Interior footing minimum depth
Interior footing minimum depth
(OP)
Are there any minimum depth requirements for spread footings under interior building spaces?
We have a single-story masonry building that will bear directly on bedrock. Rock is around 1' below the proposed slab elevation. To minimize rock excavation costs my intent is to excavate rock (which may be within inches of the floor slab) to just 12" deep and then to fill the trench so that the top of footing is equal to the top of rock.
Similarly, if the earth will be backfilled several feet against an exterior wall, and the top of floor slab is deeper than the frost depth, would the exterior wall have any minimum depth requirements?
TIA,
Miscmetals
We have a single-story masonry building that will bear directly on bedrock. Rock is around 1' below the proposed slab elevation. To minimize rock excavation costs my intent is to excavate rock (which may be within inches of the floor slab) to just 12" deep and then to fill the trench so that the top of footing is equal to the top of rock.
Similarly, if the earth will be backfilled several feet against an exterior wall, and the top of floor slab is deeper than the frost depth, would the exterior wall have any minimum depth requirements?
TIA,
Miscmetals





RE: Interior footing minimum depth
I do not understand ur idea of flushing the top of the footing to the surface of the rock. Could you please enlighten me?
I have seen interior footings being constructed at 0.5 m depth and if there are surface rocks/boulders, the footings have sometimes been placed even at the surface - this may have to do with the entire floor slab resting on the soil-boulder matrix (?)
Regds
RE: Interior footing minimum depth
As the rock extends deeper in some areas, the footing may be set directly on top of rock without the need to trench.
Thanks,
Miscmetals
RE: Interior footing minimum depth
RE: Interior footing minimum depth
Where is the site located?
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See FAQ158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"
RE: Interior footing minimum depth
The site is in New Jersey.
Thanks for the comments!
Miscmetals
RE: Interior footing minimum depth
The real issue isn't the bearing pressure - it's settlement. To achieve uniform settlement, you will need uniform support. Don't second guess your geotech -
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See FAQ158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"
RE: Interior footing minimum depth
If the space is unheated, thge footintgs should extend to below frost or may bear directly on competant rock. It sounds as if your srock is easily removed so I would remove the "weathered" rock to below frost and place the footing there.
Usually, code requires tyhat thge bottom of footing elevations be placed below the finished exterior grade, assuming a heated space. If the space is unheated, I would assume the lowere of the interior slab or the exterior grade as my "finished grade" and use that as my reference elevation.