Hi mate,
If i was building a practice are i would build the main wall with a bow in it and practice filling it out with adhesive to try and get a good finish, anyone can tile on to a perfectly straight wall. using cement adhesive might be a bit pricy though but you could mabe use cheap tub gear.
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Had another thought, you could get the wife to tell you exactly what she wants done with the tiles and then when you are about 3 or 4 hours in to it get her to come back in and change her mind, and you could also get another guy to come in and ask questions every half hour this will make it very realistic .
