Mr Softwash®
Best way to clean Render

Softwash Biocide Treatments

Modern render facades are a low maintenance finish, which will require the minimum of upkeep. We recommend low pressure soft washing from time to time. This will be dependent on factors such as weathering, spores in the atmosphere and smog in urban areas.
 

All of these factors have an influence on the overall appearance of the finished render, which has been installed or applied to any finished facade. These appearance changes are nothing to be concerned about, as they are a natural phenomenon.

Is Soft washing with biocide 

the best method for cleaning render?

Yes, bleach can damage render if used incorrectly, primarily through discolouration and surface degradation. While sodium hypochlorite (the active ingredient in bleach) is a standard professional tool for "soft washing,"  bleach is often too strong or if used at improper dilutions for delicate surfaces like Krend and Monocouche renders. 

How Bleach Can Damage Render

• Permanent Discolouration: Using bleach straight from the bottle or in high concentrations can cause patchy, white, or streaked finishes due to a pH imbalance.
• Surface Etching: As a corrosive alkaline solution, concentrated bleach can break down the surface chemistry, stripping away the water-repellent silicone layer that protects modern renders.
• Salt Residue: If not thoroughly rinsed, bleach leaves behind salt deposits (efflorescence). These salts attract moisture, which can actually encourage faster regrowth of algae and moss.
• Warranties: Using unapproved chemicals or high concentrations can void manufacturer warranties for products like K Rend or Monocouche. 

Steam cleaning render

Steam cleaning ( Doff/Torc ) render is highly effective for removing heavy carbon staining or paint, but lacks the long term residual protection against algae that biocides provide.

soft washing with a biocide is widely considered the best and safest method for cleaning modern exterior renders like K-Rend and Monocouche. 

HOW TO CLEAN RENDER

Softwash Cleaning the render is generally advised after a few years. This will sharpen the aesthetic look and rejuvenate the finished facade by removing any organic growth, bird droppings and film of weathering found on surface.

The surface can be cleaned using low pressure soft washing. Do not use pressure washers (very high pressure washers can damage the render surface). Carefully clean the render surface by softwashing using a professional biocide which will clean the surface gradually over 6-8 weeks and continue to protect against further contamination between 3-5 years. If an immediate clean is required then use a professional sodium hypochlorite. ( Chlorine or bleech ) This will clean the surface immediately but won't give any protection against further contamination as with biocides.

Soft washing biocides provide long-term protection to Render by

killing organic organisms—such as algae, moss, fungi, and lichen—at their root and leaving a residual film that prevents regrowth. 

How Biocide Protection Works

• Residual Action: Unlike bleach (sodium hypochlorite), which provides an instant clean but no lasting protection, biocides like DDAC (Didecyldimethylammonium chloride)penetrate porous surfaces. They continue to kill spores that land on the surface for months or even years after application.
• Self-Cleansing Process: Many professional biocides are "spray and leave" products. They work with natural weathering (rain and wind) to break down and wash away dead organic matter over several weeks or months.

HOW TO TREAT ALGAE

Algae is an organic growth which will grow on any surface and remains damp for prolonged periods. Locations with nearby wood land or other sources of spores are more prone to algae growth.

To remove algae from affected substrates, use a biocide or algaecide such as Algoclear pro or simular, which can clean render and protect against further contamination for 3 - 5 years.

ATTACHMENTS TO EXTERIOR FACADES

Exterior attachments, fixed to the finished surface render, can cause staining issues. Items include satellite dish brackets, L Brackets for hanging baskets, light fixings, vents etc.

All metal brackets used should be stainless steel. Cheaper metal brackets, which are mass produced, are likely not to be stainless steel and, if the paint flakes off, may cause staining to the render surface.

CRACKS IN RENDER & REPAIR

Modern render is a flexible product, designed for stability and not to crack. If a crack appears, it is important to understand with your applicator what the cause of the crack may be. Typical cracks include:

• Structural cracks
• Settlement and shrinkage cracks, as the new building "settles" on the ground
• Stress cracks, mainly found at perimeters of window or door openings
• Hairline cracks - appear on the render surface only

In general it is advisable to leave the crack for as long as possible to stabilise before any repair is carried out.

Repair products are available:

• Colour Fill - available in a range of colours to simulate the colours of the render
• Colour Enhance - a surface coating to leave a uniform facade