Exploring the Techniques and Materials Used in Plastering: A Comparative Study with Other Methods and Future Recommendations

1. Introduction

Plastering is a widely used finishing method that involves the application of a layer of material over walls, ceilings, and other surfaces to provide a smooth and even texture. It has been used for centuries across various cultures and regions, with its benefits being well documented in ancient architectural treatises. Plastering can be considered both an art and a science, where various materials including gypsum, cement, clay, lime, and chemical plasters can be effectively employed to achieve a fine finish. Over the years, a wide variety of plastering materials and methods with diverse performance based on the constituent raw materials, additives, and proportions have been studied and implemented.

The use of mortar, a mixture of binding materials and aggregates, has been widely documented in research that varied the plaster mix proportion with the investigated performances like strength, density, durability, thermal, and acoustic efficiency. Recently, there have been a fair number of reports related to the analysis of plastering methods by the degree of mechanization. Some reports study simpler forms of mechanized plastering methods and roof plastering devices, while some explore automatic robotic techniques for plastering wall surfaces of complex forms and building structures. Building automation with machine-assisted plastering is a newer research interest.

There are various plastering methods with respect to the level of mechanization in common use, which include hand plastering, mechanically assisted plastering, semi-automatically controlled plastering, and fully automatically controlled plastering. Selective plastering methods and comparative analyses of plastering methods with respect to the mode of mechanization have been documented. This work aims, however, to provide a broader overview of diverse plastering materials and methods used in a selective manner in residential buildings of particular geographical regions with diverse building codes in relation to climate, availability of local raw materials, socio-cultural, and economic factors. Globalization has altered the use of plastering materials and methods in some regions, while parts of the world still rigidly adhere to the primitive methods of plastering with little or no change even after the advent of complex construction technologies. Comparison with other finishing methods currently in practice has also been presented where possible, followed by recommendations for improvement.

2. Historical Overview of Plastering Techniques

It is a well-known fact that plastering has been around since the days of the Ancient Egyptians, if not longer. A great deal of speculation surrounds the origin of the skilled trade that is plastering. The coat that is plastered on a coat of masonry has served its purpose as a protective covering. However, in addition to its protective function, the plaster has provided an opportunity for creativity and decoration, especially the finer work, which in grand buildings may be enriched with moldings and reliefs painted to imitate rich materials such as wood, marble, alabaster, or precious metals.

The first coat that was rendered was a rough coat, formed to receive subsequent finishes. It was not until the plaster was sufficiently dry to cope with normal wetting, and this often took weeks, that shallow surfaces conceived in plan were cut into the screed. The finished coat consists of a plaster finish made with gypsum or lime plaster applied thickly and richly, not smoothed, plastered to the areas of shadow and raised to the edges and prominent angles to imitate jet work. (Cassar)

Lime plaster is made with lime, aggregate, and water, and where necessary, a pigment. First, the dry lime is mixed with the aggregate and any pigments. The limewater is then added and the mixture worked together to form a mortar sufficiently white, light, and pliable to render satisfactorily. Each batch is then tested for suitability by throwing a portion at the wall where it should stick, and if this does not happen then it is discarded. Several batches of different mixtures are prepared, and four, six, and eight layers are then alternately laid, cut, pressed, scraped, and polished smooth. (Cassar)

3. Types of Plastering Materials

Undoubtedly, plastering is one of the final processes in civil construction that enriches the beauty of the structure. Though there are several modern methods for plastering, this text focuses on one of the age-old methods of cement plastering. Starting from materials, processes, and workmanship to all the modern approaches, a detailed explanation is given here, and for all the steps taken, suggestions for improvement are provided. These suggestions focus mainly on machinery and materials for plastering. Joint fillers available in the present market can be used to plaster vertical and overhead surfaces. Though these fillers are costly, an economical choice of fillers would benefit sites where plastering is on a large scale. Carrying out plastering in 4 MPa concrete instead of 20 MPa or 25 MPa concrete would minimize material costs and be highly beneficial for cost-concerned projects. Using a mixture of plastering machine mortar and normal plastering mortar would achieve the planned thickness in a single coat instead of having two coats of plastering. (Ercan et al.2020)(Xu et al.2022)

