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How Does External Insulation Render Work Exactly?

If you find your home to often be really cold even with the heating on, there could be poor exterior wall insulation. This can either be due to cavities in the walls or deterioration of the walls in the home. If you live in a house with cavity walls, you require external insulation to render for the walls. In this blog, we will talk about what an insulated render system is, how it works, and how to apply it in the right way to make it work. We will also mention some of the products like weber paint, weber ocr, etc.

Insulated Render System

The design and installation of the insulated render system requires a specialist to do the job. These systems usually come as proprietary products, but not always. In such a case, the system manufacturer decides and determines the standard details and construction methodology for these products.

A typical insulated render system includes mechanical fixings to the wall, mesh reinforcement, attachment of standard size insulation boards, render base coat, and finish coat. These products and systems are usually guaranteed when they are installed by the contractors approved by the manufacturers. The construction techniques for applying these products remain the same. But the systems can differ through the use of their components.

Reasons for application of the system

An insulated render system is usually applied as inclusion or part of an overall refurbishment scheme. It is usually applied where external walls are either poorly insulated or are deteriorating. Another reason can be when an external wall is insufficiently weathertight and causes dampness and draught, and even heat loss in most cases.

These systems are also applied in the case where the wall cavities are bridged or blocked. This makes it unsuitable for cavity fill insulation. Another reason can be if the external appearance of the walls need updating. This is often a part of a rehabilitation scheme for housing buildings.

The installation of an insulated render system can be disruptive. It can end up altering critical internal dimensions. It can also end up making the rooms smaller. It requires great thickness of insulation when compared to what can be achieved with internal linings.

Top tips for rendering

  • Wear tinted safety glasses at the time of scarping down render. Do this just before you are finishing up. It helps you better in spotting any missed marks. The marks stand out better when you have the tinted glasses on.
  • Remember to keep a brand new sharp scratcher with you always. This will help you in breaking the surface of the render.

  • Remove any dirt and grime properly from the wall. Be very thorough while doing this. Take your time and do it properly. Use a strong jet of water and hose it down.
  • If you notice any mold growth on the wall, make use of a fungicidal wash just before you start to repair the area. At the time of using the fungicidal wash, please read all the instructions carefully.
  • Keep any pets or animals away from the area you are rendering. It is very important that you wear masks and gloves at the time of doing this. If there are any splashes on your skin, wash them off immediately and carefully. Remember that you should never handle wet cement. It can cause certain issues like burns irritations on the skin. So be very careful while doing it.
  • The traditional external render is basically a coating of cement and sand. A coating can also contain roughcast. Roughcast is basically small stones or chippings.
  • Once you apply the render on the surface, let it dry out completely. You must allow it to dry before you apply a layer of masonry paint. If the tyrolean breaks during the process, remember that it can sometimes be repaired by the manufacturers. People often get it repaired because it can be quite expensive to completely replace it.

Some important products:

  • Weber paint is a solvent-free, water-based silicone paint. It is used for the application of masonry substrates and renders. There are colour selections and they must be made against an actual sample.
  • Weber OCR is a pump or hand-applied one coast render. It can avoid the drying time that is attached to the multi-coat render systems. It offers results as good as traditional two coat renders. 
  • Weber cl150 is a water-based render and brick cleaner. It contains carefully selected biocides. It can be used as an algae treatment. It is also useful against a variety of fungus and bacteria.


At the time of doing a render job, please remember that if you haven’t done it yourself, you can get a professional to do it for you. Hire a professional for insulation sheffield, they can get you in touch with the best products and solutions be it by Weber or CMS Danskin. It is always better to let an expert handle this situation.

Cinthia Rosa
As the marketing head at Galaxy Insulation & Dry Lining in the UK, Cinthia Rosa has a reputed name in the industry. She consistently contributes her valuable knowledge to the top blogging sites.

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