be able to compact the right type of fill for you.

 

[FL Michael]

Is there a specific type of fill or compaction rate that I should be looking for, or is it all region specific?

 

[Termite]

Proper compaction of disturbed earth is commonplace in commercial construction, but isn't nearly as common in residential construction. It is normally done in lifts and then compacted, then another lift and another compaction, etc. You should insist on a soils engineer to inspect the soil DURING the compaction process and after the compaction is completed, and issue a report in writing. Improper compaction will guarantee settlement in short order.

Around here it takes about 7 years for disturbed earth to reach its pre-disturbance compressive strength values.

 

[Termite]

Is there a specific type of fill or compaction rate that I should be looking for, or is it all region specific?

It is soil-specific, and varies. Anything less than 100% compaction means it isn't as strong as it once was. 95% is normally the target here. Too much compaction can actually be problematic if you have expansive clay soils that swell when wet.

 

[Michael Thomas]

If it's only a matter of a few feet you may also be able to use a deeper (thicker, top to bottom) footer to reach down to undisturbed soil - concrete and rebar are comparatively cheap, and presumably the excavating equipment will be on-site in any case.

 

[stubborn1]

In order to ensure you have decent bearing soil, you could step your footings from the garage elevation up to the frost level in your area. Go 4 feet horizontal, step up 2 feet, etc until you hit the desired grade.