John Rumm wrote in
o.uk:

On 07/02/2019 21:23, DerbyBorn wrote:
Working on ideas for replacing bath with a shower.

1. The waste pipe exits the bathroom a few inches above floor level.
2. Lowering the waste may not be a good option.

May not? or is not?

It would need a hole boring through a joist - which also carries a few
cables. It would need alterations to the outside stack to accomodate a
lower waste. I would definately need a tray with a drain on the short edge
otherwise several joists would need boring.