Plastering is also referred to as the application of a thin layer of mortar or concrete over a brick masonry wall, stone masonry wall, concrete surface, etc., to make the surface flat and smooth. Easily workable materials are selected for plastering over the substrate to fill all voids, honeycombs, and dents and to achieve a level surface. The material used for plastering can be either cement plaster or gypsum plaster. There are many modern techniques of plastering, and most of the modern techniques are similar to the automatic plastering machine; it carries out plastering in roof panels, wall panels, columns, etc., and for vertical surface plastering, this machine demands a plastering mortar with a 4 mm size restriction. However, the present study mainly deals with the method of plastering using cement mortar and gypsum mortar. (Nascimento et al.2020)

Modern machines adopt proportioning, mixing, and applying in a central location, and it is equally important to select mortar proportion and type to achieve the desired surface finish. Moreover, there are no proper guidelines or broad studies available to fabricate these machines and to design or choose mortar for these machines in the Indian scenario. Therefore, keeping this in mind, an attempt has been made to study the types of plastering mortars available in the present scenario, their composition, workmanship, and performance of plastering using automatic machines, its issues, and remedies. In addition, the design of mortar types suitable for plastering using automatic machines is provided. (Scott & Ali, 2021)

4. Techniques and Tools Used in Plastering

Plastering is an age-old method employed to protect or supply an adequate finish to walls or ceilings and is extensively used in building structures. Despite the increasing industrialization in construction methods, plastering is still considered one of the most durable and less expensive finishes. It is usually a thin coating of mortar to give a smooth finish to the surface. Plastering is much in demand as it provides protection against atmospheric elements, fire, and has a decorative effect. A systematic approach is being undertaken to explore the various techniques used and tools required for plastering. It includes both the latest and traditional practices of plastering ceilings and walls.

Plastering consists of a mixture of ingredients in a certain proportion, which, when mixed, bind together and harden. The properties of plaster depend on the materials used, the methods of preparation, and the way of applying it. The work reports the study of various techniques, availability, and tools required for plastering. Further, the comparative study is also aimed at understanding the advantages and disadvantages of the different techniques and tools.

The tools and techniques required for plastering are reviewed and presented as follows: The traditional and basic tools are directly used on the plastering surface by an individual worker, while some tools require additional manpower support. The latest tools include machines that plaster automatically. In this type of plastering, machines will be provided on-site to plaster the wall surface, and in a labor-intensive application, plastering would be manual, which comprises placing individually adopted tools to plaster the surface. (Ercan et al.2020)

5. Comparative Analysis with Other Building Finishing Methods

Plastering has been a traditional method of finishing walls for many years and has its advantages and disadvantages. Nevertheless, many other methods can compete with plastering. This text aims to highlight some of the building finishing methods that are in competition with plastering, including drywalling, external wall cladding, and rendering. These methods were scrutinized and compared with plastering in terms of their techniques and materials being used, overall cost evaluation, suitability to different climatic conditions, performance on flexibility to damage and longevity, and advantages and disadvantages with recommendations for future research and improvements.

Drywalling, also known as gypsum board, is a modern method of wall finishing that provides a smooth, finished surface. The material consists of a flat plasterboard sandwiched between two layers of paper, coated with a finishing material. The finishing plaster is applied using a metal tape, which is first fixed to the joints. The tape is then plastered over and feather-edged to create a smooth surface. Volatile gases emitted from drywalling can be a nuisance, posing a disadvantage. Additionally, gypsum board is more prone to damage from impact loads compared to plastered walls, which are better suited for countries that experience heavy earthquakes. The overall plastering cost is approximately 25% of the drywalling method. (Hulathdoowage & Hadiwattage2022)

External wall cladding is an external surface finishing that can be made with different materials, such as wood, bricks, and glass. Its technique and material depend on the desired surface finish. External wall cladding helps protect walls from the effects of weathering. Like drywalling, it is also prone to regular maintenance. Wood cladding-treated surfaces require replacement after every 3 to 5 years as a good absorbent material for moisture. Importantly, it comes at high costs ranging from 50% to 495% compared to plastering, depending on surface materials used.

