This article is about how to repair plaster on concrete walls, plaster on concrete ceiling, plaster concrete mix, concrete plaster wall finish, gypsum plaster over concrete, concrete plaster thickness and methods of plastering pdf.
Methods of Plastering Concrete Surfaces
Plastering a concrete surface involves the use of a lean mortar to improve its appearance. This process is carried out using various methods, depending on the type of concrete surface being worked on. These can include dense concrete, low-weight concrete, and mixed concrete surfaces.
The purpose of plastering is to create a smoother, more polished surface that looks visually appealing. By applying a thin layer of mortar, any imperfections or roughness on the concrete surface can be smoothed out. Overall, plastering is an effective way to enhance the aesthetic appeal of concrete surfaces.
Plastering is the process of applying a layer of plaster to a surface, usually for decorative or protective purposes. When plastering on concrete, it’s important to prepare the surface by cleaning it thoroughly and ensuring that any cracks or holes are filled in before applying the plaster. The plaster should be applied evenly and allowed to dry completely before sanding and smoothing out any rough spots.
Plastering on different surfaces requires different techniques and materials. For example, plastering on drywall may require the use of joint compound to fill in seams and create a smooth surface, while plastering on brick or stone may require a thicker coat of plaster to cover the rough surface. It’s important to research the specific requirements for each surface before attempting to plaster it.
Safety is a crucial aspect of plastering work. Plaster contains harmful chemicals, so it’s important to wear protective gear like gloves, goggles, and a mask to prevent inhalation and skin contact. It’s also important to work in a well-ventilated area and to take breaks if necessary to prevent overexposure. Finally, it’s important to follow all safety guidelines and regulations to ensure that the plastering work is completed safely and without incident.
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Plastering Procedure on Concrete Surface
There is following steps for plastering of concrete surfaces:
1. Concrete Surface Preparation
Before beginning the plastering process, it is essential to prepare the surface of the concrete that will be receiving the plaster. This preparation involves removing any peeling paint or flaking bits of old plaster that may be present on the surface. These imperfections can prevent the plaster from adhering correctly and compromise the quality of the finished product.
In addition to removing any old plaster or paint, it is crucial to ensure that the surface is free from any other contaminants, such as oil or dust. If the surface is not properly cleaned, these substances can also prevent the plaster from bonding effectively. Proper cleaning and preparation of the concrete surface are essential to achieve a smooth and durable plaster finish.
2. Treating with Slurry
To ensure that plaster can adhere properly to a concrete wall, it is essential that the wall’s texture is sufficiently rough. To achieve this, a slurry or dash is applied to the surface of the concrete. The slurry is created by combining one part cement with one and a half parts coarse sand, and then adding enough water to create a runny consistency.
The purpose of the slurry is to create a rough texture on the surface of the concrete, which will allow the plaster to adhere more effectively. This is particularly important in cases where the wall is being plastered for decorative purposes, as a smooth finish is typically desired. By applying the slurry, the plaster can be more easily applied and will be less likely to crack or peel over time.
The process of preparing the slurry is relatively straightforward, and can be accomplished with basic building materials. It is important, however, to ensure that the correct ratios of cement, sand, and water are used to achieve the desired consistency. With the right mix, a slurry can effectively prepare a concrete wall for plastering, providing a long-lasting and attractive finish.
3. Mixing of Plaster
To obtain the desired consistency of plaster for a particular task, an appropriate amount of fine aggregate (sand), cement, and water is mixed together. It is crucial to ensure that the mixture is proportioned correctly to achieve the desired consistency.
It should be noted that the prepared plaster has a limited lifespan and must be used within two hours. After this time, the mixture may become unworkable and lose its intended properties, making it unsuitable for use. Therefore, it is important to plan the plastering process carefully to ensure that the plaster is used within the specified timeframe.
Overall, achieving the correct consistency of plaster is crucial for the success of any plastering project. By using the appropriate amount of fine aggregate (sand), cement, and water and ensuring that the plaster is used within two hours, one can achieve a high-quality finish that meets the desired standards.
4. Apply the Plaster
To begin the plastering process, a base coat of plaster is applied over the layer of dash using a steel trowel. This layer should have a thickness within the range of 10 to 15 mm. During the application, it is important to use small strokes and ensure that the layer is level and uniform.
It should be noted that if the plastering is to be completed in just one layer, then the thickness of the plaster must not exceed 10 to 15 mm. Additionally, when applying the final top coat, the thickness should be kept between 5 to 10 mm. By following these guidelines, a smooth and even plastered surface can be achieved.
5. Curing of Plaster
When working with plastered concrete walls, it is important to allow the plaster to harden and set before proceeding with further steps. Once the plaster has achieved this state, the process of curing must be initiated and maintained for a period of seven days. During this time, the plaster will continue to dry and reach its full strength.
