Is it possible to apply plaster to oil and water-based paint

In renovation projects, plastering over painted surfaces is a common challenge. Knowing the proper technique can save time and guarantee a long-lasting finish, regardless of whether you’re working with a more contemporary water-based coating or an older oil-based paint layer.

Plaster adhesion faces particular challenges on painted surfaces. Paint’s glossy, sealed texture can hinder plaster’s ability to adhere to one another, causing cracks, peeling, or even the plaster layer to fail entirely.

This post will discuss whether plastering directly onto painted surfaces is feasible and the precautions that must be taken to make sure the process goes well. We’ll go over important factors to take into account for paints that are water-based or oil-based, and offer helpful guidance on how to achieve a smooth, durable plaster finish.

Is it possible to apply plaster to paint

Maybe we mix the incompatible by adding plaster to a layer of paint. And it so happens that we blend two harmoniously complementary materials.

A favorable outcome is contingent upon multiple factors:

• the composition of the paint and solution;
• condition of the old coating (paint film);
• size of the thickness of the plaster layer (depends on the weight of the coating).

There are situations where it is just not possible to plaster over old paint finishes. As a result, we only respond to inquiries about "is it possible to plaster?" in certain circumstances. Indeed.

As long as the following criteria are satisfied, you can plaster over paint:

• compatibility of the compositions of the paint film and plaster;
• creation of an intermediate layer of material that is equally well compatible with both of them;
• performing high-quality preparation of painted walls for plastering;
• the humidity in the room should not be high.

In what cases is plastering allowed over old paint

A detailed explanation of each of the conditions should be provided so that there is no incentive to disregard them. If the requirements are not satisfied, the plaster coating may start to peel off after work and the paint layer may reveal its sneaky nature.

On the surface, a film forms during painting. The physical characteristics of fillers and additives, in addition to the chemical makeup of the binder, determine the qualities and properties of the film.

Out of the primary paint films, we examine two possibilities:

• a film formed as a result of dehydration of oil paint;
• a ​​film formed as a result of polymerization of a water-based composition.

The paint film may be in one of two states: it may be completely destroyed and peeling off or separating from the base, or it may be clinging to the base and remaining strong and integral. Plastering the painted surfaces is only feasible in the second scenario. But in this instance, take the appropriate precautions, limiting the load on the paint from the plaster.

One material with a significant dead weight is plaster mortar. It is nearly impossible to create a connection with a smooth paint film that can withstand high tear-off forces, so the plaster solution applied on top of the paint must not be thicker than the paint, up to:

• 30 mm of cement-sand mortars;
• 40 mm gypsum solutions.

Is it possible to apply plaster on water-based paint

It can occasionally be used as a base for plastering due to the composition of water-based paint. Compositions that stand out for their own light weight will readily "stick" to it, and it will respond to the neighborhood with clay or cement in a cool, collected manner. It "dislikes" gypsum, though. As a result, a primer must be used as a bridge to connect them.

Plaster on oil paint

Problematic kind of coating. oil-mixture paint applied to smooth surfaces. Plaster solutions do not "stick" to them as a result. More work needs to be done to establish the circumstances that will keep the wall plaster on the oil film.

1. mat the paintwork with sandpaper
2. make a notch (for example, with an axe)
3. be sure to use a primer (most often it is concrete contact)

Is it possible to apply decorative plaster on paint

Different bases can be used for decorative plaster. It can be combined with regular plaster according to the guidelines outlined in this article. If you are uncertain about the outcome, it is worthwhile to try plastering a test area.

How to plaster a painted wall

If, however, you choose to paint over plaster without first removing it. It is worthwhile to adhere closely to technology. Let us examine the necessary tasks in a sequential manner to ensure that the freshly applied coating remains firmly and robustly adhered to the wall.

Examination of the painted surface

What is it and why is it needed? Treatment for an oil-painted surface is different from treatment for a wall painted with a water-based composition, as is already known. As a result, ascertain the paint film’s base first.

You can use the following methods to determine what paint was used on the walls:

• look, is the surface glossy or matte;
• run your hand over the surface, check what trace remains on the skin;
• wet the coating;
• run with sandpaper.

