Honestly, the hidden cost on those old buildings is the mental tax. You burn so much focus on one stubborn spot that the rest of your install day feels rushed. My rule now is to set a hard time limit before I even start, like thirty minutes of trying fixes. If it's not working by then, I explain the physical problem to the client and offer a different, solid option right away. It keeps the job moving and usually they just want it to work, not fight a losing battle with their hundred year old trim.

Ugh, my mom still asks that.

My whole house is a nightmare to set up.