After the plaster has fully cured and the walls have dried, they will be ready for additional decorative touches such as paint or wallpaper. These finishes can be applied with confidence, knowing that the plaster has fully set and is prepared to hold the new decorative layer securely in place. By following these steps carefully, it is possible to achieve a durable and aesthetically pleasing finish for any concrete wall surface.
6. Plaster Thickness
When using Thistle Bond-it or other bonding agents in conjunction with an undercoat, it is important to ensure that the thickness of the undercoat does not exceed 11mm for walls or 8mm for soffits. This is because thicker layers may result in poor adhesion and cracking of the plaster.
To achieve a smooth and even surface, it is recommended that the finish coat applied over the undercoat should be 2mm in thickness. However, in areas where greater thicknesses are required, such as in the case of structural irregularities or uneven surfaces, it is necessary to use expanded metal lathing to provide additional support.
The expanded metal lathing should be mechanically fixed to the concrete surface before applying the plaster. This will provide a secure base for the plaster to adhere to and prevent any cracking or movement over time. By following these guidelines, it is possible to achieve a high-quality plaster finish that is both durable and long-lasting.
7. Plastering in Dense Concrete
The use of plaster on dense concrete surfaces is often problematic as the low porosity and smoothness of the surface can prevent the plaster from adhering properly. According to Section 4 of BS 5492:1990, bonding treatment can be used to address this issue, as such treatments can help to improve adhesion on surfaces with little suction and no mechanical key.
One option for preparing the surface of concrete is to use mechanical methods like scabbling or shot blasting. These techniques can remove any contamination from the surface and roughen it, which can improve adhesion. However, these methods alone may not be enough to prevent failure, as they do not increase surface absorption.
It’s important to note that concrete should not be plastered until it has had sufficient time to dry out after the shuttering has been removed. Plastering should never begin if there is free water on the surface of the concrete. However, on most new building sites, waiting for the concrete to air dry completely may not be practical since it can take months or even years in some cases.
One relatively safe option for plastering concrete is to apply the plaster to expanded metal lathing that is plugged and screwed to the concrete. While this method can be expensive, it can help ensure that the plaster adheres properly and prevent failure.
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8. Plastering on Lightweight and No-Fines Concrete
Fully compacted lightweight aggregate concrete has a different thermal movement value compared to plaster. Additionally, when it hardens, it can develop a dusty surface with high suction, which can make plastering difficult. However, this issue can be addressed by using a suitable bonding treatment such as a PVAC bonding agent or Thistle GypPrime.
Thistle GypPrime is designed to prevent the rapid dehydration of undercoat plaster that can occur with high suction backgrounds. To apply Thistle GypPrime, thin it with water based on the absorbency of the background and use a suitable roller, brush, or spray. Make sure that the solution is completely absorbed, and no shiny film remains on the surface before starting plastering.
It is crucial to wait until Thistle GypPrime is entirely dry before starting the plastering process. On the other hand, a no-fines concrete is an ideal material for plastering. It contains many large voids that provide an effective key for plastering. Therefore, plastering on no-fines concrete is relatively easy compared to compacted lightweight aggregate concrete, which requires bonding treatment before plastering.
9. Plastering on Mixed Concrete Surfaces
When continuing plastering across different backgrounds, there is a risk of cracking due to differential movements. However, this can be minimized by fixing expanded metal across the junction. This method is especially useful for small widths of one material, such as a concrete column dividing brick panels. In such cases, it is best to bridge the entire column width by fixing expanded metal over building paper onto the abutting brickwork. This will help isolate the plaster from any differential movement that may occur.
Another option to prevent unsightly irregular cracking at the junction of dissimilar materials is to make a straight knife cut through the plaster along the line of the junction. This can be done when cracks are expected to form in the plaster. By making this cut, the formation of irregular cracks can be prevented.
Alternatively, back-to-back beads may be fixed over the junction instead of making a knife cut. This involves fixing beads on both sides of the junction to provide a smooth finish. This method can be used as an alternative to a knife cut and is often preferred in situations where a more polished finish is desired. Overall, there are different methods that can be used to minimize cracking at the junction of different materials during plastering, and the choice of method will depend on various factors such as the materials involved and the desired finish.
Examples of treatments at junctions of solid backgrounds and dissimilar materials
10. Points to Remember in Plastering Concrete
When working with concrete, it is advisable to avoid plastering it as much as possible. However, in cases where plastering cannot be avoided, it is recommended to use concrete mixes that contain flint aggregate specifically for areas that require plastering.
To ensure proper application of plaster, it is recommended to use a light application of a chemical release agent instead of mould oils. Prior to applying the plaster, the concrete surface must be checked for contamination, and appropriate action should be taken. Additionally, surface dust must be removed from dense concrete surfaces, and a suitable bonding agent such as Thistle Bond-it should be applied. For absorbent backgrounds, GypPrime is a suitable alternative.
