Above grade crawlspace...best way to address using CA

[MJanelleQ]

Designing our retirement home near San Antonio, Texas.  Want to use an encapsulated crawlspace to run mechanicals as there are vaulted ceilings in the center of the house that precludes running ductwork through the ceilings to get from one side of the house to the other. Where we are building, we have bedrock within 36" of the grade, so digging down isn't a viable option.  Most homes here are built on HUGE thick slabs to compensate for terrain.  Luckily our property only slopes about 18" over the span of the footprint of the house.  Our thought process was to design the house as a slab on grade and build the crawlspace as a 40" "floor" level (level 1 in CA) and have the main floor be level 2.  When I designed it in CA that way, the foundation disappeared.  It wouldn't show in the plan or in the 3D view, nor any of the cross sections. 

 

So, I started over and built the foundation using the walls with footings approach and that worked except that the crawlspace is now below grade and I haven't been able to figure out how to raise it up so that the footings are below grade, but not the walls.  From the training videos I have watched, it looks like it's possible to adjust this when adding the terrain.  I have attempted the terrain using the survey information we received from the surveyor when we purchased the land and, to say it is difficult, is an understatement.

 

So, I have hit a proverbial wall and am not sure the best way to proceed in our design process.  Need some "outside the box" ideas and am hoping someone with some experience with this type of structure might be able to offer some advice.

 

Thanks for any thoughts you can send my way,

Janelle Quinn

CA 12 & 13, MacMini 2018 with Radeon RX 580 GPU

 

[glennw]

If you are building a slab on grade, you should be using the Monolithic Slab Foundation option which Chief will build automatically once you have built your level 1.

Although, you talk about walls, so maybe you don't want a mono slab, but rather walls with footings?

[joey_martin]

If using a conditioned crawl space, please consider no slab above the crawl space. 

[glennw]

Without knowing too much about your building, or local building practices, I would look at the possibility of forgetting the crawl space and investigate splitting the mechanicals in the roof or finding another way to handle it such as bulkheads, ducts, etc.

Around my area, this would be the method to use and would save a huge amount of money by not building the crawl space floor.

[SH_Canada]

are you trying to build a concrete floor with a crawlspace beneath it?

 

you can adjust the terrain up and down by altering the "subfloor height above terrain parameter". If the terrain is not flat I tend to use terrain regions on the sides of the house to then further adjust the terrain downward.

 

 I typically also set the terrain as 2" thick to more be like a ground elevation

 

this is then what it looks like in elevation. in the case below the stem wall also comes up 12" above the concrete floor, to keep snow out

 

[MJanelleQ]

I'm trying to build a short floor (40 in) over a slab-on-grade foundation.  Have had no luck using the monolithic slab tool and creating floor 1 as the crawlspace.  The foundation doesn't show when I have tried. CA does show that a floor 0 is there, just no details, lines, or 3D view.  Kind of like it is invisible.  When I try it with a full height floor it works just fine.  I'm sure there is probably a setting or default that I am missing, but don't have enough experience with the program to figure it out.

 

 

22 hours ago, glennw said:

Without knowing too much about your building, or local building practices, I would look at the possibility of forgetting the crawl space and investigate splitting the mechanicals in the roof or finding another way to handle it such as bulkheads, ducts, etc.

Around my area, this would be the method to use and would save a huge amount of money by not building the crawl space floor.

Glennw, this is a great idea.  So simple.  Don't know how I didn't think of it!  (Imagine a Head smack emoji!) I could put the HVAC in the ceiling spaces above the wings and let the HVAC pros figure out how to get conditioned air into the communal center areas of the house.  Might need 3 zones...

[MJanelleQ]

Think I figured out a work around.  Built the crawlspace as a full floor and added the main floor next.  Dropped the height of the crawlspace after and checked the slab foundation box in the room specifications.  Then built the foundation and it worked!  No more ghost foundation.  Did have to delete the flooring finish of the crawlspace and also had to designate it as "unfinished" vice "crawlspace".  When I used the crawlspace designation it ghosted the foundation again.  Now I have 2 options to go with!  Thanks for letting me bounce ideas with yall.  

[rgardner]

So just to point out that your AHJ will require an engineer in your area to actually design the foundation system.  Most of my experience in San Antonio has required blasting or chipping away the bedrock as there was expansive soils under the bedrock causing the foundation to heave up to 8" throughout the year.