Chapter 24

Curved and Irregular Shapes and Special Scenario Applications

Compiled by Guangdong Fortune Stone New Material Co., Ltd.

Key Points

• Curved and irregular parts are flexible stone’s “home turf”—ceramic tiles cannot bend, stone cannot bend, and aluminum panels require custom molds, while flexible stone has a bending radius of up to 20 mm and can directly fit complex shapes such as curved walls, cylinders, domes, and corners.
• Curved and irregular parts are also flexible stone’s “touchstone”—substrate curvature control, bonding agent application, compaction and air expulsion, and cutting and trimming are each more difficult than flat construction. If curved construction is not done well, the “flexibility advantage” becomes a “construction disadvantage.”
• Special scenarios require special adaptation—high-rise buildings, cold regions, coastal areas, industrial environments, and indoor irregular spaces each impose different requirements on bonding strength, freeze-thaw resistance, salt spray resistance, chemical corrosion resistance, and environmental decorative performance.
• Four curved surface types, five special scenarios, five key technologies, and three typical schemes constitute the complete framework for curved and irregular shapes and special scenario applications.
• Curved surfaces are divided into four categories by curvature and developability; flexible stone has a lower limit for bending radius, and bending stress increases as the radius decreases; the improvement of curved surface construction efficiency depends on three directions: tools, processes, and training.

24.1 The “Four Types” of Curved and Irregular Parts

Curved and irregular parts can be divided into four types according to geometric characteristics and construction difficulty: curved walls, cylindrical surfaces, domes and spherical surfaces, and free-form surfaces.

24.1.1 Type One: Curved Walls

Geometric characteristics: single-curvature curved surface, with a relatively large curvature radius (usually >500 mm).

Typical scenarios: curved exterior walls, curved balconies, curved corridors.

Construction difficulty: ★★ (relatively low).

Construction points:

Substrate curvature inspection—use a curved template to check whether the substrate curvature is uniform;

Bonding agent application—bonding agent should be applied more fully on curved parts;

Compaction and air expulsion—use a flexible pressing plate to compact from the middle toward both sides;

Joint design—joints on curved parts should follow the arc direction.

Table 24-1 Construction Points for Curved Walls

Case: A commercial complex curved exterior wall had curvature radii ranging from 500 to 1,500 mm. Before construction, a sample was made to determine the construction process under different radii, and special training was conducted for the construction team, focusing on bonding agent application and compaction methods on curved parts. After construction was completed, the appearance quality of the curved parts passed client acceptance. Curved wall construction should adhere to the principle of sample first, confirming the process through samples before large-scale construction.

24.1.2 Type Two: Cylindrical Surfaces

Geometric characteristics: single-curvature curved surface, with a relatively small curvature radius (usually 200–500 mm).

Typical scenarios: cylinders, curved columns, curved corners.

Construction difficulty: ★★★ (medium).

Construction points:

Substrate curvature inspection—use a cylindrical template to check whether the substrate curvature is uniform;

Bonding agent application—bonding agent should be applied more fully on curved parts;

Compaction and air expulsion—use a flexible pressing plate to compact from the middle toward both sides;

Cutting and trimming—use a utility knife when cutting is needed, and the cut edges should be smooth;

Joint treatment—joints on cylindrical surfaces should be as concealed as possible to avoid affecting appearance.

Table 24-2 Construction Points for Cylindrical Surfaces

24.1.3 Type Three: Domes and Spherical Surfaces

Geometric characteristics: double-curvature curved surface, bending in two directions simultaneously.

Typical scenarios: domes, spherical surfaces, hyperbolic surfaces.

Construction difficulty: ★★★★ (relatively high).

Construction points:

Substrate curvature inspection—use a spherical template to check whether the substrate curvature is uniform;

Zoned fitting—divide the spherical surface into several zones and fit them zone by zone;

Cutting and trimming—use a utility knife when cutting is needed, and the cut edges should be smooth;

Joint treatment—joints on spherical surfaces should be as concealed as possible to avoid affecting appearance;

Bonding agent application—bonding agent should be applied more fully and compacted more thoroughly on spherical parts.

Table 24-3 Construction Points for Domes and Spherical Surfaces

Table 24-4 Construction Points for Free-Form Surfaces

24.1.4 Type Four: Free-Form Surfaces

Geometric characteristics: irregularly changing curvature, non-developable curved surface.

Typical scenarios: irregular buildings, artistic buildings, landmark buildings.

Construction difficulty: ★★★★★ (highest).

Construction points:

3D scanning—use a 3D scanner to obtain precise geometric data of the free-form surface;

Digital design—carry out digital layout design based on 3D data;

Customized processing—customize flexible stone specifications and shapes based on digital design;

Sample first—make samples first, confirm the effect before large-scale construction;

Professional construction—construction by experienced construction teams.

