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Deck Piers Failing Slope Eroding Out from Under

Gangle's picture

Can this be repaired? There are 6 posts supporting this deck. They are shallow 12-16" footings and the slope has eroded around and beneath them. I tied the posts with diagonal braces, which represents the angle of the slope pretty well. I thought I was going to brace the deck, and one at a time remove a post and footing, then dig a deep hole for a new concrete footing, replacing each one. However, the soil on the slope gives way as I stand under there nosing around. I read Mike Guertin's article on making an old deck safe, which was awesome, but didn't address this issue. Any ideas?

Your plan to support and (post #215391, reply #1 of 11)

Your plan to support and replace one at a time is the way to go, but you wil need to dig fairly deep. Use sonotubes to form out the pier and you will need to add rebar to help with lateral loading

Got it. I will use tubes with (post #215391, reply #7 of 11)

Got it. I will use tubes with rebar but I'm gonna take junkhounds suggestion on adding a beam supported by two new posts, instead of replacing the existing ones.

You need a minimum of 5' (post #215391, reply #2 of 11)

You need a minimum of 5' horizontal distance from the bottom of the footing to daylight. 

I will factor that in to the (post #215391, reply #8 of 11)

I will factor that in to the depth, thanks!

You MIGHT be able to get some (post #215391, reply #3 of 11)

You MIGHT be able to get some sort of pile driver in there (eg, one attached to a bobcat).


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

90% of the work will b (post #215391, reply #4 of 11)

90% of the work will b digging the holes if you cannot get a machine there (from below??) 

Looks like rocy soil so a [CUTE LITTLE PUPPY] to dig by hand.   Hire some neighborhood teenagers to dig for you, my 14 YO grandson would love to dig 2 holes as described below for about $100., even in rocky soil, he loves to dig!

 

SO, sister up the crossbeam above, leave the; existing posts and footings.

dig  only 2 new holes 2 feet in frm the outer existing posts, add 2 new posts. 

go down  5 feet or 2 ft past  freeze depth where you are, whichever is deeper.  

Pour 4" slump max 6 sach mix with 6 vertical rebar and ties.

You can leave the existing in place till soil moves further and they are hanging there if you wish. 

So you've got a 14-year-old, (post #215391, reply #5 of 11)

So you've got a 14-year-old, 5-foot-tall kid standing in a 5-foot-deep hole in unstable soil.  On a severe slope.  What could possibly go wrong??


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

What could go wrong (post #215391, reply #10 of 11)

What could go wrong ---

hmm, a tired teen and a bent spoon posthole digger? 

how big a hole do you want OP to dig???  3 feet diameter ? 

My own grandson hs dug a 5 ft deep hole with posthole digger.

BTW, I'd just wet down the sides of the hole after digging about 15 inches in diametet.,  5 to 6 ft deep possible with clamshell type poshole digger.  Then no sonotube needed either. 

Another option:  remove sqare foot of decking above, drop an 8 foot long section of  galvanized 8WF beam thru the hole, build a tripod of 4x4 on the top of the deck. Using a small winch and trip, drive the 8WF into the soil if no big rock - however, pic does look like big rocks so probably wont work.. But would be minimal diggin'.  

Your suggestion makes a lot (post #215391, reply #6 of 11)

Your suggestion makes a lot of sense to me. I'm going to do it. Unfortunately I'll be digging the holes myself, tho I'm sure my dog will do his best to widen the top for me! BTW this was my first post here. I really appreciate the feedback! 

Junkhound, your suggestion (post #215391, reply #9 of 11)

Junkhound, your suggestion makes a lot of sense to me. That's what I'll do. Unfortunately I'll be digging the holes myself, tho I know my dog will do his best to widen the tops for me! BTW this is my first post here. I wrote a couple comments back but the site was unable to send, oh well. I really appreciate the feedback!

Get yourself a posthole (post #215391, reply #11 of 11)

Get yourself a posthole digger and dig a trial hole under there.  Then go back and consider your other options.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville