What is a composite door?

composite doors explained

What are composite doors? Roughly speaking, composite doors are made from modern materials that mimic the appearance of a natural wooden door without some of the negatives that a wooden door can bring like having to paint it for example.

There are many makes, manufactures and styles of composite doors on the market ranging from below-average quality to very good quality. Some composite doors are mass produced in three different sizes in China and then shipped over to the UK in containers ready to be machined to the right size, these have the glazing fitted already and possibly sprayed to the desired colour. A frame is made for the door, a locking system along with hinges and furniture is attached and there you have a generic composite door. These are the below-average quality of composite doors.

The doors can only be as good as the quality of materials used and the workmanship bringing it all together. Generally these are the lower cost composite doors that we tend to stay away from because we would rather fit a better standard of composite doors. After all they are built to a budget. The cheaper composite doors however make doors much more affordable (i.e what you would find on a typical new build house) but you get what you pay for.

One thing we don’t like about these door slabs shipped over in mass quantities is that because they use three different sizes you could find that the one used for your composite door has had a fair amount of material removed form the sides to get the width you require, thus weakening it in the process and making it easier to fail if someone tries to break in. The core for these composite doors is generally polystyrene or low density foam which sounds a bit lightweight but actually it is not as bad as it sounds but still not great from a security, robust and efficiency point of view.

timber composite doors

Timber composite doors are the way the likes of Rocal EnduranceSolidor and Solid core doors manufacturer composite doors. These doors are all made from different types of timber which are cut to size so there is no weakening of the edges of the slab as the strength is consistent across the entire width and height of the door. 

Timber composite doors are generally more expensive than generic foam / polystyrene doors. One reason for this as well as timber is more expensive in general is that timber is heavier than foam and polystyrene so these types of composite require hinges and external frames that need to be more robust and stronger to be reliable over a long period of time to prevent the door moving and to properly take the weight of the door.

Another reason they are more expensive is because they are considered a more premium types of door compared to the more light weight foam and polystyrene doors as they typically always have better locking mechanisms and cylinders as standard. All the composite doors mentioned above use what is called a glazing cassette so the glass unit can be added towards the end of the build process and can even be changed at any point in time if one were to be broken by say a stone. In 15 years of dealing with doors we don’t come across many broken glass units in doors to be honest.

different types of timber

On the topic of timber core composite doors, whilst Solidor, Endurance doors and Solid core doors all use a timber core, they aren't the same. Endurance Doors and Solid Core doors use a specific type of timber for their core which is called Kerto laminated veneer lumber which comes from Finland. It comes in very thin layers roughly 2mm to 3mm thick and is assembled in multiple layers ensuring that with each layer applied, the grain runs in opposite directions to the previous layer. With most timber, the grain is always a weak point and ensuring the grain runs in multiple directions eliminates this weak point.

In my opinion this is better than the core Solidor use (their timber core comes from a sustainable source in Indonesia) for the two main reasons:

- Much heavier and denser, increasing security.
- Stronger to resist climatic and weather changes.

foam filled composite doors

Another composite door called the Rockdoor is built completely different from the timber composite doors mentioned above. Rockdoor use a high density foam filled core with a 10mm aluminium box section in the door sash for proper reinforcing and is made based upon the size required so you get the same strength around the edge of the door sash on every door they make. Even though they are foam filled and having fitted over a thousand of these doors we have never come across one that has been broken into due to having a foam centre.

Many timber composite door manufacturers like to make a point of the core of their doors being made from wood thus being harder to penetrate than a foam filled door but in the real world this isn’t really an issue. Where a Rockdoor is unique is in the fact that each glazing unit is built into the door right from the start of the manufacturing process and is integral to the door. The downside would be if the glass were to break it would require a whole new door sash but I have only ever come across this once but it was shot at with an air rifle.

uPVC and ABS Skins

Most composite doors use the following types of internal and external skin for their doors.

- ABS / uPVC skin
- GRP skins

In my opinion the ABS / uPVC skins are much better than the GRP skins just down to the aesthetics. GRP skins tend to have a very heavy unrealistic grain which personally doesn’t recreate the look of a timber composite door well at all. The UPVC and ABS skin’s are very similar (ABS is the same type of material that is used to make Lego) and these look absolutely fantastic.

The uPVC and ABS skins are much better, they may not be quite as tough as GRP skins, but they are very durable to scratches still and retain the beautiful wooden grain, not to mention they don’t fade or discolour and very easy to wipe down and clean! 

All the composite doors we supply and fit use either a high impact compressed uPVC skin or an ABS skin, both very very good.


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