Is there a way to know what is behind the wall before deciding? Or will contractors not usually know until they tear it away? Also was this an exterior wall? Our is. The backside is the side backyard

generally it is mounted inside a stud cavity, but if you do a large unit, you will have to RE stud the space to accommodate, not a big deal, but it takes some thought.

look to see where your electrical line runs, and anyother utilities.

Not wanting to deal with structural issues is why you might choose a wall mounted unit, although I think a recessed mounted medicine makes for a nice clean line.

As everyone noted, a recessed medicine cabinet would provide cleaner lines but you would need to make sure nothing structural is in the way.

Can the contractor tell what is in the wall before tearing it out? What are the steps to tell if it can be recessed? Stud finders? Tapping the wall for hollow vs. density ? ????

We want to place two medicine cabinets, above each sink in a double vanity like the one pictured

The only way to know is to open up the wall. There could be plumbing lines, vent pipes and/or electrical. We've moved things before to accommodate a recessed medicine cabinet. To me, it is worth the extra cost to get a clean recessed installation.

My parents have surface mounted them in 3 houses. They were new builds, but with production builders who would not make any changes from their plans. My parents took down the plain mirror and installed the medicine cabinets.

Here are mine in the master bathroom, there is a second one to the left, from Robern 24" x 48". This was new construction so the spacing was planned during framing.

Recessed versus Surface Mount, not undermount or overmount. That is a term used for sinks.

You want recessed because it's cleaner and works better with surface mounted lighting.

If you can't place them over the sinks then perhaps you have side walls that can receive recessed medicine cabinets.

We had to move a few things around inside the wall to recess the cabinet. It was not a huge deal.

Unfortunately we had to open up the wall to find out. One solution could be getting a cab that can be installed either way. There are many. Good luck.

The only thing to add to the above- could you build out the wall instead? Worked for me in a bath where we had plumbing that couldn’t move. Never missed the 3 1/2” but really appreciate the medicine cabinet.

There really is no perfect way to make sure it will recess if you are redoing the bathroom then no big desl but if just adding cabinets make your life easy and get surface mounted no problem Usually once the wall is open it is easy to adjust most studs to make a new cabinet work. We need to see your bathroom and you need to provide info as to what is going to be done . Since it is an exterior wall you really need to open it up before choosing a cabinet IMO