No, based on what you write, your store should not be liable you did not specify the tile, so are not liable for being negligent in terms of specifications or advice you did not manufacture the tile, so are not liable for manufacturing defects and if there were no visible signs of defects, you were not negligent in not recommending against this product. This, however, does not mean that the customer can't name you in a lawsuit and force you to at least spend time and money defending and it's not impossible that, to the contrary of what you write, that a court couldn't conclude that if there was any reason to think that this tile was a bad choice for the intended use, that you should have recommended a different product--and are liable for not doing so. d on what you write, they court shouldn't find this, but all lawsuits are gambles to some extent or another you can never predict 100% what a court will do. If the customer looks litigous, you may wish to offer something to stave off the possibility of litigation.