Plaster defects: causes, types and methods of elimination

Although plastering is an essential step in building even, smooth walls, things don’t always go as planned. Defects of all kinds can arise, frustrating and disappointing anyone who is aiming for a perfect finish. To get the best results, whether you’re a professional or a do-it-yourself enthusiast, you must comprehend these plaster flaws.

Plaster flaws can range in severity from small flaws to serious problems that compromise the longevity and aesthetics of your walls. These issues frequently result from a confluence of elements, such as subpar construction, inappropriate materials, or even ambient circumstances. You can take precautions to avoid plaster flaws in future projects by being aware of their common causes.

The various kinds of plaster flaws that can occur will be discussed in this article along with workable fixes for them. We’ll walk you through the steps to get your walls back to their original smoothness and beauty, from cracks and bubbles to uneven surfaces and discoloration.

Defect	Cause	Elimination Method
Cracks	Rapid drying, poor application	Repair with plaster filler, ensure proper drying time
Blisters	Excessive moisture or air bubbles	Remove blisters, reapply plaster, and ensure proper mixing
Peeled Paint	Improper surface preparation, moisture issues	Strip old paint, fix moisture problems, prepare surface properly
Uneven Surface	Inconsistent application, surface irregularities	Smooth with additional plaster layers, sand down high spots

Plaster defects and their types

Plaster defects are defined as variations in the plaster coating’s quality from the required standards. Both technical and operational flaws exist.

The following explain the latter:

• improper preparation of the base;
• low -quality plaster mixture;
• violation of the technology for applying plaster to the base;
• non -compliance with the conditions required for grasping and setting the strength of the plaster solution.

They can be detected by looking at and tapping the finish once the solution has dried fully.

Defects in the decoration arise during operation as a result of wear, wetting, precipitation of the structure’s structures, and mechanical influences (shots, abrasion).

• cracks;
• swelling;
• dutiks;
• exfoliation;
• heights;
• spotting;
• rust;
• surface uneven;
• curvature of walls, corners.

Defects of plaster causes of their appearance and methods of elimination

We get more intimate knowledge about the plaster flaws and how to fix them.

Certain flaws are caused by a single factor; dutiks, for instance, are linked to a subpar solution. Parts can arise for a variety of causes. Different causes lead to different approaches to correction.

Dutiki

Plaster coatings containing unslaked particles develop swellings when quicklime or improperly prepared lime is used. Air bubbles with a center are the result of lime plaster lumps that have not yet been quenched. The coating lacks the necessary evenness and strength.

In order to properly prepare the base, the area of the plaster layer that contains these bumps, or puffs, is removed during the finish inspection and the surface is replastered. We thoroughly moisten the surface before removal. A solution on good lime is prepared for sealing.

The solution is made from slaked lime or lime milk that has been strained through a 0.4 x 0.4 mm sieve to avoid puffs.

Cracks in plaster

A fairly common flaw in plaster that can arise for a number of reasons. Crack appearance varies.

The following causes cobwebby cracks (depth 1-2 mm):

• insufficient reinforcement;
• a ​​large amount of water in the composition;
• too hard grout;
• application of excessively thick layers;
• drying occurred too quickly.

The following factors lead to cracks that penetrate the whole plaster layer starting at the base:

• violation of application technology;
• low-quality solution;
• a large number of additives;
• high drying speed;
• incompatibility of the compositions of adjacent layers with each other.

In addition to the previously mentioned causes, poor preparation (lack of reinforcement) or poorly executed work can also result in cracks at ends and joints.

Fracture patterns in the house’s structure suggest shrinkage or displacement.

Crack sealing techniques also differ. After expanding individual cracks, clearing out dust and debris, priming the coating, sealing it with a sealant or mortar, and ensuring that it is strong enough and does not have deep cracks or come off when tapped, the coating is applied.

Plaster is removed from structural fissures by scraping 5 cm on each side of the fissure. Once the behavior of the crack is observed using paper beacons and it is determined that it does not grow, it is primed, cleaned, reinforced, and sealed with mortar. If the cracks are movable, strengthen the house’s structural integrity as a first step in removing the cause.

