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Re: Hillside foundation question.

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Kevin-

Let me preface my comments with;

I don't know your background or the project of which you speak but
some of your comments just don't make sense to me & I question their
validity / wisdom.

"You have a classic case of overbuilding. If you are on decomposed
bedrock there is not one reason why you need all the stuff that your
geologist is recommending unless your house was poorly designed"

"a classic case of overbuilding";  on what basis do you make this claim?

"I went through 5 Geologists before I found one that would
listen to me. Then I went thru 3 civils and many structurals before I
got a hillside project rolling."

Let me get this straight, the majority of the professionals you dealt
with were "wrong" & finally you found one that was right?

Isn't it much more likely that the majority were "right" & you finally
found one that was willing to "give you the answer you wanted"?


"It took 9 months for my report to get through the city of Los Angeles
but they approved it on 3 ft wide Spread footings."


Like I said,  I know nothing about your specific project but I'm not
getting a warm feeling about it.................time will tell

btw if your house slides down the hill or shifts or settles or has e/q
problems will you be availing yourself of the tort system or FEMA
money?

Good luck

Cheers
Bob



On 6/19/05, Kevin Polin <KevinPolin(--nospam--at)cyberonic.com> wrote:
> Robert,
> 
> I have been out of town so I am a little late in responding to your
> question.
> 
> I had somewhat of a similar situation happen to me, And if you do not
> take care of this NOW!!!, it will cost you an arm and a leg in the long
> run and you have a high potential for cost over runs.
> 
> You have a classic case of overbuilding. If you are on decomposed
> bedrock there is not one reason why you need all the stuff that your
> geologist is recommending unless your house was poorly designed.
> 
> First find another geologist or double check his work. Read through the
> first 16 pages and it will give you a wealth of information about your
> lot and its geology.
> 
> Talk with a geologist like an interview. The first 3 geologists that I
> interviewed were trying to push caissons and grade beams and all kinds
> of overbuilding on me. Why do you need caissons and Grade beams when
> your house is on Solid rock? You Shouldn't. Once again I have not seen
> the design of your house but it nay be cheaper to change your house
> design than to do all of the things that you are speaking about in the
> letter.
> 
> I am assuming that your bedrock is rated at around 5000psf. If he put
> 1000psf make him check his calcs OR find a new geologist immediately.
> That means he is going way to conservative and he not thinking of your
> pocket book. Do not be scared to argue with the geologist otherwise he
> will not have any respect for you.
> 
> Your structural is making recommendations based on what the geologists
> had recommended so do not blame your structural. Everything starts with
> the geologists if your geologist did not do a good job you are in for a
> long project.
> 
> Now I have not seen your plan but I do not take the word of the first
> recommendation I went through 5 Geologists before I found one that would
> listen to me. Then I went thru 3 civils and many structurals before I
> got a hillside project rolling.
> 
> It took 9 months for my report to get through the city of Los Angeles
> but they approved it on 3 ft wide Spread footings.
> 
> I just drove 14 hrs from Colorado without stopping so I have to stop
> writing now I don't feel so good... Bye I will have to finish this
> later.
> 
> Kevin
> http://WelcomeLending.com
> 
> 
> 
> 
> 
> 
> 
> -----Original Message-----
> From: junk01(--nospam--at)sgds.com [mailto:junk01(--nospam--at)sgds.com]
> Sent: Thursday, June 16, 2005 3:23 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Hillside foundation question.
> 
> Let me first say that I am not a structural engineer and I apologize for
> the
> length of this post. I am a property owner that is trying to build a
> hillside home, in Southern California, without "breaking the bank". I
> came
> across this list as I was researching hillside foundations and have been
> following it for a few days and reading through some of the archives.
> You
> have a great wealth of information and expertise here. Although I am
> capable
> of learning and doing many things, I am fully aware that a hillside
> foundation design is well outside of my expertise. Given enough time and
> training (and not to mention the legal ability to stamp my plans) I
> would
> love to engineer my own house, but that's not going to happen (at least
> not
> in a timely manner and without ending up divorced).
> 
