Technical glossary

Ability of the surface of a material to resist wear caused by friction — pedestrian traffic, dragging of furniture, action of sand and dust. A decisive property in outdoor decking subjected to intensive use.

Arrangement of deck boards in which the ends are aligned between adjacent rows, forming continuous joints transverse to the axis of the boards.

Mechanical property that expresses the ability of a material or structural element to resist forces that tend to bend it, without fracturing or showing excessive deformation. In decking profiles, it is usually determined according to the EN 310 standard and expressed in N/mm² (megapascal).

Deterioration of a material caused by biological agents — fungi, mould, moss, termites and other wood-boring insects. It is the main cause of premature failure in natural-wood outdoor decking. WPC composites, due to the presence of the polymer matrix, offer significantly higher resistance to this type of degradation.

Composite decking board coated, during the manufacturing process, with a polymer cap that covers all or part of its surface. The cap seals the core of the material, drastically reducing moisture absorption and enhancing colour stability, abrasion resistance and ease of cleaning. Also known as «encapsulated board».

Internal cavity, usually of continuous longitudinal section, found in an extruded profile. In hollow boards for outdoor decking, cavities reduce the weight of the piece without significantly compromising its mechanical performance. Sometimes also referred to as «hollow».

Mark applied to a product by the manufacturer, declaring compliance with the applicable European legislation and allowing free commercialisation within the European Economic Area. For construction products, CE marking is regulated by Regulation (EU) No 305/2011 (Construction Products Regulation) and requires the issue of a Declaration of Performance.

Physical quantity that expresses the relative variation in the dimensions of a material (length, area or volume) per degree of temperature variation. It is usually expressed in 1/°C or 1/K. It is a design parameter for any structure or flooring subjected to thermal variations, as it determines the size of the expansion gaps to be allowed.

Ability of a material to retain its tone over time, without significant discolouration caused by solar exposure and atmospheric agents. It depends on the formulation of the material, the presence of UV stabilisers and, in composites, the possible existence of an external polymer cap.

Material resulting from the combination of two or more constituents with different properties which, together, produce a material with characteristics superior to those of the isolated components. A composite is usually formed by a matrix (continuous) and one or more fillers (discontinuous). In the outdoor decking sector, the most widely used composite is WPC, which combines wood fibres, polymer and additives.

Decking whose boards are made of composite material, typically WPC (Wood-Plastic Composite). It combines the appearance and texture of wood with greater resistance to moisture, UV radiation and biological degradation, and requires much less maintenance than natural wood.

Flooring of boards laid on a ventilated substructure, intended for outdoor spaces such as terraces, balconies, gardens, outdoor hospitality areas and pool surrounds. It can be manufactured in natural wood, composite or other materials. Also known as «decking».

Formal document provided for in Regulation (EU) No 305/2011 on construction products, which declares the performance of a product against the applicable essential characteristics. The preparation and availability of the DoP is a mandatory condition for the application of the CE marking.

Physical quantity that expresses the ratio between the mass and the volume of a material, usually in kilograms per cubic metre (kg/m³). In composite decking, density allows configurations to be distinguished: for the same cross-section, solid boards are denser than hollow boards.

Ability of a material to retain its shape and its dimensions over time, despite variations in temperature and humidity. It is one of the most relevant properties of an outdoor deck: the greater the dimensional stability, the lower the probability of cracks, warping or displacement at the joints.

Change in the dimensions of a piece (length, width or thickness) caused by variations in temperature and humidity. The smaller the dimensional variation, the more stable the material is over time and the smaller the expansion gap to be allowed for during installation.

Space left, at the time of installation, between adjacent pieces and between pieces and fixed elements (walls, kerbs, steps), to accommodate the dimensional variations of the material caused by temperature and humidity. Its size depends on the nature of the material, the length of the pieces and the climatic conditions at the site.

Manufacturing process in which a material, usually in powder or granulated form, is heated until it becomes plastic and forced through a die (an opening of defined shape), producing a profile of constant cross-section and continuous length. It is the base process for manufacturing profiles in metal, PVC, aluminium and composite materials such as WPC.

Flooring system in which the surface layer is not rigidly fixed to the base, resting only on a supporting substructure, with or without a decoupling underlay. The absence of rigid fixing allows the dimensional variations of the material to be absorbed, avoiding internal stresses, warping and cracking. It applies, with variants, to indoor laminate floors and to outdoor decks. Also known as «floating flooring».

