The first overhead press in a converted spare bedroom often ends with a barbell an inch from the ceiling fan. Ordinary residential ceilings were set for beds and dressers, not for a lifter standing at full lockout with a bar overhead, and the same goes for jump rope, wall balls and box jumps. People compare racks and bumper plates for weeks and measure the room in about five minutes, which is the wrong way round.
Floors come next. A dropped dumbbell on a tiled slab cracks the tile, and on a second story it shakes the room underneath and everyone in it. Thick rubber flooring over a plywood layer handles most ordinary lifting, and a proper platform exists for heavier work. Whether an upstairs floor should carry a loaded rack at all is a question for whoever is doing the building, not for a forum thread. Sound carries as well, so anyone sharing walls with a sleeping household should expect early sessions to be heard.
None of this replaces a gym. A coach watches positions you cannot see, a class supplies a push that a quiet room never will, and a commercial floor holds more equipment than any house can. Plenty of people split the difference: a membership for coached sessions and heavy days, and a small room at home for mobility, accessory work and the mornings when the drive across the valley is not going to happen. A home room works best when it is planned around those smaller sessions rather than built to imitate a full gym.
Sometimes the training room is one line in a bigger plan, part of a remodel that is moving walls anyway. A household at that stage might look at a design/build firm in Las Vegas such as Kingdom & Co., whose remodel FAQ lists complete floor plan reconfigurations among the work it takes on. A training room is not on that list by name, so it belongs in the first conversation, with ceiling height, floor build-up and a vent sized for a room where people breathe hard all raised before the plans are drawn.
Before buying anything, run three checks. Stand in the room with your arms locked overhead holding a broomstick where a bar would sit, and look at the clearance. Find out what the floor is made of and what sits directly under it. Then stand in the doorway and place a rack, a bench and a rower in the space with room to move between them. If those checks fail, put the money toward a membership and a good mat for the living room.