Glazed Fire Doors: Where Safety Meets Style

We need to talk about glazed fire doors. Now, before you roll your eyes and think, "fire doors? How boring!" Let us assure you, glazed fire doors are anything but dull.  In fact, fire doors are often the unsung heroes of building safety without having to sacrifice style. So, grab a cuppa and let's dive into the fiery world of glazed internal fire doors, where we'll explore how these bad boys balance aesthetics with functionality like no other door can!

What are glazed fire doors?

First things first, let's get acquainted with internal glazed fire doors. Imagine you're strolling through the sleek, modern new build house your friend has just moved into, admiring the crisp lines and minimalist decor.  Suddenly, your eyes land on a stunning glass door as you enter the kitchen - but wait, there's more! This isn't just any internal fire door. It's a glazed fire door. Blending seamlessly into the architecture while silently standing guard against potential blazes. Impressive, right? But what exactly sets glass fire doors apart from standard glass internal doors? Well, it's all in the name. Much like solid fire rated doors, fire doors with glass are specially designed to withstand the heat and flames of a fire, thanks to their fire-resistant materials, construction and comprehensive testing. Plus, they come with the added bonus of allowing natural light to filter through, brightening up your living space and creating an open, inviting atmosphere.  Talk about killing two birds with one stone - safety and style, all wrapped up in one sleek perfect door package!

Why are glazed fire doors so expensive?

It all boils down to quality and safety. Not to mention the cost involved to produce the pyro-glass itself. Internal glazed fire doors are manufactured using high-grade materials and undergo more rigorous testing than a standard door to ensure they can withstand the intense heat of a fire. Plus, they're often customised to fit specific architectural requirements, which adds to the cost.  But, when you consider the peace of mind fire doors provide, can you really put a price on safety?

How are glazed fire doors constructed? 

Fire doors with glass panels are meticulously constructed from many different parts to withstand high temperatures and prevent the spread of flames and smoke in the event of a fire.  Here's a breakdown of the typical construction of a glazed fire door:

Frame

Glazed fire door frames in a residential setting are usually made from timber. Fire door frames and linings are designed to securely hold the door leaf and the glazing components in place. The type of timber used will depend on the fire test results.

Door Leaf

The door leaf itself is always made from a solid core material, such as timber, composite or mineral core, to provide insulation and structural stability. The difference between standard internal doors and fire doors is the core and lipping.  The rest of the construction is largely the same. The core (or construction of the core if it’s a sandwich board, aka the mineral board part discussed above) is what contributes the most to fire resistance. In internal fire doors they are thicker, and generally made from a denser engineered timber than standard doors.

Glazing

The glazed portion of internal glass fire doors consists of fire-resistant glass panels that allow for visibility while maintaining fire protection. Fire-resistant glass is specially designed to meet fire safety regulations as it needs to withstand high temperatures without shattering.  The biggest difference is that 6mm pyro-glass is used in fire doors rather than 4mm toughened that’s used in standard doors. They also have an intumescent gasket around the glass unit, embedded around the glazing cassette. It may be composed of multiple layers of different types of glass with interlayers of intumescent material that expand when exposed to heat - creating an additional barrier against flames and smoke. More on this later.

Seals and Intumescent Strips 

Around the edges of the door leaf and the glazing panels, intumescent strips are often installed for further fire protection. These strips contain materials that expand when exposed to heat, effectively sealing any gaps and preventing the passage of flames and smoke. Intumescent smoke seals may also be incorporated into the door frame to further enhance fire safety and improve the fire rating of the door.

Hardware

The hardware components of glazed fire rated doors, such as hinges, handles and locks, are made to meet fire safety standards and complement the overall design of the door. Depending on the door's fire certificate, hardware will likely need to have intumescent protection too (intumescent hinge pads, intumescent jacket for the latch, etc). Fire-rated hinges are typically used to make sure the door functions properly in the event of a fire. Self-closing devices may also be installed to make sure the door automatically closes and latches shut so a seal is formed in a fire  - this is why it's imperative a fire door is never propped open.

Testing and Certification 

Before being installed in a building, fire doors with glass undergo the same rigorous testing as solid fire doors, to ensure they meet fire safety regulations. This testing covers things such as fire resistance, smoke control and structural integrity. Doors that pass these tests are then certified for production. The construction of an internal fire door with glass involves careful attention to detail above and beyond that of a regular internal door. Using specialised materials and components to create a reliable barrier against fire and smoke, while still maintaining visibility and aesthetic appeal is a delicate balancing act. The construction of a glazed fire door involves careful attention to detail above and beyond that of a regular internal door. Using specialised materials and components to create a reliable barrier against fire and smoke, while still maintaining visibility and aesthetic appeal is a delicate balancing act.

What does fire door glazing consist of?

Fire door glazing typically consists of fire-rated glass or ceramic materials designed to withstand high temperatures and prevent the spread of fire. A fire door glazing panel may be constructed using tempered glass, laminated glass or a combination of both, with internal intumescent layers that provide additional fire resistance.  Ceramic glass, such as borosilicate or soda-lime silicate glass, is also commonly used for its ability to withstand high temperatures without shattering. This is the same type of glass you’d find in the manufacture of ceramic hobs and cooker tops.

Which type of glass is most typically used in fire doors and windows?

