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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” in 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 'skins'. These skins are made from GRP (glass reinforced plastic) and is one of the most durable and strongest materials used in the door market. GRP is also used on fishing boats in the North Sea it's that good! 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 maintenance and disadvantages that timber doors bring.

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

Composite Door Slab

The door slab is what most people consider the “door”. It's the part 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” is typically 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.

A 44mm deep slab will keep in more heat in the a door the is 28mm. 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 with 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.

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 warm.

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