How to maintain tile and shingle roofs.
Chip coated metal tile roofs
These are metal tiles with an acrylic primer and chip coating.
Lifting front edge of tile: This happens when the nails have failed. Replace with additional nails. Use compatible fastenings.
Loss of stone chip coating: If the roof is within warranty, contact the manufacturer. If not, check with the manufacturer for recoating options. Alternatively, have the roof recoated by a professional.
Moss and lichen growth: This is caused by insufficient cleaning, loss of mould resistance, or a continually damp roof surface. If possible, address the cause of the dampness, for example by cutting back overhanging trees. Clean more often (using a soft bristled brush). You can also have the roof treated by a specialist cleaning company. Make sure you ask for a guarantee.
Dented or damaged tiles: From walking on the roof or poor installation. The tiles may be pushed out from underneath if the roofspace is accessible. Replace badly damaged tiles.
Moss growth: This happens in warm, moist conditions.
Wash the roof with a one part bleach and four parts water solution and a stiff broom. Disconnect the downpipes first to prevent bleach going into the storm drain. Consider installing a 150mm-wide copper or zinc strip on the roof ridge. The run-off inhibits future moss growth. Note this is not suitable where the roof water is collected for drinking.
Warped, split or missing shingles: This is caused by shrinkage or weathering. Replace badly damaged and missing shingles. If the damage is extensive, you may need to consider replacing the whole roof.
Cupping and curling of the shingle: This is caused by moisture getting in from underneath.
Check the level of ventilation in the roof space using the shingle manufacturer’s technical information. See Roof space for more information.
Lifting front edge of shingles: This could be due to wind or incorrect installation. Refix with suitable adhesive. Contact your local roofing material retailer to get advice on the right kind of adhesive for your product. Generally you shouldn’t use solvent-based adhesives.
Cracking/loss of chip coating: Due to weathering. If the shingle is less than 15 years old, check with the installer for redress under the warranty. If not, replace individual shingles. If the shingle damage is extensive it may be time to replace the roof.
Discolouration: This can be caused by fungal or algal attack or moss growth. Replace badly affected shingles. Cut back overhanging trees to reduce moisture. Treat the roof with a fungicide and clean with a soft broom. For moss, remove with a one part bleach four parts water solution with a very soft broom. Brush down the roof toward the front edge of the shingle. Don’t forget to disconnect the downpipes.
Corrosion of flashings: Remove the rust by sanding, then recoat with a compatible coating according to the roof manufacturer’s recommendations. Replace badly corroded flashing.
Missing ridge shingles: This is due to loss of adhesive. It can happen in warm weather as the adhesive softens in the heat. Refix shingles with additional fastenings or suitable adhesive.
Clay/terracotta, slate and concrete tiles
Broken or cracked tiles: Damage to tiles can be caused by extreme weather conditions or by the roof being walked on.
Some tiles may be able to be repaired with flexible (silicon) sealant or adhesive. Otherwise the tile will need replacing. Contact the manufacturer for advice.
Remember to work on planks or a roof ladder to prevent further damage to the tiles. As tiles age they become brittle and can damage more easily.
Dislodged, loose or missing tiles: This is caused by strong winds or where tiles have not been properly tied to the battens, incorrect installation or damaged fastenings.
Replace missing tiles ensuring they are tied, fixed or clipped to the roof structure. Repair any building paper cut to replace the tiles.
Speak to your tiling retailer about how best to secure the tiles used on your house.
Loose mortar: Loose mortar under ridge and hip tiles is caused by movement within the building, or incorrect installation. Carefully remove and thoroughly clean the affected ridge tiles and re-bed in new mortar. Ensure the ridge tiles are clipped or tied to the battens.
Moss or lichen growth: This is common in clay, concrete and slate tiles especially as the tiles weather with age. Cut back overhanging trees to reduce moisture. Lichen doesn’t damage the roof but you may want to remove it for aesthetic reasons. You should remove it if it is blocking valleys. Moss shouldn’t be left as it attracts moisture.
Disconnect the down pipe before water blasting with water and bleach solution available from hardware stores. Alternatively have a specialist roof cleaner clean the roof. Do not use a high pressure water blaster. Care should be taken when washing older roofs as they may not have a roofing underlay. Water could get past the tiles into the roofspace. Consider fitting a copper wire net to the ridge. The run-off inhibits future moss growth. This is not a suitable option if you collect rain water for drinking.
Corrosion of metal valleys: This could be due to weathering, the wrong material being used for the environment, the valley being full of leaves or debris or the use of cement-based mortar.
Treat minor rusting and re-paint. Consider replacing with inert material such as butyl rubber. This is a difficult job so you may want to call in a professional.
Fibre cement shingles
If you think the shingles may be asbestos cement, get professional advice.
Moss or lichen growth: This is due to moisture. Cut back overhanging trees to allow the roof to dry out. Wash with a one part bleach four parts water solution and a stiff broom. Disconnect your down pipes first.
Cracked or damaged shingles: Due to impact damage or walking on the roof. Break out the damaged shingle and replace it. Fibre cement shingles are no longer available so you will need to patch individual damaged shingles with butyl rubber.
White deposits: White salt-like deposits can occur due to moisture being absorbed into the shingle. Scrub and wash the roof. You may need to do this more than once.
Missing shingles: This is generally caused by wind. For missing shingles on the ridge, use butyl rubber under-flashing folded over the ridge before replacing it with butyl rubber shingles.
Fixing crampons missing: This is caused by weathering, or by the fastenings not being installed in the first place. Replace the fastenings, but remember to work on planks or a roof ladder to prevent damaging the roofing.