A roof is only as good as the edge that carries water off it. On this Colorbond roof in Wattle Grove, the gutter had filled with leaves, twigs and silt, so every heavy shower was spilling over the front edge instead of reaching the downpipes. Overflowing gutters do more than make a mess of the garden. Water that can't get away backs up under the last row of roof sheets, soaks the fascia boards and sits against the steel, where it starts rust from the inside out. On a metal ro