Are expansion joints required and or recommended when using pex tubing for in slab heating ??  If so, are there any specs, pics, diagrams, etc? What about protecting the pex where it crossed the joints?  I'm a little worried about saw cutting a kerf to provide a weak spot for a crack to hopefully follow, with the pex tubing in the slab.....

I'm preparing to pour our basement slab and have the same question. Note that I'm not a professional and the following is based on my research on the matter rather than experience.

My understanding is that an expansion joint is a complete separation and isolates 2 slab sections. This separation, bridged by some insulating material, is what allows movement and any pex that crosses this joint would need to pass through a rigid protective sleeve. Cutting a shallow kerf to provide a predetermined path for cracks would be a control joint, and a protective sleeve in this case may not be required.

Can someone shed some light on this? Is this correct?

Zeke is correct. In residential applications an expansion joint is rarely used indoors (it is a matter of size).

In any case, if you slab shifts, or shears enough to effect the tubing you will have bigger issues and need to contact your concrete contractor first and insurance provider second.

I see expansion joints around the perimeter, but not where one would run tubing.