Table 24-4 Construction Points for Free-Form Surfaces

The four curved surface types correspond to different geometric characteristics and construction difficulties. Curved walls correspond to the large-curvature-radius type of single-curvature surfaces, with good flexibility stone adaptability and direct fitting possible. Cylindrical surfaces correspond to the small-curvature-radius type of single-curvature surfaces, with relatively good flexibility stone adaptability, requiring attention to compaction and joint treatment. Domes and spherical surfaces correspond to double-curvature surfaces, bending in two directions simultaneously, with medium flexibility stone adaptability, requiring zoned fitting and cutting. Free-form surfaces correspond to non-developable surfaces with irregularly changing curvature, with limited flexibility stone adaptability, requiring 3D scanning, digital design, and customized processing. In actual projects, curved surface types may appear in combination, and the geometric characteristics of transition zones between substrates are complex; comprehensive judgment should be made based on on-site measurements and sample tests.

24.2 The “Five Types” of Special Scenarios

In addition to curved and irregular shapes, flexible stone also faces several “special scenarios” in facade retrofit: high-rise buildings, cold regions, coastal areas, industrial environments, and indoor irregular spaces.

24.2.1 Type One: High-Rise Buildings

Scenario characteristics: building height >100 m, large wind loads, large temperature differences.

Requirements for materials: high bonding strength, good weather resistance, high fire rating.

Flexible stone response strategies:

Select high-performance formulas—bonding strength ≥0.5 MPa, weather resistance ≥2000h;

Strengthen bonding—use special bonding agents, full coverage rate ≥90%;

Fire rating—select A2 or B1 products;

Construction safety—gondola construction, with safety protection in place.

Table 24-5 Application Points for Flexible Stone in High-Rise Buildings

24.2.2 Type Two: Cold Regions

Scenario characteristics: cold winters, frequent freeze-thaw cycles.

Requirements for materials: freeze-thaw resistance, good flexibility.

Flexible stone response strategies:

Select freeze-thaw resistant formulas—freeze-thaw resistance ≥100 cycles;

Strengthen waterproofing—strengthen the waterproofing system to prevent moisture infiltration;

Flexible design—select products with good flexibility to adapt to freeze-thaw deformation;

Construction temperature—construction temperature not lower than 5°C.

In cold region applications, the enterprise’s independently developed high-flexibility flexible stone emulsion technology provides key technical support. This technology, through monomer pre-emulsification semi-continuous seed emulsion polymerization, introduces modified additives into the core-shell structure, giving flexible stone excellent flexibility at -30°C, withstanding 100 freeze-thaw cycles without cracking or peeling, and weather resistance of 3500h. This technological breakthrough enables flexible stone to adapt to facade retrofit projects under severe cold climate conditions, providing more reliable durability assurance for cold northern regions.

Table 24-6 Application Points for Flexible Stone in Cold Regions

24.2.3 Type Three: Coastal Areas

Scenario characteristics: salt spray corrosion, high humidity, strong ultraviolet radiation.

Requirements for materials: salt spray resistance, good water resistance, weather resistance.

Flexible stone response strategies:

Select salt spray resistant formulas;

Strengthen waterproofing—strengthen the waterproofing system to prevent moisture infiltration;

Weather resistance—select products with weather resistance ≥2000h;

UV resistance—add UV absorbers to delay fading.

In coastal area applications, the enterprise’s independently developed inorganic silicone resin modified acrylic emulsion technology provides technical support. This technology, through chemical bonding, copolymerizes inorganic silicone resin with acrylate monomers, combining the weather resistance and stain resistance of inorganic silicone resin with the flexibility and bonding properties of acrylate, achieving topcoat stain resistance (whiteness recovery rate) of over 80% and weather resistance of 3500h. It can effectively resist salt spray corrosion and strong ultraviolet erosion on flexible stone surfaces in coastal areas, maintaining appearance quality over the long term.

Table 24-7 Application Points for Flexible Stone in Coastal Areas

24.2.4 Type Four: Industrial Environments

Scenario characteristics: acid-base corrosion, contamination.

Requirements for materials: chemical corrosion resistance, good stain resistance.

Flexible stone response strategies:

Select corrosion-resistant formulas—dilute acid resistance, dilute alkali resistance;

Stain-resistant topcoat—apply a stain-resistant topcoat to reduce contamination;

Regular cleaning—develop a cleaning plan and clean regularly;

Local replacement—local replacement of severely contaminated areas.

Table 24-8 Application Points for Flexible Stone in Industrial Environments

24.2.5 Type Five: Indoor Irregular Spaces

Scenario characteristics: indoor irregular spaces, such as curved walls, cylinders, and domes.

