k0ua
Epic Contributor
I'm guessing that what really happens is a garage slab bridges the voids of soft material, not good, but something a reinforced light duty slab can get away with--within limits. To be done correctly, the organic layer of soil should be removed everywhere under the slab and replaced with compacted material like sand.
James, good idea on the rain, for two trees he could use the hose to saturate the soil around the tree.
Yes it is amazing how much weaker they become after a soaking. A tree you no way you could push or pull over with a good size tractor could be pulled over with a BX under the right conditions. That is why sometimes after a good soaking rain and you get some wind, large trees can be uprooted from wind pressure alone.