Preparation:
All concrete and mineral composite surfaces shall be dry and free from contamination such as oil, grease, loose particles, decayed matter, moss and algal growth, laitance and all traces of mould release oils. This is best achieved by medium/high pressure water blasting the surface. Where moss, algae or similar growths have occurred, treatment with Andura Biocide shall be undertaken after the blasting process. If after the application of the Biocide, any residue of growth, dead or decaying matter remains, this should be rinsed/washed away. Special care must be taken to ensure that exposed edges of tiles are properly prepared. Ensure that any repair mortars used are dry, cured and free from dust and laitance. Bedding and pointing on roofs to be coated should be in sound condition and be of appropriate mix design to resist water and frost damage. Ridge tiles should be bonded using a mix of 1:3 cement : sharp sand. The incorporation of Andura SBR bonding admixture into the gauging liquid will improve adhesion and water resistance (see Andura SBR Bonding Admixture Product Data Sheet) Special consideration shall be given for the preparation of asbestos surfaces. Please contact Andura for further details.
Where application over existing sound coatings is required, trials shall be undertaken in order to ensure compatibility and retention of bond between the underlying coatings and the substrate and of the bond between Roofgard W and the existing coating. Existing coatings which exhibit poor adhesion to the background can severely reduce the performance of Roofgard W. Where any doubt exists concerning the condition of previously applied products, these must be completely removed by appropriate means.
Application:
In order to obtain the protective properties of the Roofgard W system, it is essential that the correct rates of application are achieved.
Roofs must be dry and frost free before application. Application of Roofgard W shall not be undertaken in rain nor when rain is likely within 6 hours of application, nor when ambient and/or background temperatures are below 5ºC or 5ºC and falling.
The use of a separate primer is not normally required for asbestos and concrete surfaces. However, if application is likely to a highly porous substrate then Roofgard W can be thinned up to 10% clean water and this can be used as a primer.
Roofgard W shall be applied to all prepared surfaces in two coats by brush, roller or spray. The first coat shall be applied at a minimum application rate of 0.20 litres per square metre, taking care to achieve a uniform wet film thickness of not less than 200 microns. Roofgard W will become dry and recoatable after approximately 2 hours at 20°C – 65% RH. Lower temperatures, especially if combined with high humidity and poor air circulation, will lengthen drying time. The second coat shall be applied as detailed above at a minimum application rate of 0.20 litres per square metre, taking care to achieve a uniform wet film thickness of 200 microns.
Equipment:
For spray application use Airless Spray Equipment that will support a tip size of 21 – 25 thou (0,021” – 0,025”).
Cleaning:
Roofgard W shall be removed from tools and equipment with water and detergent immediately after use. Dried material can only be removed by mechanical means.
