Post Holes - What a headache!!!

I have a heavy clay soil with a least one boulder in every hole and many smaller rocks too. I tried a power auger with no good results. It almost ripped my arms off. I have to dig six 42 inch holes. I have almost 5 holes dug. two questions:

1. When they say add 3-6 inches of gravel to the bottom of the hole before cement, is that 3-6 MORE inches or is it included in the 42 inches.

2. Do the holes have to be straight down or can they be slanted, lets say to avoid a boulder.

Any other digging tips also appreciated.

 

try renting the post hole digger with the de-tached motor unit. One person can work it fairly well. Im a lightweight pulling a solid 110, but ive used the solo units to dig footings and it was OK. The two person ones would be great if I had a clone or help. Dont forget to flare out the bottom if these are footings! Very important to load dispersion and all that. ( probably not important in heavy clay soil at all but inspectors like to see it) As for the boulder.. just crack it with a digging iron/bar. chip away until its out of your way otherwise your cardboard form will be slanty. I never add gravel to footings? concrete is sand/gravel and portland cement. But for post holes its a good idea for drainage.

Hope this helps-Josh

 

Not much you can do about large rock, you just have to bust em' up or dig down and around them to get them out. I recently had to dig 40 post holes and used the 2 man auger with 3 of us rotating turns. I ended up having to dig each one by hand afterwards to get them the way I wanted/needed them. I actually had to dig one hole so big because of a hugh boulder that I was able to jump in the hole and tie a rope around it and pull it out!

As far as slanting a hole, are you embedding the posts, or attaching at grade? If attaching the posts with a Simpson type tie, then you should be OK, but like Josh said, your sona tube isn't going to fit nicely. If you're embedding your posts, then you have to make sure the post is plum and in line with the others. I had a couple that were out of line and I had to build out my deck frame at the top to compensate.

 

I had the same issue with the rock. After an hour of getting no wear with a two man auger I hired this guy with a bobcat that had I huge auger on the end. He tore through the rock and bolders and was done with five footings in about 20 min. A well spent $180 only wish I didnt kill myself for an hour before hand.

Shawn