Rintamamiestalo floors flagged as high-risk in updated building inspection guidelines

Finnish building authorities have added a common floor structure found in post-war terrace houses to the national list of high-risk building elements.

According to the updated guidelines published by the national construction information service Rakennustieto in early June, the so-called “välipohjarakenne” used in 1950s and 1960s rintamamiestalo homes now qualifies as a risk structure in residential property inspections.

The floor assembly consists of a mineral layer topped with organic material such as sawdust. Moisture in the air can condense against the cold mineral layer, causing the organic material above to rot or absorb water, potentially leading to microbial growth even if the mineral base remains intact.

“For a structure to be classified as high-risk, there must be a cold space or a space that has previously been cold,” said Niko Rautio, lead expert at building consultancy Suster. He described a typical scenario in which a basement at 5°C sits below living areas at 20°C, allowing humidity to condense in the floor structure through air leaks.

Rautio spoke during a site visit to a 1956-built rintamamiestalo in Karkkila, where inspectors examined the newly flagged floor assembly. The house had been unoccupied since 2022 but kept heated, exposing its structures for assessment.

Inspectors accessed the floor by removing a wardrobe floor panel in a bedroom closet, revealing layered construction: hardboard, sparse planking, sawdust insulation, and finally a mineral base. Sensory checks detected no unusual odors or moisture in the sawdust.

The building information service Rakennustieto updates its technical guidance weekly to reflect new risks or regulatory changes, said Pia Rämö, the organization’s business director. The updated RT guidance cards are used nationwide to standardize property condition surveys before sales.