Monolithic Slab Insulation

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In my area, we build quite a few garages, as well as the odd home, on engineered monolithic slabs. Engineering drawings are shown like the "this is what I need for permits" picture. We need the horizontal insulation for frost protection and vertical if the building is heated. I would like to not only show this in my plans, but have an accurate materials list. So manually drawing on the cross section won't add it to the materials list.


1) I'm looking to continue the vertical insulation and cement board to cover the footing portion of my mono slab

2) And to have horizontal insulation under the slab. I can handle the 2ft perimeter horizontal foam easily enough. In fact, I used a polyline solid for the entire horizontal foam and it showed nicely in the materials list, however I can't make it form to the footings (on all four walls) for the cross sections.

3) Adding in the stone would be a bonus, and I may need to just use a poly line solid manually. This isn't a deal breaker.


My main goal is to minimize the manual manipulation as well as include in the materials list with reasonable accuracy. Is there a thread or a video that anyone can direct me to, or does anyone have a solution for even a part of it? 





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For the exterior insulation create a wall that is a partition wall that is layers of rigid and the cement board only and place it around the exterior of the slab.


For the Floor add it to the floor structure:


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3 hours ago, ValleyGuy said:

In my area, we build quite a few garages

How many? What I'd do if I were you, is model the under slab insulation and make a fixture. Set it's stretch zones, and set all the Object Information and Components. Then, I'd add it to my library as well as my template plan for heated garages. 

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Thanks Ryan, I’ve tried to add the foam to the bottom of the floor and can get to exactly where your picture is in the floor structure panel, but as soon as I press enter my curbs and footings disappear. It seems like it’s either a mono slab or a slab with the foam underneath. I’ve tried changing all kinds of things and can’t get it to work. 

Can you please explain a bit more on the partition wall around the footing? I’ve never used the partition wall yet and there really isn’t much info on it. 

I did get Gene’s idea of a curb to relief the footing but still needed to manually add in the foam and board from a 1/16” pony wall above. I didn’t check yet if it had any effect on the materials or the measurements. 

I would say that about 25% of the smaller out buildings are on engineered slabs. Attached are still on 4’ frost walls. I’ve seen more small houses being built on slabs lately. 

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1 hour ago, robdyck said:

How many? What I'd do if I were you, is model the under slab insulation and make a fixture. Set it's stretch zones, and set all the Object Information and Components. Then, I'd add it to my library as well as my template plan for heated garages. 


You could also do it with a molding profile assigned to a polyline around your perimeter (or more than one molding if you want to do the edge, skirt, and angled insulation separately).

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Here is the update so far...

It's not clean and easy thats for sure. There should be an easier way to attach insulation (and vapour barrier!) to a monolithic slab. I'm sure that it must be code most everywhere to have at least a vapour barrier under a monolithic slab. It's too bad that CA doesn't allow editing to the slab structure without losing the curbs or footings. Of course this causes the accuracy of the materials list to suffer a few holes in it as well (like missing slab vapour barrier).


If anyone is interested, here are some things that I did. Some things introduced a few issues as more items like O.H. doors were added.


Curb / Footing:

- I used a 2"x16" Brick ledge, the width of the vertical foam (1-1/2")  plus cement board (1/2"), the depth of the curb (4") floor (4") and footing (8")

- I put a 1/16" pony wall on the bottom of the 1st floor walls with just the 1-1/2" foam - because more than one layer (foam & cement board) would not show on the brick ledge, only the outer most layer does.

- So a poly line molding was used for the cement board, actually two were needed for the cement board. When I added the OH door the cement board was the curb height and therefore too tall for the doorway, so I had to make a shorter molding. Also when the door was added, the bottom part of the pony wall was lost and so the vertical insulation went with it. I made another poly line molding for the insulation under the door. I suspect the same issues will happen with any other doors that need to be added.


Monolithic Slab:

-as stated earlier, I couldn't edit any of the floor structure successfully. Maybe someone else could give it a try and let me know if you can get vapour barrier and some insulation added without losing the curbs and footings.

-I used a poly line solid for the outer insulation part, put a hole in it at the start of the slope. Another solid for the inner most insulation part. And a molding on an angle for the sloped section of insulation.


Material List:

-Everything somewhat came out fairly well on the materials list. I did quite a bit of ID changes to get the moldings and poly lines to stay with the foundation section. A little adjustment here and there regarding sizes (under slab foam here is usually 2'wide, not 4') and  changed some descriptions to explain it's location a little clearer (Rigid insulation became Rigid insulation - under doorway, vertical)

-Having said that, the anchor bolts went from 12 pcs to 3 when I added the 8' OH door. Not real world numbers. This lead me to dig into the Ruby Scrip to see about formula adjustments, to which I couldn't find much information. Anyone able to point me in a good direction beyond adding in a fudge factor? It would be nice to adjust the 'Count' column formula and see how it came up with 3 anchor bolts.

-I did this trial on just a 10'x10' building with one OH door (just walls, no roof) to see how accurate the materials list was. Most everything was right there as for the numbers. I recommend adding in the "fudge factor" as nobody will be able to use 100% of every pc of material, or you may need to adjust for 'coverage' being less than actual size (rebar has an overlap allowance, but wire mesh does not).


Anyone that may have some ideas to help alleviate any of these issues, please jump in. There seems to be way too many adjustments required to use the monolithic slab option with insulation or vapour barrier. As well, too many places are needed to double check the materials list to be confident enough to even call it a 'reliable' tool in hopes of selling it as an added bonus to a client.








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