| Reaction to Fire Classification | Under EN 13501-1, classifications range from A1 to F. Smoke production is rated s1–s3, while flaming droplets are rated d0–d2. | Request a valid classification report for the complete intended assembly, including the profile, fixing method, substrate, joints, and any coating. | Choose the classification required by the local building code and the building’s use, height, location, and escape-route conditions. Do not infer the rating from the material name alone. | Higher required fire performance may increase material, detailing, testing, and installation costs, but can prevent redesign or approval delays. |
| Flame-Spread Reference | For ASTM E84, Class A corresponds to a flame-spread index of 0–25, Class B to 26–75, and Class C to 76–200. ASTM E84 results are not automatically equivalent to EN 13501-1 classes. | Request the exact test standard, report number, specimen configuration, and whether the result applies to the finished WPC system. | Compare products only when the test method and installation configuration are comparable. Use the standard specified by the project jurisdiction. | Using the wrong test basis can create compliance risk, additional testing costs, or replacement costs after installation. |
| Profile and Density | WPC decking and cladding may be solid or hollow. Hollow profiles generally weigh less, while solid profiles usually provide greater mass and different fixing requirements. Density and dimensions vary by formulation. | Request nominal dimensions, mass per metre or square metre, dimensional tolerances, span tables, and maximum permitted cantilever. | Select the profile according to joist spacing, wind exposure, expected loads, thermal movement, and the manufacturer’s span table. | Lower material weight can reduce handling and substructure costs, but insufficient stiffness may require closer supports and increase installation cost. |
| Fastener Compatibility | Outdoor WPC systems require corrosion-resistant fasteners. 304 stainless steel is commonly used in many exterior environments; 316 stainless steel offers better resistance in marine or chloride-rich conditions. | Request approved screw, clip, starter clip, edge clip, washer, and plug specifications, plus the required torque and pilot-hole details. | Use only fasteners approved for the specific profile. For coastal, poolside, de-icing-salt, or industrial environments, verify whether 316 stainless steel is required. | Compatible fasteners reduce staining, corrosion, loosening, and premature replacement. Higher-grade fasteners cost more initially but may reduce maintenance risk. |
| Galvanic and Chemical Compatibility | Dissimilar metals can create galvanic corrosion when moisture and electrolytes are present. Chemical exposure can also affect polymers, coatings, and metal fasteners. | Request compatibility guidance for aluminium, galvanized steel, treated timber, concrete, cleaning agents, pool chemicals, and coastal exposure. | Avoid unapproved metal combinations and direct contact where the system documentation identifies a corrosion risk. Provide drainage and ventilation behind the boards. | Correct detailing can avoid hidden corrosion, staining, board movement, and costly access or replacement work. |
| Thermal Movement and Joint Design | WPC expands and contracts with temperature. The required end gaps depend on board length, installation temperature, coefficient of thermal expansion, and fixing method. | Request the specified end-gap table, perimeter clearance, expansion-joint detail, maximum board length, and installation-temperature limits. | Follow the system’s measured expansion guidance rather than using a universal gap. Allow ventilation and drainage behind the installation. | Correct gaps reduce buckling, splitting, noise, and remedial work. Poor joint design can shorten service life even when the board material is suitable. |
| Warranty Coverage | Warranty periods and coverage vary. A warranty may separately address structural integrity, rot or insect damage, colour change, staining, or surface performance, and may include exclusions. | Request the full written warranty, start date, transferability, geographic limits, approved installation requirements, maintenance obligations, and claim procedure. | Compare the covered defects and exclusions—not only the number of warranty years. Confirm whether labour, removal, disposal, and reinstallation are covered. | A longer warranty has limited value if installation, colour variation, fading, cleaning, or commercial-use exclusions are broad. |
| Expected Service Life | There is no universal service-life value for all WPC products. Performance depends on formulation, UV exposure, moisture, temperature cycles, loading, ventilation, cleaning, and installation quality. | Request documented field-performance data, accelerated-weathering information, maintenance requirements, and the conditions used for any service-life statement. | Use a documented project-specific service-life assumption in financial calculations. Do not treat the warranty period as the guaranteed service life. | A realistic service-life assumption prevents underestimating replacement, access, labour, and disposal costs. |
| Routine Maintenance | Typical maintenance may include sweeping, washing with water and a suitable mild cleaner, clearing drainage paths, and inspecting fasteners and joints. Exact procedures are product-specific. | Request the approved cleaning method, prohibited chemicals, stain-removal procedure, inspection frequency, and refinishing limitations. | Choose a surface and colour that match the site’s dirt, grease, pollen, algae, and foot-traffic conditions. Avoid unapproved pressure-washing or harsh solvents. | Maintenance frequency, labour access, cleaning equipment, and water use should be included in the total-cost model. |
| Colour and Weathering | Outdoor exposure can cause colour change, surface weathering, and differences between boards. The rate depends on pigments, surface treatment, orientation, climate, and exposure. | Request colour-change test data, sample-age information, replacement-board matching policy, and guidance for shaded versus sun-exposed areas. | Evaluate full-size samples outdoors when appearance is critical. Confirm whether normal colour change is excluded from the warranty. | Visible weathering may affect replacement timing, aesthetic upgrades, and the cost of replacing boards solely for colour consistency. |
| Installation Labour and Substructure | Total installed cost includes boards, clips, screws, joists or battens, membranes where required, trims, waste, labour, access equipment, and disposal. | Request an itemized bill of quantities, recommended support spacing, waste allowance, installation rate, and details for edges, steps, corners, and penetrations. | Compare complete installed systems rather than board price alone. Confirm that the substructure is suitable for moisture, load, and ventilation conditions. | Accessories and labour can represent a significant portion of project cost, especially for complex layouts or elevated installations. |
| Lifecycle Cost Calculation | A practical calculation is: Initial Cost + Present Value of Maintenance + Present Value of Repairs or Replacement + Disposal Cost − Residual Value. | Request prices and assumptions for installation, annual maintenance, component replacement, access, inflation, discount rate, and disposal. | Use the same service period and performance requirements for every option. Run sensitivity scenarios for maintenance frequency and replacement timing. | The lowest purchase price is not necessarily the lowest total cost when fasteners, access, cleaning, repairs, and replacement are included. |
| Documentation and Traceability | Reliable comparison requires consistent technical data, test standards, revision dates, installation instructions, and batch or product identification. | Request current technical datasheets, safety information, test reports, installation manuals, warranty terms, and quality-control documentation. | Prefer products with clear, current, independently verifiable documentation. Record the exact product configuration used for approval and purchasing. | Good documentation reduces design changes, installation errors, disputes, and the cost of proving compliance later. |