Long rows of boat houses, standing side by side with gabled roofs, are still a common sight in the Stockholm archipelago. They recall a time when this vast aquatic landscape was the home and work environment to farmers and fishermen. Construction was in wood throughout, locally sourced on the small forested islands. Timber, being a lightweight material, made it possible for two men to carry each building part from the boats to the site. As the houses were lightly placed directly onto the characteristic polished granite bedrock and on plinths of found stones, they could easily be dismantled and moved to another location. This also meant nature was left untouched if the houses disappeared. The archaic character of these vernacular constructions is the result of making maximum use of scarce local resources in the most direct and efficient way one could imagine. House Lagnö borrows its fundamental spatial organization from this configuration, but with a completely new and different logic to its construction. Entirely made in exposed in-situ-cast concrete, it appears as hollowed out from the grey bedrock.