How to Choose an Internal Fire Door: FD30, Hinges & Seals

Choosing an internal fire door is different from choosing an ordinary room door. Appearance and size still matter, but the starting point must be the required fire performance and the evidence for the complete installation. An FD30 door leaf, suitable frame or lining, fire door hinges, intumescent seals, closer and other components may need to work together as a tested assembly.

This guide explains the buying checks to make before choosing a fire-rated product from our internal doors range. It is intended to help you understand product terminology and prepare an order; it does not replace the project specification, product certification, manufacturer installation instructions or applicable building requirements.

What is an FD30 fire door?

FD30 is commonly used to describe a fire door with a stated 30-minute fire-resistance performance when tested and installed in the appropriate configuration. The rating applies to a tested system and conditions, not simply to a thick piece of timber. A door leaf can be sold as an FD30 product, but the finished installation still needs the correct frame, hardware, seals, gaps and fitting method for the evidence being relied upon.

Products such as the LPD Doors London White Prime Plus FD30 Internal Door make the rating clear in the product title, but you should still review the individual documentation for size, construction, glazing if any, trimming, hardware and installation details.

Do you need a fire door?

Whether a particular opening needs a fire-resisting door depends on the building type, layout, use and applicable regulations or approved design. Do not decide solely from the room name or copy what a neighbouring property has. New builds, loft conversions, flats, houses in multiple occupation, commercial premises and escape routes can all have different requirements.

If drawings, a fire strategy or Building Control information specify a rating, use that as the starting point. If the requirement is unclear, have it confirmed before buying the door. Ordering a standard internal leaf first and trying to upgrade it later is not a reliable substitute for a specified fire doorset.

Fire door leaf vs complete fire doorset

A fire door leaf is the moving panel. A complete fire doorset includes the leaf together with a frame and specified components, prepared and tested as an assembly. In some projects a compatible leaf and frame can be assembled on site under the relevant evidence, but every component and detail still needs to align with that evidence.

This is why it is risky to shop for each item independently by appearance. The fact that a hinge, seal and closer are each marketed for fire-door use does not automatically prove that any combination of them with any FD30 leaf will create a compliant installation.

How to choose the right fire door size

Measure the opening carefully, but do not select size until you know whether you are replacing the leaf only or the frame as well. Common UK fire-door leaves are often thicker than ordinary internal doors and may be offered in standard imperial or metric widths. Use our internal door sizes UK guide for general size context and our internal door measuring guide for the measurement process.

For fire doors, gap dimensions can be performance-critical, so the installer should follow the exact manufacturer's instructions and test evidence. Do not create fitting clearance by trimming beyond the permitted allowance.

Why fire door thickness matters

Many FD30 internal door products are around 44mm thick, compared with around 35mm for many ordinary internal doors. This affects the frame rebate, stops, hinge sizing and hardware preparation. However, 44mm thickness is not a fire rating on its own.

If you are replacing a conventional 35mm leaf with an FD30 door, the existing frame may not be appropriate. Its material, dimensions, rebate, condition and preparation all need to be considered as part of the required assembly.

Choosing fire door hinges

Hinges need to support the door mechanically and, where required, satisfy the fire-door specification. Check hinge grade, size, material, load capacity, certification and any requirements for intumescent hinge pads or specific fixings. The number and position of hinges should follow the door and hinge manufacturers' instructions or the tested doorset specification.

Do not assume the hinges from the old 35mm bedroom door can be reused simply because they fit the screw recesses. A heavier FD30 leaf places different loads on the hardware, and fire performance can introduce additional requirements.

What are intumescent door seals?

Intumescent seals are designed to react to heat and expand, helping close gaps between the door and frame in a fire. They can be installed in the door edge or frame depending on the tested configuration. Some products also incorporate smoke-control elements, but the exact function must be read from the product specification.

Choose the size, type and location required by the door's evidence rather than selecting a seal only from the width of an existing groove. Browse intumescent and door seals to see available components, then verify compatibility before purchase.

Do fire doors need door closers?

Many fire-door locations require a suitable self-closing device so the door returns to the closed position after use, but the requirement and type depend on the application. A closer must also be capable of controlling the particular leaf without preventing normal operation.

