Foundations - Mono Slab Vs Stem Wall


Joe_Carrick
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Working here in Southern California most of our homes are built using Slab on Grade Foundations.

 

I have struggled with "MonoSlabs" since they were first introduced (X5 I believe).  The Exterior Footings didn't offset outside of the Slab Edge which is the typical way they are built.  In addition, they are difficult to edit in 3D because there's no "Wall".

 

Eventually I went back to Stem Wall Foundations with the Floor Structure being a 4" Concrete Slab.  However, this results in a Stem Wall Centered on the Footing but in the real world the inside edge of the Stem Walls isn't formed and so should be like a MonoSlab Footing.  There are some settings in the Foundation dbx that allow the Stem Wall to be thicker (an additonal wall type) and the footing to be offset.  This has allowed me to get my Foundations properly defined and detailed.  But it's a bit of work to do it.

 

I Think this can all be fixed by Chief programming with a few extra options in the Foundation Defaults dbx so that Interior and Exterior footing walls would be created the way I need them in the first place.  The changes should be made for MonoSlabs so that there are options for different Interior and Exterior Footings.  There should be separate depth settings and for Exterior Footings the Footing should be offset to the Exterior.

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...... The changes should be made for MonoSlabs so that there are options for different Interior and Exterior Footings.  There should be separate depth settings and for Exterior Footings the Footing should be offset to the Exterior.

Joe,  I have been fighting for this since the beginning of the mono slabs.  I gave up.

 

In a nutshell I think what would make JC happy is if the  mono slab footing was made up of a FOOTING,  a STEM WALL that sits on the footing,  and then the SLAB that sits on the stem wall.  This way,  we could offset the FOOTING from the STEM WALL,  if you know how mono slabs are formed,  this would make sense.

 

As of now,  I believe the mono slab footing are only made up of a footing.  I did many vids on this back in the day,  nobody but maybe the PMan listened,  I gave  up.

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Joe,  I have been fighting for this since the beginning of the mono slabs.  I gave up.

 

In a nutshell I think what would make JC happy is if the  mono slab footing was made up of a FOOTING,  a STEM WALL that sits on the footing,  and then the SLAB that sits on the stem wall.  This way,  we could offset the FOOTING from the STEM WALL,  if you know how mono slabs are formed,  this would make sense.

 

As of now,  I believe the mono slab footing are only made up of a footing.  I did many vids on this back in the day,  nobody but maybe the PMan listened,  I gave  up.

I was listening, but you kept saying that it worked.  Since I couldn't get it to work I gave up. ;)

Maybe now's the time for CA to fix it.

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post-50-0-91418900-1427313796_thumb.pngI was listening, but you kept saying that it worked......

 

I do not think I ever said it worked.  I could do it,  or should I say I have done it,  but it was definitely more trouble than it was worth.

 

To restate what I am talking about and what I think JC is talking about,  take a look at the pic.....  it is the "toe" that is formed auto when forming a mono slab.....  in CA this can not be done without a lot of work.

post-50-0-51747900-1427313732_thumb.png

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That is exactly what I am talking about.  Basically, it can make a big difference in the amount of concrete is used in the foundation.  If the foundation trench is 24" deep and full width you have a lot of extra concrete (about 1-1/2 cu.ft per lineal foot of wall).  For a 40'x50' building this would be 180 x 1.5 = 270 cu.ft.  IOW, 10 cu yds of concrete extra.

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That is exactly what I am talking about.  Basically, it can make a big difference in the amount of concrete is used in the foundation.  If the foundation trench is 24" deep and full width you have a lot of extra concrete (about 1-1/2 cu.ft per lineal foot of wall).  For a 40'x50' building this would be 180 x 1.5 = 270 cu.ft.  IOW, 10 cu yds of concrete extra.

Thank you Joe for confirming what I am talking about.

 

So to restate what I think should happen,  and I have been talking about this for years,  in a mono footing situation the slab should be connected to a footing by a "stem wall".  Not a  stem wall in the convention use of the word,  but for lack of a better term,  the usage of "stem wall" works.

 

Just a side note.......  I think I just noticed something else that was  wrong with mono slabs prior to X7,  has now been fixed in X7......  thanks I think.....  I have not spent much time exploring mono slabs in X7,  but I think something is working better than it was.

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