Plastering internal and external corners of walls with your own hands

For any do-it-yourselfer, plastering corners—whether they are inside or outside of a room—can be a difficult undertaking. Compared to flat walls, the sharp angles and varied surfaces coming together at a corner call for a little more care and expertise. However, you can achieve a polished, long-lasting finish with the appropriate method and equipment.

We’ll take you step-by-step through the plastering of both interior and exterior corners in this guide. Everything from the equipment you’ll need to the methods that will make the work easier will be covered. Plastering corners correctly is an important skill that can save you time and money, whether you’re painting a small section or an entire room.

It’s critical to comprehend the distinction between internal and external corners before beginning. The interior corner of a room is the point where two walls meet at an inward angle. The edges of windows and doors are examples of external corners, which are formed when two walls meet at an outward angle. You can become proficient in both types with time and practice, though each type calls for a slightly different strategy.

How to properly plaster even corners of a wall with plaster

Although the walls of residential or commercial buildings may intersect at different angles, it is imperative to guarantee a consistent vertical line at the point where the planes meet during the repair process.

Plastering over a cement or gypsum base necessitates surface processing in accordance with technology and initial surface preparation. The hardened material crumbles or cracks if the specifications are broken; to improve mechanical strength, a synthetic mesh reinforcement is inserted into the gypsum layer.

1. Using wooden or metal beacons, which are then removed or left in the thickness of the finishing material.
2. Using a metal or plastic profile with planes located perpendicularly. Suitable for applying plaster up to 10 mm thick, provide increased edge strength.
3. Cutting corners using a removable board and spatula, the resulting edge does not have high mechanical strength.
4. Shaped design of surface connection lines using a special template. The method is used to obtain decorative cornices, requires high qualifications and is performed by hired workers.
5. Manual removal using finishing putty and a shaped spatula. The technology requires the master to have skills in performing plastering works.

Furniture and other foreign objects must be removed from the room before plastering can begin (e.g., move them out or place them in the middle of the space and cover them with polyethylene film). If you want to replace the room’s electrical wiring, you should make grooves and install the power cables in line with the plan that was created. In order to level the walls, the last marking must be made after the wires have been sealed.

Use 24-48-hour-hardening gypsum plasters at home to level surfaces. An electric mixer or a small concrete mixer is used to mix the water into the dry mixture.

The mixture ought to be thick, stick to the walls firmly, and not collapse under its own weight. Small pieces of dry mix are not permitted if they make it difficult to properly bring out the internal or external corners.

How to make markings when plastering

The quality of the wall layout determines how accurately a right internal angle can be obtained; in order to complete the task, the following must be done:

1. Use a plumb line or level to determine the deviation of the adjoining walls from the vertical position. To improve the quality of the marking, use a laser level.
2. Draw lines on the floor and ceiling that correspond to the virtual vertical surface. When using a laser device, it is necessary to draw lines along the beam trajectory.
3. Attach metal beacons using quick-drying gypsum and plasterboard spacers. Supports should be located every 500-600 mm, the profile should not bend when moving the rule or move away from the attachment points.
4. Use a similar scheme to lay out the adjacent wall, and then begin plastering work. At the initial stage, it is necessary to seal the cracks by laying a reinforcing mesh. Large cracks (for example, between slabs) can be filled with polyurethane foam, the protruding excess can be cut off after polymerization. If there are metal elements on the walls, they should be dismantled or covered with paint or anti-corrosion mastic. If the rule is violated, rust stains will appear on the plaster, which will transfer to the finishing.

Some artisans employ a different technique that involves measuring the wall’s distortions with diagonally stretched cords. They start installing the profiles by positioning them along the stretched twine once the location with the greatest protrusion has been identified. Following the marking process, the cord is cut and the surfaces are plastered or covered with plasterboard sheets, with beacons serving as a foundation for support.

1. Before performing work, the walls must be cleaned of dust and covered with primer. In damp rooms, materials with antibacterial additives should be used.
2. When processing, follow the manufacturer"s recommendations for the layer thickness, which should not exceed 50 mm. To level deep holes, you will need to apply several layers with intermediate drying.
3. When dissolving, pour the dry mixture into water, while stirring the solution with a mixer. If you do not have the skills to prepare gypsum mortar, it is recommended to use ready-made plasters supplied in plastic buckets.
4. You should not prepare a large portion of the solution, since the material has a limited shelf life and gradually loses its properties.
5. Gypsum applied to the walls must be quickly leveled – lumps formed on the surface worsen the quality of the finish.
6. Plastering work should not be carried out in rooms at an air temperature below + 5 ° C or above + 35 ° C.
7. Application of the finishing (for example, wallpaper) is allowed 12-14 days after completion of the work. Otherwise, the moisture remaining in the plaster will damage the paper or vinyl wallpaper and cause peeling of the coating.

