Slab and Stemwall Question

	Slab and Stemwall Question

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Subject

Author

Date

Slab and Stemwall Question

bfitzwater

09-06-2006

Re: Slab and Stemwall Question

Bob Morrison

09-06-2006

Re: Slab and Stemwall Question

Bobk207

09-06-2006

Re: Slab and Stemwall Question

Glenn

09-06-2006

Re: Slab and Stemwall Question

Italian Mason

09-06-2006

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Posted by bfitzwater on September 6, 2006, 2:41 am

Greetings, I am designing my next house to be built in Campbell Ca. It
will have a 2,500 sq ft basement. Instead of placing footings for the
stem walls I am planning on pouring a monolithic slab with the top edge
of the slab keyed to accept the stem walls. I plan to use 24" thick
slab reinforced with rebar and post tension. The edges will likely be
36" thick. The basement will also be used for my shop which needs to
support the weight of a small 10,000 pound forklift for moving my
projects. The Slab will also be the finished floor so I want it to be
as perfectly flat as possible for my machinery etc. It just seems
easier and cleaner to me to have one massive slab instead of separate
slabs, footings etc.

Question is: with the weight of the 12" x 12' concrete stem walls
be a problem to place on the edge of the slab even though it is heavily
overbuilt or will the slab be strong enough to support the stem walls
without excessive cracking? I realize there are a lot of variables
here but I just want to get a "feel" for what you experts think or
if you have seen anything like this before. I will have an engineer
spec out the job, but just wanted to see if anyone has done something
similar before.

The houses that were just built next to my property are all monolithic
slabs ranging in depth from 12" to 36", even the garage is part the
single pour.

I don't have a lot of experience in building, maybe about 8 additions
built from the ground up, so any suggestions are appreciated.

Posted by Bob Morrison on September 6, 2006, 10:05 am

In a previous post bfitzwater wrote...

> I will have an engineer

> spec out the job, but just wanted to see if anyone has done something

> similar before.

You answered your own question. Your engineer will will let you know if
the system you propose will work correctly. That's his/her job.

--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com

Posted by Bobk207 on September 6, 2006, 11:26 am

bfitzwater wrote:

> Greetings, I am designing my next house to be built in Campbell Ca. It

> will have a 2,500 sq ft basement. Instead of placing footings for the

> stem walls I am planning on pouring a monolithic slab with the top edge

> of the slab keyed to accept the stem walls. I plan to use 24" thick

> slab reinforced with rebar and post tension. The edges will likely be

> 36" thick. The basement will also be used for my shop which needs to

> support the weight of a small 10,000 pound forklift for moving my

> projects. The Slab will also be the finished floor so I want it to be

> as perfectly flat as possible for my machinery etc. It just seems

> easier and cleaner to me to have one massive slab instead of separate

> slabs, footings etc.

> Question is: with the weight of the 12" x 12' concrete stem walls

> be a problem to place on the edge of the slab even though it is heavily

> overbuilt or will the slab be strong enough to support the stem walls

> without excessive cracking? I realize there are a lot of variables

> here but I just want to get a "feel" for what you experts think or

> if you have seen anything like this before. I will have an engineer

> spec out the job, but just wanted to see if anyone has done something

> similar before.

> The houses that were just built next to my property are all monolithic

> slabs ranging in depth from 12" to 36", even the garage is part the

> single pour.

> I don't have a lot of experience in building, maybe about 8 additions

> built from the ground up, so any suggestions are appreciated.

Help me out here Bob M

but a 24" PT slab on grade seems kinda burly

In my experience most machine shops in SoCal are in tilt building that
have SOG of 6" or less.

Unless you have some special soil conditions this seems like a LOT of
concrete, even for me :)

I just spent nearly 18 years working in a structural lab that had 24"
slab (not PT) over basement shear walls at 10' on center, so now you
know why I think a 24" SOG is kinda burly.......the lab basement SOG
was only 12"

all this issues can be easily dealt with by your engineer

cheers
Bob

Posted by Glenn on September 6, 2006, 12:07 pm

Is that 24" a typo? Most airport runways aren't that heavy.
Explain what you mean by a stem wall. Not a term I'm familiar
with in my part of the world..

> Greetings, I am designing my next house to be built in

> Campbell Ca. It will have a 2,500 sq ft basement.

> Instead of placing footings for the stem walls I am

> planning on pouring a monolithic slab with the top edge

> of the slab keyed to accept the stem walls. I plan to

> use 24" thick slab reinforced with rebar and post

> tension. The edges will likely be 36" thick. The

> basement will also be used for my shop which needs to

> support the weight of a small 10,000 pound forklift for

> moving my projects. The Slab will also be the finished

> floor so I want it to be as perfectly flat as possible

> for my machinery etc. It just seems easier and cleaner

> to me to have one massive slab instead of separate slabs,

> footings etc.

> Question is: with the weight of the 12" x 12' concrete

> stem walls

> be a problem to place on the edge of the slab even though

> it is heavily overbuilt or will the slab be strong enough

> to support the stem walls without excessive cracking? I

> realize there are a lot of variables here but I just want

> to get a "feel" for what you experts think or

> if you have seen anything like this before. I will have

> an engineer spec out the job, but just wanted to see if

> anyone has done something similar before.

> The houses that were just built next to my property are

> all monolithic slabs ranging in depth from 12" to 36",

> even the garage is part the single pour.

> I don't have a lot of experience in building, maybe about

> 8 additions built from the ground up, so any suggestions

> are appreciated.

Posted by Italian Mason on September 6, 2006, 11:46 pm

We have been seeing alot of "basments" in this area recently. The last
one we did was in down town Santa Clara by the college. It was a
historic house that had the basment re-done and expanded.

> Question is: with the weight of the 12" x 12' concrete stem walls

> be a problem to place on the edge of the slab even though it is heavily

> overbuilt or will the slab be strong enough to support the stem walls

> without excessive cracking?

The footings for the job above were 4'x6', the walls were 12" x 10' I
believe. I do not believe you will be able to do as you palnned in this
area aside from that, the thickness of the slab is not always the
answer.
I can tell you that the building department wanted nothing to do with
the design. the customer had an eng. draw the plans. There were a
couple of changes that had to be made but not without a huge mess and
lots of paperwork. You my friend are in the middle of liability county
where everything is over eng. and nobody wants to take responsibility
for it without a hefty price tag.. when your ready to build e-mail me
directly and we will check it out.

bfitzwater wrote: