As part of the Wood Program at Helsinki University of Technology, the Lastu Sauna concept originated with architect Peter Westerlund and was developed by a team from the Wood Program.

In addition to general creative contributions and construction work, project responsibilities focused on the design of the outer skin of the building, which is designed to both screen and reflect light.

Design development and construction of a modular summer sauna.

A project part of the Wood Program · Helsinki University of Technology

Peter Westerlund (Finland) with Adam Guernier (Australia), Nathalie Pozzi (Italy), Isshin Sasaki and Koji Hashimoto  (Japan), Max Lönnqvist (Sweden), Sevra Davis and Nathaniel Moore (Usa).

Fiskars · Finland


Lastu Sauna is built along the Fiskars River. The entire structure is a single wall, curled like a wood shaving.

The flow of the wall leads bathers through the sauna, taking them from the bright light of an open terrace to the dim illumination of an enclosed sauna built out of solid wood.

As it transforms from open to being enclosed, its grid-like wood wall divides the building into functional areas: a terrace, a changing room and a sauna.

The sauna is built of 1”x4” spruce boards. The planks have been fastened at their joints by four hot-dipped galvanized machine nails. The high number of joints ensures the structural integrity of this small building.

The inner surfaces of the wall structure are planed boards and the outer layers are fine-sawn. The building has been finished with a white, oil-based wood preservative.

The open wall of the terrace is built from three layers of wood, and the solid-wood walls of the sauna are constructed out of seven distinct layers of wood.