Comparing the properties of gypsum and cement plaster: when which is better to choose, and can they be mixed?

The choice between cement and gypsum plaster when plastering walls can have a significant impact on the outcome. Each material has distinct qualities of its own, and knowing these will help you determine which is most appropriate for your particular project.

Gypsum plaster is highly regarded for its effortless application and silky sheen. It is ideal for interior walls where a smooth, even surface is required and it sets quickly. Conversely, cement plaster is well-known for being robust and long-lasting, which makes it perfect for exterior walls or damp areas.

What occurs, though, if you require the advantages of both? Should gypsum and cement plaster always be applied separately, or can they be combined? We’ll examine the benefits and drawbacks of each material in this post to assist you in choosing wisely for your upcoming plastering project.

Properties of gypsum and cement plaster

Cement-sand and gypsum plasters have quite different properties. The binder base is mostly to blame for this. Similar application circumstances will apply, with a room or street temperature between +5 and +25 C. Furthermore, the solutions dry completely in an enclosed space with an air humidity of no more than 70%.

The variations between these kinds of plaster are displayed in the table below.

Comparison of advantages and disadvantages

Cement plaster benefits include:

• the solution can be prepared independently;
• not afraid of moisture, does not absorb water, steam from the air, does not change properties when wet;
• resistant to temperature changes;
• high adhesion (reliability of adhesion to surfaces), including natural, artificial stone, concrete, brick, cinder blocks;
• the highest strength of all types of plaster, suitable for finishing places with increased operational load;
• the lowest price among all plasters;
• universality — suitability for any surface, including rooms with unfavorable conditions.

Frost resistance must be taken into consideration while selecting a mixture for outdoor maintenance. Usually, the number of freeze-thaw cycles is used to express it.

The benefits of gypsum plaster

• plasticity;
• gains strength faster than cement, even when applied in the thickest layer – no more than 1 week;
• easy to apply, easy to achieve perfect evenness, no experience in finishing work is required;
• no shrinkage;
• white color, does not show through under wallpaper or paint;
• the surface is smoother, experienced craftsmen bring the finishing layer to the level of putty;
• it is possible to make three-dimensional patterns and decorative relief;
• lightweight, there is no need to strengthen the foundation and walls;
• does not need reinforcement (if the layer is up to 50 mm);
• vapor permeability – walls plastered with gypsum mortar "breathe";
• higher sound and heat insulation properties;
• lower material consumption;
• faster repair times;

We go on to compare the finishing materials and take a look at their shortcomings.

Cement-sand plaster solutions’ drawbacks:

• poor adhesion to wood, paint, ceramics; To increase adhesion with these materials, an abrasive primer, notch or a reinforcing mesh are required, but these measures do not always give the desired strength;
• The final strength is gained for a long time – up to 4 weeks;
• The application process is relatively complex, the solution under its severity is inclined to the influx; Experience with such material is necessary, otherwise it will not be possible to achieve a perfectly flat surface;
• The finished surface is porous, it requires grout, grinding, an additional finish layer from another material (this does not apply to decorative plasters);
• an accurate calculation of the load on the wall and foundation is necessary, since cement plaster has a high density and significantly makes the walls heavier; it is also undesirable for finishing ceilings;
• gives shrinkage, possibly cracking.

Plasticizers are modifiable additives that can be added to to mitigate most of these drawbacks.

Lime enhances the solution’s qualities as well. See our article for more information about cement-license plaster and its characteristics.

Applying in three layers or covering a plastered surface alerts the user to the potential for cracks. Putty is needed if the cement mixture is used to decorate the walls and ceiling in preparation for painting or pasting wallpaper.

The drawbacks of gypsum plasters include:

• They are afraid of high humidity, when in contact with water, they swell and fall off;
• low strength;
• relatively high cost;
• They are mainly used by finished gypsum mixtures, for independent selection of additives to gypsum and their proportions, experience is required;
• the solution can only be prepared in small portions due to rapid setting, adding water to the hardened mixture will not restore the desired properties of the plaster, the coating will be fragile.

