because the water could seep through the joints between the new tiles and sit between the two layers and affect the seal and also raise the height of the floor and affect the slope to the waste outlets..but, why do you want to retile if you're not using the bathroom??...for immediate resale consider bathroom wall to wall bathroom carpet, new wall paint, new vanity, taps and light fittings which should also be cheaper than tiling over the top and, if it's not allowed by the body corporate, it will be a risk to future sales as it should not satisfy a proper building inspection

Nup, a good tiling job requires a good substrate. The best tiler in the world can't make a bad substrate look clean and good. No point on spending money on new tiles and a good tiler over an inferior base. Rip it all down, start again and get it right before tiling. Best of luck, Dr Retro Of Dr Retro House Calls

Have you priced having the whole lot re waterproofed and tiled? You are already doing the hardest section, it may not be that much more to do the lot. Otherwise agree with above match to the white tiles in the rest of the bathroom. But it will always look like a repair.

Tile selection can have a big impact on the cost of your bathroom reno. The cost of the tiles per sqm is one thing, but did you know that most tilers charge different rates for the "Type" of tile laid large format and or vitrified tiles will cost more to install These are a few hard and fast rules we give our clients when they are selecting tiles for a bathroom renovation 1 - opt for darker tiles and darker grout for the floor - as a wet area light coloured tiles on the ground are harder to keep clean 2 - If you are opting for a feature tile - let it be the hero. That means make the rest of the tiles plain - large format subway tiles give you enough texture without detracting from the feature 3 - always opt for square tiles on the ground - trying to get the correct falls using rectangular tiles will mean you will have extra cuts and the floor will look a mess. The second reason we opt for square format for the floor is because of subway tiles You see, back when everyone was opting for square tiles on walls, it was easy to install square on the floor and get all the grout lines to match. Now most people are opting for subway tiles, you can never get all the grout lines to match, therefore installing square means you dont have to match grout lines as they are different format. If you are installing your subway tiles vertically, then there is a chance you will still be able to get all grout lines to match if you have selected the same sized square format tile hope this makes sense I have added a link to a blog that explains more about tile selection