It all depends on the mechanical properties of the rock formation. Some
rock is mechanically stable, and many are not!
Ultimately the safety of the installation is the paramount concern. Thus:
Option 1: Have a licensed geologist obtain a core sample, have a
goetechnical report completed by a licensed engineer, and follow their
Option 2: Install the foundation to spec. This may/will require rock
removal to create the approriate sized hole for the recommended foundation
At the end of the day option 2 will probably cost much less. It will
involve either an experienced jackhammer operator or a licensed explosives
expert, or both.
73, Scott W3TX
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