Reply for toejam and others :thumbsup:
Most new tents do have what’s called a "tub floor". It's a seamless, heavy-duty waterproof material that lines the floor of the tent. It should go up the wall a few inches before it is sewn into the wall. Its purpose is to keep side seams away from the ground so that leaks can’t occur.
Older tents with bad seems will leak. Tents that are put away wet will leak. A good ground cloth should keep the floor dry, don't let the ends stick out, as many scouts find out that is a water magnet and now you have trapped water between two layers of fabric.
When we buy new tents, (more often than you think) we use sealer. We also setup the tent in the hall to become used to the setup and take down