Careful preparation for the painting of existing roofs is essential. Here Resene Paints outlines a step-by-step guide on preparing cementitious roofing tiles, including cement tiles and Super Six Surface preparation.
• Remove powdery layers and efflorescence
Remove any powdery layers, laitance or efflorescence by vigorous wire brushing or, preferably, waterblasting.
• Special attention needed
Fibre reinforced cement may contain asbestos. The removal and/or disposal of asbestos-containing materials (or just the cleaning down of them) requires special permission and a licence.
Contact your local council offices to determine your obligations under their bylaws.
Free asbestos is likely to be released during surface preparation and, therefore, suitable dust masks or respirators must be worn by all operators involved in surface preparation and disposal of waste.
Special care must be taken to contain all debris, and this should be kept wet and disposed of in a landfill. This material must not be left to dry out. All washings must be collected and professional tradespeople must be involved.
• Degrease and clean surfaces *
Thoroughly degrease by scrubbing or brushing down with detergent to remove all dirt, dust, grease, chalk, cobwebs and other contaminants.
Rinse clean with copious amounts of clean water and test that the surface is degreased by wiping with clean cotton wool. Repeat the process if necessary.
Remove all moss and mould *
Thoroughly clean down to remove all loosely adhered material. Treat areas of moss or mould infestation with Resene Moss & Mould Killer, correctly diluted with clean water. Leave for up to 48 hours to achieve full kill.
For heavy infestations further applications may be needed. Wash thoroughly with clean water to remove residues.
Waterblast 3000 psi *
This may not be necessary, but waterblasting will ensure an excellent surface for painting.
Carefully waterblast at 3000psi to remove all dirt, chalk, moss and mould residue and any other contaminants.
Allow the surface to dry out for at least 24 hours. Care needs to be taken with concrete and terracotta tiles.
* This preparation is also suitable for terracotta tiles.
Prime with one coat of Resene Sureseal.
If the surface you propose to paint is already painted and in good condition, then you can go straight to the “Topcoats” below.
Apply two coats of Resene Hi-Glo. The choice of Resene Hi-Glo micaceous iron oxide-based colours will also give superior protection.
Follow label instructions at all times.