Hello
favored,
I am not sure about the epoxy overcoat peeling, cos i have never done it before. Many are doing the overcoat cos it is an alternative to the messy hacking of the existing tiles. Easy to apply, and a quick solution to breathing new life to the existing toilets at the minimum possible time.
If you find that the epoxy coat can meet your needs and you like the variety presented to you, by all means go for it.
We did some research during our reno search and found that the pricing of epoxy coating and overlaying of tiles are about the same, so it is worth a look if you are looking for more alternatives for your toilet designs.
As for overlay, usually people will overlay once. More layer of overlay means more weight of your toilet walls/floor on the existing structure, and this may not be advisable.
This decision to allow more overlay or not is usually determined by the PE during the submission of permit for the overlay to be done. So cannot advise you there on the number of overlay layers as well.
As long as the overlay is done properly, you will not even know there is a layer of old tiles behind the overlaid tiles, so drilling should not cause any issue, unless your old tiles underneath are hollow, then that may cause a problem. Do a check of your existing tiles by knocking on them with a metal spoon first to see how many of them are hollow before making a decision to overlay or not. If there are too many hollow tiles, then it is advisable to hack the old ones before laying the new tiles over
as for which is better, personally, we prefer the overlay, cos the feeling on the feet from the new tiles are nicer. FW and myself dun like the feeling of the epoxy on the feet when we tried them during the exhibition... so decided on a overlay instead