Not sure who to ask since I don't trust contractor--figure woodworkers may be able to help me. Doing a bath remodel and planning wall hung sink. Asked contractor to add structural support in wall and all my research says 2/x4 should be used. But there were plumbing pipes in way and only room for 1 inch. Contractor said he'd use a thinner board and beef it up in back where there was space...but didnt. Just a 3/4" poplar board from joist to joist. I felt certain that wasn't going to be enough so I cut into wall below that board and saw there was a lot of space behind wood but no way to add anything horizontally. I figured I'd just fill the space between back of board and drywall (of back wall) to give it massive support. Was able to jam 3 small 2x4 pieces, sandwiched together behind board that I woodglued into place. It was rock solid. I closed up wall and inserted lag bolt. All good. But then the fear--what about wood expansion? Have I just done something that is a terrible idea? I'm planning to tile wall in bathroom so I don't want it to crack, etc. Fixing at this point would be a major surgery b/c of all that I've jammed up there, but I'm on verge of tiling, so I thought I better get some advice before it's too late. Hope someone can tell me that it's okay!!

Thanks--