What's the Difference Between External and Internal Fire Rated Steel Doors?

Fire doors aren’t all the same. For the moment, legislation treats steel internal fire doors and external steel fire doors as two separate products, and they must be handled accordingly. In practice, that means Approved Document B sets different requirements for a steel internal fire door than it does for an external one. 

Lets first take a look at the reason why internal and external doors need to be differentiated. Under the Construction Products Regulation 305/2011, any construction product that is covered by a Harmonised European Standard must carry a CE mark. The key word here is harmonised—this means the standard has been adopted into legislation and must be used for those products, with compliance proven through CE marking. 

All pedestrian doors in buildings are covered by EN 14351, which has two parts: 

• EN 14351-1 – External doors 
• EN 14351-2 – Internal doors 

Part 1 (external doors) has been harmonised, but Part 2 (internal doors) has not. This is why internal and external doors must be differentiated: different rules apply when declaring performance characteristics, and only external doors can legally carry CE marking. 

What is required of an external fire door?  

Let’s look in more detail at what defines an external door.

An external door is defined as any door which separates the internal climate from the external climate of a construction for which the main intended use is the passage of pedestrians. External pedestrian door assemblies fulfilling the provisions of the European Standard under the responsibility of one identified manufacturer are considered to be external pedestrian doorsets.

External pedestrian fire-rated steel doorsets have been legally required to carry CE marking since 1 July 2013, with UKCA marking accepted for the UK market from 2019. 

Because EN 14351-1 is harmonised, all new external doors installed in any building in the UK must be CE marked, and this has been the law since before November 2019. 

Does it matter where a door is being installed in? Yes, it does, see below the various accepted certifications by area.  

• England, Scotland and Wales - UKCA or CE.  
• Ireland - UKNI and CE or CE (UKCA not accepted). 
• Europe – CE (UKCA not accepted). 

Regardless of which markings are required, all external doorsets must be supported by a Declaration of Performance that outlines key characteristics, such as thermal transmittance and acoustic performance, and they must be tested to EN 1634-1.  

Unlike Internal doors, External steel doors must be tested as a whole, including their components and steel door hardware in the same fire test. This includes the likes of the leaf, handles, frame, and anything else that makes up the configuration.  

Their fire rating and classification—such as E120, EW90 or EI20—must be clearly displayed, and the original, tested hardware must remain unchanged, as any alteration will invalidate the fire certification. 

For the customer, this means that if a product carries the CE mark to EN 14351-1, they can be assured that the declared performance of that doorset has been audited and verified by an independent UKAS-accredited certification body. 

What is required for an internal fire door? 

Now we take a look at what defines an internal door.
An internal door is defined as any door which is entirely within the building’s internal envelope, separating one indoor space from another and is never exposed to external weather conditions.

These doors cannot carry CE or UKCA marking, and while manufacturers may choose to undertake additional testing, this does not make the product certified. There is no harmonised standard available for internal doors, so there should never be a CE or UKCA marking on the label.  

Internal doors can be tested to EN 1634-1, the same standard as external doors.  Because the doors can still be tested to the standard BS 476 part 22, they can be configured for hardware through an assessment. This is opinion-based and allows testing of the components and hardware separately. 

 Third-party schemes—such as the Effectis Certified process used at Strongdor—can provide additional assurance, but they issue a certificate rather than a formal product certification. It’s also important to note that BS 476-22 will no longer be acceptable after 2029, meaning traditional FD ratings will be phased out. 

Fire testing for doors is being moved to EN 1634-1, at Strongdor we are proud that, all our fire-rated products have been tested to EN1634-1 for both internal and external products.  

So, What Does This Mean as A Steel Door Buyer or Fitter? 

If you are replacing a fire door which initially had FD30/60, etc on any door after 2nd September 2029, this standard will no longer be acceptable in building legislation. If the doors were bought and installed before September 2029, they may still be acceptable until the need for replacement. There has been no guidance on what is expected so far.  

If you see a CE marking on an internal door, this is not correct under building legislation, however external doors must hold a CE or UKCA marking on the door. 

How to Check Your Door 

The label on a fire door should be visible. On this label, it will tell you the testing facility, the standard tested to, and the performance of the door (usually the easiest indicator if FD, it was tested to BS 476 part 22).  
For more information on making sure your doors are compliant, we have ample documents available online. Alternatively, you can also sign up for our fire door CPD.