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Cleaning a stone wall
A limestone wall or limestone cladding are cleaned to prevent them from becoming black from mosses, lichens and especially through pollution. Depending on the dirt of the wall or the cladding - several solutions are possibles. We recommend that you start with the least aggressive for the stone in terms of product and then increase the power of the treatment if the first results are not good enough.
The classic cleaning
The first step is to clean the wall with a rubble vacuum cleaner and clear water. Often cobwebs, insects... have been housed for years in the gaps of your massive wall (low wall stone, rubble) or cladding.
Then for the second step, several techniques exist : metal or nylon brush soaked in baking soda and clear water; same idea with soda crystals (more effective); mixture of warm water and black soap, alkaline product specific natural stone as Detercal in our product range.
Otherwise, use specific natural stone fungicides such as our product Determousse. We are getting closer to roof fungicides but adapted for natural stones and especially limestone.
We do not recommend the use of "Decapfour" or petrochemical products to clean oven, on your stone wall. Beyond polluting your soil and your environment (risks for children or animals who would play in this soiled environment), the risk of cracking the stones is real because of the aggressiveness of the product.
No main difference for the cleaning of an interior or exterior wall, except that for inside you will think of protecting the floor especially if it is a wooden floor or a "fragile" material.
What to do for a very dirty wall (entirely black) ?
If the wall has not been maintained for years (several decades), the cleaning methods presented above will probably have a limited effect. If your wall is black, use a pressure washer. This is the exception to the rule ! We generally never use a high-pressure cleaner on the stone but to get results on this type of wall, it's probably the only way. Start with a non-visible surface to adjust the power and distance from the stone. Too powerful or too close, the stone will burst - Too far or not powerful enough the result will not live up to expectations.
Another extreme solution is to use sandblasting. A sandblaster will propel sand and thus clean the limestone. This method is frequently used for stone facade renovations. You can rent a sandblasting machine and a compressor from equipment rental companies. Otherwise call a professional. A variant, if stubborn stains are localized, is to use a grinder with a sanding head.
Protect with a water repellent
Once your wall is cleaned, it would be a shame to stop there. You may have to repeat the operation in 1 or 2 years. Apply a water repellent (example: Impepierre) to limit the appearance of mosses, dirt, various pollutions... We recommend applying 2 layers using a garden sprayer. Do this step when weather conditions allow it : no strong wind, no rain expected within 24 hours.
Do not hesitate to contact us for any question about the maintenance of your wall or your cladding.
