When a hotel closes a floor for refurbishment, most of the money and nearly all of the difficulty sit in the bathrooms. The reasons are structural and they shape how hotels age.
Bathrooms are the only wet rooms in the building
A guest bathroom involves supply plumbing, drainage, ventilation and waterproofing, all concealed behind finishes. Replacing any of it means opening the structure.
Bedrooms by comparison can be refreshed with furniture, fabric, paint and lighting, none of which requires touching what is behind the wall.
This is why a hotel can look updated and still feel dated. The soft refurbishment happened and the bathrooms did not.
Vertical services connect rooms to each other
Plumbing runs in stacks serving rooms on every floor, so work on one bathroom can affect the column above and below it.
Sensible programmes therefore renovate a vertical slice rather than a horizontal floor, which is why closures sometimes look oddly distributed across a building.
Where a stack must be replaced entirely, every room on it comes out of service simultaneously, and that is the most expensive form of hotel refurbishment.
Drainage falls are difficult to change
Waste pipes need a gradient, and in an existing building the available depth between floors is fixed. Moving a shower or a toilet may be impossible without raising the floor.
This constrains layout changes far more than guests expect, and it explains why a renovated bathroom often has the same arrangement as the old one.
Level-access showers, now expected at the top end, are particularly demanding because they need drainage within a very shallow build-up.
Standards have risen faster than in bedrooms
Expectations for bathroom size, separate bath and shower, twin basins and water pressure have moved substantially over the past few decades.
Bedrooms have changed less, because a bed and a desk have not fundamentally altered. Bathrooms therefore date more visibly against current norms.
Meeting the newer expectations frequently requires taking space from the bedroom, which reduces the room count or the room size and has to be justified commercially.
The consequences are visible to guests
Hotels running a phased programme will have inconsistent bathrooms across the building, which is why two rooms in the same property can feel a decade apart.
Asking whether a room is in a renovated section is a legitimate question at booking, and properties midway through a programme will usually answer it plainly.
It is also why closures are announced by wing rather than by floor, and why the noisiest rooms during a refurbishment are those directly above and below the work.