Would pulling up the wood boards and placing a plastic membrane layer directly to the joists before reapplying the boards work?

I read about a boy that became infected with the fatal protozoan species Naegleria fowleri while swimming in lake Havasu about a week ago.It enters the nasal cavity,attaches to an olfactory nerve,migrates to the brain and the waste it produces destroys the brain.

I really cant tell if that is membrane or asphalteither way I never really cared for flat roofsbest fix is to have it hot mopped with new membraneshould last upwards of 25-30 yearsor you could go with a metal roof, pretty easy to install and are good for life if installed correctly, flashing ect...enjoy

You may only need to use them in the stubborn areas.Also, if the floor is a large area such as a 2 car garage and or has any cracks, you'll want to put down an isolation membrane first. this will keep the cracks from telegraphing through your tile.

I have rebuilt the walls and have coated with redguard (the pink paint), which acts as a waterproof membrane. 

https://www.homedepot.com/p/Custom-Building-Products-RedGard-1-Gal-Waterproofing-and-Crack-Prevention-Membrane-LQWAF1/100169081

I was thinking of using a piece a hardbacker and cover that with red guard waterproof membrane, angling the shelf slightly in towards the shower so water runs back into the shower.

Here is two of the systems I have used in the past.https://www.amazon.com/Ceramic-Stone-Electric-Floo...https://www.schluter.com/schluter-us/en_US/Floor-W...Schluter system is an excellent system a bit more expensive but it works as a uncoupling membrane as well and helps avoid tiles from cracking in the future I am using it now in a high end master bathroom remodel.  

We raised the drain, put down a new waterproofing membrane, thinset and tile.

He'll remove all vents and roof jacks, and replace with new.Second contractor will remove existing roofing membrane down to wood deck substrate. clean, apply1 layer #15 lb base underlayment, install Malarkey Highlands laminated 30 year asphalt fiberglass shingles, seal all roof projections, ground clean up and haul away for $4524.( http://www.malarkey-rfg.com/PDFFiles/MRP%20WebFliers/HighlanderFlierWeb.pdf) Highlander-CS™ ~ Malarkey's 30 Year Laminated ShingleBuilt with the strength of a highland castle, the Highlander protects your home while providing distinction, security and value that is prized by today's homeowner.