# Drilled Poured-Concrete Piers on Steep Site



## 333onlyhalfevil (Mar 21, 2018)

Hello everyone,

I have a question: How would I go about building drilled pier foundation (and grade beams but that's the easy part) on a steep sloped site? I guess a more specific question would be what slope it's safe for a drill rig to ascend/descend? Or are there other ways to go about doing this?

Thanks in advance.


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## greg24k (May 19, 2007)

They have special slope drilling units so your best bet is to contact a company who specializes in that and see what is available.


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## Dan_Watson (Mar 1, 2008)

I would use helical piers. Where are you located?


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## Davisentnw (Jun 19, 2017)

If I were you I'd call the drill rig company and get specs and capabilities. I done this quite a bit for my excavation / logging business and I have found the manufacturer service lines to be really useful and quick. Good luck.

Joe
Davis Enterprises NW


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## Fouthgeneration (Jan 7, 2014)

Any rocks? Sounds like something smart people sub out, watch and take notes for a few years then risk all your equity on a boo-boo.

As a mason I'd consider scaffolding up to the site, or using a "swinging" stage from above, on wheels for work platforms, A smaller Top slewing trailer mount Crane "Potain" brand? sky hook would durn handy.

I'd want an Soil engineer to look everything over, even the lay down plan and any very large loads on the hillside, such as cranes, concrete trucks, pumpers, delivery trucks . 22 ton forklifts etc.....

Survey control points checked for subsidence would take a little worry off ones mind if done daily.


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## 333onlyhalfevil (Mar 21, 2018)

I'm not doing an actual job, fyi. I just don't know how I'd generally go about building something like this so I'm asking 

Thanks for the pics greg. That helps a lot actually and preemptively answers my follow up question: how would I do it if it was a super-steep cliff face. I like the ropes/cable suspending the drill. Didn't think of that. I was trying to visualize the drills that are attached to a vehicle trying to drive up a steel hill to drill. Those drills in the pics are hand-moved ones, right? Do you know how wide diameter holes they can drill?

Dan, why would you want to use helical piers? You're talking about the big screw piers that basically screw into the ground, right? Located in California, san francisco bay area.

I'll certainly call a drill rig company if I ever decide to do something like this in the future. I'm just looking for general info at the moment as opposed to specific information such as "here's my project, what drill do I need".

@Fouthgeneration: How does rocks change it? Are you talking about rocks in the soil or large boulders on the site? or both? or bedrock? or rock/cliff face? Also, would you mind maybe posting some pics/links to the equipment you're talking about in the 2nd paragraph of your post? I looked on google and believe I found what you're talking about but not 100% sure..

Thank you for the replies everyone! Appreciate it


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## dayexco (Mar 4, 2006)

Dan_Watson said:


> I would use helical piers. Where are you located?



what is the engineered/design life guarantee of these piers? look interesting.


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## Fouthgeneration (Jan 7, 2014)

RE : rocks, Hitting a medium sized boulder with a hand held 12" auger on a 100% slope isn't going to end well.... Unless you are in a river valley around here rocks are rare...

Hill sides are much more likely to have rocks, or they would flattened out long ago....?

what does the soil/structural engineer say on about half dirt half rock sub footings?.

I wouldn't want to live a hillside death ride because some cheapskate couldn't/didn't bore the footings down to solid/ non-moving soil...

What is the game plan if the top 3-6 feet of material is "fluid" in heavy rains/ mild E-Quakes??? your 12-16" poured piers survive the massive side loads?

Build the House on safe ground, and build a look out/detached deck on the might not be there tomorrow hillside. IMHO.

Sell the "scenic Home Site", to a "greater fool", survive the next "Big One".....:thumbsup:

landslide rider is 40 cents a 100.00$ of home value, thus 500K$home = 2K$ every year FOREVER......

The Cranes I was considering for a super tight built up area, were "Potain" trailer mounted, self erecting, top slew, wireless operated cranes, made in Europe? sold in North America by Manitowoc cranes. 
The "big" one only has a 1.2 ton rating at a 40 Meter radius tip, rising to quickly to ~5000lbs at ~20 meters? more or less. 

They might not cover enough ground if you're building a Manse...

many many types in Europe, not so many here....


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