The finish will need to be removed and the wall replastered if the lack of reinforcement, subpar mortar, damp base, and incompatibility of the compositions were the root causes of the cracks. The wall is ground for minor surface fissures.

Swelling and peeling of plaster

The plaster layers peel and swell when materials (mostly plasters made of lime or gypsum) get wet. It’s possible that the wall wasn’t completely dry before the solution was applied, or that moisture from the room’s humid air caused condensation to seep into the plaster. It will be necessary to remove this coating, let the wall dry, and then plaster it again.

Replace this type of plaster composition with one that doesn’t mind getting wet (like sanitizing or waterproofing plasters) if the room is too humid for it.

Cracks in the shells

Several factors can cause plaster to fracture in the shells:

• joints of structures of different materials were not prepared correctly;
• the solution was applied to overdried wooden surfaces that absorbed moisture and increased in volume;
• the structures being plastered, for example, partitions, were not firmly fixed;
• insufficient stickiness and strength of the solution.

Joints made of different materials need to be strengthened before plastering. Before plastering, overdried wooden bases are wet with water. Explore our website’s pages to learn more about plastering over wood. Every structural component needs to be firmly fastened. By removing the plaster layer, correctly preparing the base, and applying a fresh coating, the defect is fixed.

Vysols

In one-off construction, vapors are common. This is the process of eliminating salts from plaster composition that is prone to rising moisture in buildings. Their cause is the movement of water within the structures, which can occur from a variety of sources, such as improper waterproofing, water absorption from the air in raw rooms, or a failure to follow waterproofing regulations. When building materials are impregnated with water, the salts are either carried to the surface by water or are dissolved from the soil and the building material’s substances.

On the plastering covering of brick, concrete, wooden, or steel surfaces, valves may show up. Ground water contains a significant amount of dissolved salts, particularly in regions that are enriched with mineral waters. These salts can just be carried to the finish’s surface and form stains there without reacting with the materials of the structures. However, it gets worse when internal chemical reactions take place and alter the characteristics of the building’s materials. The "cement bacillus" is the most dangerous type of devastation.

Efflorescence can occasionally be the result of chemical reactions that take place as the plaster mortar hardens. Thus, slaked lime in a lime mortar is a hydrate of calcium oxide that, in normal reactions, combines with atmospheric dioxide on the surface to form limestone. However, calcium bicarbonate instead of limestone forms when there is leftover water in the solution.

Insufficient heat and moisture during the plastering process cause the excess water in the solution to evaporate, the bicarbonate to accumulate as a white efflorescence layer on the surface, and the hardening plaster to become deficient in lime.

Gases found in urban atmospheres have the potential to produce sulfuric acid when precipitation occurs. When it comes into contact with calcium oxide, gypsum efflorescence results. Moreover, biological pollutants have the ability to react with elements from contaminated air to produce efflorescence. They discuss atmospheric (chemical) corrosion in both instances.

Errors in the plastering material selection may be the source of efflorescence. For instance, the use of silicate dye for tinting may be the cause of efflorescence on a gypsum coating.

Eliminating efflorescence is a difficult undertaking. To appropriately neutralize the efflorescence, one must first ascertain its chemical makeup. Determining the source and mechanism of the moisture is crucial. There are steps taken to prevent access to water. After that, remove the salts that are sticking out.

Rust stains

Stains that resemble rust but are not actually caused by it can be very bothersome.

• metal parts left in the coating were not covered with oil paint or other insulating material;
• metal beacons were not removed from the plaster layer;
• metal utility pipes located in the wall are leaking;
• stains on the ceiling may appear as a result of a roof leak;
• stains (similar to rust) may appear near the fireplace or stove due to the interaction of oil and soot;
• there are types of mold and fungus that form colonies with a characteristic "rusty" appearance.

Plaster flaws resulting from the initial causes are the hardest to remove. In order to replace leaking pipes and remove beacons, you will need to cut a groove in the wall and then plaster the damaged area once more.

After neutralizing the source of the biodamage, the area needs to be primed, cleaned, and puttied. After removing wallpaper or paint, grease stains are treated with a degreasing agent or "Whiteness," allowed to dry, primed twice, and then painted over with white paint. The purpose of this process is to see if the stains reappear.