Rendering is a method of finishing walls with solid materials, such as cement, lime, and concrete. It helps prevent the permeation of moisture; however, mixture ratios heavily depend on climatic conditions. Rendering walls with 1:2 hollow cement bricks is recommended for tropical wet climates to resist pressure from soil moisture against the wall. It fails under heavy seismic loads and is prone to cracking and crazing on concrete surfaces due to brittleness. Also, its window detailing requires careful design while rendering. Inside building rendering coatings are highly porous and absorbent, dampening inside surfaces. (Muhammed et al.2024)

6. Future Trends and Recommendations for Plastering Studies

Future trends in plastering technology are geared towards innovation that is environmentally conscious and economically advantageous, focused on the demand from architects and project developers for renewable technology regarding plaster material and application. Researchers advocate for the use of bio-based construction materials in building plastering. Bio-based plaster is a smart choice because of its availability, low ecological and carbon footprints, and energy efficiency advantage in terms of thermal insulation properties during extreme weather. The smooth internal wall surface of bio-based plaster is also ideal for painting with water-based paints, enabling the application of other mural techniques that are not suitable for painted lime or plaster surfaces, such as oat straw, cork, and hemp. These surfacing techniques can be applied with as little as a 6mm-thick bio-based plastering layer. Referring to the discussion on environmental awareness, regardless of whether it is a family house, school, or office building, it will be forbidden to build a new house or large building made completely of concrete, bricks, and plastic foam. Plastering with bio-based materials is being investigated throughout building projects with a focus on the entire building climate concept. An educational building as a demonstration object is to be transformed from a consuming building into a self-sufficient bio-based energy unit. There will be a focus on transparent outside walls, maintaining building shells solar passive during summers, and bio-based energy plants for heating and cooling. It is also being investigated how to move this building into the eve of its life span, ending up as a decaying building. What buildings decay into, how materials can be recovered for reuse, and how bio-based materials can be applied when the building bio-degrades into dust are considered. As bio-based end-of-life plastering is well documented and better known than other materials, their properties and gluing abilities are being studied. The decay properties of usual clay-based stony and straw and non-stony lump bio-based plasters are studied due to their bio-composite wall structure. Regarding recommendations, a plastering standard specification according to EN 998-1 or equivalent national standards is recommended. In Sweden, the Swedish Institute for Standards is being delegated to prepare Swedish standards according to EN 998-1 and monitor the plastering market before and after its arrival. The aim is to find out plastering standards and performance criteria used in other countries, so a similar approach can be taken in Sweden. (Marut et al., 2020)(Laveglia et al.2024)

References:

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Xu, Z., Zhu, Z., Zhao, Y., Guo, Z., Chen, G., Liu, C., Gao, J. and Chen, X., 2022. Production of sustainable plastering mortar containing waste clay brick aggregates. Case Studies in Construction Materials, 16, p.e01120. sciencedirect.com

Nascimento, A.S., dos Santos, C.P., de Melo, F.M.C., Oliveira, V.G.A., Oliveira, R.M.P.B., Macedo, Z.S. and de Oliveira, H.A., 2020. Production of plaster mortar with incorporation of granite cutting wastes. Journal of Cleaner Production, 265, p.121808. [HTML]

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Muhammed, A., Folorunso, C.O. and Fadairo, G., 2024. Assessment of sandcrete hollow blocks’ thermal performance as a walling material for tropical buildings in Lokoja, Nigeria. International Journal of Building Pathology and Adaptation, 42(4), pp.653-671. [HTML]

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Laveglia, A., Ukrainczyk, N., De Belie, N. and Koenders, E., 2024. Cradle-to-grave environmental and economic sustainability of lime-based plasters manufactured with upcycled materials. Journal of Cleaner Production, 452, p.142088. sciencedirect.com