Various issues may arise during the construction of exterior wall coatings. Below we share common problems and corresponding solutions in exterior wall coating construction.
01 Slow Drying & Tackiness Recurrence
After brushing the coating, if the paint film fails to dry within the specified time, it is defined as slow drying. If the film is formed yet still sticky to touch, this phenomenon is called tackiness recurrence.
Causes
- Excessively thick paint film applied by brushing.
- Applying the second coat before the previous one is fully dry.
- Improper use of driers.
- Unclean base surface.
- Incompletely dried base surface.
Solutions
- For mild slow drying and tackiness recurrence, enhance ventilation and raise ambient temperature appropriately.
- For severely affected paint films, clean thoroughly with strong solvent and repaint again.
02 Chalking
The paint film turns powdery after exterior wall coating application.
Causes
- Poor weather resistance of coating resin.
- Poor wall surface treatment.
- Low construction temperature leading to poor film formation.
- Excessive water dilution of paint during application.
Solutions
Thoroughly remove all chalked residues first. Apply high-performance sealing primer as base coat, then repaint with weather-resistant real stone paint.
03 Discoloration and Fading
Causes
- Excessively high moisture content in the substrate; crystallized water-soluble salts on the wall surface cause discoloration and fading.
- Inferior real stone paint uses non-natural colored sand. Alkaline base materials damage pigments and resins with poor alkali resistance.
- Harsh weather conditions.
- Improper selection of coatings.
Solutions
Once the problem occurs during construction, scrape or wipe off the defective surface, let the cement dry thoroughly, apply a layer of sealing primer, and use high-quality real stone paint.
04 Peeling and Flaking
Causes
Excessive substrate moisture, uncleaned surface, incorrect painting methods or inferior primer lead to separation of paint film from the base surface.
Solutions
First check for wall water seepage and fix it if any. Remove peeled paint and loose substances, fill defective areas with durable putty, then apply sealing primer.
05 Blistering
After full drying, uneven bulges appear on the paint film with slight elasticity when pressed.
Causes
- Damp substrate; water evaporation causes paint film blistering.
- Water vapor mixed into compressed air during spraying.
- Topcoat applied on undried primer in rainy days; gas generated from dried primer jacks up the topcoat.
Solutions
For slight blistering, sand smoothly with water abrasive paper after full drying and touch up with topcoat. For severe blistering, completely remove the paint film, fully dry the base, eliminate root causes, then re-spray real stone paint.
06 Lifting (also known as Substrate Erosion)
Causes
The underlying primer is not fully dry during painting. Thinner in the top coat swells the primer, resulting in paint film shrinkage and peeling.
Solutions
Follow the specified interval time for coating application. Avoid overly thick coats. Apply top coat only after the primer is completely dry.
07 Sagging
Paint flows or drips down walls on construction sites, forming tear-shaped or wavy marks.
Causes
- Excessively thick single coating layer.
- Excessive dilution ratio.
- Direct painting on unpolished old paint surfaces.
Solutions
- Apply multiple thin coats instead of one thick coat.
- Reduce the dilution ratio.
- Polish old paint surfaces with sandpaper before construction.
08 Wrinkling
Uneven wrinkles form on the paint film surface.
Causes
- Over-thick paint film causes surface shrinkage.
- Second coat applied before the first coat dries thoroughly.
- Excessively high drying temperature.
Solutions
Avoid thick coating and ensure even application. Leave sufficient interval between two coats, and apply the second coat only when the first coat is fully dried.
09 Severe Cross Contamination
Causes
Improper layout on dividing joints during top coat construction leads to irregular appearance.
Solutions
Strictly follow standard construction procedures to reduce cross contamination. Use auxiliary coatings with excellent anti-aging, high-temperature resistant and anti-ultraviolet properties for repair and protection.
10 Uneven Trowel Marks
Causes
Large-area cement mortar dries slowly, easily causing cracking and hollowing. Bentonite MT-217 added into real stone paint ensures smooth construction and easy troweling.
Solutions
Adopt reasonable dividing joint treatment and prepare cement mortar evenly during base plastering.
11 Whitening When Exposed to Water & Poor Water Resistance
Phenomenon & Main Causes
Some real stone paints turn visibly white after rain erosion and soaking, and restore original color in sunny weather, which is a direct sign of poor water resistance.
- Low-quality emulsionLow-grade emulsions contain excessive surfactants to enhance stability, which greatly weaken water resistance.
- Insufficient emulsion dosageTo cut costs, manufacturers add too little emulsion, leading to loose, non-dense paint films with high water absorption and low bonding strength. Long-term rainy weather allows rainwater to penetrate and cause whitening.
