drewsteele
Registered Users
New Member
Posts:15
 |
| 07/28/2008 1:40 AM |
|
Hey guys - Ive got 2 stories that set back into the hillside. The bottom floor is kinda like a walkout basement so it retains hillside on 3 sides. The main floor only retains in the back. It's a stepped hillside ( see attached image)
|
|
|
|
|
|
|
drewsteele
Registered Users
New Member
Posts:15
|
| 07/28/2008 1:53 AM |
|
here's the rest - the pic cut off the post -
So the question is - the engineer Im working with says that rule of thumb for concrete walls is 1" for each foot of wall height -So assuming 2 stories at 9' each Im at 19' give or take - so rule of thumb would be a 19" wall????
Im located in the santa cruz mountains in California so siesmic is a concern.
I mean, he started talking about tie backs and all kinda stuff...
any thoughts?
And while I have you ; )
He's very concerned with the shoring when I excavate out the hillside. He's talking about 100k shoring jobs and elaborate sacrificial piers to stitch the hiilside...
Im an owner builder with my own equipment - I was planning on just scooping out the hillside over a couple weeks in the summer and being quick about it. The soils are moderately clay/loam - have been stable the five years Ive been here - even in really wet winters I dont get any slippage even from my steepest cuts... Have you guys experienced this on your jobs? Do you know if the building dept's require you to have a shoring plan?
Also - If anyone knows any good engineers in my area that are particularly good Id love to get a second opinion - Im not in contract with the current guy Im talking to - Ive just had a couple of consulting sessions.
thanks for reading
Andy
|
|
|
|
|
Paul Stevens
Registered Users
Basic Member
Posts:147
|
| 07/28/2008 11:08 AM |
|
Andy,
contact Chris Johnson at 925-260-6080, he is located in the Napa Valley. He should have the answers that you need, if not he will know where to get them from. He is in contact with many different ICF friendly engineers, which is something that you want on your side before you start your project. Working with an engineer who is unfamiliar with the product can be tough!
Tell Chris l say hi!!
Paul Stevens
|
|
|
|
|
slenzen
Registered Users
Basic Member
Posts:179
|
| 07/28/2008 5:49 PM |
|
| I've got the same type lot that I am planning to build on but in MN. |
|
|
|
|
Chris Johnson
Registered Users
Basic Member
Posts:358
|
| 07/28/2008 9:07 PM |
|
Andy,
Engineers need to do various calcs to determine the size of the wall needed. I have seen specs require 36" wide walls on 24' retaining in the Oakland hills, so don't be over quick to discard the engineers theory. Many things to consider are the soils report, 'moderate clay/loam' is one thing, but the length of the wall it is against and the density and retention are all factors. In your area I would deal with Issac Kim P.E. 510.872.9881.
For the shoring, you need to meet Cal-OSHA requirements at a minimum, 1:1 cut back on the hill or build shoring to retain until ready to backfill. Because of the height of the backfill good chance the engineer wants you to have tiebacks to reduce the pressure against the hill. Don't forgot during earthquakes the ground can literally 'liquify' casing extreme undue pressure and take out the foundation.
Slezen, again soil conditions will dictate your wall thickness, chances are you will need an 8 or 10" wall on the bottom portion and reduce thickness at floor intervals as you get closer to the top of grade which can normally switch to 6" before you get out of the ground. Being siesmic is not a major concern you are in a little more of a forgiving area |
|
Chris Johnson - Pro ICF
Napa, CA
Come for the wine, Stay for the ICF work |
|
|
icfcontractor
Registered Users
Basic Member
Posts:237
|
| 07/28/2008 10:10 PM |
|
Drew,
We are currently working on a 3 story home in Washington in a seismicly active zone. Here is a sketch of what we are doing and a link to the blog of the home owner. He is a Home Owner General (HOG) and if you read his blog you will see some of the successes he has had and the pitfalls also.
http://www.icicleearthhome.blogspot.com/
As far as your engineers rule of thumb, I have not heard of it. Any time we run into a complex concrete design issue, we only us one engineer. He nows concrete inside and out and the home that we are working on is a combination of 6" and 8". Some of our walls extend 40 feet from the footing to the roof. Your building may have some complex issues and you may need an experienced concrete engineer.
