I've skimmed the previous three maybe four pages for an answer to my specific question but am still at a loss... I am building a 30 x 40 shop on top of a knee wall. The knee wall is extending 12" above the top of the slab. Pex tubing is going into the slab. I've installed the r-10 foam barrier around the perimeter inside the foundation to a depth of 24",and am ready to install the foam board on top of the vibra-packed 1" clean, but am at a loss as to how to maintain that thermal barrier at the three garage doors. If the foam is to be extended out over the top of the notch in the knee wall it will then pass over the vertical barrier on the inside of the foundation. How then is the integrity of the thermal barrier for the perimeter maintained at the three garage doors??? There will ultimately be at the minimum a concrete apron poured outside of the building, at the same grade at the interior slab with slight slope to shed rain water. Any suggestions would be appreciated.

Right where the garage doors will contact the slab, install your R10 2" of vertical foam. Keep the top of the foam 3/4" below the top of the slab. Secure in place with vertical rebar dowels driven on both sides of the foam into the sub-grade and wire tie in place (if over the top of the footing, you may have to drill shallow holes in the footing to place the rebar dowels. On top of this foam and rebar dowels, lay a piece of 1x4 (3/4"x3-1/2") cellular PVC trim board (or composite deck trim board) centered over the foam so that you have 3/4" overhang on both sides. Glue the PVC trim to the top of the foam and rebar dowels with polyurethane construction adhesive such as LocTite PL Premium. You may want to drill a series of "dimples" in the underside of the PVC trim using a 1/4" drill bit ~1/4" deep every 6" or so to give the glue an opportunity to grip the slippery PVC trim. When placing the concrete, you will want to place it on both sides of the foam thermal break to keep it from shifting due to side loading. Unless you are pouring the outside concrete apron at the same time as the slab, this may require that you place a rigid form board to the outside of the wall and you will have just a strip of slab between the thermal break under the doors and the outside of the wall. Another thing you can do to help lock the top trim board in place is to cut a shallow groove ~1/4" deep on each edge of the board with a table saw so the concrete will grip the sides and prevent it from popping up later if heavy loads across it might tend to cause the middle to deflect downward.

That sounds quite simple and logical at the same time. The aprons will not be poured at the same time, so we will form the outside of the openings appropriately. I wouldn't have thought of drilling dimples and cutting keyways into the trim board with a table saw.... Good idea , and I will do it. Thank you for the input.

I do have another question : Cutting control cuts into the slab seems a tad bit touchy with the Pex in the slab....just how deep should they be cut ?? .....OR... should they be cut in at all ??

Someone else can chime in with a definitive answer and numbers, but if you have a 4" slab with pex.... if the pex is on bottom, that's about 3 1/2" of concrete on top... even floating in middle, its 1.5" Control joints aren't cut that deep to ding them unless your pex accidentally lifted up shallow (another reason for stapling on the bottom just to be sure where it is?)

control joint cut depth 1/4 depth of the slab... so an inch?

...or consider using concrete crack inducer strips in lieu of cutting any control joints at all. These strips can also be used to place/support the PEX/reinforcement at any depth in the slab and completely eliminate the risk of damaging the PEX by not needing to cut control joints. Also consider sleeving the PEX where your controlled cracking will occur to minimize risk of future PEX damage from this controlled cracking.

1/4 – 1/3 the slab thickness is the typical recommend control joint cutting depth. For a HR slab, 1/4 is likely the most common cutting depth.

We normally cut a 1/4 to 1/2 inch deep cut directly over the crack inducer to give the crack a target. This gives a cleaner look. Unless the inducer has been placed where we know a wall will cover it.

Fortunately, there'll be no inside walls to be concerned about....the crack inducer concept sounds like the best idea for me at this point. Its still a week or two away for the pour due to the holidays and the current heavy rainfall here in the Midwest. Our local weatherman stated this was the third warmest December in recorded history and that has worked in my favor so far. Thanks for the suggestions.