Knowing what your roof is made of and the features of that material will help you to understand how to repair it if it gets damaged.
Before you start on any repairs, you should firstly read our factsheet [insert factsheet link] on how to detect a leak as leaks are a common reason for roofing needing to be repaired.
• Tiles rarely need repair.
• They do not become more porous over time. If anything, concrete tiles become more impermeable to water. The argument that "because a tile absorbs water it needs to be replaced" is not valid, since all tiles absorb water. It is even normal for the underside of the tile to be damp, though if it drips water of course you have a problem. In such a case it is most likely that the tile is cracked.
• Ageing tiles become more brittle, so the older they are, the more likely you'll crack them when walking on them. If you have to walk on the roof, tread where one tile overlaps the other (the tile "nose") as this is the strongest point.
• Often minor leaks in tiled roofs occur through mortar cracking away from ridge or capping tiles or mortar joins near valley gutters. A simple remedy is to plug the (often hairline) cracks with a suitable silicone product. Preferably seal the cracks from the roofspace, to minimise deterioration of the silicone product, and to avoid having to climb on the roof. Significant roof leaking may demand removal and re-bedding of all the capping or other tiles in new mortar.
• Slipped tiles most often occur when fixings deteriorate or mortar joins break down. Such tiles need to be re-bedded in new mortar or re-fixed by re-nailing or renewing the ties. Tiles which slip into a gutter through mishandling whilst climbing on the roof for example may often be simply repositioned.
• It is possible to insert "slips" of new corrugated iron between the overlaps of corroded metal sheets, this being a common deterioration site.
• These "slips" need to match the profile of the existing corrugations. This repair technique is especially common in Queensland.
• Silicone sealant and paint can sometimes extend the life of a partly decayed metal roof, otherwise replacement will be your best option.
• Care must be taken when accessing a metal deck roof. Although you can’t crack the surface, scratching the surface may compromise the protective coating giving rise to deterioration (rust) over time.
• The other main concern with roofs is sagging. A roof has to sag noticeably before any serious framing problem exists.
• When significant sagging occurs, tiled roofs will deflect, allowing windblown water to come in. You may decide, before this stage, that the appearance of the roof is unsatisfactory, and replace it for this reason alone.
• A sagging roof may occur through deterioration due to age, or when lightweight roofing materials, like corrugated iron or slate, have been replaced with heavier materials, like concrete or terracotta tiles. The roof framing should have been reinforced during the change-over, but often this is not done.
• Sagging can also be caused by purlins incorrectly affixed to the house frame. Purlins support the roof frame and should be attached to the tops of walls, not to the ceiling joists which will bow under such weight.
• Weakening and sometimes sagging of the roof frame can also be caused by tradesmen who have cut too deeply into rafters to make way for wiring, pipes and vents.
• All of the structural defects mentioned above can lead to costly repairs and should be professionally assessed before they are fixed.
The other area that home owners may be concerned about is lichen or dark mould appearing on their roofs. While this doesn’t damage your roof as such, if you find them unsightly and want to remove them, we have some tips for you to follow.