Raised Slab on Stem Wall

[HowardStronglast]

I'm trying to create a raised slab foundation with a stem wall that is 30" above grade.  So the top of the slap is 30" above grade.  The garage should be at grade obviously.  This should be easy, but I'm struggling.

 

Thanks.

[joey_martin]

Open the floor dialog box and delete the sub-floor layer, then change the framing layer to 4" and concrete, uncheck the framing box. That's it, don't overthink it.

[Doug_N]

 

10 hours ago, joey_martin said:

Open the floor dialog box and delete the sub-floor layer, then change the framing layer to 4" and concrete, uncheck the framing box. That's it, don't overthink it.

 

I am sure that Joey was using 4" as an example only.  You set that dimension to whatever the slab thickness is.  4" might be a bit thin for a suspended slab with significant spans.

[mtldesigns]

On 7/25/2025 at 9:43 PM, HowardStronglast said:

This should be easy, but I'm struggling

What part are you struggling with Howard?  The floor of the garage at grade?

Remember, your main floor is always (well most of the time) at zero inches.  Set your terrain at -30".  Set the floor elevation of the garage at -30" as well.  (that would be in the room dbx, under structure at the FLOOR input.

[HowardStronglast]

Thank you to all.  Neither suggestion seems to achieve my desired goal:

• Garage floor at grade
• Stem wall 30" from grade to top
• 6" concrete slab from 24" to 30" inside stem wall

Setting terrain to -30" did lower the terrain.  Setting the garage floor to -30" did lower the garage floor.  But

• The garage room did not drop with the floor
• So, the garage doors are 30" above the floor

Thanks.

[Doug_N]

Howard,

 

Your best bet is to post the plan file in your next post.  Then one of us can see what is going on, and perhaps offer a more complete suggestion.

 

In order to upload the plan file to this forum, please exit Chief Architect to make sure that the file is not locked, then upload the file.

I am sure that one of us can resolve the problem.

[mtldesigns]

4 hours ago, HowardStronglast said:

Setting the garage floor to -30" did lower the garage floor

I apologize..  the 30" was to be a positive as its "Subfloor Height Above Terrain"

[PitMan71]

On 7/25/2025 at 8:43 PM, HowardStronglast said:

raised slab foundation

Hey, foundations can be complicated at first because there are so many settings. I assume what you mean is a block up raised slab filled with sand?

[joey_martin]

[HowardStronglast]

Thanks again to all.

 

I got this figured out.

 

Lowering the terrain 30" was the solution.  The obstacle I discovered was an invisible room I had put at the entrance to the three garages.  I placed the invisible room to get a shed roof over the garage entrances.  The invisible room got in the way of CA lowering the garage floor.  Once I removed the invisible room.  The garage floor dropped correctly.