Paint made with water appears whitewashed. When you wipe whitewash over your skin, a white residue is left behind. Water-based paint does not change color when wet; instead, it "foams" and will partially rub off when rubbed with a sponge. Whitewash darkens when wet. The water-based film leaves smeared marks on sandpaper (after rubbing), whereas oil and enamel coatings leave small fragments. The surface of enamel paint compositions is glossy, while water-based and whitewash paints have a matte, porous finish.

For painting, oil and water-based bases are most frequently utilized. Plaster solution does not "stick" to the thick, non-breathable layer that is formed by oil well. Conversely, the pores in water emulsion facilitate good airflow, which makes plaster mortars stick to it more securely.

Preparatory work

The goal of this type of work is to take action to remove any flaws that could lead to the plaster coating peeling off later on, improve adhesion, and reinforce the plaster mortar.

1. Check the condition of the paint film by tapping the wall surface. Areas where the coating moves away from the base or crumbles are cleaned with a spatula. Loose pieces of paint can be removed more easily if the painted wall is wetted.
2. To increase adhesion to a wall covered with an oil or enamel paint base, notches are applied to the finish to such a depth that they also “touch” the underlying material.
3. The surface is treated with sandpaper to get rid of the thinnest glossy smoothest layer. Sandpaper with a grain size of 60-80 is selected.
4. The resulting dust is removed from the wall. Wipe the top with a cloth, dry. In the kitchen, where the smallest fat droplets have stuck to the finish, degreasing is required.
5. The surface is coated twice with a primer. The first pass is performed with a composition that seals pores, penetrating deeply. After drying, concrete contact is applied, which contains quartz sand grains. This method increases adhesion. Please note that application requires a special concrete contact compound intended for application over alkyl or oil coatings (different from concrete intended for priming).
6. For additional reinforcement of the plaster coating, screw a plaster mesh to the wall. For interior work, a PVC or polypropylene mesh is suitable; it is not screwed on, but pressed into the solution, as when reinforcing wet facades. It is important that the solution goes not only into the cells, but also between the mesh and the wall. It is better to attach the metal mesh to the ceiling with self-tapping screws.

There is another article with more details on priming the surface for plastering.

Ordinary primer cannot be applied to concrete bases, and betonokontakt cannot be used in restrooms. Betonkontakt is used on surfaces that don’t absorb moisture, like ceramic tiles.

Applying plaster to paint

It is necessary to dry the walls after preparation. Apply plaster over paint using the same techniques as before; for instance, beacons can be used for leveling. Plastering can be carried out mechanically or by hand. (Depending on the type of finishing, for example, wallpapering) The top layer is rubbed and smoothed.

Plastering over oil- or water-based painted walls requires careful surface preparation and assessment of the surface’s state. These paint types can be plastered over, but the plaster has to be stable and firmly attached to the wall. If not, there’s a chance the plaster won’t adhere well, which could cause peeling or cracking. In order to guarantee that the plaster adheres firmly and endures over time, proper surface preparation is necessary. This includes cleaning, sanding, and applying an appropriate primer.

In what cases plastering cannot be applied to old paint

It used to be considered improper to apply plaster to a painted base. Plastering is no longer prohibited in all situations due to the use of contemporary tools and techniques for mixing paint and mortar.

Plastering a painted surface will not be possible if:

• the paint layer is deteriorating or fragile (the paint is easily scraped off with a spatula, crumbles from the walls);
• if in order to level the surface it is necessary to apply a layer of plaster thicker than the dimensions specified above;
• if the paint on the wall is water-based, and the plaster mortar contains gypsum;
• in rooms with high air humidity (moisture, penetrating through the pores of the plaster, will cause it to peel off);
• oil film plastered directly (need a primer to increase adhesion).

In these situations, you should either take action to alter the starting circumstances (such as switching out gypsum compositions for cement, clay, or acrylic) or remove the paint film entirely. For example, plasterboard, or dry plaster, can be used to level the wall.

How to remove old paint from walls for plastering

Paint removal is a difficult task. In some areas, paint can cling firmly to the base, but in other areas, a spatula can easily remove the paint. Various techniques are employed to clean the surface, depending on the state of the paint coating and the skill of the finishers. Similar techniques are applied to the removal of ornamental plaster.

• mechanically;
• thermally;
• chemically.

Mechanical method

Traditional grinding (abrasive removal) or scraping (manual or mechanical). It can be done by hand, with electric or pneumatic tools, or both. Removal usually starts with it.

