LOG SCHOOL’S SAFE AND NATURAL FIRE PROTECTION
In the spring of 2021, in the small town of Märynummi near Salo, a log-frame building that would house a school and day-care centre was completed. It is the first modern log building built by the city of Salo. Together with the older, renovated building, it serves the residents of Märynummi as a school and day-care centre, and as a recreational space in the evenings.
Images: Juho Kokki and Tasoite ja Maalaus Virolainen Oy
Prior to this building project, the school and day-care centre for the town of Märynummi operated in several different buildings. Of the two buildings that the school had been using, one was demolished due to indoor air problems, and the second underwent a renovation. For the new building, non-settling pine logs were selected as the building material, as they are a breathable natural material well-suited to the surrounding forested environment.
RESULTS WERE ACHIEVED WITH GREAT COLLABORATION
The overall job included building an approximately 1,500 m2 modern log building on the site of the demolished school. One of the two old buildings was renovated. Architect Kristiina Krapu from the city of Salo was responsible for the design, and the project was implemented by Varpe Oy.
“We had already been thinking about the possibility of building log structures on the city’s own land. The Märynummi school was a suitable project based on its size, its location, and our goals. We wanted a school and day-care facility that was cosy, modern, adaptable and multi-use.”
Kristiina Krapu, Architect, City of Salo
Kristiina Krapu explains that the building was designed in close collaboration with its future users, the building contractor, and the suppliers: “The use of non-settling logs makes it possible to combine different materials together, but it had an effect on how we planned (for example) the distribution of bulk and the locations of the openings. With a fast-paced schedule, this was a challenge, but thanks to the smooth collaboration, we got great results.”
SUCCESSFULLY FIRE PROTECTING PINE LOGS
The non-settling log frame of the new building was supplied by Kontio and the painting and surface-treating was done by Tasoite ja Maalaus Virolainen Oy.
At this site, the reaction to fire performance requirement for indoor surfaces of log walls was to meet Euroclass C-s2, d1. The log walls were treated with Nordtreat’s clear flame retardant, which allowed them to achieve an even higher fire-class of B-s1, d0. Kontio had used Nordtreat’s products for the fire protection of log buildings in the past as well – there is no comparable product on the market that delivers the required reaction to fire performance in a way that is environmentally friendly and allows the wood's natural fibres to remain visible.
Tasoite ja Maalaus Virolainen is a traditional painting company, and the Märynummi school was their first wood fire protection completed using Nordtreat’s flame retardant products. Subsequently, several jobs involving the fire protection of log beams, wooden facades and CLT elements have been completed at various sites, such as the Inkoonranta wooden housing complex.
“We spread the flame retardant on the material using a syringe with a fairly small nozzle. Pine is a more challenging type of wood to fire protect than spruce – it took some patience to ensure that the required 350 g/m2 of flame retardant had set into the wood. We also researched the situation together with one of Nordtreat’s experts. After a stabilisation period of about a month, the end result was great.”
Mika Virolainen, Tasoite ja Maalaus Virolainen Oy
The bio-based NT DECO flame retardant has been on the market for over 10 years. The product has an M1 indoor air emission classification, and is certified for the fire protection of wood products made from spruce, larch, cedar, and more.
“NT DECO is a low-viscosity, water-dilutable product. Of course, what's most important is whether the product works, i.e. whether it achieves the required fire rating. The product is reasonably easy to work with, as it does not give off odors and is not an irritant. Nordtreat’s expertise and service were excellent: over the course of the project, we got all sorts of valuable information about the fire protection of pine wood.”
Mika Virolainen, Tasoite ja Maalaus Virolainen Oy
RESULTS EVERYONE IS SATISFIED WITH
Kristiina Krapu was not previously familiar with Nordtreat's bio-based fire protection solutions either. The client’s most important requirements were getting the approvals for the flame retardant and preserving the natural hue of the wood. Although the project involved some learning processes in regards to the stabilisation of the flame retardant, the final results were very satisfying.
“Colourless fire protection fits very well with the building's surrounding natural atmosphere, and the authentic log surfaces are safe as well. Even after the fire protection, the rooms still smell like pine, and their acoustics are excellent.”
Kristiina Krapu, Architect, City of Salo
All parties involved in the project, including the users, are satisfied with the modern log building’s appearance and functionality.
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