As mentioned above, there are a number of different fire safety glass types used in the manufacturing of fire doors today, here’s a breakdown of those different types and how they’re designed to perform: 

• Wired - The glass fractures and the internal wire mesh holds the glass together to maintain its integrity.
• Ceramic - The glass has a near zero thermal expansion coefficient and a very high softening point, this helps maintain its integrity in the event of a fire.
• Heat Soaked Modified Thermally Toughened Soda Lime Silicate - The toughening process develops high stresses in the glass, and this helps retain strength in the glass on exposure to fire.
• Modified Toughened Soda Lime Silicate - As with heat soaked, the toughening process develops high stresses, helping to maintain the integrity of the glass on exposure to fire.
• Resin Laminated - These types of glass have a resin-based interlayer formulated to resist against fire and flaming.
• Modified Toughened Laminated - A combination glass, the toughening process develops high stresses which is paired with an intumescent interlayer to provide resistance against fire.
• Thermally Toughened Borosilicate - These glass types remain intact due to its composition and low thermal expansion, much like ceramic.
• Laminated Intumescent - These types of glass have intumescent interlayers formulated to turn opaque and swell on exposure to fire to provide resistance.
• Gel Laminated - Like laminate, these types of glass will turn opaque and swell on exposure to heat to effectively seal the door and resist fire.

What is the British standard for fire door glazing?

In the UK, glazed fire doors must meet stringent standards set out by the British Standards Institution (BSI). Specifically, fire door glazing must comply with BS EN 1634-1:2014, which evaluates the fire resistance of various building elements, including doors and windows. You can learn more in our Fire Door Regulations Guide.

Do glazed fire doors have the same safety ratings as regular fire doors?

Glazed fire doors typically undergo similar tests as solid fire doors to make sure they meet specific safety standards and regulations. However, the addition of glass does introduce further considerations. Like standard fire doors, the safety ratings of glazed fire doors are determined by such factors as fire resistance, smoke control and integrity during testing.  These ratings are often given in terms of fire resistance duration, such as 30 minutes (FD30), 60 minutes (FD60), or 90 minutes (FD90) - each one indicating the length of time the door can withstand exposure to fire and prevent its spread. If you add an S on to these (e.g. FD30S) it means they are also smoke resistant. During testing, glazed fire doors are subjected to conditions that simulate a fire, including exposure to high temperatures, flames and smoke. The door's ability to maintain its structural integrity, prevent the passage of flames and smoke, and resist heat will be heavily scrutinised before it can go into production. It's important to note that glazed fire doors may have different safety ratings depending on things such as the type of glass used, the framing system and any additional features incorporated into the door design. In addition, fire doors with glass are tested not only for integrity, but also insulation (i.e. how hot the glass is to touch). Some are as low as 15 minutes before they become "too hot to touch", some have the same minute rating (i.e. FD30, FD60, FD90). It's essential to select glazed fire doors that have been tested and certified to meet the specific safety standards needed for their intended location, always refer to the manufacturers test certificate before buying.  All of our glazed fire doors are FD30 rated as a minimum, with a range of FD60 glazed fire doors also available. Below is a glazed fire door test situation. One door has a Lorient intumescent smoke seal kit installed around the glazing and door lippings, the other does not, demonstrating just how much difference a fire-rated door can make should the worst happen:

What is the maximum size of glazing in fire doors?

Size matters. And that’s especially true when it comes to fire doors with glass.  According to fire-rated glazing regulations, the maximum size of a glass panel in a fire door depends on factors such as the fire rating of the door and the type of glazing used.  Generally speaking, larger glazed areas may compromise the integrity of the door's fire resistance, so it's essential to stick to the specified size limits to ensure maximum safety. For example, an FD90 glazed fire door must have no more than 100 square inches of glass. Lower rated doors, such as an FD30 fire door, can have more.

Can fire doors have frosted glass?

While frosted glass certainly has its appeal, it's not typically used in glazed fire doors.  Why? Because for the most part, when it comes to fire safety, clarity is key.  In an emergency situation, firefighters can benefit from being able to see through the glass to assess the situation in other rooms and navigate the building safely. So, while frosted glass might look pretty, when it comes to glazed fire doors, keeping things crystal clear is much better. Also, it shouldn’t be assumed that decorative effects can be added to all types of fire-resistant glass without affecting its fire-resistance. Some types of glass can be decorated with surface treatments, e.g. sandblasting, screen printing etc, but others can’t. That’s not to say frosted glazed fire doors don’t exist, though. If you plan to add some sort of decoration to a clear glazed fire door, it’s important to seek advice from the manufacturer first.

Turning Your Space Into a Stylish Safe Haven

And there you have it, folks. Internal glazed fire doors - the ultimate fusion of safety and style.  Whether you're outfitting a sleek office space or a cosy cottage, glazed fire doors are the perfect blend of form and function. So, the next time you pass through one of these fire-resistant beauties, take a moment to appreciate the craftsmanship and innovation that goes into keeping us safe… one stylish swing at a time.

Unsure where to start when it comes to fire rated doors? Not to worry! Our expert team is always on hand to guide you through the buying process. So whether it's an internal fire door, door furniture or building regulations you have questions about, we'll be able to help. Just get in touch!