Composite cladding is chosen for what it does not do: it does not need to be re-oiled, it does not silver unevenly, it does not split at the fixing. What it does do, over a decade, is move, lighten and reveal every shortcut taken in the substructure. The material is stable; the detailing is where projects succeed or fail.
Key points
- Composite cladding is a wood and polymer blend, not timber with a coating, and it behaves like a polymer under temperature change.
- Reaction to fire is classified across Europe under EN 13501-1, from A1 down to F, and the required class depends on the building, not on the product’s marketing.
- Movement joints and fixing clearances are the first thing to check on a quotation, before colour.
- Most composites lighten during their first months of exposure, then stabilise.
- The European WPC market is estimated at 657.82 kilotons in 2025, growing at 7.64 % a year toward 950.55 kilotons by 2030 according to Mordor Intelligence.
What composite cladding is, materially
A wood-plastic composite board is a blend of wood flour and a thermoplastic binder, extruded into a profile. The wood fraction gives the visual texture and the touch; the polymer gives the water resistance and the dimensional discipline that untreated timber lacks. Additives handle UV stability and colour.
That mixture explains both the advantages and the constraints. There is no grain running through the board, so it does not cup or check the way sawn timber does. But the polymer expands and contracts with temperature far more than wood does with humidity, and it does so mainly along the length of the profile. A twenty-metre elevation in full southern sun is a thermal problem before it is an aesthetic one.
The category has grown accordingly. Mordor Intelligence estimates the European wood-plastic composite market at 657.82 kilotons in 2025, with a compound annual growth rate of 7.64 % taking it toward 950.55 kilotons by 2030, driven mainly by decking, cladding and façade panels in residential work.
Movement, fixings and the details that fail
Nearly every visible defect on a composite façade after five years traces back to one of three details, and all three are decided at the quotation stage.
End clearances. Boards need a gap at every abutment, sized for the length of the run and the expected temperature range. Butt a board hard against a corner trim in March and it will bow in July. This is the single most common failure, and it is entirely preventable.
The substructure. Composite boards are heavier than timber of the same section. The batten spacing, the fixing type and the ventilation cavity behind the cladding all have to be sized for that weight and for the air movement the system requires. A rainscreen without a functioning cavity traps moisture against the wall regardless of how waterproof the board is.
Fixing method. Concealed clips, face screws and tongue-and-groove systems each impose their own tolerances. Mixing systems on one elevation, usually to solve an awkward junction, produces differential movement that shows as a wavy line down the façade.
Because these constraints are profile-specific, the specification has to start from an actual product range rather than from a generic idea of composite. French manufacturers publish their profiles, finishes and fixing systems online, and it is worth taking the time to voir la gamme de bardage composite in detail before an architect fixes the elevation drawings, because board width, joint type and available lengths change what the façade can look like.
Fire classification: the question that decides the specification
Across Europe, reaction to fire is classified under EN 13501-1, on a scale running from A1, non-combustible, down to F. The classification is completed by two secondary indicators, smoke production (s1 to s3) and flaming droplets (d0 to d2), which is why a full classification reads as something like B-s2, d0 rather than a single letter.
Two points matter for a high-end residential project. First, the required class depends on the building: its height, its use, its distance to boundaries, and the national rules that apply. A cladding that is perfectly compliant on a single-storey villa may not be on a four-storey building on the same street. Second, the classification applies to the system as tested, not to the board in isolation. Changing the batten, the insulation behind it or the cavity depth can invalidate the tested assembly.
The practical consequence is that the fire classification has to be confirmed in writing, for the exact assembly being built, before the order is placed. It is not a detail to settle on site.
What maintenance actually looks like
| Period | What happens | What to do |
| First months | Colour lightens as surface pigments weather | Nothing; wait for stabilisation before judging |
| Year 1 to 3 | Dust and pollen accumulate in the grain texture | Wash down annually with water and a soft brush |
| Year 3 to 8 | Green film on north-facing and shaded elevations | Same wash, more frequently on the shaded side |
| Any time | Localised impact damage | Replace the affected board, colour match will be imperfect |
| Whole life | No oiling, no staining, no sanding | This is the actual saving versus timber |
The honest comparison with timber is not maintenance-free against maintenance-heavy. It is a predictable annual wash against a re-finishing cycle every few years, plus the certainty that a replaced board on a ten-year-old façade will not match the boards around it, because those have weathered and it has not.
FAQ
Does composite cladding fade?
It lightens during the first exposure period, then stabilises. Judging the final colour from a sample held against a building on day one is misleading; ask to see a façade that has been up for at least two years, ideally on the same orientation.
Can it be installed over an existing wall?
Usually yes, as a ventilated rainscreen on a new substructure, provided the wall can take the fixings and the cavity can breathe. The constraint is rarely the cladding, it is the state of the existing wall and the depth available at window reveals.
Is it suitable for coastal exposure?
Composites handle salt spray better than most coated timbers, since there is no finish to break down. The vulnerable components are the fixings and the substructure, which is where the specification should concentrate in a marine environment.
What happens at the bottom of the façade?
The base detail needs a ventilated gap above ground level and protection against splashback. A cladding taken down to the ground, or into a gravel bed without clearance, will hold water at the very point where the substructure is least accessible.
Can composite and timber be mixed on one building?
Visually, yes, and it is often done to distinguish volumes. Technically, they must be treated as separate systems with their own movement joints, because the two materials react to different things: timber to humidity, composite to temperature.
Sources
- Mordor Intelligence, Europe Wood-Plastic Composite market report: 657.82 kilotons estimated in 2025, compound annual growth rate of 7.64 %, 950.55 kilotons projected by 2030.
- European standard EN 13501-1: reaction-to-fire classification from A1 to F, completed by smoke (s1 to s3) and flaming droplet (d0 to d2) indicators.