In Kaleva, Tampere, an extensive transformation is underway as the iconic Hippostalo building from the 1970s and 1980s is set to be replaced, marking the largest project in the history of the Tampere Student Housing Foundation TOAS.
TOAS Hippos is a new timber-based student housing block accommodating over 800 students in approximately 650 flats. TOAS Hippos will have a total floor area of approximately 35,000 square meters and will be built mainly of CLT modular elements as a single building. In addition to residential space, the building will also include meeting rooms, offices, and a supermarket. Our experts carried out fire dynamic calculations, fire resistance tests, and risk analysis of the CLT firewall planned for the site, as well as fire and evacuation simulations due to the exceedingly prescriptively allowed size of the fire compartment and the number of people in the building. The design of the project was also closely followed during the implementation phase, and expert supervision was carried out on-site during the works, as required by the building control authorities.
The regulations required the 35,000 square meters of floor area to have two non-combustible firewall structures to limit maximum potential fire spread in the large mass timber building. However, the pouring of the concrete firewall proved to be a challenge, as it did not fit into the schedule of the prefab construction. However, there was no justification for not building the firewalls, and the challenge was addressed through performance-based design using fire severity calculations, fire resistance tests, and risk analysis.
Based on the performance based design, a double-wall structure was designed for TOAS Hippos that was proved to meet or exceed the performance of the prescriptive non-combustible firewall. The wall structure was subjected to the necessary fire tests to demonstrate its resistance to the required impact loads. The tests were also used to assess the time of onset of charring, which was one of the acceptance criteria.
The construction method of TOAS Hippos, based on CLT modular elements, required an exceptional firewall solution due to the construction schedule, as it was not desirable to build firewalls several tens of meters high using concrete. The double-wall structure designed and tested meets the fire resistance of a firewall built out of non-combustible material, but now the firewall structure can be completed off-site at the modular factory, and construction can proceed as planned. These innovative solutions contributed to the development of the vibrant urban student village of the future in Tampere's Kaleva.