I had posted before about getting upcharged on the installation of AO Catarina. It's a rectified tile that's supposed to look like carrara marble. AO recommends a 1/8" grout line for floor installations.

Basically, I was told that to do 1/8" grout lines instead of 3/16" lines would be an extra $650 for the floor and shower walls. That seemed really high for a small difference, and I postulated that it should really not take a professional tile installer 50% more time to install 1/8" grout rather than 3/16".

Now my builder is saying that the charge is to make the joists and studs more even to support the tighter lines. Here are some samples of his emails on the subject.

"It is with the edges and the tightness of the grout joints. From stud to stud and joist to joist there is always a certain variation in level that can be hidden in a wider joint that cannot be hidden without extra work in a tight joint"

"In the older homes the tiles all had rounded edges unless they were true slate,marble limestone or granite. If they were, we always upcharged because the product was sharp edged, uneven due to being natural and in the case of marble and granite laid with a tight joint. When you look accross a sharp edged floor even a 1/32 jumps out with a sharp edged product. We would be using a cement based underlayment with this product not plywood. We could skip the extra proccess and lay it as we would normal ceramic like most builders do but we do not think it is the best way to go. We pride our selves in the best lumber quallity and use plywood as opposed to OSB for our floor systems but all joists and studs vary slightley in size and straightness."

Does this make any sense? Or am I being taken here?