External wall rendering

Types of External Wall Rendering

External wall rendering is the process of applying a thin layer of cement, lime, or acrylic-based mixture to the external walls of a house or building. It is commonly used for stone construction and aims to improve the wall's appearance, increase weatherproofing, and provide a base for painting or further decoration.

Depending on the wall's structure, various types of external wall rendering methods are used.

• Wet mix

  Three layers of this wet mix are applied to the external walls. The bottom layer is called scratch coat and is embedded with concrete grooves. After the cement has dried, concrete is scratched on the surface to form a rough texture. The second layer is called floating coat and is usually 10-12 mm thick. It is made of sand, cement, and lime that lend it more strength. It is smoothed to create an even surface. The final layer is called the finishing coat. It can be either a wet mix (thin cement slurry) or dry mix (thin layer of gypsum and lime), which gives the wall a polished look. This type of rendering is used in masonry walls (brick, stone, concrete).

• Dry mix

  In the dry mix process, the mortar mix is prepared and applied to the wall in a dry state. Water is then sprayed over it to activate the curing and hydration process. This helps reduce the cement paste required and speeds up the application process. Dry mix is normally used for single-coat renders with polymer add-ons over concrete blockwork and lightweight concrete.

• Monocouche renders

  Monocouche renders are premixed monolayers applied directly to background surfaces in a single pass without requiring scratch and float coats. They can be applied between 5 and 20 mm and come in many finishes and colors. Depending on the binder, monocouche renders can be cement-based or lime-based. They are typically used with polymer additives to increase flexibility, adhesion, workability, and impact resistance. The renders may be applied using hand or machine application methods onto solid walls with minimal through-wall voids. Machine-applied monocouche renders must be cement-based. Monocouche renders require solid, strongly adhering, and non-absorbent backgrounds. Using monocouche renders on lightweight, porous, and independence is not suitable because one through one background may rapidly absorb water and not adequately cure the mortar.

• Textured wall rendering

  Textured wall rendering is used artistic effects on the wall by creating different textures, such as smooth or rough, patterned or striped, etc. It consists of grinding the wall to remove any irregularities and making the surface prone to the glue. Subsequently, a texture pasty or spray is used to paint the wall with the desired pattern. Finally, the painted wall is protected with a varnish layer.

Specifications and Maintenance of External Wall Rendering

The external wall rendering is available in different formulations and specifications to meet various substrate conditions and architectural requirements. Here are some key specifications and their corresponding maintenance requirements.

• Thickness: The thickness of the external wall render can vary depending on the type of render and the desired finish. Typically, it ranges from 5mm to 25mm. Applying a suitable render with the correct thickness can improve the durability of the maintenance layer, thus reducing maintenance frequency.
• Textures: External wall renders offer a variety of texture options, such as scraped, dish, cat face, pebble dash, knockdown, etc. When cleaning the surface of the texture, care should be taken to avoid excessive force that may damage the texture. Use appropriate cleaning methods for different types of textures.
• Materials: Proper maintenance of the substrate can greatly extend the lifespan of the external wall render. Regularly check the substrate status, including promptly repairing or replacing damaged areas, ensuring good bonding, and preventing external interference, such as water damage and more.
• Colors: Color renders can fade or become discolored. Regularly inspect the rendered surface and promptly deal with the factors that cause discoloration. For example, remove pollutants, repair damage, and more.

In addition to the above, it is also important to maintain the surrounding environment of the external wall rendering. Avoiding areas with high pollution or excessive exposure to harmful substances can minimize the risk of damage to the rendering. At the same time, keep a proper distance from high-temperature, high-humidity, and other adverse environmental conditions to reduce the rendering maintenance burden.

Scenarios of external wall rendering

Many buildings and institutions use external wall rendering service. Here are some common applications of rendering walls.

• Residential houses

  Rendering improves the aesthetic appeal of beloved homes. It gives owners a chance to improve the beauty of their houses with different colors and textures. Once used to cover up rough bricks, wall renders have transformed into fashion statements for classic and contemporary houses.

• Commercial buildings

  Rendering is a popular way of beautifying external walls of commercial premises. Whether it is a storefront, office space, or hotel, attractive facades matter a lot. Rendering enhances visibility and makes a business come off as serious and professional.

• Public buildings

  Schools, universities, museums, hospitals, town halls and other public buildings often opt for rendering as a cheap and effective way to upgrade the external wall and boost durability. The highly customizable character of rendering allows local authorities to choose an appealing color that complements the neighborhood.

• Recreational centers

  Rendering gives community sporting and social facilities a welcoming look. Rendering improves aesthetic appeal and encourages people to work out and participate in social activities.

• Historic buildings

  Careful rendering of historical buildings helps to protect them. The building's significance, architectural characteristics, and traditional materials and techniques must all be taken into consideration in the rendering approach.

• Industrial buildings

  Rendering can change the unappealing look of industrial buildings. Factories, warehouses, and other facilities become more presentable with rendered walls. Durable rendering materials are often used because they are well-suited to locations with production activities and involve the movement of heavy machinery.

How to choose external wall renderings

Before purchasing external wall rendering materials, stakeholders such as business buyers, builders, and architects should evaluate several factors.

• Wall substrate compatibility

  The external wall render chosen must be compatible with the substrate it will be applied to. Whether the substrate is made of concrete, brick, block, or another material, good adhesion is promoted by compatibility between the substrate and render.

• Location and climate

  The climate in which a building is located and its geographical position are also key considerations for the choice of wall render. Various external renders are available that can withstand specific climatic conditions. For instance, buildings exposed to coastal environments with high salt concentrations need renders resistant to salt corrosion. Similarly, in locations where extreme temperature fluctuations occur, renders with low thermal conductivity that reduce thermal bridging are preferred.

• Design requirements

  The selected exterior wall render should meet the project's design and aesthetic requirements. Renders are available in various textures that can achieve different visual effects. Business buyers should consider the desired texture and look for the building and select the render that will achieve it.

• Budget considerations

  Budget constraints are an important factor in determining external wall renders. Business buyers should assess their budget and choose a render that meets their needs while remaining within their financial limits. It's also important to consider the total cost of the project, including labor costs and other materials.

External wall rendering Q&A

Q1. What are the pros and cons of external wall rendering?

A1. The main pros of rendering stone or brick walls are that it improves aesthetics, protects buildings against the weather, and enhances insulation and fire resistance. The main cons are that rendering is expensive, and if done poorly, it can affect the structural integrity of the building.

Q2. Can poor external wall rendering be corrected?

A2. If the rendering has air gaps, bubbles, or cracks, it can be partially or wholly repaired. Poor rendering can also cause dampness or water infiltration inside the building, which will need to be rectified. The only way to be sure is to call an expert who can assess the situation and recommend the right course of action.

Q3. Why should an expert do external wall rendering?

A3. An expert will ensure that the rendering comprises the right mix of materials for the underlying surface and climate. They will also ensure that the surface is prepared correctly, that the rendering is applied uniformly with the right tools, and that proper curing takes place afterwards.

Q4. What are some modern alternatives to traditional external wall rendering?

A4. Some modern alternatives include cladding systems, ventilated façades, texture coatings, spray-on polymer membranes, and external insulation and finishing systems (EIFS).

Q5. Is external wall rendering the same as a dash coat?

A5. No, a dash coat is a very thin coat of mortar applied to masonry units to enhance the bond of the subsequent layers. Rendering, on the other hand, refers to applying multiple layers of mortar for protective and decorative purposes.