When applying the plaster, it is essential to use firm pressure. After the plaster has hardened, it is essential to check for the development of hollowness as the plaster dries out. This is particularly important when heating the building for the first time. To prevent damage to the plaster, it is recommended to avoid suddenly heating the building. Instead, it is best to increase the temperature gradually.
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11. Personal Protection for Plastering
When working in an area where there is dust, it is important to ventilate the space to ensure that the air is clean and safe to breathe. However, if the dust cannot be controlled, it is recommended to wear a half face mask that meets the standards of EN 149 Class FFP1. This will help protect the respiratory system from harmful particles that could be inhaled.
To protect the skin from prolonged or repeated wet contact, it is important to wear impermeable gloves, protective overalls, and safety footwear. These items will create a barrier between the skin and any hazardous substances that may be present. Additionally, applying a barrier cream to the hands can further reduce the harmful effects of skin contact.
If working with plaster powder or there is a risk of splashes, it is important to wear safety goggles that meet the standards of BS EN 166 type 2A5. This will help protect the eyes from harmful particles that could cause irritation or injury. By taking these precautions, workers can ensure that they are protected from potential hazards and can work safely and effectively.
Read Also: Heat Resistant Concrete Installation and Applications
References
BS 8000-10: 1995 Workmanship on building sites. Code of practice for plastering and rendering.
BS 5492: 1990 Code of practice for internal plastering. Chemicals (Hazards Information and Packaging for Supply) (CHIPS) Regulations 1994
concrete plaster wall finish, gypsum plaster over concrete, concrete plaster thickness and methods of plastering pdf.
FAQs about Methods of Plastering Concrete
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1. How to repair plaster on concrete walls?
To repair plaster on concrete walls:u003cbru003e1. Remove loose or damaged plaster.u003cbru003e2. Apply a bonding agent.u003cbru003e3. Mix plaster and apply it evenly.u003cbru003e4. Allow the plaster to dry.u003cbru003e5. Sand the surface and apply primer and paint.
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How to do plaster on concrete ceiling?
To repair plaster on a concrete ceiling:u003cbru003e1. Remove any loose or damaged plaster.u003cbru003e2. Clean the surface and remove dust and debris.u003cbru003e3. Apply a bonding agent to help the new plaster adhere to the ceiling.u003cbru003e4. Mix the plaster according to the manufacturer’s instructions.u003cbru003e5. Apply the plaster evenly to the ceiling using a trowel or putty knife.u003cbru003e6. Smooth the surface of the plaster and allow it to dry completely.u003cbru003e7. Sand the dried plaster if necessary to achieve a smooth finish.u003cbru003e8. Prime the repaired area and paint it to match the surrounding ceiling.
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How to do plaster concrete mix?
To make a plaster concrete mix, combine cement and sand in a ratio of 1 part cement to 3 parts sand. Gradually add water while mixing until you achieve a workable consistency. Apply the mixture to the desired surface using a trowel or putty knife. Allow it to cure according to instructions or standard concrete curing times.
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How to do concrete plaster wall finish?
Concrete plaster wall finish refers to the application of a layer of plaster onto concrete walls to achieve a smooth and decorative surface. The process typically involves preparing the wall surface, applying a base coat of plaster, and then adding a finishing coat to achieve the desired texture or appearance. The plaster can be customized with pigments or additives to create various colors and effects. The finished result is a durable and visually appealing wall surface that enhances the aesthetics of the space.
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Gypsum plaster over concrete?
Gypsum plaster over concrete refers to the application of gypsum-based plaster onto concrete surfaces. It is a common technique used to create smooth and even finishes on concrete walls or ceilings. The process involves preparing the concrete surface by cleaning and priming it, applying a basecoat of gypsum plaster, and then finishing it with a topcoat for added smoothness. u003cbru003eu003cbru003eGypsum plaster provides excellent adhesion to concrete and offers a high-quality finish that is resistant to cracking and shrinkage. It is a popular choice for interior applications as it provides a smooth, durable, and aesthetically pleasing surface for painting or other decorative treatments.
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What is concrete plaster thickness?
Concrete plaster thickness can vary depending on the specific application and requirements. In general, the thickness of concrete plaster can range from 10mm to 20mm (0.4 to 0.8 inches) for interior walls and ceilings. For exterior surfaces, such as concrete facades, the thickness may be greater, typically ranging from 20mm to 25mm (0.8 to 1 inch) or more. u003cbru003eu003cbru003eIt’s important to consider factors such as the desired finish, structural integrity, and the substrate’s condition when determining the appropriate thickness for concrete plaster. Additionally, specific project specifications and local building codes may provide guidelines for minimum and maximum plaster thickness. Consulting with a professional contractor or engineer can help ensure the appropriate thickness is chosen for your specific project.