How to plaster the corners of walls on beacons at 90 degrees

When plastering with beacons, you must first prepare a gypsum solution and a building level (either a hydraulic or laser level) before drawing the corners. Although it is not necessary to finish the walls beforehand in order to complete the work, it is advised to identify the areas that protrude the most.

If not, additional mortar may be applied to the partitions’ contact line during subsequent surface leveling, necessitating redoing the entire process.

1. Install beacons on the surface of adjacent walls, ensuring the vertical position of the elements. Use quick-drying gypsum and plasterboard trimmings for fixing. The guides should be at a distance of 100-120 mm from the line of the joint of the walls.
2. Wait for the gypsum to harden, and then fill the voids with mortar, smoothing the material with a rule and removing excess with a spatula.
3. Place the angle tool on the beacons and carefully form a joint line, moving the spatula from top to bottom. To obtain a smooth surface, the rule should be periodically moistened with water.
4. After the mixture has hardened, you can remove the beacons, but since the profiles are made of galvanized steel, many craftsmen leave the elements in the thickness of the building mixture. If painting or pasting the walls is planned, then a leveling layer of fine-grained finishing putty is applied, which is then cleaned with a float or sandpaper.

It may become necessary to restore the even line of the internal joint of previously plastered walls when performing independent repairs. In this instance, reinforcing mesh is installed on a metal profile. The profile is pressed into the material after a small quantity of gypsum mixture is thrown onto the walls. The excess mortar is removed by smoothing it out; avoid using too much force as this could cause the metal guide to distort. It is necessary to fully seal the corner beneath the plaster layer at the end.

Plastering internal corners with your own hands

• a metal perforated profile, providing a straight line and increased strength;
• a fine mesh made of synthetic material, reinforcing the gypsum mixture.

The walls must be properly aligned before drawing out the corner. It is not permitted to have protrusions or depressions that cause the joint line to curve. You can use a wooden block or a rule to check. Some artisans use varying angles to shine a light stream onto the walls to identify any irregularities.

How to align a wall corner using perforated profiles

1. Apply the solution to the walls along the joint line with a spatula.
2. Carefully lay the profile, pressing the element into the mixture with a rule.
3. Smooth out the gypsum plaster protruding through the holes with a spatula.
4. Wait for the solution to harden and treat the walls with sandpaper; any defects found should be eliminated with finishing putty.

Some artisans make their own tools that let you draw a straight angle. Use plasterboard U-shaped profiles, fastened with screws and extra spacers, to create a template. The final drawing is created after the solution has been applied to the walls and roughly smoothed with a spatula. In order to improve sliding and lessen the amount of plaster flaws, the template is moved up from the floor and wetted down. To create a template, a wooden block can be utilized in place of a metal profile.

How to plaster an internal corner using a serpyanka

This method is applied when plasterboard sheets are used to finish wall surfaces; if the solution is applied without a reinforcing mesh, the joint may develop cracks. It is necessary to prepare the solution and a rectangular wooden block 500–600 mm long in advance before plastering the internal corners.

A synthetic reinforcing tape with an adhesive base is used to increase strength; in manufacturers’ catalogs, it is referred to as serpyanka. Because the material is supplied in rolls of varying widths, you can work with a variety of surfaces.

1. Treat the edges of the sheets with a primer that improves the adhesion of building materials.
2. Apply gypsum to the walls along the joint line with a spatula, the width of the strip is 80-100 mm.
3. Unwind the roll of serpyanka and apply the end of the tape to the top of the wall, and then evenly lower the coil down. Use a wooden block to press in the reinforcing stack, the mesh should be evenly distributed over the mating surfaces.
4. Carefully level the mixture with a spatula, preventing displacement or damage to the synthetic fabric.
5. Wait for the solution to harden and perform the final finishing using an angled spatula.
6. Treat the surfaces with a float or sandpaper, removing small irregularities. Before painting or wallpapering, remove fine dust and saturate the plaster with acrylic primer.

Plastering external corners

1. A metal perforated pad (counter-splitter), which remains in the hardened gypsum mixture and increases the strength of the edge.
2. Spatulas and a template made of a wooden beam. The technique is suitable provided that the walls are carefully aligned.

How to make a right angle without using a counter-splitter

1. Prepare a wooden block with carefully processed surfaces corresponding to the height of the surface being leveled.
2. Fasten the board to the wall using dowels or anchors, providing for an overhang relative to the wall to which the gypsum mortar will be applied. If the craftsman does not want to damage the partitions, then it is necessary to install a template between the floor and the ceiling.
3. Throw the plaster mixture and smooth it out with a metal square or rule, moving the tool along the bar. It is allowed to repeat the operation with intermediate drying of the building material.
4. Wait for the moisture to evaporate, and then install a template for processing another wall.
5. Remove the block after 2-3 days, eliminate minor defects with finishing putty and treat the surfaces with sandpaper. The disadvantage of the technique is the risk of damaging the edge with an abrasive tool or during subsequent use of the room.

