Building a laundry/bath house with old tyres, eco bricks and mud/cement - part one; planning

We need a real kitchen...at the moment our kitchen is cobbled together from bits of unused furniture (my bench space is an old massage table) and a sink unit I was given. My partner's brother was given an old modular kitchen (from the 70's, so it will have some interesting colour combinations) which he is storing for us, but we can't put it in the humpy until we have a floor to put it on, which involves moving the current bathroom out.
The current bathroom has a floor made from an metal old window shade (one of those industrial metal grid things) with sheets of aluminium screwed onto it and lino over the top. This all has to come out (as well as the bath) and a new tire and ply floor go in. This means that we need a new bathroom away from the humpy while we build.

This is the current floor, you can see the metal frame around the lino. Not pretty, but it works.

The bathroom floor (please ignore the dirty shower curtain) 

The plan is to build a laundry/bath house up the slope from the vegetable growing area so that all that lovely (nutrient rich) water can use gravity to find it's way back to the Hugelkultur vegetable beds, instead of being carried out in buckets which is how I do it at the moment. Eventually there will be a shower in the house also (for those cold winter nights), but until then we will have the bath house. I want to have a go at building with old tyres and my eco bricks, because we have plenty of them around and because they create a negative carbon footprint when reused for building.

My plan so far is very simple;

 As usual my madness is being fueled by Youtube and internet research;

Technical tests on walls

Building with eco bricks

General information about Earthships (not exactly what I'm building)
Alternative building methods

The plan is to use a small excavator (hired for the occasion) to dig the foundation out (amongst other things), put the strip footing (tires and mud) and the four corner poles in. Then we will put up the pole frame and the roof. After that comes the corrugated iron outer walls, the floor and the bath put in (complete with outlet to drain to the vegetable garden). The first layer of eco bricks will go in around then too, but we will have to keep chipping away at the inner walls as eco bricks become available (we only make one or two per week). Getting water into the laundry for washing is easy; we will tap into the pipe running from the header tank up the hill to the humpy, and let gravity do it's thing. Getting water for the shower is another story as the fall is not great enough to gravity feed water to an overhead shower. That is a problem for part two.

Next comes getting the shower operational and putting up a new clothes line. Look out for part two.