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weather conditions for rendering

The Best Weather Conditions for Rendering?

The Ideal Weather Conditions for Rendering?

Things don’t always go to plan when working on a construction site, and sometimes poor weather conditions can affect whether or not you’re able to start rendering. At the time of writing, the UK is experiencing a heatwave, which has meant that we’ve received many enquiries from renderers and homeowners about whether these are the best conditions for rendering, and we endeavour to give as much advice as possible to avoid situations where the materials fail.

The ideal temperatures for installing render varies between manufacturers, however for EWI Pro renders it is advised that the optimal temperature for applying the renders should be between +5 and +25 degrees Celsius.

This isn’t to say that this unprecedented heat wave should put a halt to all works, as we know that the daily temperatures have been well over 25. Renderers simply need to be able to find ways to work around the heat, and the same goes for when the weather’s cold. So here’s our advice on what to do when the weather conditions aren’t ideal for rendering!

Working in Hot Weather

We always advise not to use our materials in temperatures over 30 degrees. Most especially, we advise that if it’s a warm day it’s best not to render in direct sunlight, as this is the most probable cause of the render drying out too fast. Render that has dried out too fast can result in cracking and damage, or even a patchy finish.

An old trick that lots of renderers use is to start before the sun has fully risen (many of our installers start out at around 5 am!). Start by applying on a wall that is not exposed to sunlight, and follow the sun around the building working on the walls that are in the shade. This allows you to continue to work in sunny weather, but prevents issues with the render drying out too fast in direct sunlight (it’s also much better for the installer to be out of the sun anyway – safety first!).

Another way to avoid cracking when the weather conditions for rendering are not ideal is to wet the walls before application, or even better apply the Water Based Primer. This primer limits the absorptive capacity of the substrate. During hot weather, ordinary masonry will have dried out and the absorptive capacity of the substrate will be extremely high. Using a primer ensures that the substrate is prevented from absorbing too much water from the render and causing it to crack during the curing process.

For our thin coat render systems, we always advise the use of Fibreglass Mesh embedded within the basecoat layer. We also advise that mesh is embedded within the first layer of Monocouche. This is even more essential when the weather conditions for rendering are not ideal, as the Fibreglass Mesh increases the tensile strength of the whole system, so when the render shrinks during the process of drying, the mesh will help to prevent cracking.

Working in Cold Weather

Cold weather means that the render may not dry out fast enough. If this is the case, the render may retain moisture for too long and thus become susceptible to damage from this trapped moisture.

Mineral Render is a great option when it comes to applying thin coat render in colder conditions. This is because it’s a dry-mix render and is therefore much more quick-drying than our ready-to-use thin coat renders. It also has much faster drying times than our Monocouche Scratch Render because this is applied in a very thick layer, which increases its curing time.

Using a Render Accelerator in the colder weather is also excellent if you are installing our Silicone Silicate, Silicone or Acrylic Renders. Simply mix in 100ml of Render Accelerator per 25kg bucket of render and you can gain faster drying times, reduced cracking and water retention in the winter.

When it comes to the basecoat layer, the Winter Adhesive has been specifically designed for use in colder temperatures when the weather conditions are not ideal – it can be used even down to zero degrees. When you use the Winter Adhesive, you are ensuring that you have a strong and crack-free surface onto which you can apply your thin coat renders. By doing this, you increase your chances of achieving a great finish – even when the weather is not ideal!

We upload every Tuesday and Thursday, so stay tuned for more content all about our systems.

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The Best Primers for Rendering?

You wouldn’t bake a cake without greasing the tin, in the same way that you wouldn’t install EWI or render without first applying a primer. Priming isn’t really something that is spoken a lot about with regards to rendering, yet nevertheless it’s an important step in the process to ensure good adhesion of materials and a long-lasting finish.

Here at EWI store, we offer a range of different primers for different purposes and products, and often customers struggle to understand which primers are required for their particular property. In this blog post we hope to set out the difference between each of our primers, and explain their purposes; so keep reading to find out more!

Substrate Primers

Substrate Primers are as the name suggests. They are used to prime the wall before anything is applied to it. This is the very first step in a rendering or EWI Process, and often the substrate primer that you choose will depend upon the absorptivity and the type of substrate that you are applying the basecoat onto.

EWI-301 Water Based Primer

The EWI-301 Water Based Primer is used to limit the absorptivity of a substrate. Over-absorption can have a damaging effect on EWI systems because it can affect the structural integrity of the materials. The EWI-301 is therefore used on an as-needed basis and applied directly to the substrate prior to anything else; it will basically prevent too much water from being absorbed from the basecoat. It can be applied to walls made of bricks, blocks, aerated concrete, structural clay tiles, gypsum plasterboards, gypsum panels and plaster coats.

EWI-310 Universal Primer

The EWI-310 Universal Primer is a particularly great primer if you have a smooth substrate, i.e. concrete. It limits absorption by the substrate and the presence of quartz aggregate within the primer helps to create an artificial key, facilitating adhesion and application of basecoats and adhesives… one of its ‘key’ benefits if you see what I’m saying. Another one of the great things about the EWI-310 Universal Primer is that it helpfully dries red on the wall so that you can see where you’ve already applied it – therefore limiting over-application, saving you money by making the product go further!