- Excessive thickenerOveruse of water-soluble thickeners such as CMC and hydroxyethyl cellulose remains in the coating and severely reduces water resistance.
Solutions
- Adopt high-quality emulsionSelect high-performance acrylic polymer film-forming materials to improve water resistance fundamentally.
- Increase emulsion proportionDetermine optimal emulsion dosage via comparative tests to form dense and complete paint films against rainwater penetration.
- Adjust proportion of hydrophilic substancesControl content of cellulose and similar materials properly to balance construction performance, stability and water resistance.
12 Severe Overspray & Material Waste
Phenomenon & Main Causes
Sand shedding and splashing often occur during spraying, causing up to about one third material waste.
- Improper aggregate gradationSingle-size stone sand instead of mixed particle sizes triggers splashing.
- Improper construction operationUnsuitable nozzle caliber and air pressure lead to spattering.
- Inappropriate coating consistencyWrong viscosity causes sand loss and waste.
Solutions
- Optimize stone aggregate gradationMatch coarse and fine sand reasonably for uniform texture and less splashing.
- Standardize construction parametersAdjust spray gun nozzle size and working pressure.
- Modulate coating viscosity to proper range.
13 Color Mottling of Real Stone Paint
Phenomenon & Main Causes
- Excessively high substrate pH value (over 9) causes uneven color.
- Uneven coating thickness and insufficient spraying quantity lead to mottling.
- Excess cellulose added during production is a direct cause.
Solutions
- Control substrate pH strictly and apply alkali-resistant sealing primer.
- Follow standard spreading capacity: 3.0-4.5kg per square meter.
- Use cellulose thickener in rational proportion.
14 Yellowing of Real Stone Paint
Phenomenon & Main Causes
Poor-grade acrylic binders degrade under UV radiation and release colored substances, resulting in yellow discoloration.
Solutions
Choose high-quality anti-yellowing emulsion as binder to upgrade product quality.
15 Soft Paint Film
Phenomenon & Main Causes
Qualified real stone paint forms hard scratch-resistant film. Soft film is caused by improper emulsion selection or insufficient dosage leading to loose film structure.
Solutions
Adopt special composite emulsion with strong adhesion and low film-forming temperature instead of common latex paint emulsion.
16 Color Difference
Phenomenon & Main Causes
- Different batches of coatings used on the same wall. Color deviation exists among natural colored sand from different mining batches.
- Insufficient stirring after long-term storage causes floating color and layering.
Solutions
Use coatings and colored sand from the same batch for whole wall construction; stir fully before use; store classifiedly.
17 Uneven Coating, Obvious Joint Marks & Obvious Repair Joints
Phenomenon & Main Causes
Different paint batches, uneven viscosity, unstable spraying pressure, worn nozzles, inconsistent mixing ratio and unstandardized joint reservation all cause prominent joints.
Solutions
Unify mixing ratio and coating consistency; finish pre-construction sealing in advance; use same-batch materials; inspect spray guns regularly; reserve joints at dividing lines; control coating thickness during secondary repair to avoid overlapping shade difference.
18 Coating Blistering, Bulging & Cracking
Phenomenon & Main Causes
Excessive substrate moisture, insufficient base mortar strength, no sealing primer, topcoat applied on undried base coat, unreasonable dividing joints, over-thick coating, defective paint performance and large temperature difference all cause cracking.
Solutions
Construct base plastering with standard division and layered application; follow construction specifications; adopt small-caliber spray gun for multiple thin coats with proper spraying distance.
19 Coating Falling Off & Surface Damage
Phenomenon & Main Causes
High substrate moisture, mechanical impact, low construction temperature, improper tape removal, lack of cement skirting line and missing matched primer lead to damage and peeling.
Solutions
Construct in strict accordance with specifications and strengthen finished product protection.
20 Severe Cross Contamination & Discoloration during Construction
Phenomenon & Main Causes
Fading caused by weathering and disordered construction procedures result in cross contamination.
Solutions
Use UV-resistant and anti-aging colorants; forbid random water dilution; apply top finish coat 24 hours after main coating completion; avoid sagging and uneven coating; arrange construction process reasonably to prevent cross interference.
21 Cracks on Internal & External Corners
Phenomenon & Main Causes
Corners bear bidirectional tensile stress during drying, which easily triggers cracks.
Solutions
Re-spray cracked corners thinly at half-hour intervals to cover cracks. For new construction, apply multiple thin coats with distant spray distance and fast moving speed; spray side faces indirectly instead of direct vertical spraying on corners.
Statement: Some articles and materials published on this official account are sourced from the Internet, only for study and communication purposes. We have no intention of infringement. Please contact us for deletion if there is any infringement. Thank you for your understanding.