I did an inspection yesterday on a 3 year old home and the fiber cement siding had 1/4" to 3/8" gaps between the boards. Is this something to call out? I am used to seeing 1/8" gaps but nothing this large and it was in several places. They are also not using a metal flashing, it looks like house wrap.
Thanks for your help in advance!
Unlike PVC products (vinyl siding), a cement siding is stable and does not expand/contract with heat/cold like PVC. “moderate contact” at butt joints is recommended with flashing. The older method from hardie called for a gap that gets caulked. That caused issues so they changed it to no gap with flashing behind the joints. The 1/4 GAPs at butt joints will allow UV light from sun that will destroy most of typical home WRBs prematurely. Cheapest fix now would be to caulk those gaps. Of course caulking does not last… so it would have to be maintained. Amateur hour 
Chose the one that correlates to your zone.
…and a graphic to go along with your authoritative sources😁