Render Primers

Render Primers are applied directly onto the basecoat before application of the render itself. Choosing your render primer will depend upon the type of render that you are about to apply. We have a range of render primers that are suitable for use with our entire render range.

EWI-330 Mineral Acrylic Primer

The Mineral Acrylic Primer is used as means of final preparation before you apply your render. This basically means that it is applied on top of the basecoat/adhesive before you render. The EWI-330 is specifically designed for use with our Mineral, Acrylic and Mosaic renders, and it can be tinted to match the colour of the render for strong opacity. EWI-330 comes in both 7kg and 21kg tubs so you can purchase the right size for your particular requirements.

EWI-333 SiSi (Silicone Silicate) Primer

Much like the EWI-330, the EWI-333 SiSi render primer is applied to the basecoat/bedding adhesive as a means of final preparation before render application. It’s ready to use and comes in 21kg and 7kg tubs; designed for use with the EWI-075 Silicone render or the EWI-040 Silicone Silicate render. This primer can also be tinted to match the colour of the render that you are going to be applying for strong opacity and a uniform finish.


Worth mentioning, the Fungicidal Wash and Render Accelerator are additional steps that an installer may decide to take as best practice depending upon the situation.

Fungicidal Wash

Fungicidal Wash is a proven biocide and is used to clear the substrate of any kind of moss or growth before you do anything. It needs to be applied 24 hours prior to applying anything else to the substrate, after which time it should have killed off all organic growth.

Render Accelerator

The EWI-020 Render Accelerator is designed to be added to your render in order to speed up the drying process. It’s a liquid additive which is perfect for use when the weather is more damp or cold – many of our installers have raved about how much time the Render Accelerator has saved them when rendering in unpredictable weather.

So there you have it! Hopefully this will enable correct decision making over which primers are required for different jobs. Usually our sales representatives would be able to advise you if you are placing an order over the phone, however it’s always good to be well informed and prepared ahead of making your purchase. We upload to our blog every Tuesday and Thursday, answering frequently asked customer questions and tackling some of the technical problems faced when installing EWI in different circumstances. So don’t forget to stay tuned for more and follow us on social media for updates and exclusive offers!

Interested in having render installed on your property? Fill out the form below and we will be in touch!


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What is Mineral Render? EWI Pro Coloured Renders

So, you’re looking to re-render your property, and whilst looking at our selection of renders you are unsure as to which render is the right choice for you. Well, this is understandable because all of our renders have different properties and therefore can offer you different things at different price points. Allow us to help you by shedding some light on the wonders of our Mineral render

Mineral render is a popular render choice for EWI and render-only systems that are going to be installed in colder climates. It’s a dry-mix finish and is our fastest drying render – therefore it’s a better choice for you if you live somewhere blessed with cold and rain every other day (Scotland, Wales… we’re looking at you). As long as the temperatures are above freezing, you can still go ahead with installing your mineral render without problems – which reduces so many complications for both the installer and the homeowner.

Mineral render comes in a variety of different grain sizes – so it’s great if you want a more customisable render finish to suit your tastes. If you are familiar with our silicone render  (you can read our blog post all about silicone render) then it can basically give you the same result as this (except without the silicone, and it’s cheaper), because Mineral render is a thin-coat render, so it still allows for breathability, flexibility and resistance to cracks. The breathability of Mineral render is also great for if you are installing a Mineral Wool external wall insulation system, because Rockwool is highly breathable as well.

Mineral Render and Silicone Render Paint

However, a lot of people can be put off by the fact that the Mineral render needs painting after it has been applied to the substrate. This does rack up the price – although mineral render is less expensive in the first place, so it can balance out somewhat.

Mineral render needs painting with a render paint because when it has been left unsealed it is susceptible to lime bloom (otherwise known as efflorescence). This is because Mineral render contains Portland cement. Lime bloom occurs in white patches and discolouration where “lime” (calcium hydroxide) settles on the surface of the render due to a chemical reaction. This can cause the formation of crystals on your render which can damage the system.

To combat this, we recommend that once dry, you immediately seal your mineral render with our EWI-005 Silicone paint, because silicone offers hydrophobic properties which will further protect your render finish. This also means that the external finish of your property will be more low maintenance, because silicone resists organic growth – so you won’t have to keep washing the property.

Although having to paint the render after installation can be more time consuming, it can actually be a good thing because silicone paint can be layered. Therefore, if you wanted to brighten up the property or change the colour of your external finish further down the line, then you can easily just paint over it again.

How to apply Mineral Render

Because mineral render comes as a dry mix, it needs combining with water before application. You can do this using a mechanical mixture or manually with a paddle mix. The render is then applied to the substrate using a Notched trowel. Usually, you’d apply your render to the same thickness as the grain size – so if you went for a 3mm grain size you’d apply the render at a thickness of 3mm.

So, once you’ve applied the mineral render it should take roughly 12 hours to dry (depending upon the conditions). After that, you are free to use the Silicone paint to seal it! You can apply our silicone paint with a spray machine, a roller or simply by using a paint brush.

Why Choose EWI Renders?

Here at EWI Store, we prioritise providing our customers with the best quality products on the market. We are confident in the abilities of our renders to deliver fantastic results, so you can be sure that they will meet your expectations!