Guesthouse in Ośno Lubuskie — precast walls and floor slabs

A concrete wall has mass by nature and is homogeneous through its whole thickness. There are no voids in it for sound to travel through, and the services are run in it at the factory — we cast the boxes and conduits into the unit during production instead of breaking through the wall after the event. For a guesthouse, where rooms adjoin one another and the circulation routes, that is the difference between a place guests come back to and one they write about in the reviews.

The walls on the lake side arrived with wide openings and lintels cast in, with no need to form beams on site. Large glazing and good acoustics inside are, in this building, the same structural unit, resolved in the mould.

At Ośno this division of materials is written into the design. The external and partition walls are 12 and 15 cm thick and are in lightweight concrete — lighter, warmer, and sufficient where the wall does not separate two let rooms. The separating walls between rooms are 18 cm of C30/37 concrete, the heaviest option that makes sense at that thickness.

That last wall was tested in the laboratory. A 180 mm unit in C30/37 concrete achieved a weighted sound reduction index R′w = 59 dB (C = −1; Ctr = −4) in a test carried out by KFB Acoustics to PN-EN ISO 10140-2:2021-10. For comparison, the same thickness in LC16/18 lightweight concrete gives 55 dB, and 160 mm of normal-weight concrete 54 dB. A difference of four decibels between the materials is audible, which is why the wall between rooms is in normal-weight concrete rather than lightweight.

Scope of work: lightweight concrete external and partition walls 12 and 15 cm thick, separating walls between rooms 18 cm thick in C30/37 concrete, floor slabs, transport and erection.