Due to a lack of more common building and thatching materials, the islanders traditionally constructed the roofs of their buildings from seaweed.  To construct the roofs, eelgrass (Zostera marina), was sustainably harvested from the shallows around Læsø, dried, bundled, and layered thickly onto the frames, often up to a meter thick.  The dried eelgrass made an ideal material as it was naturally resistant to rotting, and provided great insulation, keeping the houses cool in the summer and warm in the winter.

Today, though modern roofing materials are used preferentially in new building projects on the island, a great amount of effort and money is put towards the restoration and preservation of the traditional houses that remain.  These efforts are supported by both the local communities and the cultural heritage organizations, and the roofs themselves remain an important cultural symbol of the island.