Requirements for materials: environmental protection, decorative performance, flexibility.

Flexible stone response strategies:

Select environmentally friendly formulas—VOC not detected, no formaldehyde;

Decorative performance—rich colors, diverse textures;

Flexibility—adapt to irregular spaces;

Convenient construction—indoor construction, no large equipment required.

Table 24-9 Application Points for Flexible Stone in Indoor Irregular Spaces

The five special scenarios correspond to different environmental dimensions. High-rise buildings correspond to wind load and temperature difference environments, requiring high bonding strength and high weather resistance; cold regions correspond to freeze-thaw cycles and low-temperature environments, requiring high freeze-thaw resistance and flexibility; coastal areas correspond to salt spray corrosion and high-humidity environments, requiring high salt spray resistance and water resistance; industrial environments correspond to acid-base corrosion and contamination environments, requiring high chemical corrosion resistance and stain resistance; indoor irregular spaces correspond to environmental protection and decorative environments, requiring high environmental protection and flexibility. In actual projects, multiple environmental factors may act simultaneously. For example, coastal areas simultaneously have salt spray, high temperature, and strong ultraviolet radiation, while cold regions simultaneously have freeze-thaw, low temperature, and temperature differences. Comprehensive judgment should be made based on material test data and engineering experience.

24.3 The “Five Key Technologies” for Curved and Irregular Construction

Curved and irregular construction involves five key technologies: substrate curvature control, bonding agent application, compaction and air expulsion, cutting and trimming, and joint treatment.

24.3.1 Substrate Curvature Control

Technical points:

Use a curved template to check whether the substrate curvature is uniform;

For parts with uneven curvature, repair with leveling mortar;

For parts with too small curvature radius, evaluate flexible stone adaptability.

Table 24-10 Substrate Curvature Control Points

24.3.2 Bonding Agent Application

Technical points:

Bonding agent should be applied more fully on curved parts;

Use a notched trowel, with the notch specification selected according to the curvature radius;

Application should be uniform and full, with no omissions or thin spots.

Table 24-11 Bonding Agent Application Points

24.3.3 Compaction and Air Expulsion

Technical points:

Use a flexible pressing plate to compact from the middle toward both sides;

The compaction force should be uniform, not excessive;

Compaction should be sufficient to expel air in the bonding agent.

Table 24-12 Compaction and Air Expulsion Points

Case: After a curved project applied flexible stone, the hollowing rate on curved parts was relatively high. Investigation found that the construction team did not compact sufficiently, and air existed between the bonding agent and flexible stone. After switching to a flexible pressing plate to compact from the middle toward both sides, the hollowing rate significantly decreased. This case shows that hollowing problems are not necessarily bonding agent problems; the compaction process is also a key control link.

24.3.4 Cutting and Trimming

Technical points:

Use a utility knife or special cutting knife;

Cut edges should be smooth, without burrs;

When cutting is needed on curved parts, measure first, then cut.

In curved surface cutting, the enterprise’s independently developed flexible stone cutting device provides technical support. The device integrates cutting, fixing, pushing, and dust removal. Through the coordinated cooperation of the positioning base, folding assembly, cutting assembly, pushing assembly, and dust removal assembly, the cutting process is more precise, efficient, and environmentally friendly, especially suitable for precise cutting of curved and irregular parts, solving the problems of large dust and easy material damage in traditional cutting.

Table 24-13 Cutting and Trimming Points

24.3.5 Joint Treatment

Technical points:

Joints on curved parts should be as concealed as possible;

Special joint filler or sealant should be used at joints;

Joints should be full, dense, and flat.

Table 24-14 Joint Treatment Points

24.4 The “Three Typical Schemes” for Special Scenarios

According to the environmental requirements and material requirements of special scenarios, three typical schemes can be summarized: standard scheme, strengthened scheme, and customized scheme. The general system logic of the three schemes is detailed in Chapter 15; this section focuses on parameter selection and applicable scope for special scenarios.

24.4.1 Standard Scheme (General Special Scenarios)

Applicable conditions: high-rise buildings, cold regions, coastal areas, and other general special scenarios.

Scheme content: standard formula + standard system + standard construction.

Advantages: moderate cost, wide applicability. Disadvantages: performance margin may be insufficient in extreme environments.

Table 24-15 Standard Scheme

24.4.2 Strengthened Scheme (Extreme Special Scenarios)

Applicable conditions: super high-rise buildings, extremely cold regions, strong salt spray areas, and other extreme special scenarios.

Scheme content: high-performance formula + strengthened system + professional construction.

Advantages: adapts to extreme environments. Disadvantages: relatively high cost.