Understanding the special qualities and recommended uses of each material is crucial when choosing between cement and gypsum plaster. Gypsum plaster is ideal for interior walls where moisture isn’t a problem because it has a smoother finish and dries faster. Cement plaster, on the other hand, is more resilient to moisture and more appropriate for exterior walls or damp settings. Combining the two is usually discouraged since it may lessen their respective advantages. Understanding when to use each type of plaster will guarantee your walls a high-quality, long-lasting finish.

Where it is used

Uses for cement plaster include:

• interior or exterior work in any premises, even in unheated and damp ones, including basements, utility rooms, garages, entrances, balconies, loggias;
• finishing facades, basements, fences, especially those exposed to aggressive mechanical influences;
• filling joints when laying walls from foam or gas blocks;
• processing concrete structures in order to improve thermal insulation properties;
• restoration, subject to compatibility with the previous material;
• finishing surfaces exposed to temperature changes;
• decoration of walls or ceilings where frequent repairs are impossible.

Uses for gypsum plaster include:

• leveling, finishing interior walls in rooms with normal humidity;
• ceiling decoration;
• leveling walls with large differences, application in several layers is permissible;
• finishing surfaces for which cement is unsuitable – wooden, painted, ceramic;
• preparing walls and ceilings for painting or wallpapering.

Crucial! Because of their poor resistance to moisture, gypsum mortars are not appropriate for finishing the facade. It is not advised to install additional waterproofing in kitchens, bathrooms, or showers.

Gypsum can be treated against moisture by using an acrylic primer. Additionally, the walls are tiled or covered with waterproofing mastic if direct contact with water is possible.

Combination of gypsum and cement

Is it feasible to use putty or gypsum plaster over cement? Indeed, this is a standard procedure. When finishing, walls are frequently coated with a smooth layer of Rotband after using a cement-based composition.

Important guidelines: make sure to apply a primer in between each layer after the base has dried.

However, covering a gypsum wall with cement plaster is not a good idea. Its weight will simply be too much for the gypsum, and the entire finish will crumble.

It is noteworthy that cement-gypsum compositions—like Starateli MIXTER / MIXTER—that combine the benefits of both kinds are offered for purchase. This gypsum-cement plaster is meant for indoor spaces with normal to high humidity, just as the manufacturer states. This vapor-permeable, flexible material is resistant to moisture and is simple to use.

The technical properties of this mixture were found to be in the middle of cement plaster and gypsum:

• Consumption for a 10 mm layer – 10-11 kg / m2
• Water consumption – 0.36-0.42 l / kg
• Setting time – 40 min
• Adhesion to the base – 0.5 MPa
• Layer thickness – up to 60 mm! without using a plaster mesh
• Price – 320 rubles per 30 kg bag.

This mixture includes premium modifying additives and a light filler in addition to the primary ingredients.

Is it possible to combine cement and gypsum plaster on your own to create a solution that is flexible, strong, and resistant to moisture? That won’t work, sorry. Because gypsum and cement dry at different rates and can become covered in cracks when mixed by hand without the use of modifiers, the plaster layer on the wall will be affected. In order to save time and money, it is preferable to avoid experimenting with such works.

Selecting cement or gypsum plaster primarily relies on the particular requirements of your project. When time is of the essence and a smooth finish is required for interior work, gypsum plaster works best. It is a favorite for interior walls and ceilings due to its short setting time and simplicity of application. Because it can absorb water and weaken over time, it is not recommended for locations with high levels of moisture.

Conversely, cement plaster is a better option for exterior surfaces and damp areas because it is more resilient and moisture-resistant. Cement plaster can be more difficult to work with and take longer to set, but in the long run, its strength and resistance to weathering can make up for these drawbacks.

It is generally not advised to mix gypsum and cement plaster because of the potential problems with application and durability resulting from their different properties. It is preferable to use them in different project areas or layers if you require the benefits of both. The best decision ultimately boils down to knowing the kinds of challenges your walls will encounter and choosing a material that can withstand them.

Video on the topic

Gypsum plaster in bathrooms | Incompatibility of gypsum and cement

Which is cheaper? Gypsum or cement? The subtleties of working with plaster.

What to mix solutions with. Which mixer to choose.