Designation given, in the formulation of composite materials, to components that occupy volume and contribute to the final properties of the material, but which do not constitute its matrix. In wood-plastic composites (WPC), wood fibres are the main functional filler: higher percentages reduce cost but increase moisture absorption; lower percentages favour dimensional stability but reduce mechanical performance.

Arrangement of pieces in a herringbone pattern, in which each piece is placed perpendicular to the next, forming successive angles. When applied to decking, it requires specific planning of the supporting structure and of the gaps between the ends of the pieces.

Decking board whose profile presents internal cavities along its entire length. Lighter than a solid board of equivalent cross-section, it retains a good weight-to-strength ratio. It is the most common configuration in composite decking.

Continuous component of a composite material, within which the fillers or reinforcements are dispersed. In WPC composites, the matrix is polymeric — typically PVC, PE (polyethylene) or PP (polypropylene) — and it is the component that ensures the cohesion of the material, resistance to atmospheric agents and durability.

Finishing solution in which two pieces forming a corner are cut at 45° and meet at a bevel. Aesthetic alternative to the perpendicular joint, frequently used in decking with regular geometry to achieve clean corners with no end grain showing.

Property of a material that reflects the amount of water it retains when exposed to ambient humidity or in direct contact with water. It is one of the most decisive properties for outdoor materials, as it is the source of dimensional variation, rotting and biological degradation.

Material composed of long molecular chains formed by the repetition of simple chemical units (monomers). There are natural polymers (such as cellulose or natural rubber) and synthetic polymers (plastics). In composites for outdoor use, the most commonly used polymers are PVC, polyethylene (PE) and polypropylene (PP), due to their mechanical strength, thermal stability and durability against atmospheric agents.

Outer layer, formed by a high-strength polymer composition, that covers the core of a composite profile. It seals the surface of the material, drastically reducing moisture absorption and reinforcing colour stability and abrasion resistance.

Continuous membrane, typically made of modified bitumen or PVC, applied over slabs, roofs and terraces to prevent water infiltration into the structures below. It cannot be drilled without compromising its function, and therefore, when decking is to be installed over a protective membrane, a self-supporting structure must be used. Also known as «waterproofing membrane».

Polyvinyl Chloride. Thermoplastic used in a very wide range of applications, from construction to healthcare, due to its high chemical and mechanical resistance, good thermal stability and strong resistance to UV radiation and other climatic elements. It is one of the polymers most widely used as a matrix in WPC composites.

Set of properties that reflect the contribution of a material to the development and propagation of a fire. In the European Union, it is classified according to standard EN 13501-1 («Euroclasses»), which defines seven main classes for construction products — A1, A2, B, C, D, E and F — where A1 corresponds to materials that contribute least to a fire and F to those that contribute most. It is distinct from fire resistance, which refers to the ability of construction elements to maintain their function during a fire.

Structure that stands on its own supports or pedestals, without being fixed to the underlying slab or flooring. It is the solution adopted when it is not possible to drill into the base (for example, over protective membranes on terraces) or when the deck level needs to be raised to accommodate technical installations, drainage or changes in level.

Decking board with a solid cross-section, without internal cavities. Heavier and denser than a hollow board, it is used in applications where greater inertia or load-bearing capacity is required. It can have the same external configuration as hollow boards, allowing the two configurations to be combined in the same installation.

Arrangement of deck boards in which the ends are offset between adjacent rows, like a stretcher bond. It is the most common assembly for outdoor decks.

Plastic that softens when heated and hardens when cooled, and can be reprocessed several times without significant alteration of its properties. This characteristic makes thermoplastics recyclable and suitable for processing by extrusion, injection or blow moulding. PVC, polyethylene (PE) and polypropylene (PP) are thermoplastics.

Ability of a material to resist the degradation caused by the ultraviolet rays of the sun, in particular the surface discolouration and the embrittlement of the polymer matrix. It is a decisive property in the choice of any material used outdoors and depends, to a large extent, on the presence of UV stabilisers in the formulation.

Particles or filaments of wood, obtained from residues or by-products of the wood industry, used as functional filler in composite materials. They contribute to the appearance, texture and part of the mechanical properties of the material. They are the natural component of WPC composites.

Acronym for Wood-Plastic Composite. Material resulting from the combination of wood fibres, polymer matrix (PVC, PE or PP) and additives. It is the international designation used in technical data sheets, European standards and customs documentation, and it is used in the manufacture of decking, façade cladding, fencing, urban furniture and other outdoor products.