Undesired gap in the stem wall ?

[CrossFireDesign]

Modeling an older existing house that has an added on storage room sitting on a adjoining patio slab. (this drawing required for demolition permit for the storage room and eventual addition to same side of house.) I've drawn the three walls needed for the add on (similar to a bump out),

Then applied an extended slope roof with a 2/12 pitch, also specified "room open below", and unchecked " build foundation below." 

 

Everything works great except unexpectedly the program creates a undesired gap in the stem wall of the adjoining main house, then fills the gap with a wall plate, short studs and a short beam beneath the now otherwise unsupported section of main house floor frame. I've drawn and redrawn this seemingly simple structure repeatedly trying slightly different methods and defaults, but get a similar result every time. 

It seems to always cut the stem wall down in-line with the lower level of the add on storage room and I can not find any reference to this behavior in Users Manual or videos. 

Is there a way to prevent this stem wall gap?

 

Thank you. Any suggestions will be appreciated.

[y-g-m-n]

I have issues once in a while with stem walls since they are "AUTOMATIC" and you do not have a way to edit them.

 

SO I just make a little slab and slip it under wall to replace stem walls and no is the wiser

[CrossFireDesign]

Hi  Y-G-M-N and Thank you kindly for the short slab suggestion, if I find no other solution I will employ that. On the other hand If this is a program deficiency It should be addressed by the maker of Home Designer, I'll Look to see if there is a way to give feedback for that? Otherwise I see two persistent problems with the error; One is the obvious gap which would be worse with basements, the other is the unwanted use of framing lumber which even if obscured by a small slab might still add cost inappropriately to the estimating side of the program. 

[Rookie65]

Without seeing the plan and your settings, my thought is why is that room "open below" if it looks like it has a floor? You could possibly just lower the floor of that room by whatever distance below the house floor that it is?

[CrossFireDesign]

The house and slab was built in 1960's, with the storage room added later and built on to the side of the house and the walls were simply anchored to the existing slab,

and modeling that is not a problem. The problem in the model is that when the stud walls are lowered to meet the slab it creates a inappropriate gap in the adjoining stem wall beneath the a now unsupported section of main house floor framing, even though I've done nothing to directly affect that wall. So far nothing I can find prevents this. Please see red highlight in attached image. 

Thank you

[Rookie65]

Yes, I saw/see that, which is why I asked why the room was named as "Open Below" when it doesn't seem to be.

[CrossFireDesign]

Because the much larger slab becomes the floor. My understanding and brief experience is that open below prevents the program from building a floor that would conflict with the existing slab. It was also recommended by 'Solver" for a similar application and it worked, however in that situation I saw no change to and adjacent stem wall. 

[Rookie65]

Is this closer to what you want?

Use Room Type "Patio", change room name to Storage room"

Under the "Structure > Floor Tab", check

Floor supplied by the foundation room below

Monolithic slab foundation

Build foundation below

[CrossFireDesign]

Yes, however, the existing slab and stick walls are 14 inches below the top of the adjoining stem wall while your version shows it flush. The stem wall gap does not occur until I push it lower. Not sure If  I tried tried "patio" (it was getting late) but I tried every other floor version I could find and the gap problem persisted whenever I lowered the slab and walls down below the top of the adjoining stem wall.

I really appreciate your input, And I will try again including "patio" just in case I missed something .

 

[Rookie65]

Lower the floor the 14" you need. Also, what is the wall type of the existing house where those 2 rooms meet? I do get some framing showing when it's a 2x6 wall, yet if it's a 2x4 and flush w/the inside, it goes away. Or create a wall just under the size of the exterior wall

[CrossFireDesign]

I'm experimenting for a while for experience before I attempt to draw the real thing, So I never really gave any thought to "wall types, but Yes my model is all 2x6. "Siding-6",

 

I'm a little unclear about your suggestion "Or create a wall just under the size of the exterior wall"? are you suggesting adding something like a surrogate wall somewhere or somehow reducing the three walls used to form the storage room? 

 

I have some flooring showing up so as soon as we get that unloaded I'll try more of your suggestions. 

One again your help is sincerely appreciated.

[Rookie65]

What I mean is take the wall that is on the house inside the room that you are drawing. If you make the depth of it less than the thickness of the exterior wall that runs through it now, the framing will go away. If it was built as an interior 4 when constructed, and the drywall is aligned on the inside of the house, the framing will go away.

[CrossFireDesign]

My test based on Rookie65 suggestions;

1) On house wall above the stem wall in question; selected for "Wall specification"> "General" and changed "Thickness" from 6-15/16" to 4.5" ..  Stem wall gap remains.

2) Restored "Thickness" to 6-15/16"

3) Selected Storage room sidewalls that intersect with House wall  changed "Thickness" from 6-15/16" to 4.5" .. Stem wall gap remains.

4) Returned all Wall specifications back to "Siding-6" 

Solution used as Suggested by Rookie65

5) Changed Room Specification>General> Room Type to; "Patio"

6) Changed Room Specification> Structure> Floor to; "floor under this room"  Result - No more Stem wall gap!  

7) Changed Room Specification> Absolute elevations> Floor > to  "0" then; "-10" then; "-14" then;  "-20" then back to "-14"    Result = floor moves up and down at will and no stem wall gap occurs.

I must have read a hundred pages and viewed a half dozen videos and don't recall seeing anything about this.  Now I can move on to the next unknown (for me)

Great Job Rookie65 !  Thank you Kindly. The results are repeatable and this is just what I need.