A composite door is made of several materials pressed into one slab: a tough outer skin, an insulating core, and a reinforced frame, with a multi-point lock built into the strongest part of the door. The name just means “made of more than one thing”.
The skin
The face of the door is usually GRP (glass reinforced plastic, which is fibreglass), moulded with a woodgrain or smooth texture and coloured at the factory. Some ranges use a thermoplastic skin such as ABS instead. Either way, the colour is part of the skin rather than a coat on top of it, which is why composite doors don’t need repainting.
The core
This is where doors differ most. The composite doors we fit have a dense insulated core, which is what gives the door its weight and its warmth. Across the market you’ll meet two types:
- A foam core, typically high-density polyurethane injected between the skins, is the common construction and usually comes as a 44mm slab. Foam is an excellent insulator, so these doors tend to have the best thermal figures.
- A solid timber core uses layers of engineered timber laminated together, usually in a 48mm slab. It’s heavier, feels more like a traditional hardwood door when it closes, and is sometimes preferred by insurers. Thermally it’s still good, just not always quite as good as foam.
Both are a long way ahead of a standard uPVC door, which is generally built around a 28mm panel.
The frame and edges
The slab sits in an outer frame, most often uPVC with steel reinforcement, and the slab’s own edges are banded so the core is sealed against moisture. A reinforced lock block runs down the locking edge so the multi-point lock and cylinder are anchored into solid material rather than foam.
Glass and hardware
Any glazing is a sealed double-glazed unit (toughened where safety glazing is required) held in a cassette. Handles, hinges, letterplates and knockers are separate, which is why the choice of hardware affects both the look and the price.
Thinking about a composite door? We supply and fit them across Wolverhampton, and you deal directly with us, the owners. Call 01902 633355, message us on WhatsApp, or design your door online and we’ll put a proper price together for you. Finance options are available if you’d like to spread the cost.