Designing Gravel sub-base
Designing Gravel sub-base
(OP)
Building 50 x 100 house on non-expansive sandy-clay sub-surface. Depth to foundation is nine feet. Perimeter footing is 12" x 36", with 12" wide poured walls.
For the sub-base, intend to use 4" depth of 2" stone (#3), covered with 4" of 1" stone (#57).
House has 80,000 lbs of steel concentrating the bulk of the upper-storyweight on 14 points along the foundation footings.
The combined 8" of gravel seems like surely enough for stability and load distribution.
Is there a structural risk associated with mixing the two gravel sizes and using a total of 8" of gravel?
Believe this would help distribute the high load points better . . . but have located no experts to confirm or challenge the design.
Please contribute thoughts and advice!
Larry (in Virginia)
For the sub-base, intend to use 4" depth of 2" stone (#3), covered with 4" of 1" stone (#57).
House has 80,000 lbs of steel concentrating the bulk of the upper-storyweight on 14 points along the foundation footings.
The combined 8" of gravel seems like surely enough for stability and load distribution.
Is there a structural risk associated with mixing the two gravel sizes and using a total of 8" of gravel?
Believe this would help distribute the high load points better . . . but have located no experts to confirm or challenge the design.
Please contribute thoughts and advice!
Larry (in Virginia)





RE: Designing Gravel sub-base
RE: Designing Gravel sub-base
Appreciate the reply . . . you are a star!
. . . and yes, was intending to use a geofabric.
. . . so, I gather, using two different gravel sizes would not be a problem. The additional gravel is only about $1,600. The additional stability and ability to distribute the loads seems to make economic sense.
. . . The original drawings say a "minimum" of 4" of gravel, but we could not determine the "desirable" depth.
Does the use of the larger rock, on the bottom layer, add to stability and load distribution . . . or is this just something I picked up in a text book back in school?
Appreciate the tips!
Yours,
Larry
RE: Designing Gravel sub-base