Indoor WPC Against Outdoor WPC and What Actually Separates Them

Both are wood plastic composite, and that is where it ends

Interior and exterior WPC share a material family: wood fibre bound in a polymer. What separates them is the surface, the section and the way water is handled behind the board. Treating them as interchangeable is the most expensive mistake in this category, because the failure shows up on an elevation after the scaffold has gone.

Co-extrusion is the real difference

Outdoor boards carry a skin that is co-extruded with the core in the same pass. It cannot delaminate the way a surface bonded on afterwards can, and it is what gives the board fade resistance under direct sun. Interior panels carry a laminated veneer applied by hot and cold pressing, which is the right answer indoors and the wrong one outdoors.

Section depth and density

Outdoor sections run 219x26mm and 156x21mm with a high density, thickened body for impact and aging resistance, acid and alkali resistance and insect resistance. Interior panels run 10mm to 23mm deep because they only ever have to stay flat in a room.

Fixing and the cavity behind the board

Indoors, a panel goes onto a flat wall or a batten grid and that is the end of it. Outdoors the board needs a ventilated batten or aluminium substructure, concealed clips, expansion gaps at board ends and a drainage cavity behind. Water that cannot drain is what ends a facade, whatever the board is made of.

Decking is a third product, not a variant

WPC decking is a 140x25mm hollow chambered board in 2.4, 2.9, 3 and 5.4m lengths, made from 30% HDPE, 60% wood fibre and 10% additive, and fixed over a joist grid with edge clips. It is a walking surface with a different section and a different fixing method from any wall board.

Colour consistency across an elevation

Two production batches on one facade are visible from the street. Order the full elevation area in one run, and quote the original reference for any later phase so the colour can be matched as closely as extrusion allows.