Recessed bathroom slabs ready from the factory

Recessor E9 making a recess to a part of a hollow core slab.

Methods for making recesses in hollow core slabs vary hugely from country to country. Elematic Recessor E9 offers a well-proven method to create ready recesses at the factory, saving money and time on-site.

In a ready home, there should not be level differences between the bathroom and the rest of the rooms, so it is possible for anybody to get around the house, also for example wheelchair users.

At the same time, piping, floor heating and other fittings are hidden inside bathroom floors. To make room for all this, the concrete subfloor under a bathroom needs to be lower than the rest of the floors in the apartment or house. In other words, a recess is needed in the floor slab.

Recessed bathroom slabs on a precast product stockyard.

Thick topping slows down construction

How can a bathroom recess be made in a smart, sustainable, and cost-efficient way that fits the industrial nature of precasting? The answer depends on whom you ask and where they live.

Many designers opt for a thinner hollow core slab or a half slab. A thick topping layer is then added on-site to create the recess. This otherwise well-functioning method also has disadvantages: More material is needed in the form of reinforcement and concrete, and building cannot be continued until the topping has dried.

“Recesses made by adding topping can add work and costs and delay construction,” says Jani Eilola, Product Director, Floor Technologies at Elematic.

Eilola explains that in Finland it is common to transform part of a hollow core slab into a thinner solid slab right after extrusion in the factory. This can be done with Elematic Recessor E9.

Elematic Recessor E9 making a recess on a hollow core slab straight after casting.

Recesses fit for bathroom modules

The recessor works by crushing part of a hollow core slab and compacting the crushed concrete, making it into a solid slab instead. The result is typically a 370mm hollow core slab with a recessed area consisting of a 200mm solid slab.

When the bathroom slabs hit the construction site, the recess is all set, and the concrete is dry and ready for the installation of a bathroom.

“The 200mm thick solid slab can carry the load of the bathroom, whether it is cast at the construction site or built with Leca blocks, Elematic Acotec panels, or any wall material, and you can also place a bathroom module directly in the recess,” says Eilola.

He notes that bathroom modules are gaining popularity, and so is Elematic Recessor E9. “There is a general increase in the readiness level of building components. It reduces a lot of work which was earlier done at the site.”

“Builders in Finland have used this method for the past 30 years or so. The needs are quite similar elsewhere in Europe, so I think it is worth it to consider the pros and cons to find out if a recessor could be helpful in your production,” suggests Eilola.

Jani Eilola, Product Director, Floor Technologies at Elematic

Elematic Recessor E9

Recessor E9 runs on the bed straight after the extruder.
Rotating cylinders with protruding bars mechanically crush the top part of the hollow core slab.
The crushed concrete in the recessed area is compacted by vibrating beams.
The hollow core slab is typically 370mm thick, and in the recessed area, it then becomes a 200mm solid slab.
The process is designed so the amount of concrete in the 370mm hollow core slab matches the concrete need of a 200mm solid slab. The machine is equipped with a hopper to dose additional concrete if needed.
Recessor E9 can handle hollow core slabs of different thicknesses, depending on how the requirements for the recess.

Quality, strength, and water savings

Five years ago, Finnish precast manufacturer Betset invested in a new Recessor E9. Since then, it has produced more than 200,000 square meters of high-quality bathroom slabs.

Recessor E9 is at work every day at Betset’s precast plant in Nurmijärvi, Finland.

Out of the 267,000 square meters of hollow core slabs that the factory delivered in 2022, 41,000 square meters – or a good 15 percent – were recessed bathroom slabs. And there are no signs of a decline in demand, says Factory Manager Tuomas Puoliväli.

“There is a trend towards more and more ready elements. Bathroom slabs are in high demand, and the designs are complicated with more recesses and lots of different angles and details,” Puoliväli notes.

Betset’s factory in Nurmijärvi has offered bathroom slabs since 1996 when Tuomas Puoliväli’s father was part of starting up production there. In the beginning, recesses were made by hand, but they have come a long way since.

Even with challenging slab designs, the plant can deliver what its customers require, partly due to Recessor E9.

“The quality of the slabs is much better compared to our previous recessor: They look better, they are stronger, and Recessor E9 uses a dryer concrete mix, which gives us substantial savings on water.”

From a user perspective, the Betset team is also satisfied with the recessor from Elematic. It was easy to take into use and is simple to operate.

“I have nothing negative to say about the machine. I’d buy it again any day,” concludes Puoliväli.