ICF Contractor |
|
|
|
|
icfcontractor
Registered Users
Basic Member
Posts:237
|
| 07/28/2008 11:13 PM |
|
Drew,
After thinking about it I know where your engineer came up with the "Rule of Thumb". This is used for unrestrained fully cantilevered retaining walls. Kind of like the ones you see along the highway. They usually taper are very thick to hold back the unrestrained backfill.
What you are building hear is not an unrestrained retaining wall. You could go at this in a couple of different ways and make it fully restrained retaining walls or you could use a buttress system, inside and/or out, that would very effectively deal with your loads. The buttress method is my preference because I can use small footings and save on tons of materials. As far as the high wall and shoring , this really depends on your soil type and the amount of room you have to dig out and terrace. One thing to keep in mind is that residential basements are exempt from OSHA's trench, digging, and shoring standards.
ICF Contractor |
|
|
|
|
SoCalScott
Registered Users
New Member
Posts:41
|
| 07/29/2008 12:54 AM |
|
retaining wall vs. pin wall. in a pin wall the diaphram of the 2nd story floor acts to support the back wall that is retaining the hillside, reducing the strain on the wall itself. the term "retaining wall" gets used in this situation frequently.
|
|
|
|
|
glzman
Registered Users
New Member
Posts:5
|
| 08/02/2008 11:33 AM |
|
| I built a house in Santa Rosa with an excavation similar to yours, below you will find the engineer my
architect used. I also understand him to be experienced in ICF issues, if I remember a previous post of yours you're considering ICF's. We didn't do any shoring of the excavation but my hill was more rock and clay, we also didn't do any tiebacks and we're definately in a siesmic area. If memory serves the lower retaining wall was 14 inches thick and I think the upper wall was 8 inches thick. If you have any questions I might be able to answer you can email me at sonomapolysteel@gmail.com.
Dave Vinson
Vinson Engineering
1121 S Gravenstein Hwy
Sebastopol, Ca 95472
1-707-824-1134
dave@vinsonengineering.com
Good Luck
Greg Z |
|
|
|
|
drewsteele
Registered Users
New Member
Posts:15
|
| 08/03/2008 3:30 PM |
|
Thanks guys for ALL the good info!
ICFcontractor - your scenario looks similar to mine. What type of foundation is being called for on your project? Also- you're saying that that first floor that's retaining on 3 sides is only 10" thick?? Can you provide any more detail? The guy Im talkin to wont discuss anything thinner than 10"-12" and thats without having the foggiest idea what my soils conditions are. And that was for one floor retaining - not the 2 floors as in my sketch above. And - when you refer to "restrained retaining wall" are referring to the 90degree turns at the outside walls? Or is that any condition such as butresses?
Chris & Greg - thanks for the referrals - I will definately be following up.
Cheers!
Andy
SoCalSCott - First - I googled Pin Wall and came up empty handed - any more detail? One note that again is fishy is the guy that Im talking to mentioned MANY times that the floor diaphram has no impact on the wall's ability to withstand flexure. Im not quite sure how that would be the case - If I knew more about the pin wall that youre reffering to would this all become clear?
One point of reference - The current engineer is primarily a commercial guy - - I would assume with very large budgets. Dont know if that matters much but I could see it possible that there would be 2 ways of thinking or approaching a large budget/large commercial structure and a modest budget residential hillside home ; )
|
|
|
|
|
icfcontractor
Registered Users
Basic Member
Posts:237
|
| 08/03/2008 3:45 PM |
|
Drew,
The house is using a combination of 8" concrete core and 6" concrete core walls. This house has some walls that extend over 40 feet and that are retaining over 22 feet of soil. If you email me I can send you a list of a couple of great engineers that do these types of concrete structures on the west coast routinely. I believe they are both licensed in CA, if not you could use one of them as a consultant to teach your engineer some new tricks.
Icfcontractor@comcast.net
ICF Contractor |
|
|
|
|