Cement Tile Colourings, SEALATEX Coatings and Textures Other improvements have followed including improved colourings, coatings and surface textures. These are now making it possible for concrete roof tiles to offer the look of more traditional roofing tiles, figure 1. Modern concrete tiles typically have the appearance of clay tiles or natural slates.
It is important to achieve the desired colour using the minimum amount of pigment, as the pigment is usually the most expensive component in a concrete roof tile. The pigment must therefore be used efficiently, and so it is vital to ensure that it does not form agglomerates and that individual pigment particles are dispersed as widely as possible in the concrete mixture. A dispersion of iron oxide pigment particles - the high density white specs distributed throughout the mortar microstructure
A major enemy of bright colours is excessive efflorescence, the formation of a powdery deposit on the tiles. This arises from hydrated calcium hydroxide, which is present in hardened Portland cement. Calcium hydroxide seeps through the pores of the concrete to the surface of the tile, where it is carbonated by atmospheric carbon dioxide and forms calcium carbonate. A light dusting of calcium carbonate is not harmful, as it will be washed off by rain, leaving a pristine surface. However, a severe case of efflorescence will reduce the apparent brightness of the tiles and at worst could ruin the appearance of a roof.
Reducing Efflorescence
Efflorescence can occur not only in service on the roof but also during the manufacturing process or in packaging. Roof tile manufacturers therefore use a number of measures to eliminate its occurrence. It is a complex area, but most manufacturers simply aim to reduce the quantity of calcium hydroxide present in the hardened mortar, thereby reducing the risk of surface carbonation. If any efflorescence does then form, it can be easily removed in the production process by an acid washing treatment.
Another widespread technique is to protect the mortar from atmospheric carbon dioxide by applying a polymeric coating. Simple coatings can be formed using clear polymers or paints, but complex multi-layer coatings can also be produced that give a surface virtually indistinguishable from locally available clay tiles. Such surface texture is another important parameter in the manufacture of concrete roof tiles - for example, there is a market in the UK for flat concrete tiles that look like weathered, hand made clay tiles.
Life Expectancy and Design Criteria
Irrespective of the desired appearance, the functional performance of roof tiles is essential an must be maintained throughout a tile’s life. Guarantees of 60 years or longer are often demanded, and so concrete roof tiles must keep water out for many decades while withstanding a wide rang of weather conditions. Tiles are made by extruding the sand cement mortar onto a metal support pallet that gives the tiles their underside detail. The top surface of the tile is normally smooth, the profile being defined by the shape of the pallet and the extruder itself. This design is critical to maintaining the properties of the tile. Tiles are designed to minimise total weight while retaining enough tensile strength to withstand all handling stress The design must ensure that the tiles remain totally impermeable to water, and also has to take into account the need for adequate fixing, to ensure that the roof remains in place during event of the strongest storms.
Roof Tile Testing
Roof tile manufacturers carry out extensive durability testing to check the tiles will survive their long guarantees such as SEALATEX with a 7 year warranty.
Restoration of a concrete tile roof is necessary when the surface of a tile becomes porous due to the effects of sunlight and rain on the existing coatings of the tile from new.
Manufacturers generally give a 7 year warranty on new concrete tiles. After that time the tile surface deteriorates with a loss of colour and gloss, an increase in porosity and an oxidisation of the tile.
This generally results in cracking of the bedding and pointing of ridge caps.
The roof will eventually leak and there is also the real danger of loose and broken lumps of mortar or tiles falling into the gutters and blocking downpipes.
Leakage may not be immediately visible as an unrestored roof would leak only about 1 to 2 litres of water, consisting of drops in several areas over the roof, not necessarily concentrated in the one area. Over time, those drops become black marks on the ceiling with fungus and lichen forming in the roof tile, the ceiling plaster and in any roofing insulation.
SEALATEX tile sealer WILL ensure all ridge caps are secured by using a flexible pointing compound pre sealer application . The tiles should be pressure cleaned and primer coats, followed by at least two top coats to ensure a long lasting and efficient finish that is as good as new.
A renovated roof not only provides protection and peace of mind, it also looks fantastic. There is a good range of colours to change to and it is a worthwhile investment.
SEALATEX ROOF TILE SEALER has a 7 year warranty
www.sealatex.com.au
Phone David Shillinglaw on 0406 255 970
