Alcove: the standard three-wall install
An alcove tub nests into a space enclosed by walls on three sides, finished only on the front apron, and relies on the surrounding wall studs for support.[1]
Because the plumbing wall is already built around a standard alcove opening in most bathrooms, this is usually the simplest of the three styles to swap in a like-for-like replacement.[1]
Drop-in: more construction, more labor
A drop-in tub sits inside a framed deck or platform with a hole cut for it, leaving a visible lip around the rim while the sides stay hidden under the surround.[1]
Building and finishing that surround, often in tile, stone or a solid surface, is what makes a drop-in install take longer and cost more than dropping a tub into an existing alcove.[1]
Freestanding: simple plumbing, particular placement
A freestanding tub is finished on every side and sits away from the walls, on its own feet or directly on the floor, connected to the plumbing rather than built into it.[1]
Installation is comparatively quick and can sometimes be handled by a plumber alone, but the filler and drain have to land at a precise point, through the floor for a floor-mounted filler or from the wall for a wall-mounted one.[1]
Who is licensed to move that plumbing
Washington requires a plumbing contractor license, backed by a certified plumber on staff, for work beyond a straight fixture swap.[2]
In California, a general or residential-remodeling license only stretches to small fixture swaps. Anything past that, relocating a freestanding tub's floor-mounted filler included, calls for a dedicated plumbing classification instead.[3]
Florida defines plumbing contracting as its own category, separate from building and residential contracting, under the same licensing statute.[4]
Matching the style to the bathroom you have
Swapping an alcove tub for another alcove tub is the path of least resistance for the plumbing. Moving to a freestanding or drop-in style in a bathroom that was not built for one is a bigger project than the tub itself suggests.
That gap in scope is also a gap in price: expect a like-for-like alcove swap to price closer to the low end of a full bath's cost range, and a style change to price closer to the top of it.
What to ask before you pick a style
A freestanding tub's filler location is fixed once the floor or wall connection is set, so it is worth confirming that spot on paper before any plumbing is roughed in, not after.[1]
A drop-in tub's surround material, tile, stone or solid surface, is priced separately from the tub itself, so ask for that as its own line item on a bid.[1]
An alcove tub's dimensions are set by the existing three-wall opening, so measure that opening before shopping for a replacement rather than after one arrives at your door.[1]