A roofing contractor just re-roofed my house. before he started, i pointed out my refrigerated a/c units that are outside, on the ground, and said it is very important to protect these during the process, they are fragile. he assured me he would, nothing to worry about. During the re-roofing, i walked outside to find one of his employees standing on my oldest a/c unit. I told him to get down, asked if he had been doing that all along, and he admitted he had. i texted the owner who told his foreman to put a stop to it. But i have previous experience with someone standing on one of these units, and rendering it inoperable, due to cracked coils or some other mechanism. we can't test the coils until its warmer outside so i want to withhold payment of $5000 of the cost until i can have it tested. This should be a reason that a mechanics lien cannot be filed against my home, shouldn't it?