Cyclical planned maintenance of EWI and thincoat render systems within the Social Housing sector.

Cyclical planned maintenance of EWI and thincoat render systems within the Social Housing sector.

Project Surveyors and Managers have expert knowledge of many differing methods of build and materials used as part of their building expertise – much needed when considering planned maintenance programmes of housing stock facades.

In this article we discuss some of the most common non-invasive cleaning methods for External Wall Insulation (EWI) and thincoat, through colour, render systems to maintain in prime condition for the longest whole life - without compromising system manufacturers warranties.

We’re concentrating on cleaning and maintaining the façade, in other words the “finish” coat, but it helps to understand what sits within.


There are many brands of external wall insulation system (EWI), mainly specified

to insulate solid wall properties and reduce carbon footprint, they all seek to achieve similar results and vary in the type of insulation and the fixings that attach the system and the type of render or topcoat finish.

The main insulation systems are Polystyrene (EPS), Mineral Wool and Phenolic Resin. Expanded polystyrene is the most popular. Inexpensive, durable, lightweight, non-toxic, and completely recyclable. Price and ease of use make it a favourite wall insulation and the most stable of sheet insulations. Mineral wool insulation is not the same product as used in loft insulation! This wool comes in panels and can be handled in the same way as EPS. Phenolic resin is more expensive tends to have thermal properties which are very high – so you can achieve the same thermal ratings with a much thinner amount of material.

Outer face finishes are typically scraped finish, dry dash, brick or brick effect, ashlar detailing and sprayed roughcast.


Sometimes referred to as monocouche these newer render systems are quick and easy to apply in one coat over new blockwork so very popular for new build developments. Most monocouche system manufacturers also provide EWI systems. 


Many system providers sell their packages to include warranty performance of their product, often for up to 25 years. Such warranties are very appealing however there may be limitations on cyclical maintenance activity, for example some will exclude re-painting programmes, regardless of colour fading due to UV. They may also exclude the use of ammonia, acid or sodium hypochlorite based “cleaners”. They will all exclude the use of aggressive pressure washing.


Modern render systems will have a total build-up of silicone render at just 6mm-10mm. That compares to around 25mm for a traditional cement render. High pressure washing can, and will, burst through the outer protective coat, expose and compromise the performance of thermal insulation layers and long term, allow damaging water ingress.

GK Pro from GK Products UK is an HSE Approved quaternary ammonium biocide – think of it as a soap with disinfectant – Applied at typical garden tap pressure, it will not damage outer coatings.

Very little chemical (2% chemical, 98% water) is required to effectively kill off 99·9% bacterial staining on your façade. GK Pro, derived from soya bean, is not only self-neutralising and biodegradable it is the most sustainable method of cleaning buildings, requiring no rinsing off, it uses half the water of other, conventional means of building cleaning. 

Because GK Pro works by cationic action its only activated by live bacterial spores it does not possess the chemical potential (see “Cationic & Anionic action” below) to engage with the substrate to which its applied, it cannot harm, alter or discolour your façade in any way and is non-invasive. As a very powerful surfactant cleaner it has the supplementary benefit of being a super cleaner so, like washing up liquid, takes up grease and dirt into the foam.   


GK Pro is easy to apply, if you follow dilution rates and saturate the surface a successful outcome is predicable. GK Pro doesn’t demand expensive specialist equipment, it’s flexible enough to be applied with a watering can if you have nothing else, although larger projects will easily justify the use of chemical injection boxes and extendable water fed poles which allow all works to be carried out from kerbside, thereby avoiding the cost implication of mobile towers or MUPE’s. On the Tamar Tower (shown here), one of three fifteen storey towers in Plymouth the Rope Access contractors selected by Plymouth Community Homes, elected to use battery operated backpack sprayers.


GK Products UK provide free “Toolbox talk” training for the social housing sector, either your own direct labour tams or preferred contractors. The sessions include and understanding of the chemicals used, application methods employed, PPE recommendations, and recommendations as to appropriate equipment for individual contracts.


Anionic surface-active agents such as Sodium Hypochlorite, Phosphoric Acid, Hydrogen Peroxide and Nitric acid, commonly used as external 

surface cleaners, have a negative charge on their hydrophilic end. While anionic surfactants are excellent for lifting particulates, their negative charge means they extract energy and remove electrons from other molecules they encounter. The most common examples of oxidising agents such as Sodium Hypochlorite (bleach) altering surface molecules is the way denim jeans immediately “bleach” white on contact, other negative effects can be metal corrosion, yellowing of UPVC window frames, blistering on aluminium. Mixing liquid bleach with other products such as acids found in limescale-removing products produces chlorine gas, (used as a chemical weapon in the First World War). These toxic fumes are known to aggravate those who live with COPD or other respiratory conditions and can cause breathing difficulties.

Cationic Surface-active agents such as GK Pro (a Quaternary ammonium compound – Quat’s control viruses, bacteria, and other germs on surfaces) have a positive charge on their hydrophilic end and work by breaking open the membrane call walls of bacteria and outer coatings of viruses. The positive charge gives off energy in the act of disrupting, therefore rendering them self-neutralising, easily biodegradable and very stable. Cationic surfactants serve as antimicrobial agents and are often used in disinfectants.



  • Effective Against Algae and other bacterial staining: Targets and kills harmful biofilms without damaging the surface.
  • Environmentally Friendly: Uses less water and is free from caustic substances.
  • Ease of Use: Can be applied easily under low pressure.
  • Professional Support: Training for staff and sub-contractors in application methods ensures expert handling.


Protecting the character and longevity of your housing stock doesn’t have to be a daunting task. It is only a little more complex than a window cleaning programme. With GK Pro, you get a reliable, effective, and eco-friendly solution that keeps your homes looking “best in show”. Visit the site for more information.