I’m in the process of digging post holes for my decks on my project house. I’ve run into a few pieces of concrete about 32″ down. I’m having quite a hard time getting around them. I’ve tried pry bars, an SDS Hammer, and swearing all to no avail. Does anyone have any suggestions? Unfortunately I cant move the holes. Further away from the house is too far and closer puts me further into the cement.
I need to get down to 42″, so far i’m 1 for 3.
Replies
Try a pointy spud?
Thats what i'm using, sorry I called it a pry bar. Problem is, is that I can hardly clean the dirt out from around the cement and the surrounding dirt/clay absorbs so much of the impact from the pointy spud. I can drive the spud into the cement but I havent been able to crack it just yet.
Try drilling a hole in the CC where you're going at it with the bar, it may make it easier to crack it though.
short of that
dynamite
Don't know if this will help any, but, here goes anyway.
I read recently about a powder used to bust up concrete. The article was about busting slabs. Drill hole, put some magic powder in hole (maybe moisten) go home. Come back in moring and slab is all in chunks ready to haul away.
Might have been in Fine Homebuilding or maybe someone else can chime in with the name of the powder. Seems like it might work for you.
I think it was in the last FH, in the back area under "Master ....."
Trouble is ya still gotta drill into it.
MSA1, you sure Hilti doesn't have something for you?Quality repairs for your home.
AaronR ConstructionVancouver, Canada
Hilti didnt, but Bosch did. I bought an SDS yesterday so I can drill holes in the block. I think I just need to work at it for awhile. Its raining here now though so it looks like i'll be working inside today.
FHB mentioned it awhile back, I wrote it down to look it up, they are:Dexpan: http://archerusa.com/and Bristar: http://demolitiontechnologies.com/MSA1 This stuff may be just what you want - drill a hole, fill with goop and watch the block snap apart. Really impressive stuff from the FHB write up.ack! Just found this while looking for a distributor: guy was blinded ("melted his eyeball in about seven seconds") by the stuff blowing out: http://www.rgj.com/news/stories/html/2004/03/30/67425.php wear those goggles!
Edited 11/1/2005 10:00 pm ET by storme
Uhhh, maybe before you drill/bust those suckers up, you should figure out what the heck they are?
SEPTIC TANK!......lol
I know what they are, we had most of the front yard dug up for waterproofing. We had an 8 foot deep porch foundation (which still failed) and I thought we pulled it all out. I'm pretty sure that one of the holes just has a chunk that was in with backfill.
About 3 sticks of dynamite ought to do the trick!
No electrons were harmed in the making of this post.
Had to dig a hole through engineered fill compacted to about 98% inside a finished comercial building for an elevator ram. The dirt was far too hard for a post hole digger, but the concept is close enough to a post hole that this might be useful for you.
I took a chisel bit from an SDS-Max hammer and cut it in half with a grinder. Split both ends of a piece of 3/4" black pipe a few inches back so it could flex and expose some of the bit. Drove the chisel end of the bit into one end of the pipe and the spline drive into the other end. Welded the splits with 6010 a little on the hot side followed by 7018.
This gives you a 5 foot long SDS-Max chisel bit.
While one person runs the hammer another runs the shop vac down the hole. You would not believe how well this works.
Murphy's 6th Law of Combat Operations -- "If it's a stupid idea but it works, it isn't stupid." <G>
But really, I would make sure that it isn't the septic tank. <G>
Sweet idea, wish I knew how to weld. Thats just about what I need.
I'd bet that if you made the assembly up and took it to a shop you could get it welded. Your local independant motorcyle shop would probably even do it. We're talking about a half hour of work from the time you show up and explain it to the time the mechanic goes back to whatever he was doing.BTW, the concerns expressed here about putting wooden posts in concrete really are well founded (oops, there we go again <G>).Maybe your inspector would consider a longer-lasting equivalent.
Problem solved! Got past the concrete. The posts are not going in the concrete but on the concrete.
Cool -- glad to hear it.
I ran into a simular situation when I was digging post holes for a fence a few years ago. 'cept I got down about about 2 feet before hitting concrete. I simply dug a big (wide) enough hole to get at the concrete. turned out it was where they had dumped a pile of left over concrete from when they did the foundation. while it took a good amount of digging and sweat from my brow, it sure was a good feeling not to let it get the best of me.
your hole would be a more difficult dig because it is deeper. I do however have a couple of questions. you said post is for your deck. do you mean you are sticking wood posts into the ground? (I hope not) or are the holes for pouring piers? if so do you plan for footings? depending on your deck you may or may not need them. in any case you will have at least one post with a good size footing.
I like the idea given for making extended chisel bit. that sounds to me like it may be worth a try 1st.
Footings for a porch. Lets just say me and the inspector dont see eye to eye on this. He wants cement on the bottom of the hole and then a post. I feel this will allow water to collect and speed up decay. In the past i've filled the bottom of the hole w/ pea gravel as I believe this will allow the water to flow away from the post.
I'm sure a hole other thread could/would be started from this.
Tell the inspector you're one step ahead of him--the concrete is already in the bottom of the hole!
