Algae,Mold, and Lichen can cause a roof to leak, leading to increased repair costs. Algae,Mold, and Lichen can cause a roof to leak, leading to increased repair costs. Algae,Mold, and Lichen can cause a roof to leak, leading to increased repair costs. Algae,Mold, and Lichen can cause a roof to leak, leading to increased repair costs.