Cassandras Trädgård: Precision Greenhouse Foundations on Soft Ground

Paalupiste completed two large greenhouses for Cassandras Trädgård in its hometown of Porvoo: one measuring 840 m² and the other 300 m². Both structures were founded on helical piles. The aim was to support the concrete slab with piles in a way that minimised the amount of concrete and reinforcement required. In the smaller 300 m² greenhouse, no concrete was used at all – the entire structure was built directly on the piles.

The projects were carried out separately, yet each was finished efficiently in just two days using a single excavator and a two-person team from Paalupiste. The soil was predominantly clay, which proved ideal for helical piles. The necessary installation torque and load capacity were achieved reliably without having to penetrate into harder layers, allowing the use of relatively short pile lengths.

The smaller greenhouse used 3.0-metre piles (60.3 × 5.0 mm with a 200 mm helix). The larger 840 m² facility required heavier-duty 76.1 × 6.3 mm piles with a 250 mm helix and varying lengths.

Helical piles bring clear advantages to greenhouse construction. They eliminate the need for extensive excavation, and if required, the piles can simply be unscrewed for relocation or complete removal of the structure without leaving any trace. Greenhouses are just one application in agriculture – helical piles have also been successfully used for foundations in automated berry-picking systems, fencing, and nursery structures.