Feel for you. Dug some fence posts this summer and found a sidewalk under about 6" of dirt. The house had formerly been condemned, and a mortgage company bought it and renovated it. The house is fine, but someone (either former owners or the crew that repaired it) covered all the sidewalks with dirt. The wife had dug up one sidewalk, but we didn't even know this one existed. Explains why grass won't grow there.Wasn't hard to break thru that sidewalk and keep digging, but I couldn't imagine doing it 32" down. The field-welded 5'-0" chisel idea sounds like your best bet (if you can find someone brave enough to hold it while you're doing the swinging). If that's too much effort, maybe improvise with one of those metal stakes for attaching wire gauge fencing. Or an old steel tube fence post if you've got one (take your aggressions out on one end to pound it into something resembling a point). I also put gravel at the bottom of the holes before pouring concrete for the post holes, but used post anchors for the wood posts. You can get them elevated above grade if you're worried about rot. Would your inspector be o.k. with this?
Seems like gravel around the bottom would attract/collect water. Unless you have a "conduit" of gravel leading away from that spot, how does the water get away? Either way, isn't some PT wood suitable for ground contact?
Regarding the existing concrete chunks, if the bearing for the porch failed previously, won't it be necessary to extend the new footings not only thru the old concrete but sufficiently below them to reach undisturbed soil? Are you within the zone of the original basement overdig? Regardless of the weight (or lightweightness) of the new deck, would the inspector require "undisturbed soil" for the bearing surface of the new footings?
Instead of getting thru the stuff perhaps it would be easier to dig down on two sides of the existing chunk and bridge over the top of it with new concrete.
The old failed footing extended 8' down. When we dug for the waterproofing we stepped the hole so we are in undisturbed soil. Not only undisturbed but clay so i'm hoping it'll be fine.
As I said before we got past the block and got the joists in place. Now all we need is the hole inspection so we can install the posts.
I would never just stick wood posts in the ground for a deck or porch ( PT or otherwise) perhaps some will say nothing wrong with it.
it's one thing for a fence but not for something that people's familys are gonna be walking on for decades to come.
why do you not want to keep your posts above ground? You're digging holes anyways why not stick a tube in and fill with concrete? wether you need footing or not depends on your deck. What's your frost line? if you got a high frostline, maybe you only need to be digging 18" for piers, instead of 42" to stick posts down.
I'd go along with the idea of pouring a pier atop of concrete that you've found. save the time and effort used on getting thru that concrete and pour some piers.
anyway, that's just my opinion.
we always bury our posts... for decks we use Ground Contact ( .40 ) and for pole buildings we use (.60)
our frost design depth is 40" .. we dig to 40" , pour a footing of 1 bag of Quikcrete..
screed the top , and set our posts / poles the next day... we backfill with tamped gravel..
i think we've been doing it this way since PT became available... say late '70's..
we do repeat business with our customers from 30 years ago, occasionally we see some rot in old PT.. but it has nothing to do with wether or not it's ground -bury.. it has a lot to do with pitch pockets keeping the treatment from penetrating
ie: i have never seen a single one of he posts we've buried develop rot... but i have seen occasional PT framing develop rot in some locations... and it is always a unique occurence
Mike Smith Rhode Island : Design / Build / Repair / Restore
I've never seen it done that way. But if it works then it works. You gotta go down alot farther then the 18" we have to go down. so that probably helps for the stability of your posts as a whole. 18" might not be enough to offer the stability needed on a good sized deck.
the stabilizing factor is a big part of my decision to bury them..
you know the post at the bottom of a set of exterior stairs ?
normally , it gets bolted to the stringer, and fastened to the top of a pier..
but the leverage of a kid swinging around it will usually knock it out of plumb..
burying 3' of it sure does help
Mike Smith Rhode Island : Design / Build / Repair / Restore
Edited 11/1/2005 7:20 pm ET by MikeSmith
here's a sample..
View Image
View Image
Mike Smith Rhode Island : Design / Build / Repair / Restore
Edited 11/1/2005 7:30 pm ET by MikeSmith
Edited 11/1/2005 7:31 pm ET by MikeSmith
Thanks for info and pics. what kinda of post is that - PT that is primed white?
also nice post caps, that'l also help keep that kid from swinging off the post when the corner digs into his ribs.
sometimes we just use plain PT posts and paint them.. so we often have some laying around that have been primed..
we buy extra and dry them to see which ones are going to twistMike Smith Rhode Island : Design / Build / Repair / Restore
you're at 32", need to get to 42" ... how thick is the concrete obstacle? about 10"? declare success and move on .... pour on top of it & incorporate it into your footing ...
(warning - i'm not a pro - but this is 'just' a deck, right?)
That wont work on this hole. Unfortuntely I know this is just a chunk and the holes have to be inspected.
MSA1, after I read about your plight, I have been looking around for a few extra post holes I had laying around, I'm sure they were at least 42 inchers, but the kids must have been playing with them, I can't find them, if I do, I will send them to you.
The heck, you say?
while you're looking for those post holes keep an eye out for my board stretchers - I can never seem to find them when I need em.