JJ Building Materials stocks door closers, but choose one only after confirming the doorset and project requirement. Installation position, power size and adjustment can matter.

Fire door handles, latches and locks

Handles themselves are only one part of the ironmongery. The latch or lock case cuts into the door edge, so its size and position can influence performance. The permitted hardware preparation should be stated in the doorset documentation or door instructions. Large lock cases or unnecessary cut-outs should not be added without checking.

For general information about door handles, hinges and latch furniture, see our internal door hardware guide, but treat the fire-door specification as the higher priority.

Glazed fire doors

A glazed fire door needs fire-resisting glazing and an appropriate glazing system that is part of the tested design. You cannot take a standard glazed door and infer a fire rating from the glass appearance, nor should an unglazed fire door be cut for glazing unless the manufacturer's approved system permits it and the work is carried out correctly.

If you need both shared light and fire resistance, choose a product that is specifically supplied or documented for that configuration.

Frames and door linings for fire doors

The frame or lining forms a critical part of the opening. Material, density, dimensions, rebate, fixings, packers and sealing around the frame can all be relevant. An old lining that is sound enough for a normal internal door may still be unsuitable for a fire-door upgrade.

Browse door linings for general products, but have the exact fire-door frame requirement verified from the chosen door evidence before ordering.

Trimming an FD30 door

Never assume a fire-rated door can be trimmed like a standard internal leaf. The manufacturer may allow limited trimming from specified edges, but removing too much can cut into essential lippings or change the tested construction. The allowed amount can differ between the top, bottom and sides.

Measure accurately first, select the closest appropriate size and follow the exact trimming instructions. If the opening is too far outside the permitted range, the frame or door solution may need to change.

Finishing and decorating a fire door

Primed, unfinished and pre-finished fire doors have different decorating requirements. The finish should not obscure labels, damage seals or interfere with hardware. Follow the manufacturer's instructions for edge treatment, top and bottom edges, glazing beads and any areas that must remain visible for identification.

A product such as a white primed FD30 door may still require final decorating even though it arrives with a factory primer. Check before installation.

Fire door installation checks

• Confirm the required fire-resistance rating for the opening.
• Choose a door leaf or doorset with appropriate evidence.
• Confirm leaf height, width and thickness.
• Verify the frame or lining specification.
• Use suitable hinges and required fixings or pads.
• Fit the specified intumescent and smoke seals where required.
• Confirm latch, lock and handle preparation.
• Fit a suitable closer where required.
• Maintain the gap dimensions stated in the installation instructions.
• Do not exceed trimming limits.
• Keep product labels and documentation for the project record where required.

Common fire door buying mistakes

Common errors include choosing a door because it is 44mm thick, assuming all FD30 leaves work with any frame, reusing ordinary hinges without checking, buying seals by guesswork, excessive trimming, cutting large lock cases into the leaf and forgetting the closer or smoke-control requirement. Another mistake is focusing on the leaf price while overlooking the rest of the hardware and installation needed for the complete opening.

Prepare the full doorset schedule before ordering so the door, frame, seals, hinges, closer and lockset can be checked together.

Frequently asked questions

Does FD30 mean 30 minutes?

FD30 is commonly used for a door with a stated 30-minute fire-resistance classification under the relevant testing and installation conditions. The final installation must match the required evidence and specification.

Is every 44mm door a fire door?

No. Thickness alone does not establish fire performance. Check the exact product certification and rating.

Can I put a fire door in an existing frame?

Only if the frame is suitable for the required doorset configuration and can be installed in accordance with the evidence. Have the frame specification and condition checked.

Do FD30 doors need intumescent strips?

The required seals and their size and position depend on the tested doorset and project specification. Follow the door manufacturer's documentation.

Can I trim an FD30 fire door?

Only within the exact limits permitted for that product. Excessive trimming can affect the construction and performance.

Where can I find fire-rated internal doors?

Browse the internal doors range at JJ Building Materials and check individual product titles and specifications for stated FD30 options.

Choose the whole fire-door system, not just the leaf

The safest buying approach is to start with the required rating, then select a documented door system and compatible components. Use JJ Building Materials to source the relevant door, hinges, seals and closers, but make sure the complete combination is supported by the project specification and manufacturer evidence before installation.