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Is rendering waterproof?

Is rendering waterproof?

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What is render?

Render is a material that is used to cover the outside of a property in order to:

  • protect the property from the elements
  • add an extra layer of external insulation
  • improve the appearance of the external walls

There are a number of materials that are used as render, each of which with its own advantages and disadvantages. The material covers exposed brick and other construction materials, and can even help to improve the curb appeal of a property.

Is render waterproof?

If you’re attaching materials to the outside of your home, you’ll want to make sure that it isn’t going to be a waste of money. So is render waterproof?

Well, the answer is not a simple one. All render, whether it is waterproof render or not, will eventually degrade under the elements. Even the best, highest quality waterproof render will eventually need replacing in order to keep your external walls safe. Moist and warm weather alike will take their toll on pretty much any building materials. There are a few types of render that boast better water resistance or water repellent properties than others, though, and these are the ones that are likely to be the best choice for anyone worried about waterproof render.

It is important to note, though, that even these are not 100% foolproof. Even the most waterproof render may end up failing against things like penetrating damp issues or structural damp. Nothing is really completely waterproof, but there are some renders that work better as waterproof coatings.

Which is the most waterproof render for external walls?

There are a few types of render to choose from when looking to upgrade your external walls and exterior house rendering. They are:

  • silicone render
  • cement render
  • traditional render (sand and cement render)
  • lime render
  • acrylic render
  • polymer render
  • pebbledash render

All of these types of render can make a big change to your exterior walls, but some of them are more worth their cost than others. The most waterproof renders are:

Silicone render

Silicone render is a render mix with silicone added in to provide it with water resistance and breathable flexibility. It is much more modern than the other more traditional render materials and it boasts a much higher chance of protecting your home from things like penetrating damp. However, it does boast a much higher price tag, too.

Why is silicone render waterproof?

Whilst silicone render isn’t completely waterproof, because nothing is, silicone renders have a better chance at battling things like rising damp and water vapour because they are so highly breathable. Rendering materials with low breathability prevent moisture from escaping as water vapour, causing it to get trapped beneath the render. This causes cracks in the material as the water desperately tries to escape.

Silicone render is also specifically designed to work as a waterproofing render, in that it has hydrophobic qualities. This makes it much more reliable as a waterproof coating.

Polymer render

Polymer render is a very vague name given to specially designed render mixes that work to target certain issues. These are often created to be damp proof and to have relatively high weather resistance. A lot of polymer renders will contain silicone because of its weather resistant properties, as well as other chemicals that help to battle things like water absorption. They are, however, quite often more expensive.

Why is waterproof render so important?

Your external walls are faced with the natural elements and the weather 24/7. According to Mister Render this can cause a number of problems for the property, and these can be expensive to tackle and fix. Using waterproof render can help to prevent these problems and keep your internal wall and external wall safe from things like significant wind driven rain, mould, and moisture. It can help to reduce issues like:

Penetrating damp

Penetrating damp issues are very common. It is the process of moisture moving from the outside (exterior walls) to the inside. It is usually caused by significant amounts of wind-driven rain sitting on the walls or ceilings of the building. When left untreated, this can cause mould.

Rising damp

Rising damp is when water appears to be working its way up the internal walls of a building. It will look like giant wet patches and can cause black mould to appear in the property.

Algae growth

When cracks develop and moisture is let into the render, it can build up. This can then form the perfect environment for algae growth. This usually affects external walls more than interior walls, and whilst it may not directly damage anything, it is unattractive and could be a sign of further damp problems within the rendered walls.

Heat loss

One of the reasons that people get their building rendered is to add a layer of external insulation. This helps to reduce the loss of heat throughout the building and can reduce things like your carbon footprint and your gas bill. If your render is not waterproof and begins to crack, allowing moisture into it, it is no longer a single coat of protection and the cool air is more likely to reach the property. Likewise, you’re more likely to lose heat through the surfaces.

Are the other rendering materials waterproof at all?

Sadly, the other more traditional render materials are very unlikely to stand up against moisture. They are not breathable or particularly sturdy, and so despite their lower price tag they are more likely to become damaged and need re-rendering sooner than the more modern renders like silicone. Sand and cement render in particular is not waterproof, and homeowners will quickly see cracks in the surfaces.

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