How to Install a Fire Door – Ultimate Guide

by | Jul 26, 2023 | Uncategorized | 0 comments

How to Install a Fire Door

Fire doors are a critical component in fire safety. They are specially engineered devices, designed to save lives and prevent damage to your premises.  

They work on the principle of compartmentalisation by dividing large spaces into smaller, fire-resistant compartments to prevent or slow the spread of fire and smoke within a building. This gives occupants time to seek refuge and firefighters the chance to put out the fire.  

But fire doors can only be effective if they are installed correctly. In this blog, we’ll guide you through a complete fire door installation. We’ll look at the importance of each installation stage, why you should employ certified professionals to carry out the work, and the implications of poor installation.  

Preparing the Frame

The door frame is a crucial component in a fire door system because its job is to provide structure and support for the door leaf.  

However because door leaves are made from a variety of different cores, the installation requirements for the frame will vary.  

That’s why it’s essential that the fire door frame is installed in accordance with the instructions from the door leaf manufacturer.  

In fact, on the door leaf manufacturer’s data sheet, you’ll find details of the required architrave, frame material, intumescent seal, hinges, frame construction, fixing points, ironmongery and door stops.

So, always refer to these documents before starting any work on the fire door frame.  

To begin the frame installation, start by fixing the corners of the frame together. To prevent the timber from splitting, it’s a good idea to drill pilot holes for each of the screws. You’ll then need to check that all joints are tight and square. And if you’ve used any adhesive, make sure you’ve given it enough time to set.  

When fixing the frame to the supporting construction, install the frame fixings at 100mm from the corners and at no more than 500mm centres. Frame fixing must have a minimum of 50mm penetration into the wall.

If there are any gaps between the frame and supporting construction, these should be filled with an intumescent sealant (fire mastic) or fire-rated packers.   

Hanging the Door Leaf

When it comes to hanging the door leaf to the door frame, hinges are an essential piece of ironmongery. Unlike normal door hinges, hinges for fire doors need to be fire-rated, CE marked, or UKCA marked to BS EN 1935, and have a durability grade of 11. You’ll also need to make sure that you have the correct size and type of fixing screws for your specific hinges.  

Most fire doors will require three hinges for installation. But if a door leaf is particularly heavy, it may require more.  

Hinges can reach over 800 degrees centigrade in the event of a fire. That’s why most manufacturers recommend using intumescent hinge pads. These provide additional protection to the timber of a door and prevent excessive charring in the event of a fire. It’s important not to use any combustible materials, such as plastic or cardboard, behind the hinges as this will lead to early failure of the fire door.  

During installation, it’s a good idea to mark the hinge positions when machining the frame and door leaf, working from the top down, and making sure you don’t over-mortice the timber.  

When the door leaf is in place, there should be a consistent gap between the door leaf and the frame as specified by the manufacturer. Generally, the accepted door-to-frame gap is 2mm – 4mm, with most certificate data sheets stating that gaps should not exceed 4mm at the top edge and vertical edges, and 3.5mm at the meeting edge of double-leaf doors. We recommend using a taper gauge tool to check these gaps.  

The threshold gap (the gap between the bottom of the door to the floor) will also be stated on the certificate data sheet. Typically, this is 8mm – 10mm. However, if the door is FD30s or FD60s for smoke control then the threshold gap can be no larger than 3mm as stated in BS 8214.  

Most fire doors have no tolerance for misalignment and should not stand proud of the door frame at any point. Some fire doors have very limited allowances, typically 1mm. So, check with the data-sheet or other evidence for the particular fire door leaf where possible.  

Fitting Ironmongery

Some fire doors might require additional ironmongery. In this case, you must check that the ironmongery is compatible with the door leaf and installed as specified in the manufacturer’s instruction manual and certificate data sheet.  

You also need to ensure that any ironmongery is installed with the fixings supplied. For ironmongery that requires mortice work, or face fixed items, the certificate data sheet will detail the materials and fixing locations that are permitted during installation. Always check this certificate data sheet to ensure you’re working within the allowed parameters.  

In some instances, additional intumescent protection is required around lock cases or flush bolts. Again, the certificate data sheet will tell you whether or not this is necessary.  

Ensure that any mortice work is accurate, and you don’t remove too much timber. Any over-morticing will need to be repaired with timber or non-combustible materials. It’s also important to note that the fire rating of these components can affect the overall performance of the fire door.  

Intumescent Strips and Smoke Seals

In every fire door installation, there needs to be a gap between the door frame and door leaf to help the door open and close freely. However, if there’s a fire, this gap could pose risks to life and property by allowing fire and smoke to escape.  

That’s why every fire door needs a fire door seal. Installed between the door frame and the door, fire door seals fill these gaps to prevent the spread of fire and smoke.  

Intumescent strips are designed to expand when they heat up. If there’s a fire, the rise in temperature activates the material inside the PVC casing, causing it to swell. The expanded strip then plugs the gap, preventing the heat and fire from spreading to another area of the building.  

