Can this product be used in a restroom under a toilet over subfloor

We appreciate you sharing your question concerning Newcastle. This product can be installed in a restroom and the toilet can be installed on top of the flooring. You will need to install the flooring up to the flange with the expansion space and we recommend that you use silicone caulk to prevent any water from getting under the flooring. The expansion space should not be completely filled which will eliminate the required gap; create a water seal. We have a Consumer Concierge team available if you should have any further questions or concerns. Please contact this team at askshaw@shawinc.com or (844) 742-7429, Monday through Friday, 8 am until 6 pm est. Thank you again for the wonderful question and have an awesome day!~clf