Had a day last month where every post hole hit ledge rock

Was putting up a 200 foot run of welded wire on a property outside town. First three holes were fine, then every single one after that hit solid ledge about 18 inches down. Spent 6 hours with a digging bar and rented a demo hammer from Home Depot to get through it. Anyone else deal with ledge rock this bad or was I just unlucky?

4 comments

4 Comments

ray_campbell4621d ago

Started digging a post hole for a mailbox last spring and hit ledge at 8 inches. Rented a rock hammer from the same place and it still took me two hours to get through just that one hole. Youre not unlucky, thats pretty normal around here depending on the soil. The thing is, if you hit ledge that shallow, you might want to check if theres a frost line issue too. Where I am, you need posts down at least 30 inches or theyll heave up every winter. Sounds like you did the right thing with the demo hammer.

julia54921d ago

Nah you said "frost line issue" and honestly that got me thinking. Did you check the actual frost depth before you gave up? Because around here I know people who hit ledge at like 6 inches and just set the post in concrete anyway thinking it would hold, then next spring the whole mailbox is leaning at a 45 degree angle. Even with a demo hammer, if youre only going 8 inches down and your frost line is 36, you might as well be setting that post on top of the ground. When you say "sounds like you did the right thing" are you saying you walked away from that hole completely? Or did you just set it shallow and hope for the best? Because i've been there and neither option feels great honestly.

kellyjones21d ago

Man, that 45 degree angle thing hits too close to home... been there with my own mailbox last year.

the_grace21d agoTop Commenter

Honestly, just setting it shallow and hoping for the best is gonna be a problem down the road... frost heave is no joke. Ive seen people put a post in 12 inches of concrete on top of ledge and it still pushes up over winter. The ground freezes and lifts the whole thing like a bottle cap. If you got through the ledge but only went 8 or 10 inches deep, you might be better off pulling the post and trying a different spot nearby where the bedrock dips lower. Sometimes just moving it a foot or two can save you a whole day of chipping. Or you could pour a sonotube footing anchored into the ledge with rebar if youre set on that location.