The definition of a free standing tub is pretty much in it's name: it's a tub that can stand on it's own. That means that all of it's sides are finished and it looks more like a furniture piece than anything else but it functions just the same as any regular tub.
A built-in tub is your more well-known version of a tub; it's the one that probably comes to mind when you think of 'tub'. Another name for the built-in tub is the tub-shower combo since most often times the tub is built into the shower area whereas those two functions being separated (though that design also exists). Built-in tubs aren't finished all around and are attached to a wall.
Tubs have always existed, in the past however free standing ones were considered a luxury item but nowadays they're just as affordable as a built-in one. But all in all there isn't an exact "this is expensive and this is not" scenario because of certain factors that come into play that could affect cost-wise.
For instance, fixtures are something to consider for both types of tubs and depending on what one goes with, it can add up or be budget friendly. Another thing to consider is if one decides to decorate a built-in tub. That could also get expensive due to its surround compared to the free standing tub which doesn't require a surround. Plumbing can make a free standing tub expensive since you might end up having to move it around and it's harder to "hide", compared to a built-in tub.
Pros and Cons of Each
Aside from the pricing differences as explained above, there are other things to consider with each tub. When it comes to a free standing tub, they take up more space compared to a built-in one because of the all-round tub itself as well as the fixture constraints.
For instance, floor mount faucets take up more space compared to the ones that go on walls. Built-in tubs are easier when it comes to the whole tub/shower combo however there are people who've been able to pull that off with free standing tubs. Also if this isn't obvious enough, free standing tubs can be placed anywhere in the bathroom whereas built-in tubs are stuck to corners. Now when it comes to the aesthetics, free standing tubs make a bigger (and for some better) impact but there are built-in tubs that can be competitive with that notion.
Storage capacity and accessibility is generally for built-in tubs because free standing tubs need that room to "breathe", so to speak. There are creative ways to fix that for those who have free standing tubs, things like tub trays and carts can make things more accessible.
In regards to weight, free standing tubs are generally heavier than built-in tubs. I say generally because there are fiberglass options for free standing tubs which not only are the lightest, but the least expensive and easiest one to install. But regardless, going with a free standing tub would more often than not require reinforced flooring.
Also built-in tubs are more appropriate for the elderly and those with disability or mobility issues since they can come adequately designed for them whereas free standing requires physical work. Both types overall offer different styles and looks but many say that free standing tubs are considered to be more modern or vintage (depending on the style you go with). When it comes to having that spa aesthetic, free standing tubs usually win, though there are some built-in options that equally give off that luxurious pampering vibe.
All in all, both styles are equally popular at the moment, though it's fair to point out that free standing have been gaining popularity. But as a whole it all depends on what the individual person wants and is willing to put in to get the tub they want. So out of the two different ones, which one is your favorite?
Til Next Time,