A smoke seal is like an intumescent strip, but its primary function is to prevent the spread of smoke. Unlike intumescent strips, smoke seals usually have a brush or fin that stops the smoke, allowing time for residents to escape and preventing the spread of poisonous gases.    

Combined intumescent and smoke seals are also available. However, the smoke brush can often bind on the fire door when it self-closes which stops the door closing properly. As you know, a fire door that doesn’t close is useless in a fire. So, if you’re using combined intumescent and smoke seals, it’s important to take action to stop binding from occurring.  

Any seals that you do install should be sourced from reputable manufacturers, have third-party certification and proof of performance. Before you begin fitting your seals, read the certificate data sheet to check whether the seal you want to use is compatible with the door leaf.  

If the door frame or fire door already has the right grooves in place, then fitting intumescent strips and smoke seals is relatively easy. If they don’t, you’ll need a competent person to carry out this work.  

When your groove is in place, run a dry cloth down it to remove any loose debris or dust. Once clean, check that the seal you’re using is the correct depth for the groove. Remove the adhesive on the back of the seal then place it in the groove, taking care to ensure the fit is tight and the seal is flush with the frame or door leaf.  

The final step is to check that the door opens and closes freely with no friction or binding issues.  

The Linear Gap Seal

The linear gap seal is the gap between the surrounding structure (the wall) and the door frame. It’s a crucial step in fire door installation but one that’s often done incorrectly.  

Some manufacturers are very clear about which materials and methods should be used for the linear gap seal. But they also vary depending on the door type, with several variables affecting your choice:  

  • Thickness and width of the architrave
  • Smoke control
  • Rating of the door leaf
  • Width of the gap from the frame to the wall
  • Wall type

If the manufacturer does not provide specifics on the certificate data sheet then it is best to consult BS 8214: 2016 (usually the door leaf manufacturers make reference to this British Standard anyway).

Acceptable materials for the linear gap seal include mineral rock fibre (Rockwool) and intumescent mastics. The use of foam is sometimes permitted but you must check that there is evidence of its fire performance to BS 476 part 20 or EN 1366-4.  

If a door is required to also hold back smoke, then you need to cap the mineral rock fibre or foam with 10mm of intumescent mastic that’s been tested to BS 476-22 or BS EN 1634-1. Plastic packers are acceptable, but they must be trimmed back by 10mm on either side of the frame and covered in 10mm of mastic.  

Fixing the Self-Closing Device

The final step of the installation is fitting the fire door’s self-closing device. Every fire door needs a self-closing device as they ensure the door can self-close all the way to the rebate stop and latch, if necessary. There are several things to consider when sourcing and installing fire door closers:  

Where is your fire door located?

You’ll need to consider where you fire door is located and whether the closer is suitable. Some door closers can only be installed on outward opening doors or require the purchase of an angle bracket. Others are made of rust-prone materials or aren’t secure enough for use on exterior doors.  

Does the door require a closer?

Flat entrance doors, hotel rooms, and cross corridor doors, will almost always require a closer. But cleaner’s cupboards, dry risers, and some plant rooms don’t. In this case, you can install a ‘Fire Door Keep Locked’ sign instead.  

Is the closer compliant?

You need to have evidence of the closer’s fire performance and proof that it’s been tested using the particular fire door leaf and configuration that you’re planning to use. For example, most door closers are installed on the pull side of the door. But for certain fire door configurations, it might need to be on the push side.  

What environment is the closer being used in?

Location and environment play a key role in determining the best type of closer. A heavy-duty closer would not be appropriate in a care home for example. In this instance, a closer with a swing-free device would be more suitable as they offer little resistance when pushed.   When you come to install the closer, always make sure you carefully follow the fitting instructions provided. It’s imperative that you use the fixings that are supplied with your closer because these are specialist fire safety fixings.    

It’s also important that the door doesn’t bind on any seals or the frame when it closes. The closer must be able to overcome this friction. If it can’t, it means the fire door is non-compliant. To test this, check that the door closes and latches from a 90-degree and 45-degree angle. Then check that it also closes from 75 millimetres.  

Final Thoughts

As you can see, fire door installation is so much more than simply hanging a door leaf. A thorough, compliant fire door installation is made up of many different steps and components, with each one playing a vital role in the door’s effectiveness and ability to save lives. 

It’s a complex process and one small mistake can lead to fire door failure. That’s why it’s so important to check the certification of each component and adhere to the manufacturer’s instructions at every stage.  

At UK Fire Door Training, we’ve designed a course specifically to improve your skills, knowledge and competency when installing fire doors. Perfect for site carpenters, fire door technicians, site managers or anyone looking to improve their knowledge of fire door installation, you’ll learn:  

  • The importance and role of fire doors
  • What fire doors are made from and how they work
  • The laws, regulations and standards that affect fire doors
  • Finding and using certificate data sheets and installation instructions
  • What fire door ratings are
  • How to successfully plan a fire door installation
  • How to successfully install a fire door
  • What to do post-installation

 To book your place on our Fire Door Installation Course, click here.


Jonny Millard

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