Underground antenna cable from detached garage
If you have to rent a cherry picker, that would be the same way to top a tower. If you have a brick chimney, that is another way to attach the antenna. I would hire a company that does this work if you do not feel like doing it. As for the stretch from garage to house, how far? You may be able to run from the antenna to a splitter, then feed one leg to the TV in the garage without amp, and when it gets inside the house in the basement, then hook up the amp there.
Check with either avsforum.com which has a lot of people that do OTA with satellite, also a local company that specializes in DBS systems, since they would also tell you what is the best amp, and which antenna for your area.
As for the NEC, as long as the antenna is grounded at the start, and when the coax gets to the house, you would have a static block with the ground wire (#10) connected to the ground rod outside, do not connect to the cold water. What surprises me, is OTA was huge not even forty years ago, and seems that most people have forgotten how this stuff works.