Defects of decorative plaster

Decorative plaster can also develop any of the aforementioned kinds of flaws. The removal is typically completed in a similar manner. Repairing certain decorative coatings can be more challenging. For instance, travertine or Venetian plaster. Following the removal of the damaged layer, the edges of the intact Venetian plaster/travertine sections are lubricated with a base solution made of one part PVA glue to five parts water. This precaution guarantees that the new coating will stick to the previous one.

After that, fresh plaster layers are applied and allowed to dry on the damaged area. Using a sponge to create roughness and spatulas to provide relief, the area being repaired is simultaneously given the texture of the remaining coating. In order to make the finish appear as one cohesive piece, the areas where the old and new coatings overlap are smoothed as much as possible. Using a wet spatula, the protrusions of the relief on the newly added section are smoothed during the drying process. The surface is painted, with the experimental area’s color chosen, once the plaster has dried.

Final table of defects

Below is a table listing the primary defects to make orientation in defects easier.

Defects (types)	Causes of occurrence	Elimination measures
Peeling, swelling	Constant moisture ingress or plastering of a undried base	The detached, swollen plaster layer is knocked off with a hammer, the base is dried, plastered again
Dutiks	Poorly slaked lime	The coating is soaked, removed and the area is plastered again
Peeling	The base is not prepared properly, the solution is applied "dry"	Peeled areas are knocked down, properly prepared, plastered
Cracks	Violations at any stage of plastering, as well as shrinkage and movement of building structures	Surface cracks are ground, deeper ones are repaired with sealant or mortar, observing the technology
Wall plane fractures	Incorrectly installed beacons	The finishing is removed, the wall is plastered again
Rusty stains	The beacons left in the coating have rusted, hidden pipes are leaking,	The wall is chased, the beacons are removed, the pipes are repaired, bioaggressors are eliminated, the stains are cleaned
Efflorescence	Groundwater ingress into materials	Carrying out waterproofing and sanitization works

You can read about how to identify plaster flaws in the following section.

Search for defects

The majority of flaws are visible.

Surface irregularities are detected using a rule; occasionally, side lighting may be required. After applying the rule to the surface, the irregularities show up as spaces between the rule’s and the wall’s surfaces. You can see even the tiniest lumps, protrusions, and pores thanks to side lighting. Puffs, efflorescence, rust stains, and cracks are instantly apparent.

Using a wooden hammer handle, tap the coating’s surface to identify flaking or peeling. Vapors have a very muted sound. Occasionally, the plaster comes off when tapped.

A plumb line and level can be used to reveal the curvature of the walls and corners. A square can be used to assess whether or not a 90-degree angle is being maintained. In the absence of a square with an internal right angle, place plywood on one side of the corner and fasten a school triangle to it so that the corner rests on the wall on one side and the plywood on the other. The angle is not maintained if the side of the square does not fit against the wall firmly.

A flaw can also be the finish’s inadequate strength. When you run your fingers over the plaster, it becomes gritty and crumbles in small pieces because there isn’t a strong enough bond between the filler particles.

Maintaining the caliber and aesthetic appeal of your walls requires an understanding of plaster flaws. Common problems like peeling, cracking, and efflorescence can be found and fixed early to stop further damage. Every flaw has a distinct cause, which can range from improper application methods to underlying moisture problems.

Finding the source of the issue is essential to solving it successfully. For example, peeling may indicate poor surface preparation, while cracks may result from structural movement. Finding the root of the problem helps prevent reoccurring problems and guarantees the longevity of the repairs.

Most plaster flaws can be successfully repaired with the appropriate technique. Fixing cracks, reapplying primer, and controlling moisture levels are all important tasks that when done correctly will produce better results and a longer-lasting finish. You can maintain the excellent appearance of your plastered walls for many years to come by being watchful and proactive.

Defects in plaster can vary in severity, from small flaws to serious problems that compromise durability and appearance. Effectively addressing these issues requires an understanding of the common causes, which may include inadequate surface preparation, improper mixing ratios, or environmental influences. Determine the kind of defect—whether it’s bubbling, peeling, or cracking—so that you can select the appropriate repair technique. In order to return your plasterwork to a smooth, faultless finish, this article will walk you through the diagnosis of these problems and offer workable solutions.

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