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On returning from holidays i found my ensuite toilet had sprung a leak somewhere behind it in the wall.
Ive had plumber remove toilet and repair said leak, but now i have questions and suggestions please.
My plan is to replace old wet underlay with cement sheet and tile over.
The vanity is sitting on existing hardwood floor boards and the old vinlyl flooring and underlay was laid up to it, im planning on keeping this the same with new flooring. The toilet was sitting on top of underlay with vinyl cut around toilet and again im planning on doing same with new. Im also planning on using vj lining as a dado height around the room to give some texture. The plasterboard is slighty damp behind toilet, should i cut this wet part out and replace with villaboard? Questions are as follows;
1. in what order should i do things?
2. villaboard down to existing floor boards, lay cement sheet up to this then waterproof then vj lining down to floor?
You can see where the current plasterboard is quite some way from floor (big gap)
Please see pics attached and thanks for any and all help! 
Hello @Dani64
Thanks for the photo and clear outline—you're definitely on the right track. Based on your plan to replace the wet underlay with cement sheet and tile over, here’s a suggested order of operations using current store-available products that’ll suit your ensuite reno.
First, yes, cut out any damp plasterboard behind the toilet. If it feels soft, crumbly or smells musty, it’s better replaced. Use James Hardie Villaboard 6mm for the bottom section behind the toilet, as it’s designed for wet areas. Run it all the way down to the subfloor or existing hardwood.
Next, lay your tile underlay over the timber floor, cut to butt up against the Villaboard. Screw it down as per manufacturer instructions.
Then, apply a good quality waterproofing membrane like Davco K10 Plus for example, across the floor. Please note that any waterproofing installed in the bathroom must be carried out by a registered and trained individual as it will need to be sighted and signed off.
After that, install your Easycraft EasyVJ 900mm panels as dado to add texture, this can go over the Villaboard and up to the desired height. Just make sure any VJ near water is sealed and painted well.
Lastly, tile the floor and reinstall the toilet and skirting.
Let me call on our experienced members @Dave-1 and @Nailbag for their recommendations.
If you need further assistance, please let us know.
Eric
Hi @Dani64
Is this actually a bathroom with a shower and or bath or is it a powder room? If it's a bathroom, then proper waterproofing construction should be implemented which @EricL has outlined. For example all the skirting removed and the damp damaged walls replaced at least past the height of the damage. Cement sheeting then laid and the floor and up 150mm on the walls (non-shower which are 1800mm) would be waterproofed. Tiles can then be laid, skirting replaced and everything painted to completion.
Just a note on waterproofing. You can do it yourself as long as you follow the guidelines to the letter if you want it to be effective. However the advantage of getting a certified waterproofer is that should anything happen like this again and the water proofing failed causing unnecessary damage then you would be covered by insurance being theirs or your own. just make sure they are actually "Certified" and can provide a certificate. because plenty of trades advertise the service but aren't certified. I have always used a certified waterproofing despite being very capable of doing it myself just for the peace of mind.
I have attached a couple of examples of certification.
Nailbag
Nailbag
