In the beginning of the 20th century most of the houses on Læsø had a seaweed roof. But unfortunately attacked a disease the Island's eelgrass in the 1930s which made it difficult to maintain the roofs. This marked the decline of this type of roofing on the island so that there are now only 19 houses with a seaweed roof. Eleven of these 19 houses are under protection.
Since Læsø is no longer self-sufficient on the eelgrass, they are importing eelgrass from Bogø and Lolland-Falster. Because of their experiences in the production of seaweed mattresses their seaweed has a high quality.