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What Does Weber Saint-Gobain Say About Maintaining Render?

Weber Saint-Gobain are one of the oldest render manufacturers in the world. Compagnie de Saint-Gobain S.A. is a French multinational corporation, founded in 1665 in Paris. Originally a mirror manufacturer, it now also produces a variety of construction and high-performance materials. Weber are one of the most well-known render manufacturers have a full range of render products on the market.

Weber Saint Gobain advices that there is no better time to clean than now! The company has said, "Over the years, the warmer temperatures and prolonged damp weather has meant there has been an increase in the formation of algae growth on buildings. Algae is not just limited to porous textured surfaces in fact algae can grow on nearly all types of surfaces."

When it comes to maintaining your render there are various options available to you, all with very different requirements and price points. We have broken down the options recommended by Weber Saint-Gobain to give you a better idea of what the manufacturers are saying! 

OPTION ONE: Using a decorative finish over existing render
Applying a decorative finish over existing render is the preferred option when refreshing the appearance of existing render as opposed to removing the existing render (which is a large undertaking and may cause significant damage to the substrate) or rendering over existing render (which can cause a range of issues relating to the strength, bond and key of the existing render). For sound, site-batched renders which were not manufactured by Weber, they should be checked first for suitability of condition and be free from anything which may impair adhesion of the new decorative finish.

STAGE 1: Clean existing render
It is important all dirt and organic growth is fully removed and cleaned as this can create a weak intermediate layer and affect the performance of the new decorative finish.Larger pieces of dirt and organic growth may be removed with a soft brush. Following this, a render biocide cleaner such as weber CL150 must be used to kill spores and prevent further growth. See our guide on cleaning render to find out how to do this.

STAGE 2: Apply primer
Now the existing render is clean, prime with weber PR310 using a brush, roller or spray and allow to dry for 24 hours – drying time may vary depending on weather conditions. For product details or a more detailed application tutorial, please visit the weber PR310 product page.

STAGE 3: Apply decorative finish
Once primer is fully dried, apply a decorative finish coating. Visit the links below for application instructions for each: webersil P silicone render paint / webersil TF silicone textured finish / weberplast TF acrylic textured finish.

OPTION TWO: Removing and replacing existing render
Removing existing render is a large undertaking and is likely to result in damage to the substrate. If damage does occur, it will need checking for suitability by a professional. The substrate may also require any necessary repairs prior to rendering being carried out.

STAGE ONE: Remove existing render
Use mechanical tools to remove the existing render and try to make minimal impact on the substrate beneath. If damage occurs, you may need to consult a structural engineer before moving forward. If you need any clarification on this process, please contact us.

STAGE TWO: Treat substrate
Apply weber CL150 to all areas and leave to dry for 48 hours. Once dry, remove surface materials with a stiff brush and power wash any stubborn areas.

STAGE THREE: Apply key coat
Apply weberend aid at a 2-3mm thickness approximately 1m² at a time with a stipple roller. Texture immediately with a deep, heavy stipple key and make sure to apply on all elevations to be rendered. Leave to cure for at least 48 hours.

STAGE 4: Level surface
If removing the existing render has caused damage to the substrate, use weberend OCR to level out the surface, incorporating a horizontal scratch to create a key.Leave to dry for 2-3 days if covering with monocouche render, or leave to dry for 1 hour if the next layer is another layer of weberend OCR.Note: Any damage to the substrate may need checking by a structural engineer before leveling.

STAGE FIVE: Apply new render
Apply choice of new render and finish as desired, bearing in mind that the entire render system must not exceed a total thickness of 25mm – this includes the layer of weberend aid, and weberend OCR if you used this to level the surface. We recommend using a through-colour monocouche render: weberpral M monocouche render, known as weberpral D in Ireland, or weberpral MF finer texture monocouche render. If preferred, you could instead use a base coat render such as weberend OCR and then add a decorative finish.

OPTION THREE: Cleaning Render
Render offers a clean, modern, and attractive finish for your home which will last for more than 20 years if properly maintained. Although render is low maintenance, you may need to wash it down from time to time, which is why we’ve created this handy guide on how to clean coloured render and keep it looking fresh for years to come. This guide will also teach you how to remove green algae, which is a common concern for those with rendered walls.

STAGE ONE: Treat the building with Weber CL150
Even if there’s no sign of growth on the building. weber CL150, will kill a broad range of bacterial, fungal and algal species including green algae. It is a good idea to leave this to work over 24/48 Hours.

STAGE TWO: Wash it down
If you're looking to remove stains from your render, or if it's just looking a bit grubby, give the building a good wash using a pressure washer. Take care to adjust the pressure washer to a fan action rather than a jet action as this could damage the render. There’s no exact rule as to how often you should be washing your render — once a year or as often as necessary to keep it looking great. 

At Spectrum we understand the challenges you can face around maintaining modern render: 
- Mixed Messages: Each manufacturer offers a different solution, how do you know which one is best for you?
- Price: The access costs alone can be huge with scaffolding / cherry pickers/ BMU Cradles. 
-Voiding manufacturers warranties
Going against manufacturers recommendations, you could be invalidating warranties. 

We have over 10 years experience with maintaining render, and throughout this time have developed a system we refer to as P.A.S.T. We have four distinct stages to help you maintain your render in the best possible way:

Pre-Work and planning

In addition to this specialist method, we have developed, 3D printed and patented a specialist cleaning head and connection for the tubes which enables us to be able to clean render up to 8 floors from the ground, safely and with steam. As stated in the Weber Guidelines jet washing can actually cause the surface of the render damage so we would always recommend using steam.

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