New Shower on Concrete: Re-Cement ?

[LittleBear]

I'm having a plumber complete the installation of a new 1-piece shower in the basement (concrete floor). He 'hammered' out the existing concrete and then moved the p-trap and drain. He then re-cemented up to near the drain - leaving about a 6" diameter area around the drain cement free to allow for more flexibility when he actually moves the shower in place. Now, here's my question - should I ask him to cement this remaining 'open' area up to the drain or is it okay to leave this 'open'. If it were to remain open (without cement), what are the options to cover the dirt area.

[jimbo]

You should not have this large an unsupported area under the shower. You could cement the hole, but for future convenience, pack it with sand. Pack it well as you lay it in and compact it level or slightly above level. Use gypcrete or equivalent under the pan if recommended by mfgr.

[Pharmhand3]

I have an unfinished basement were the bath is stubbed. I am currently in the research stage of things. It was my understanding that all drains had to have a p-trap to gaurd against sewer gases entering the house. Around the stubbed shower drain is a boxed area (1' x 1') filled with gravel. I removed the gravel to verify what was underneath. The pipe is a simple right angle and no p-trap is present. I therfore thought that I would have to cut at the horizontal pipe and install a p-trap.

However, according to the original message in this post, the pro-plumber went to great efforts to remove the p-trap. Am I not thinking clearly in installing a p-trap or is a right angle drain sufficient?