Shower pan curb construction
We recently noticed a slow leak on the ceiling under the shower and, after some investigation, hired a contractor to rebuild the shower pan for probably the fifth time. Since we have had several issues with this shower, we decided to carefully monitor the process and unfortunately discovered the contractor screwing cement board through the pan liner to the wood curb on all of the three sides. This technique is obviously unacceptable due to the likelihood of a leak developing, but it is unclear to us what the standard technique is. The guides that we have seen recommend shaping metal lath over the liner over the curb. Our contractor is claiming that this is unnecessary and suggesting putting cement board on the outside and the top and only thinset on the inside. This technique appears to be unreliable, since the thinset may not remain in place and may not bond to the existing mortar in the rest of the pan, which, for some incomprehensible reason, is already built and tiled. The contractor is repairing the punctured liner over the curb by gluing a patch of liner over it. Is this sufficient, or should we insist that the liner be replaced and the rest of the pan be rebuilt? I would appreciate any advice on this topic.