What is a Composite Door?

Doors are one of the most important items in any house. They are the primary source of security from both the worst elements of the weather and would-be burglars trying to force their way in. They are the barrier that protects a family from the dangers outside. Because of this, it is important that when choosing a new door - be it front, back or side - it is a high-quality one, fitted correctly.

So you may have heard of a “composite door” on your travels. This is because the composite door is now probably the most popular type of door sold in the UK right now. But knowing exactly what a composite door actually is might be a different matter. So here's the breakdown as to what a composite door is, and why they are one of the best door products on the market right now.

GRP Doors are Composite Doors

Composite Doors have what are called 'skins'. These skins are made from GRP (glass reinforced plastic) and are one of the most durable and strongest materials used in the door market. GRP is that good, it is used on fishing boats in the North Sea! The GRP skins are compressed moulded in order to give them their realistic wood grain effect. One reason why composite doors have become so popular is because of their realistic timber finish, but without the inherent maintenance disadvantages that timber brings.

GRP skins are available in a very wide range of colours. Just like the timber doors of old, which used to be painted in all manner of colour and style, modern day composite doors come in just as many colours. For those looking for a traditional looking door with traditional colours, this is a key element.

composite door

Composite Door Slab

The door slab is what most people consider the “door”. It's the bit that sits in the outer frame and is what really sets a composite door out from the rest of the other products on the market.

A composite door “slab” typically is 44mm deep, with other options thicker than this. Compare this to the 28mm deep panels in a traditional PVCu panel door, the 44mm door slab brings with it many advantages.

For example, a 44mm deep slab inherently keeps in more heat. The thicker something is, the harder it is for heat to escape to the outside. But it's what inside that makes the biggest difference. Composite doors are commonly reinforced internally with a mixture of timber, CFC free polyurethane insulating foam and recycled PVC. It is these materials which give significant weight and strength to the door slabs, making it incredibly difficult for burglars to break them down. No other type of door is reinforced like this, which again has made them a popular choice for people looking to upgrade to new doors.


U-Values are how heat loss is measured. The lower the U-Value, the better that particular product does in keeping valuable and precious heat in. Composite doors, due to their wider construction and heavy reinforcement, achieve very low U-Values. In fact, some are that low they reach Passivhaus standards!

The focus on energy efficiency and heat loss has grown year on year and is an issue that will only become more important in the future. Composite doors, because of their excellent heat insulation properties, will play a big part in keeping the homes of the United Kingdom.


Due to the nature of the materials in a composite door, it has been possible to create a plethora of designs and styles. Again, harking back to the days of timber, there would be all sorts of intricate and bold designs. With modern day composite doors it is no different. With almost limitless choice on door styles, as well as glass options (including bespoke designed units), colours and traditional and contemporary hardware, there literally is millions of configurations to choose from.

With technology and customization as advanced as it is, being able to pick a new stunning front door is vital. No one wants a “me too” type of front door that everyone has seen for the last 15 years. It's great being able to start from scratch with a design YOU like, then building your door according to what colour scheme and glass options you prefer. That way, you have YOUR door, not one that looks like your neighbour's down the road. Composite doors do this brilliantly and this is why they have become so popular in a relatively short space of time.


As you would expect with any high-quality product, a composite door comes with an array of high-security features. Anti-everything door cylinders, reinforced outer frames, high-security multi-point locking mechanisms, low thresholds for easy access and many more.

Composite Doors are the physical proof of how far the industry has come over the past 20 years or so. A world of colour, endless designs, energy efficiency and choice has been opened up thanks to composite doors and they are transforming the looks of houses up and down the UK. They have become one of the UK's most popular home improvement products and from all the above, it is very easy to see why.