Clearly you will need to consult with your structural engineer who designed your unique building structure before undertaking any repairs. Depending on what you learn, it might make sense to abandon HR and perhaps go with a different heating approach. The answer will likely depend on what you learn from your insurance agent and your attorney (if there is a contractor negligence case here) relative to recovery costs.

There is not a reasonable way to grind off 4-6" of concrete.

I was so hoping that that wouldn't be the case. In that case, I have no idea how to rectify this situation as I cannot imagine a jackhammer being a good solution for fear of damaging the sub-structure. Ideas?

Yup, consulting with the structural engineer is the plan, all right. I was just hoping that the concrete could be ground out, the pex put back down, and everything re-poured. What a bad deal. I suppose I'll start the process with the insurance company, then. Thanks so very much for all your insight, guys.

Heavy sigh.

I am still not convinced that your PEX froze and caused this problem. I believe there is something else in play here. I wonder how your PEX was placed (e.g., were the PEX bends overly tight and was the PEX tied to the rebar with metal wire)? Do you have control breaks and how did the installer address them (e.g., was the PEX kept low enough to avoid control cuts and was the PEX properly sleeved)? Concrete slabs can significantly contract/expand with temp variation. If the installation details were not properly addressed, a small amount of slab movement can stress the PEX.

High pressure water demo is feasible but expensive. Finding the right location of the leak is the bigger problem.

I would start by removing the litedeck insulation in the area under the garage door. It is likely that you will find broken concrete on the underside or at least water stained concrete in the location of the leak. Also your camera may now see a difference between the dry concrete and the wet concrete. If you can locate it, you should be able to chip out enough concrete to make repairs.

The other thing to look at is the way the lite deck is laid. The leak will be inline with the beams as the water will not flow across the beams. So if the leak is in the center and the garage door is in the center, and the beams run that way, that is probably the area of the leak.

Pex certainly does freeze and burst when exposed to the wrong conditions. We have seen it when the pipe is water charged to check for leaks and to hold down the pex during the pour but forgotten when winter kicks in before the heat is turned on. If it is a frost problem, the garage door is suspect one. Alternate points could be along exterior walls if the wall above the slab is stick framed. If there is gross air infiltration at these areas, frost could penetrate the slab. The room temperature of the garage could easily be above set point so that there is no water flowing through the loop but the area around the garage door could be freezing 6 to 30" into the room. Without fluid circulating, the 8" exposed to the outside will definitely freeze and in sever weather could freeze even with fluid circulating. If the 8" just outside the door is frozen, if would not take much to freeze the water in the pipe next to it, so that even if the stat again called for heat, the water in that loop will no longer circulate and allow more of the loop to freeze.

There is also the chance that one of the loops was air locked and the fluid was flowing through the rest allowing that first loop to freeze.

As Dan has suggested you may be able to abandon the leaking loop. As you only keep the garage at 50º the balance of the pex should be able to handle it. Not ideal but doable.
Another alternative is to relay pipe on the existing floor and pour an 1.5" or 2" thin slab over it, abandoning the original pex altogether. Check with your engineer, but I suspect the structure would have enough redundancy built into it to handle the extra weight.

FWIW, I watched a You Tube vid on installing a PEX system over existing concrete using an 8X4 plated snap in grid for the tubing then pouring 3 inches of a self-leveling slurry over it. I think it was in Germany, but that would eliminate the need to jack hammer and remove 3-4 inches of concrete and then do a new install. Can you get away with a 3 inch lower ceiling? Is your deck support engineered for the added weight? No need to watch the vid unless you enjoy watching 2 men walking around in the soup with a screed.

We have built several HR test slabs (10’x10’x4”) over the years that we have used to develop/refine our integrated passive solar and HR design engineering equations. These test slabs are located on property that results in them freezing every winter. It should be noted that we always properly place our PEX in the middle of the slab. We have yet to experience a single PEX failure in any of our slabs. So this is why I am somewhat skeptical that just frozen PEX caused this problem.

Water has a density of 1 gram/cc. Water typically expands about 9% when forming Ice 1h (the most common phase of ice that we experience on this planet) which has a density of about 0.91 grams/cc. There are also other Ice phases that have a higher density than 1 and do not expand at all. One can form these various other Ice phases by freezing water in a rigid volume that creates high pressures, but I digress. PEX that is NOT encased in any concrete can easily expand 9% and is not be typically damaged by freezing water that creates Ice 1h. This is one of the reasons PEX has become so popular for general plumbing. PEX that is FULLY encased in concrete can tolerate a much higher pressure above its rated pressure before failing. Furthermore, the ice formed in PEX that is fully encased in concrete is likely Ice 2 which has a density of 1.16 grams/cc and does not expand.

