Troubleshooting Guide - Limewash washing off

Limewash Washing off

1. Incompatibility with the application. Limewash requires both a physical key and a suction bond for best results and longevity of coating. So limewash has difficulty adhering to modern finishes and materials such as concrete and also to hard stone. Additives to limewash such as tallow and linseed oil reduce its porosity and hence can reduce the bond of subsequent coats of limewash. Surface dusting of previous coats of limewash will not provide a consolidated surface for the new application to key into.
2. Lack of carbonation for various reasons. Refer to ‘Dusting’ of limewash (above). 

 Resolution

Surfaces should be assessed for compatibility before the application, if the surfaces are concrete or cement then using a mineral paint such as Beeckosil or Earthborn masonry paint in accordance with the manufacturer’s guideline may well be the best option.

 It is best to work out why the limewash is washing off before remedial action is taken. A stiff brush or a jet wash should be used to remove areas that are washing off. If the reason that the limewash is washing off is due to a lack of a key then it may be appropriate to apply a shelter coat prior to the reapplication of the limewash in accordance with the manufacturer.

If too much additive has been added to the previous coats then it may be best to just let natural weathering takes place on the surface of the limewash before any more coats are applied. If this is not an option, for example, the specification demands a certain number of coats of limewash, then a pressure washer will need to be used to carefully etch the surface to a sufficient degree to remove the coat/coats of limewash that is causing the problem before reapplying in accordance with the manufacturers.