> I have a couple of questions regarding hillside foundations. I designed
> this
> house myself and tried to simplify the design to make it as economical
> as
> possible (like aligning upper and lower story walls and windows,
> providing
> plenty of shear wall space, etc). I have done a lot of research in
> various
> areas and am trying to work my way through a very steep learning curve.
> After interviewing a few recommended structural engineers, I hired one
> and
> he has been working on the foundation design (I am self-contracting the
> construction). We have a great working relationship and he has made some
> good additional recommendations to cut costs. I want to make sure I do
> not
> offend him by questioning his design.
> 
> Where I am stuck is on the basic design of the foundation. The engineer
> has
> come up with a system composing of 24" grade beams and 10-12 24"
> friction
> piles located at the corners and main interior walls. I would not even
> question this design if it were not for a) that many piles sounds like
> too
> many, and b) Arthur Levin's book "Hillside Building: Design and
> Construction" implies that many engineers over design hillside
> foundations
> and use too many friction piles. I have read through Levin's book
> numerous
> times over the last few years in anticipation of building this house.
> Specifically, Levin says "Grade beams can span and cantilever farther
> than
> most engineers expect". I realize the book is over simplified and hardly
> touches on the actual mathematical engineering of a design, but with the
> increased costs of steel and concrete, I am trying to be as efficient as
> possible.
> 
> What I am looking for are some generalizations regarding grade beam
> spans
> and the number of friction piles. I realize that no one here can know
> enough
> of the details of my project to make any firm recommendations. In
> Levin's
> book he talks of designing 30'x50' hillside buildings with 4 piles by
> increasing the size of the grade beams and cantilevering them. He also
> talks
> about a design that spec'd 24 piles, but only needed six. I understand
> these
> are general examples not relating to the specifics of my design. As a
> lay
> person, am I wrong to second guess my engineer's preliminary design? I
> know
> I am only basing my opinion on Levin's book, which may be totally
> outdated
> (second edition, 1999). Perhaps codes have changed significantly since
> then.
> I only want to end up with reasonable foundation costs so I can afford
> to
> build the rest of the house. I could easily live with six friction
> piles.
> 
> Project details:
> 2 story hillside home composed of two appx. 30'x20' sections (the second
> one
> angled and intersecting the first one by about 25 degrees to match the
> angle
> of the hillside). Floor area about 1300 sq ft per floor. The building
> pad is
> relatively flat (+/- 4'). No special loads except for some cantilevered
> decks on the downhill side. (The engineer is recommending a concrete
> floor
> on the first level with a cantilevered deck to help mitigate any fire
> hazard.)
> 
> Hillside height 135', average slope angle 45 degrees.
> Friction piles along the top of the hill will need to be 40' deep to
> meet
> the H/3 requirements (40' to daylight). The back row of piles would be
> about
> 20' deep since they are set back about 20' from the slope edge. The
> engineer
> said that without the H/3 requirement the front piles would be about 32'
> deep.
> 
> Soils Report:
> Soil consists of competent, granitic bedrock (decomposed granite)
> starting
> at about 1.5' in depth and is considered suitable for building.
> Seismic zone: 4, Soil profile type: Sc
> Recommended to use friction piles, minimum 24" diameter. Minimum 10'
> into
> bedrock and minimum of H/3 (not to exceed 40')
> Skin friction of piles: 700psf
> 
> Since I have to have these 40' deep friction piles, it seems like I
> should
> get something back for that additional depth. Am I wrong for thinking
> that a
> larger, more rigid, grade beam design with fewer friction piles, might
> be a
> more efficient way to go, rather than designing a simpler plan of a
> friction
> pile at every major wall? The current design has the piles about 15'
> apart.
> Is it horribly complex to design a foundation where the piles do not
> necessarily line up with the building shear walls? How did Levin design
> 30'x50' foundations with only 4 piles? He says "Use 4 piles wherever
> possible. Grade beams are relatively easy to construct, can be increased
> in
> depth to span farther, and can be cantilevered a considerable distance".
> 
> 
> I'm sorry this is so long, but would appreciate any input I can get. If
> this
> is the wrong place to ask a question like this then just say so and I
> will
> leave you all alone.  :)
> 
> Robert
> 
> 
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