So what happens to PEX when it freezes when it is just stapled to the lower slab insulation such that perhaps 85% of the PEX wall is fully encased in concrete, but 15% of the PEX wall is just resting on the insulation and not receiving any structural support from the concrete? Well, this 15% of the PEX wall will now have to accommodate all of the 9% Ice 1h expansion. I think one can reasonably surmise that this PEX installation would be much more prone to failure when subject to freezing conditions.  So I suspect there is a strong correlation between HR installation approach and cold weather PEX failure.

" It should be noted that we always properly place our PEX in the middle of the slab"
I disagree, pex is much more likely to be damaged by control cuts, fasteners or anything else done to the slab. Besides where do you put the rebar. PEX goes on the bottom.

As any structural engineer will tell you, rebar goes in the middle of the slab too. Correct, if you do NOT pre-mark the locations control breaks and inner walls that will use concrete fasteners and properly address these details during the installation, the PEX is certainly much more likely to get damaged. This is most likely the cause of the problem described in this post.

Right so rebar goes in the middle, and the most often cause for damage to PEX comes from above and marking PEX layout won't prevent cuts from going over them. Therefore the best place for PEX is in the bottom. And Pex makes good rebar chairs.

True, if you only mark the control breaks AND don't also address the details during the installation, the control break cuts may indeed damage the PEX. This is why best practice is to first minimize having PEX in the control break and interior wall areas. Where this can’t be avoided (and it hardly can be completely avoided), the PEX is routed lower in these areas and the PEX is also properly sleeved. Simply tying PEX in direct contact with rebar also increases the risk of damaging the PEX.

I am not going to hijack this thread to debate the “best place for PEX” as many installers trade quality of installation for their time/expense. That is a personal/company decision. We have not experienced any damaged PEX from freezing or otherwise in our slabs. However, it has now become obvious to me why others have.

Has anyone here actually seen, in person, and repaired a PEX tubing encased in any kind of concrete slab damaged by freezing water? And still, how you go on...

As I seem to recall Badger, you are a strong advocate of just stapling PEX to insulation. As such, I would fully expect that you have seen many of your slabs damaged by freezing water in MN. I also expect that you have seen many of your Weil-McLain boiler installations fail too.

Weil-McLain Boilers

Badger - yes - colony east of Calgary. No it wasn't repair. New pex laid down and new slab poured.

Borst - I don't know Badger except from the advice he gives on this forum but I would not expect him to not charge a garage slab with glycol. Anyone you would not put protection in a slab that has a portion of its area exposed to -40º should not be let out of the corral by themselves. This is not a case of where the pex should go.

With regards to the link you posted, I don't see how this is to the benefit of the readers on this forum and certainly below what I would expect from you. For myself, I would appreciate it if you would remove it. ***Integrity and Professionalism are integral to all that we do!****

Agreed FBBP,

Check that you have glycol. If you feel it is needed add some,perhaps 30% ....50%
Abandon the loop, if you are lucky you can isolate it on the manifold. So it goes, not good but the fix is a crazy amount of effort.
Keep the garage at 50 and wear your shoes, you feet will never know.
Move on,
The alternatives are a year + of wasted stress, and you still will be where you were, lawyers will be happy.
it happens,
Some time our baggage becomes our teacher.
Has been so with me anyway.
As always, good luck we will need it in these times.
Dan

Therefore the best place for PEX is in the bottom.

I put mine towards the top, for efficiency.

Neanderthals living in glass buildings should learn not to cast stones at attractive, intelligent and strong ladies. Regrettably, my patience with bullies and ignorant people has reached an all time low too.

I would agree ICF, the top is slightly more efficient.

So, as I see it,
Undetermined source of leak, one loop, all loops, one loop with many leaks? Kinky pipe :-)
Unknown if Glycol was added if so what percentage? Was their contract to do so with specifications? Glycol is expensive, who's credit card for that?
Underlying desire to blame and create legal action ( responsible party? Cost? Target? Fix? Time months? Years?)
Unknown reason why apron was extended outside the building line, Architect? Home owner? General contractor? Cement contractor?
Solution to fix first understand leak source.
Ok, possibly tear out and re-pour slab? Tunnel up and patch or patches? Top down with patch or patches? $$$$ budget/value of fix?
Sometimes it is better to move on, loosing a loop in the garage may be the simplest way to go, it is not in the home, clearly it is sad that there is a failure but how much time, effort, anger, is it worth?
Personal choices
Dan
Only my opinion,

Dan - the one thing you missed. Does the contractor have any asset to seize? I have seen way to many cases go to litigation where the complainant wins, sometimes because it isn't even contested. The contractor just folds and starts another company and the homeowner still hasn't got the problem fixed but still has to pay his own lawyer because the is no way to collect. I know there are some on the forum that love to support lawyers but these are often cases where when you win, you still lose.

So you are absolutely right. Find the leak first! Then you can determine the cost. If it is a small leak, the contractor might fix it. If not, it might be a whole lot cheaper and less stressful to hire someone else to fix it then paying lawyers. In any case, the insurer will likely not do anything till you can tell them what the problem really is.

Failing the above, as you say, live with it.