Formation of external corners using a perforated aluminum profile

1. Apply a gypsum mixture to the walls, and then lay a perforated corner on the edge, aligning the element vertically using a building level.
2. Remove excess mortar squeezed out through the holes with a spatula, carefully distributing the mixture over the wall surfaces.
3. Make sure the profile is positioned correctly and wait for the mortar to harden.
4. Treat the surfaces with fine sandpaper, and then eliminate the identified defects with finishing plaster. The metal profile allows you to quickly bring out the end edges, the plates provide protection of the surfaces from accidental damage. When working, you should use solid pads, the use of profile sections leads to the formation of cracks on the joint line.

Although plastering walls’ internal and external corners by yourself may seem difficult, you can complete the task on your own if you have the appropriate equipment and know-how. This post will walk you through the process step-by-step and provide helpful advice on how to create clean, polished corners whether you’re working indoors or outdoors. You can make improvements to your house, save money, and feel good about doing the work yourself if you follow these easy instructions.

Tools for plastering internal and external corners

• metal spatulas with different widths of the working surface, allowing you to level the layer of finishing;
• graters for removing small irregularities (with a set of abrasive pads);
• a tray with a roller for applying primer;
• a plastic bucket and an electric drill with a nozzle for mixing cement or gypsum mixture with water;
• an angular spatula, allowing you to get an even angle;
• drawing devices (rulers, tape measures, plumb lines) for marking surfaces;
• masking tape to protect the mating surfaces from contamination with the solution;
• adjustable corner spatula (bevel), allowing to bring out external corners along the perimeter of window openings;
• metal brush and chisel for cleaning concrete or brick surfaces.

The variety of tools is contingent upon the wall’s composition. For instance, plastering planes with three to four blades are used to process surfaces made of foamed concrete, which has a loose structure. The protrusions are cut off by moving the tool along the wall. The work must be done skillfully to avoid creating waves and bumps on the concrete surfaces, which will need to be covered with cement or gypsum mortar.

An example of a particular tool is an angular trowel with a handle and a metal working part. The master moves the tool vertically to highlight the internal type’s corners, which are perpendicular to the planes. Additionally, adjustments are made for handling external contact lines.

It takes tool experience to achieve a high-quality joint; the line is uneven if there are deviations from the vertical or changes in force.

How to carry out preparatory work when plastering the outer and inner corners of walls

1. Remove furniture and interior items from the room or cover things with thick cellophane film.
2. Carefully clean surfaces of old finishing materials, remove areas with a loose structure, wash off grease stains and remove traces of mold or rust from reinforcement bars.
3. Apply notches to improve adhesion on a concrete base or embroider seam joints on brick walls.
4. Cut out fittings and other metal elements located close to the surface. It is possible to paint over areas with oil paint, but a layer of synthetic material impairs the adhesion of the plaster.
5. Remove fine dust and saturate the surfaces with primer with antibacterial additives.
6. Fill large potholes with gypsum mortar, and then re-soak the walls with soil.
7. Mark the surface and begin reinforcing (with a mesh of synthetic fiber) the wall or installing beacons and a perforated corner made of steel tape.

By taking these precautions, the finishing strength can be increased while the likelihood of the base becoming saturated with moisture is decreased. Correct preparation is key to the durability of the gypsum layer, which will withstand temperature and humidity changes in the room without pealing off the surface of the partitions. Antibacterial compounds used during impregnation lessen the likelihood of mold and fungi growing there, which would otherwise wreak havoc on the property’s odor and appearance, especially in apartments and houses.

The ability to plaster corners, whether they are internal or external, can significantly improve the way your walls look. If you have the correct tools and a little perseverance, you can accomplish professional-looking results on your own. The secret is to prepare ahead of time and take your time applying the plaster smoothly and evenly.

You can complete the process quickly and effectively by adhering to the specified steps, from base coat application to final smoothing. While internal corners benefit from careful troweling and clean lines, external corners must be protected and kept sharp by using corner beads.

Recall that practice makes perfect. If your first attempt isn’t perfect, don’t give up. You’ll become more confident and hone your technique with each plaster. All plastering projects around your house can be completed with a little perseverance on your part.

Video on the topic

How to align the internal corners of the walls of the apartment using the Construction Rule.

Plastering the external corner

Accurate setting of the wall angle 90 °. How to make MARKING correctly? Plastering walls.