Will the floor hold a freestanding bath?
A stone bath with water and a person weighs 400 to 800 kg, and an ordinary residential floor may not carry it without a check. In a new building the problem is rare; in an old Barcelona building with timber or steel beams and a brick vault, it is always calculated before ordering.
The imposed load for housing under the CTE (DB SE-AE, category A1) is 2 kN/m², about 200 kg per square metre, plus a concentrated load of 2 kN over a 50 mm square for local checks. A bath standing on a small footprint exceeds that figure, but the structural engineer calculates the spread and the margin, not just compares numbers.
An example. A cast mineral bath of 120 kg, about 200 l of water, a person of 80 kg: roughly 400 kg over 1.2 m², on the order of 330 kg/m². A monolithic stone bath of 500 kg gives about 780 kg, which is already 650 kg/m². These numbers are not a verdict, but they are a reason to call the engineer.
How much does a bath weigh: stone, cast mineral, cast iron, acrylic?
Weight depends on material more than size. As a guide for a bath 1.6 to 1.8 m long: acrylic 30 to 50 kg; cast mineral (resin with filler) 70 to 150 kg; enamelled cast iron 130 to 200 kg; a monolith of marble or travertine from 300 to 800 kg and more.
Add the water and the person. A bath with a capacity of 250 to 300 l holds about 200 l in use, which is 200 kg, plus 80 kg for the person.
The bath's weight must be given on its data sheet. Until you have it, you do not order the bath or calculate the floor. Ask the supplier for the empty weight and the stated water volume, and send them to the structural engineer with the plan showing where the bath stands.
When does an old building's floor need calculating?
It needs calculating if the bath weighs more than 150 to 200 kg empty, if it stands in the middle of the span between walls, or if there are timber beams below. For a light acrylic bath an extra calculation is usually unnecessary, but the condition of the beams is still looked at.
The engineer opens the floor in one or two places, sees the floor type and the beam condition, measures the span and issues a report. Possible solutions: place the bath over a load-bearing wall or along the beams, add a steel plate or spreader beam, strengthen the floor from below, choose a lighter material.
Keep the report: when you sell the flat it confirms the bath was installed with a calculation. For the order of decisions in a bathroom renovation, see our full bathroom renovation guide.
How do you bring water to a bath in the middle of the room?
A floor-standing tap is connected with pipes from the floor: water and drain are run in the screed to where the bath will stand. For a floor-mounted tap a concealed valve body is set into the floor and the decorative column goes on top. The position of the body must match the bath and tap model to within a centimetre.
Alternatives: a wall-mounted tap behind the bath (you need a gap of about 10 to 15 cm between bath and wall), a tap on the rim of the bath, or on a separate column fixed to the floor.
The main rule: first choose the bath and the tap, and only then the pipes. Do it the other way round and the distance to the tap or the drain will not match the curve of the bath, and adjusting it without lifting the floor is not possible.
Drain and access for repairs
The drain of a freestanding bath sits right under the bath. The trap should be removable or with an inspection point, and the 40 mm pipe runs to the stack with a fall of at least 2%. Under the bath that fall needs depth, which we discuss in our article on the curbless shower.
Access to the trap is designed in advance. If the trap is hidden in the screed, a blockage means opening the floor. Better to plan an access hatch in the bath's plinth or the wall beside it, and bring the isolating valves of the floor tap to an accessible place.
On a model with a cast mineral base and concealed feet, access is made from below through a removable panel. Ask the supplier exactly how the drain is replaced on that model before you buy, not after.
How much space do you need around it?
At the sides about 60 cm of free passage for cleaning and bathing, and on the entry side about 75 to 80 cm. If the tap is wall-mounted, add 10 to 15 cm behind the back. A bath without these clearances looks fine on the plan but is in the way of daily life.
Around the bath the floor is made of a material that does not fear water: stone, tile or microcement. Better not to lay parquet within 50 cm of the bath. If the bath is in a bedroom, the rules are stricter: we describe them in our article on the master bathroom.
Do not forget height: the bath rim is 55 to 60 cm, and above it you need free space to climb out without hitting a sill or a light fitting. The window next to which the bath stands must close: moisture collects on the glass.
Cast mineral or acrylic: what to choose
Cast mineral is heavier, keeps heat better, has a pleasant matt surface and allows small scratches to be polished out. Acrylic is lighter and cheaper and warms up quickly, but its surface scratches more easily and loses gloss.
In an old building with a weak floor, acrylic or lightweight cast mineral removes the load problem. In a new build or on a ground floor, you can choose a stone bath if the design calls for it.
BCN YARD checks the floor before the bath is ordered, agrees model, tap and drain on one plan and lays the pipes before tiling. If you are choosing a freestanding bath, we visit, look at the floor structure and propose a solution. The exact price is calculated in the estimate after the visit and measurements.
Frequently asked questions
Will the floor hold a stone bath?
It cannot be guaranteed without a check. A stone bath with water and a person weighs 400 to 800 kg, and the CTE housing imposed load is about 200 kg/m². In an old building with beams and a vault, the floor is opened in one or two places and the engineer calculates the span. Options: strengthening, moving the bath to a load-bearing wall, or a lighter material.
How do you bring water to a bath in the middle of the room?
Through the floor: water and drain pipes are run in the screed to the bath position, and a concealed tap body is set into the floor. Its position must match the bath and tap model to within a centimetre, so models are chosen before pipes. Isolating valves go in an accessible place.
How much space do you need around a freestanding bath?
About 60 cm of passage at the sides for cleaning and bathing, and about 75 to 80 cm on the entry side. With a wall-mounted tap, another 10 to 15 cm behind the back. The floor around is stone, tile or microcement, with no parquet within 50 cm. You also need free height above the rim.
Cast mineral or acrylic?
Cast mineral is heavier, holds heat longer and lets you polish out scratches. Acrylic is lighter and cheaper and warms up fast, but scratches sooner and loses gloss. In an old building with a weak floor, acrylic or lightweight cast mineral removes the load problem. Check the weight on the data sheet.