Interior Foundation ?


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I have a need for a foundation where the garage meets the interior of the house.

There is a 4 or 6 inch step down to the garage floor & the wall is bearing so I need a foundation.

This is slab on fill so the foundation is a thickened area in the slab with a 6" step down.


Is there a foundation tool for this or do I need to add hidden wall in the foundation plan & use primitives to draw the foundation?

Any advice is appreciated.




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Obviously I don't know what I need to do.

I'm in plan view on level zero. I use the foundation wall tool to draw the wall & foundation.

Now I need to delete the CMU wall & change the foundation to look like the above example & raise it to the floor elevation.

And you do that how?


I'm not looking for a cross section detail, I used that to show what the structure should be built like.

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Attached is a plan I am practicing on.

The exterior foundations need to be 16" tall stem wall foundations, 8" stem wall centered on 16" wide foundations.

The interior foundation needs to be a thickened slab with 4" lower garage floor slab the bedroom floor.

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on level one , on the interior wall between the house and garage did you open the wall's DBX and specify it to have a foundation? (on the general tab)  it should build auto as specified in the defaults ,but on level 0 you can select it and change it if needed.





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sorry bad pic I guess I meant for you to CHECK the foundation option , you can also use the foundation Tab in the same DBX to reset default sizes  and the chamfer etc




you may need to delete the foundation and rebuilt it ,to reset all the settings you have tried to default

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Thanks so much Perry, close but I want the exterior footings to be stem wall.

Only the interior will be Mono.


Here in Florida this is a common condition as the lots are so flat that only a 4 to 8" step in the garage is needed.

Can you change the exterior footings back to Stem wall?


Off to get dinner.


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So my conclusion is that you can not mix "Stem wall Foundations" and "Monolithic Foundations" on the same slab?


My only successful solution is to use a solid for the thickened slab foundation & a Divider wall for the step down on the foundation plan.

See attached.


I drew a cad line in section view the shape of the foundation, converted it to a polyline solid with a depth of 20'

In plan view I lengthened it to fit the garage & had trouble elevating it into proper position.

I had to use a prospective view to look from under the slab to select it & use Transform/Replicate to elevate it.


I'd say that 80 plus percent of my houses have some interior bearing wall "Thickened Slab Foundations".

This is very frustrating.


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Boy i hate to be such a dummy but every time I change the partition wall to mono the perimeter foundations change too.


I want three side of the room to be stem wall. These are exterior walls & carrying three story block structure & therefor must be larger that the partition wall which only carries some floor trusses.

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Perry you make it sound so easy but for the life of me I can not get it.


Could I trouble you to post a plan file as follows:

Four exterior walls on stem wall foundations.
One partition wall separating living area from garage.
Garage floor dropped 4 to 6 inches
Thickened slab foundation under the partition wall shaped as per my detail.


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Thanks Scott, I have a bad cold today and just not up to it right now, This blows my party plans. Oh well.

Typically we party it up on NYE too,  but this year is going to be quiet for us.  Hope you feel better soon,  sorry about you blown party plans,  a quiet NYE is not always a bad thing.

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Great videos Scott, Thanks so much.

I enjoy watching the process.


The goal is to make the partition wall foundation a "Thickened Slab" 

All other walls are stem wall.

Here is the cross section.


Don't worry about as I'm out for the rest of the day & you should be too.

Happy New Year.





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Getting closer, Footing on left should be identical to one on right.

Can't be done? I suspect all the exterior garage footings now have the chamfer like the one on the left. Correct?

You got a lot closer than I did. :)


Thanks Perry.

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