All about gypsum plaster: a detailed article with tips and videos

Gypsum plaster has grown in popularity as a wall finishing material because it provides an easy-to-work-with, smooth, and long-lasting surface. Your project will go more smoothly if you know the ins and outs of gypsum plaster, whether you’re remodeling a single room or the entire house.

We’ll look at what makes gypsum plaster a popular choice for DIY enthusiasts and professionals in this post. We’ll walk you through the process by going over the fundamentals, offering practical advice, and even including some videos.

You’ve come to the correct spot if you want to learn more about plastering or if you want to get professional-looking results. Let’s explore all the information you require about gypsum plaster.

Application of gypsum plaster

Plaster mixtures with a gypsum base are generally used for finishing living room walls and ceilings, as well as other rooms with typical humidity levels.

It can be placed on the following bases:

• brickwork and clay walls;
• on top of concrete walls and cement plaster (needs concrete contact treatment);
• on old gypsum plaster, provided that it is strong enough;
• on cellular foam concrete, aerated concrete and expanded clay concrete;

Gypsum is only used for interior decoration in dry rooms when priming the surface for painting or wallpapering because of its moisture-absorbing properties.

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What is included in the composition

Building gypsum, or calcium sulfate hydrate, is the primary ingredient in this kind of plaster. It is made by burning gypsum stone and crushing it into a powder. The composition may additionally consist of:

• fillers that reduce weight and increase the heat-insulating properties of lightweight plaster: perlite, vermiculite, foam glass or expanded polystyrene;
• plasticizers and setting retarders;
• additives that increase the whiteness of the surface – salts of various metals (zinc or titanium white) or lime;
• components that increase their strength;
• additives that regulate the setting time of the solution and its hardening time.

Gypsum plaster poses no health risks and is an environmentally friendly material. Furthermore, because of its hygroscopicity, it can "breathe," or take in excess moisture and release it, controlling the microclimate in the space.

Gypsum polymer is a different kind of gypsum plaster. It is applied to concrete and brick surfaces to level them. In certain circumstances, gypsum polymer compositions can also be applied to exterior finishing projects.

Technical characteristics

GOST 31377-2008 governs the quality of mixtures on a gypsum binder. This document states that the following are the primary signs of dry material:

• humidity: the permissible moisture content is no more than 0.30% of the total mass;
• maximum size of granules (grains);
• bulk density: 800-1100 kg/m3 (in a loose bulk state) and 1250-1450 kg/m3 (in compacted form).

Characteristics of the ready-made solutions

• water consumption during mixing — 0.6-0.65 l/kg
• mobility: the ability to spread under the influence of its own weight; according to GOST 31376, the diameter of the spreading sample of the prepared solution (~600 g) should not exceed 165 mm (±5);
• setting time — at least 90 min for machine-applied mixtures and 45 min for manual plastering;
• complete drying time — after 5-7 days; this indicator depends on the additives in the mixture and varies among different manufacturers; you can find out exactly how long the plaster dries in the instructions on the packaging;
• the ability to retain moisture without allowing it to drain: at least 90%;
• consumption for a 10 mm layer — 8.5-10 kg/m2 (manual application) and 7.5-9 kg/m2 (machine application).

The following characteristics of hardened gypsum plaster:

• compressive strength – 2.5 MPa;
• surface adhesion force – 0.3 MPa;
• density – 950 kg/m3;
• vapor permeability – 0.11-0.14 mg/ppa;
• thermal conductivity – 0.25-0.3 W/m*C;
• shrinkage – does not shrink

While not governed by GOST, vapor permeability—the capacity of plastered surfaces to transfer water vapor—is a crucial technical attribute that establishes the plaster’s range of applications.

The shelf life of gypsum mixtures should be carefully considered before making a purchase. They should not be kept in storage for more than six months after the date of release because of how quickly they absorb moisture. After this time, they start to clump and lose their original qualities, making it difficult to level walls of high quality with them. It’s important to consider the packaging’s tightness as well, as this guards against excessive moisture; plaster shouldn’t be purchased in ripped bags.

Pros and cons

The primary drawbacks ofthis content consist of

• Low moisture resistance;
• Low strength – a surface plastered with gypsum can be scratched or chipped quite easily.
• The cost is slightly higher than the cement-sand mixture, about 15-20%, but this is an insignificant disadvantage.

However, gypsum still has a lot more benefits.