Table 24-16 Strengthened Scheme

24.4.3 Customized Scheme (Free-Form Surfaces and Ultra-Special Scenarios)

Applicable conditions: free-form surfaces, ultra-special scenarios.

Scheme content: customized formula + customized system + customized construction.

Advantages: fully adapts to special needs. Disadvantages: highest cost.

Table 24-17 Customized Scheme

Case: An artistic building project had a free-form facade with irregularly changing curvature. A customized scheme was adopted: 3D scanning to obtain precise geometric data → digital layout design → customized flexible stone specifications and shapes → sample first → professional construction. After construction was completed, the curved surface effect was confirmed by the client. This case shows that free-form surfaces require customized schemes, and only customized schemes can realize design freedom.

Decision Reference for Facade Retrofit Offices

I. Applicable Object Determination: This chapter applies to two types of projects—facade retrofit of curved and irregular parts (curved walls, cylindrical surfaces, domes and spherical surfaces, free-form surfaces) and facade retrofit of special scenarios (high-rise buildings, cold regions, coastal areas, industrial environments, indoor irregular spaces). Before decision-making, first determine which type the project belongs to; different types have different technical priorities and risk control focuses.

II. Key Decision Indicators: Curved and irregular projects use the “four curved surface types” to determine construction strategies—curved walls can be directly fitted, cylindrical surfaces focus on compaction and joints, domes and spherical surfaces use zoned fitting, and free-form surfaces require 3D scanning, digital design, and customized processing. Special scenario projects use the “five scenario types” to determine material parameters—high-rise buildings focus on bonding strength (≥0.5 MPa) and fire rating, cold regions focus on freeze-thaw resistance (≥100 cycles) and construction temperature (≥5°C), coastal areas focus on salt spray resistance (≥1000h) and UV resistance, industrial environments focus on corrosion resistance and stain resistance, and indoor irregular spaces focus on environmental protection and flexibility.

III. Scheme Comparison Recommendations: General special scenarios choose the standard scheme; super high-rise, extremely cold, strong salt spray, and other extreme scenarios choose the strengthened scheme; free-form surfaces and ultra-special scenarios choose the customized scheme. Scheme selection should follow the cost principle of “use standard rather than strengthened where possible, use strengthened rather than customized where possible,” but free-form surfaces and extreme environments should not be downgraded to control costs.

IV. Cost and Schedule Reference: Curved construction unit prices increase with curved surface complexity—curved walls are close to flat unit prices, cylindrical surfaces increase by about 20%–30%, domes and spherical surfaces increase by about 40%–60%, and free-form surfaces have the highest unit prices due to 3D scanning, digital design, and customized processing. Cost differences in special scenarios mainly come from formula upgrades and system strengthening. In terms of schedule, curved projects should first make samples to confirm the process; sample period is generally 1–3 days, and large-area schedule should be appropriately enlarged according to curved surface complexity. Costs for night construction or off-peak construction should be included in the budget before the scheme is determined.

V. Implementation Risk Warnings: The three major risks are curved surface hollowing, insufficient performance in special scenarios, and deviation of free-form surface effects from expectations. Hollowing risk is controlled through compaction and air expulsion processes; insufficient performance risk is controlled through formula and system selection; effect deviation risk is controlled through sample first and digital design. Quality acceptance of curved projects should include curvature fit inspection; special scenario projects should verify the matching of material test reports with on-site conditions.

Reflections on Stone, Insights on Fortune

Curved and irregular shapes are flexible stone’s “home turf” and also its “touchstone.” Done well, they are highlights; done poorly, they are pain points. Flexible stone’s flexibility advantage is not something that can be realized by nature; substrate curvature control, bonding agent fullness, compaction and air expulsion, cutting and joints—only when every process is in place is flexibility an advantage; if any process is lax, flexibility becomes a defect. The same applies to special scenarios: material performance adaptation is not “the higher the better,” but “matching the environment is what matters.” Making curved surfaces flat and matching scenarios accurately—this is the engineering attitude this chapter wants to convey.

References

[1] GB 50210—2018, Standard for Construction Quality Acceptance of Building Decoration[S].

[2] GB 50300—2013, Unified Standard for Constructional Quality Acceptance of Building Engineering[S].

[3] JGJ/T 29—2015, Specification for Construction and Acceptance of Building Painting[S].

[4] GB/T 3810.7—2016, Test Methods of Ceramic Tiles—Part 7: Determination of Surface Abrasion Resistance of Glazed Tiles (related bending test clauses)[S].

[5] T/CECS 728—2020, Technical Standard for Comprehensive Renovation of Old Urban Residential Areas[S].

[6] Related general clauses in Chapters 15, 17, 18, and 19 of this book.