The in floor design gives tubs a more luxurious and stylish appeal than traditional tubs have.
Floor under bath tub.
By choosing the right material from the start your bathroom will stand a better chance of withstanding long term damage.
If your house floor is concrete then yes this is normal.
Flooring repairs can be intimidating but the subfloor under the tub generally consists of.
Bathroom floors are notorious for suffering water damage and the area under the bathtub is no exception.
Keep in mind this is all done before the walls roof are done so the hole also allows for some changes to the where the tub sits.
The floor framing for bathtubs requires special attention.
All the plumbing is done under the concrete and in tub areas they keep a area to allow for the p trap.
A standard bathtub can hold between 40 and 60 gallons of water.
Excess moisture in the subfloor is a common reason for early replacement of bathroom flooring but it can be prevented by choosing the right material from the beginning.
You must consider all of the weight the floor joists must be able to support.
Such design makes tubes easy to get in and out because there is no need to climb over and out of the standard tub.
The floor under your bathtub is the main element in supporting the tub.
So yes this is normal.
The most common reasons to replace this floor are that it can no longer support your bathtub and the wood has become rotten.