• High plasticity: working with gypsum mortar is easier than with others; the labor intensity of the process is significantly reduced, and this is a significant plus;
• No shrinkage: for cement mixtures it is a couple of millimeters per square meter;
• Surfaces plastered with gypsum are smoother, without pores or graininess;
• Good adhesion: gypsum mortar adheres to the surface much better than sand-cement; therefore, you can not use a reinforcing mesh to strengthen the surface; it is required only in new buildings due to possible shrinkage of the building;
• Good heat and sound insulation properties: a wall covered with a layer of gypsum retains heat and protects against noise better than concrete surfaces;
• It can be applied in a thicker layer (up to 50 mm) without a reinforcing mesh;
• Light weight: walls covered with gypsum put less load on the foundation;
• Efficiency: when comparing costs, many people only pay attention to the weight of the pack; however, it is also necessary to take into account the specific gravity of the mixture – after all, the consumption of gypsum per 1 m2 is 9-10 kg, while cement for plastering the same area will require 16-18 kg.

A common explanation for gypsum’s benefits is that it sets faster than cement-sand mortar. That said, it is hard to characterize this as a major benefit. In fact, gypsum plaster treated surfaces harden 1-1.5 hours faster than cement composition-coated surfaces.

Working with it should not be delayed because it will be difficult to smooth out the solution as it begins to solidify. If working alone, do not dilute too much of the mixture. It is preferable if one person works on preparation and the other applies plaster.

Smooth, long-lasting walls and ceilings can be achieved with the help of gypsum plaster, a material that is both easy to work with and adaptable. This article will walk you through the advantages of gypsum plaster, show you how to apply it, and provide helpful hints to ensure the best possible outcome. You can also watch useful videos to see the procedure in action.

How to dilute a dry mixture

Let’s talk about the proportions and preparation method for gypsum mortar. A prepared container that has already been filled with water is filled with a dry mixture from a bag. The instructions state that 600–700 ml of liquid are needed for every kg, or roughly 20 liters of water for a 30-kg bag of gypsum.

Using a trowel or trowel, a small amount of solution can be simply mixed. It is preferable to use a construction mixer or a hammer drill with a mixing attachment if producing big quantities by hand is difficult.

Based on the components’ reaction times, the solution should stand for three to five minutes. After that, it is thoroughly mixed once more until all lumps are gone. In any case, the solution should be plastic and viscous, but it should never flow off the tool.

Gypsum plasticizers

The manufacturers strongly advise against adding any foreign additives to ready-made mixtures. Ultimately, overuse of plasticizers can adversely impact the ultimate surface strength.

On the other hand, you can easily create gypsum-based mixtures at home using your hands; one such mixture is a somewhat plastic lime-gypsum. However, gypsum and water react quite quickly, which is why gypsum plaster hardens quickly.

It is necessary to add one of the plasticizers to a solution in order to make it suitable for work:

• diluted PVA glue, about 1% of the total volume;
• lime, is used as a plasticizer and to increase the hardening time;
• tartaric, citric acid will also slow down the setting. Special liquids, for example, Plast Retard PE, can extend the setting time to several hours, prevent cracks and improve the wear resistance of gypsum.

Application in damp rooms and outdoors

Gypsum plaster can absorb moisture, as we have already discussed, so it is not recommended to use it in damp rooms, especially when finishing a facade.

If the gypsum surface needs to be made moisture-resistant (for instance, when getting ready to tile the bathroom), a deep penetration primer on an acrylic base is applied. For tiles, Betonokontakt primer is perfect.

For example, "Plitonit Gidroelast," a polymer waterproofing mastic, has good moisture-proof qualities. Using a brush or roller, it is applied in multiple layers over a plaster layer that has completely dried. After the prior one has dried, each one needs to be applied. After application, tiles can only be glued a day later. It is advised to use this mastic to seal pipe exits and the corners of different buildings.

A great option for building smooth, long-lasting walls with a polished appearance is gypsum plaster. It’s a common option for both new construction and renovations because it’s simple to apply and works well on a range of surfaces.

Using the proper tools and techniques when applying gypsum plaster is essential to getting the best results. Whether you’re an experienced professional or a do-it-yourself enthusiast, knowing the essential steps will guarantee that your walls look perfect.

Gypsum plaster can change your walls and give them a long-lasting, sleek, modern look if done properly. You can confidently navigate the process with the help of the advice and videos provided in this article.

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