11-27-2009, 10:00 AM
If you’re talking about drilling a hole to set a marina grade fiberglass piling pier to build a house… better stop right there and go back to the drawing board. Those are not made for vertical type bearing loads nor intended to provide shear under such bearing loads.
If you’re just setting up a power pole or something, set it at about 24” if in solid Lava and fill the gaps with mortar mix then drill a small hole in the side and fill it just above grade with concrete.
A footing on solid rock for a post and beam supported structure only requires that the footing be pinned to the rock so there's no comparable answer to your question with regard to depth.
In that light if your setting a fiberglass piling pier for a power pole on solid rock just drill some small holes in the rock about the inner perimeter of the inner diameter of the tubes. Pump some epoxy in the holes and set some rebar sticking up out of the holes about 8- 14" and then bent over at 90 a few inches. Set the tubes around the rebar, drill a hole in the side of the tubes and fill them with concrete about 16" deep. That should secure them and keep them upright fairly stout.
If you’re just setting up a power pole or something, set it at about 24” if in solid Lava and fill the gaps with mortar mix then drill a small hole in the side and fill it just above grade with concrete.
A footing on solid rock for a post and beam supported structure only requires that the footing be pinned to the rock so there's no comparable answer to your question with regard to depth.
In that light if your setting a fiberglass piling pier for a power pole on solid rock just drill some small holes in the rock about the inner perimeter of the inner diameter of the tubes. Pump some epoxy in the holes and set some rebar sticking up out of the holes about 8- 14" and then bent over at 90 a few inches. Set the tubes around the rebar, drill a hole in the side of the tubes and fill them with concrete about 16" deep. That should secure them and keep them upright fairly stout.