Profiled Sheeting Damp Patches
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Profiled Sheeting Damp Patches Eternit profiled sheets meet the highest strength category of BS EN 494. Shade variations may occur in the material depending on cement batches. Occasionally damp patches may occur on the underside of new sheets, particularly on low pitch roofs with slow drainage discharge. They are generally caused by a combination of permeability and condensation, as the material can absorb up to 25% of its dry weight in moisture. The amount of water that the material can absorb diminishes in time as the material continues to cure and any pores within the cement matrix become filled with crystals, thereby reducing the incidence of damp patches. Damp patches are more likely to occur when the building is still drying out and the sheets are new and can be reduced by providing ventilation into the building. If Profiled Sheets are installed below the recommended pitch, there would be insufficient water run-off, causing the water to sit on top of the sheets. The recommended pitch for the Farmtec Sheets is 10° and UrbanPro is 7°. Condensation can occur on the internal surface when the temperature of the material is below the dew point of the air, such as on frosty nights or a cold rainstorm. Much of the moisture can be absorbed by the fibre cement, although if this already has a high moisture content, the condensation may drip from the underside of the roof. Please note that the condensate is alkali and in the case of droplets falling onto a parked car, may affect the paintwork if it is allowed to dry out. Impermeability tests are carried out on the material by sealing a frame to the top side of a sheet and filling it with water to a depth of 60mm. After 24 hours, damp patches occasionally occur on the underside, but drips never form. The material therefore meets the impermeabilty requirements of BS EN 494. After several years, moss and lichen may start to grow on the sheets. Many owners prefer this natural mellowing of the surface, but if you want to remove the growth please contact the Technical Department for further advice. Disclaimer The information in this Material Information Sheet is correct at time issuing. However, due to our committed program of continuous material and system development we reserve the right to amend or alter the information contained therein without prior notice. Please contact your local Etex Exteriors Sales Organization to ensure you have the most current version. All figures contained in this document are illustrations and should not be used as construction drawings. This information is supplied in good faith and no liability can be accepted for any loss or damage resulting from its use. This document is protected by international copyright laws. Reproduction and distribution in whole or in part without prior written permission is strictly prohibited. Eternit and logos are trademarks of Etex NV or an affiliate thereof. Any use without authorisation is strictly prohibited and may violate trademark laws. Publication Date : June 2023 Etex (Exteriors) UK, Wellington Street, Burton-upon-Trent, Staffordshire DE14 2AP Tel 01283 501505 Email techuk@etexgroup.com Page 1/1