How to clean k rend render

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K render has become a very popular wall finish in recent years. It is the modern ‘clean’ look which many architects ,builders and homeowners desire. BUT…look around the landscapes you will see black, green and red stains spoiling these cream white and grey rendered walls!


What has stained my K render ?The cause is most probably water run off. This is usually due to architects not allowing for proper drainage of rainwater ,from the roof and down the building walls. When the surface is constantly damp , this encourages the growth of algae, lichens and even moss. This organic or biological growth is actually quite simple to contain and remove. It needs to be treated with a biocide – a specific type of industrial disinfectant which will effectively break down the living matter, while causing zero damage to the render itself. It will take a short time for the results to show but in most cases they will be very pleasing. 

Should I pressure wash it ?We would not advise this. Although it may be necessary at times , it’s very easy to cause irreversible damage on render , with a pressure washer. 

Do I need to paint it? No, in most cases it will clean up well. Painting is the last resort If the stains cannot be removed. These Renders are sold as ‘low maintenance ‘ so painting should be avoided if possible. Some difficult stains result from water running through mortar joints and leeching minerals down the render. Carbon stains from traffic pollution also provide a challenge. We can also provide a quote to repaint with a suitable ‘ breathable’ paint where necessary. 

How long will it stay clean ?Generally we answer this with – How long did it take to get this bad? You can expect a similar pattern as nature takes its toll on ANY surface.  We may be able to recommend specific alterations that will help keep the building look good e.g add a drip groove under capping stones. Or perhaps changing the surroundings will help , you may able to trim back trees which are creating shade and encouraging algae growth. We will give you a maintenance plan and recommend the frequency which you should have the building cleaned. We hope that answers your question ‘ what has stained my K render ‘

 Please contact us for advice on your K render