I am preparing footings for an outbuilding, using pier blocks. Our frost depth is only 12". There is a significant amount of clay in the soil, so I am putting gravel under the pier blocks.
The plan was: excavate holes to 12". Fill with 4" of 1 1/4" rock, compacted. Then 4" of 3/4" rock, compacted and leveled. This leaves the pier block 4" below grade. Fill around the block with soil, to resist sideways movement.
I have excavated to frost depth and bought a load of gravel. It's not exactly what I expected: it's smooth, round drain rock, and I was expecting coarse crushed rock. I assumed that coarse rock was important to make a stable base for the footings.
Is it OK to use round, smooth rock in this application, or would that doom my building project?