Simple, low-cost tools like scrapers and spatulas are available. The thin, broad blades on these instruments are inserted beneath the paint layer. When the tool is pressed, it acts like a wedge, converting longitudinal force into transverse force. The tool is held at a slight angle to the surface being cleaned. Weakly held paint can be readily snapped off.

The scraper or spatula is fastened to an extended handle to widen the "swing." Even when cleaning the ceiling, you can use a tool like this from the floor thanks to its telescopic handle. A scraper is something you can buy or make yourself. For scrapers, replacement blades are made. You don’t need to purchase the strongest thinnest blades for our work. Enough of the cheap Chinese ones. Using a scraper or spatula is a quiet way to work that won’t bother your neighbors.

A chisel and hammer are carpentry tools used to separate the paint’s layer if there is a strong bond between the paint and the base. Because you can lightly tap the end of the chisel handle with a hammer, impact force is used in this instance rather than manual pressing "to the wedge." A drawback is the peelable coating’s tiny size. It would therefore make sense to start by using a spatula to clean the wall whenever possible.

Using a drill and a long bolt with a chain attached, for example, the old paint layer is also removed. Here, the layer is removed by the chain links’ chaotic blows. However, the underlying plaster is frequently knocked off along with the paint. The process produces more noise and dust. In terms of work safety and cleaning speed, ideal.

Drill models with impact action are available. These instruments that come with a spatula attachment can also be used to remove paint layer films. A brush-type attachment with wire-stiff bristles is one option.

There are rotary hammer nozzles with blades, brushes, and abrasive disks for removing film. For rotary hammers, nozzles with dust outlets are available that can be connected to a construction vacuum cleaner hose.

Bulgarians or angle grinders are frequently used for removal. used, with a brush or abrasive disk attached. There are two categories into which all mechanical assistants are produced: those for professionals and those for homes.

In the event that impact-action "assistants" were used to remove the coating, leveling the wall surface is also necessary after dusting. For instance, thin-layer decorative plasters like Venetian plaster are inappropriate for use on such an uneven base. Get your puttying gear on.

Thermal method

Heating paint films to high temperatures can cause them to soften. Using a spatula or scraper, the softened mass is easily removed mechanically from the walls. Hot spots are heated locally using hair dryers. Heating with a blowtorch was once commonplace.

The drawbacks of thermal removal are evident: when paint is heated, it releases disagreeable and toxic compounds, and the melted material cools quickly, requiring additional heating.

Chemical method

The actual method is combined, just like the previous one. The coating layer is softened with the application of a chemical agent, and then scraped off with a spatula. Products (washes) have been created to soften the paint compositions of various kinds. Additionally, universal washes exist. This method requires the least amount of labor and is not difficult. However, because many volatile substances are harmful, it is imperative to ensure that there is air exchange in the room. You must wear a respirator when performing such cleaning.

Washes work best on "fresh" paint layers, meaning they can last up to two or three years. Refinishing old finishes is challenging.

The wash can be substituted with a certain product. This is applied as a thin layer of liquid glass. The "glass" film peels off with paint particles once it has dried. It is taken out. If required, the process is carried out multiple times. Glass in liquid form is less corrosive than compounds in stripping.

Surface Type	Plaster Application Feasibility
Oil-Based Paint	Challenging – Requires proper surface preparation, such as sanding and priming, to ensure plaster adhesion.
Water-Based Paint	Possible – Generally easier than oil-based, but still requires cleaning and sometimes priming for better results.

While it can be challenging, plastering directly over oil- or water-based paint surfaces is not impossible. Adequate preparation of the surface is essential for the success of this process. If the proper procedures aren’t followed, the plaster might not adhere well and cause problems later on.

Sanding the surface thoroughly is essential if you’re working with oil-based paint in order to achieve a rough texture. This improves the plaster’s grip. Although there is usually less preparation needed for water-based paint, it is still necessary to clean the surface and ensure that there are no loose or peeling areas.

To improve adhesion, a primer or bonding agent may occasionally be required. These products improve the adhesion between the plaster and paint, guaranteeing a longer-lasting finish. But since every circumstance is different, it’s best to test a small area first to help you avoid any potential issues.

In the end, plaster can be successfully applied over painted surfaces—whether they are water- or oil-based—if it is prepared carefully. These tips will help you get a finish that is durable and flawless.

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