| Material composition | A consistent mixture of wood fibre or wood flour, thermoplastic resin, coupling agents, pigments and processing additives. | Declared polymer type, wood content range, filler content, additive list and batch-to-batch consistency. | GB/T 29418-2012, Wood-Plastic Composites; supplier technical specifications. | Material declaration, formulation control records and an independent composition or identification report. |
| Product types suitable for outdoor use | Solid, hollow and capped/co-extruded boards can all be suitable when the design, drainage and installation system match the application. | Typical board width: approximately 135–180 mm; typical thickness: approximately 20–30 mm; actual values depend on the product design. | GB/T 24508-2009, Wood-Plastic Flooring; approved product drawings and specifications. | Dimension tolerances, cross-section drawings, installation spacing and load tables. |
| Dimensional stability | Boards should remain straight and maintain usable joints after temperature and moisture changes. | Check length, width, thickness, straightness, warpage and gap movement under the supplier’s stated test conditions. | GB/T 24508-2009; GB/T 29418-2012; applicable dimensional test procedures. | Third-party dimensional inspection and installation calculations for the project climate. |
| Water absorption and moisture resistance | Low water uptake, limited swelling and no visible delamination, cracking or surface separation after wet exposure. | Water absorption and thickness swelling should be reported as percentages after the specified immersion period. | GB/T 24508-2009; GB/T 29418-2012; relevant procedures in GB/T 17657-2013. | Original laboratory report showing test duration, specimen size, conditioning and calculated results. |
| Mechanical strength | Sufficient bending strength and stiffness for the selected joist spacing, pedestrian traffic and expected service load. | Report flexural strength, flexural modulus, screw-holding performance and allowable span rather than relying on board appearance alone. | GB/T 24508-2009; GB/T 29418-2012; project structural design requirements. | Load-span chart, mechanical test report and installation instructions specifying joist centres. |
| Surface slip resistance | A textured or brushed surface that maintains appropriate slip resistance when wet, without creating excessive dirt retention. | Wet and dry slip results should be supplied using a clearly identified test method and footwear or slider condition. | Project safety requirements and the declared slip-resistance test method; acceptance criteria may vary by application. | Wet-condition test report, maintenance instructions and samples with the production surface finish. |
| Weathering and colour retention | UV stabilisers, suitable pigments and a surface layer that reduce fading, chalking and cracking during outdoor exposure. | Artificial weathering duration, colour change, surface defects and gloss change should be recorded; laboratory exposure is not a direct guarantee of service life. | GB/T 24508-2009; GB/T 29418-2012; relevant accelerated-weathering methods such as GB/T 16422 series. | UV-weathering report, colour tolerance specification and written warranty conditions. |
| Rot, mould and biological resistance | The formulation and drainage design should limit moisture retention and visible fungal growth; WPC should not be described as completely maintenance-free. | Mould-resistance, fungal-resistance or accelerated durability results should identify the organisms, exposure conditions and rating scale. | GB/T 29418-2012 and the specific biological-resistance method declared by the testing laboratory. | Test report, cleaning schedule, ventilation requirements and installation details preventing standing water. |
| Fire performance | Fire performance must be evaluated for the complete intended assembly where required, including boards, substructure, clips and surrounding materials. | Reaction-to-fire classification, ignition behaviour, smoke production and flaming droplets should be stated only from a valid test or classification report. | GB 8624-2012, Classification for Burning Behaviour of Building Materials and Products. | Valid fire-test or classification report for the exact product construction and thickness. |
| Formaldehyde and restricted substances | A compliant product should control formaldehyde and other restricted substances from wood components, additives, pigments and recycled polymer sources. | Formaldehyde emission should be reported using the applicable chamber, desiccator or perforator method; recycled content should be traceable. | GB 18580-2017 where applicable to wood-based materials; GB/T 17657-2013 test methods; project chemical restrictions. | Recent chemical test report, safety data sheet and raw-material traceability records. |
| Surface finish and appearance | Uniform embossing, colour and edge quality with no major voids, cracks, delamination, exposed fibres or unstable co-extruded layers. | Inspect colour difference, surface defects, edge straightness, cavity integrity and consistency across production batches. | GB/T 24508-2009; approved visual inspection criteria and product drawings. | Pre-production sample approval, retained reference sample and incoming inspection checklist. |
| Installation-system compatibility | Boards, clips, screws, joists, edge trims and drainage details should be designed as one compatible system. | Check clip fit, screw pull-out, expansion gaps, ventilation clearance, joist spacing and maximum unsupported span. | GB/T 24508-2009; manufacturer installation specification; applicable building and structural requirements. | Detailed installation manual, section drawings, fastener specification and project-specific method statement. |
| Quality-control consistency | Stable extrusion conditions, controlled moisture, documented raw-material batches and routine finished-product testing. | Review production-batch records, dimensional checks, mechanical tests, appearance inspections and nonconformity records. | GB/T 29418-2012; ISO 9001-based quality systems may support control but do not replace product testing. | Factory audit, batch certificate, inspection plan and traceability from raw materials to shipment. |
