Exterior wall render and paint buying guide

Render is a type of coating that creates a uniform finish on exterior walls. It offers protection against weather, bacteria growth and moss. It also adds to the appearance of the front of your home meaning it is important to make the right choice!

The 3 types of render

1. Cement render (sand + cement)

2. Lime-based render (sand + lime + possibly cement) ;

3. Plaster finish. 

Non-hydraulic lime sets slowly upon contact with the air while hydraulic lime sets upon contact with water followed by air.

• Lime-based renders are particularly easy to use thanks to their slow drying process. They are also excellent insecticides.

• Cement renders, on the other hand, are more hardwearing.

Traditional render

Render is traditionally cement- or lime-based (or a mixture of the two) and is applied with a trowel in three layers.

1. The first bonding coat has a runny consistency and is trowelled on in a thin layer.

2. The second layer is a straightening coat which gives depth to the render and allows you to level out inconsistencies; this is applied with a float.

3. The third layer is a finishing coat used for aesthetic purposes. 

The look of your render will depend, of course, on the colour you add and the texture provided by the components (such as sand). Traditional render is prepared on-site using a cement mixer and has a lifespan of 50-100 years.

Monocouche render  

Monocouche render is an industrial render containing lime and cement. It comes ready to use in your chosen colour and is usually contained in a bag. Its increased efficiency makes it a popular choice: it can cover an entire facade in less than 3 days. However, monocouche render cannot be applied over plaster or earth-based substrates such as cob. It has a lifespan of 30-50 years.

It's crucial to choose the right render depending on the surface you're going to apply it over. Generally speaking, it should be softer and less waterproof than its supporting surface. In the vast majority of cases, walls will be made of concrete block, concrete or bricks. A highly water-repellent industrial render with a thickness of 10-15mm is perfectly suited to these materials.

However, if applying over aerated concrete, insulation materials or any other low strength substrates, it's best to use a specialist render.

Choosing your render also means choosing the finish. There are four main types:

• sprayed;

• crushed;

• scraped;

• trowelled.

Spray finish

This is the classic render finish. Render is projected onto the substrate using a compressor hose or Tyrolean gun. A second coat is applied a few hours after the first. The rough surface will make the facade appear darker due to the texture it creates.

Crushed finish

For a crushed finish, render is sprayed on and then crushed with a trowel.

Scraped finish

To produce a scraped finish, the render is sprayed on and then scraped using a float or a scratch tool as it sets.

Trowel finish

For a trowel finish, the render is smoothed with a plastic trowel or sponge, giving a smooth but grainy appearance.

'Ready-made' renders are typically sold in 15kg tubs and simply need to be diluted before application. These will generally cover an area of about 15m² and can either be trowelled on or applied with a roller.

Many types of render can be applied indoors using a roller. Interior render is usually made from acrylic resin, and is designed to decorate or freshen up old surfaces. In terms of application, a special honeycomb roller is recommended. Choose your grain size according to the desired result (this will dictate the size of the small 'spikes' or protrusions in your render finish).

Exterior wall paint must be waterproof, allow the wall to breathe and be able to let out water vapour. Depending on the condition of the wall and its material, you may choose from the following types of paint:

Acrylic

Acrylic paints are easy to apply, odourless, cost-effective, and can be applied quickly (4-20 hours). They provide effective wall protection for 7-10 years, and are therefore entirely sufficient if your facade is in good condition. Paint rollers and brushes can be cleaned with water.

Siloxane

Siloxane paints combine a silicone-based resin with an acrylic resin. They are suitable on virtually all surfaces. Highly water-repellent yet water vapour permeable, siloxane paints are popular with painters thanks to their ease of application, durability and matt appearance which resembles mineral paints. Painting tools can be cleaned with water.

Pliolite / hydropliolite

Pliolite and hydropliolite paints are composed of a resin derived from rubber; they are microporous and adhere well to surfaces. Pliolites and hydropliolite paints are suitable for damaged, porous or damp walls and offer an impressive lifespan of 7-10 years. Pliolite paints can be cleaned off using white spirit-type solvents. Hydropliolite paints offer similar performance but can be cleaned with water.

Mineral paints 

Mineral paint is a rather outdated option made from a base of either lime or silicate. Bacteria-resistant and breathable, these paints are enjoying a recent resurgence in popularity.

When choosing a paint, your substrate is a key deciding factor along with the location of your home. You'll need to choose a paint that is suited to the surrounding environment.

Mountainous environments

Exposure to UV rays and low temperatures will require you to choose an appropriately durable, weather-resistant paint. You can find some siloxane paints that are specifically designed for "adverse climatic conditions" and even "extreme conditions".

Marine environments

Exposure to sand, salt, UV and moisture requires a special kind of protection often provided by specialist "marine" siloxane paints.

Wet and wooded environments

Siloxane paints come in yet more specialised varieties for facades exposed to high levels of moisture, moss and lichens.

Other types of paints may also be suitable but the most important thing is to choose a paint that is well-suited to your environment (industrial environments, high-traffic areas, etc. also count!).

Please note that exterior wall colours may be regulated by local authorities, more general regulations or, of course, by housing developers / associations (if you live in a block of flats). It may be necessary to obtain planning permission for substantial alterations to the exterior of your property. You can keep up to date with UK regulations here.

It can be tricky to choose a colour or finish using a tiny colour chart. Instead, get some pictures of existing facades with the colours or finishes you'd like to get a better idea of the end result. Better yet, have a look around your neighbourhood for inspiration!