44mm Fire Doors

Why 44mm is the standard fire door thickness

Most ordinary internal doors are 35mm thick. A fire door needs a denser, deeper core to hold back fire for half an hour, which is why 44mm is the standard FD30 thickness.

A standard 35mm door isn’t a fire door, and adding strips or paint won’t turn it into one. The rating comes from testing the leaf with its frame, seals and hardware, so a 44mm fire door only performs as part of that complete doorset.

The range comes from LPD, Deanta and Premdor, plus a Jeld-Wen flush door. The thicker 54mm leaf is the FD60 standard.

Because FD30 doors are usually 44mm thick, this range overlaps closely with our FD30 fire doors. If you’re comparing ratings rather than thickness, start there.

Choosing a 44mm fire door by finish

Our 44mm internal fire doors come in most of the finishes used on standard internal doors. The table below shows which designs are ready to hang and which need painting or sealing before they go up.

A pre-finished 44mm oak fire door is finished at the factory, so it’s ready to hang once trimmed. Unfinished oak is the better bet when you’re matching existing joinery and want to choose your own oil or lacquer.

A 44mm white fire door comes either primed, ready for your decorator, or pre-finished so it can go straight on. Primed suits landlords who repaint between tenancies, while pre-finished white and laminate save a return visit with the brush.

Grey, black and walnut doors come in two forms: real veneer, such as Deanta’s Montreal Light Grey Ash, or a laminate face, as on LPD’s laminate Vancouver designs. Laminate isn’t real wood. It’s a printed, wipe-clean surface that copes well in busy rentals, but it can’t be sanded or re-stained if it gets damaged.

Glazed designs run across most finishes, with clear, clear toughened, wired and frosted-line glass depending on the design. Each 44mm glazed fire door arrives with its glass already fitted as part of the tested door, so don’t swap or recut it on site. For wide openings, Premdor’s white primed long-side glazed double door gives you a matching pair.

Most 44mm fire door designs come in the imperial 1981mm (78-inch) height in widths from 610mm to 838mm, and many are also made in metric 2040mm heights up to 926mm wide. Our guide to fire door sizes explains how to measure the opening before you order.

Every 44mm fire door in this range carries a 10-year manufacturer’s warranty. Fitting out a whole block? Open a trade account before you place the order.

Frames and linings for a 44mm fire door

Swapping a 35mm door for a 44mm fire door usually means changing the frame too. Check each of the points below before you order the door.

• Lining size: when you order a 44mm fire door lining, choose a width that matches the wall from one finished face to the other. Our FD30 linings come in 95mm, 108mm, 125mm and 133mm widths.
• Stops: the frame rebate depth, or the position of a loose stop, has to suit the 44mm leaf, and fitting instructions usually ask for at least 12mm. The loose stops supplied with our FD30 linings are set to the door on site.
• Intumescent seals: 30-minute doors typically take a 15mm by 4mm intumescent strip in the head and both jambs. LPD’s FD30 linings have an intumescent strip groove machined in, though the strip is sold separately.
• Smoke seals: where the door schedule says FD30S, fit a smoke seal as well. The S means the doorset also holds back cold smoke.
• Hinges: fit three fire-rated hinges to each 44mm fire door, as our product pages recommend. The usual hinge size for a 44mm leaf is 100mm (4in), tested to BS EN 1935.
• Gaps and trimming: keep the gap at the sides and head to about 3mm. Trimming allowances are small, so pick the 44mm fire door size closest to your opening.

We stock FD30 frames and linings from LPD and Deanta in white primed, black primed, oak and walnut, so you can match the 44mm fire door frame to the finish of the leaf. Have a look at our internal door frames and pick the ones marked FD30. If you’re unsure which lining suits your wall, get in touch before you order and we’ll help you choose.

44mm vs 54mm fire door: when you need the thicker leaf

If the fire strategy, building control or your fire risk assessor asks for 60 minutes, none of the doors here will do. You’ll need an FD60 door, with a frame, seals and hardware rated to match.

For anything else, a 44mm FD30 fire door is lighter to handle and comes in a wider choice of styles.

Bear in mind that the two aren’t interchangeable: an FD60 door won’t go into a lining set up for a 44mm fire door, and the stops and seals differ too. Our 54mm fire doors cover the FD60 options.

44mm fire doors: your questions answered (FAQ)

Is every 44mm fire door FD30?

Yes. Every door in this category is rated FD30, including the glazed and office designs.

How thick is a fire door?

It depends on the rating. An FD30 door is usually 44mm and an FD60 door usually 54mm, while ordinary internal doors are typically 35mm.

Can a 44mm door be FD60?

Not in our range. Our FD60 doors all use the thicker leaf, so look at that range if your schedule asks for a full hour.

What frame do I need for a 44mm fire door?

An FD30-rated frame or lining with stops set for the leaf, an intumescent strip in the head and jambs, and three fire-rated hinges. The door’s fitting instructions have the final say.

Can I fit a 44mm fire door in my existing frame?

Usually not. A frame built for a 35mm door wasn’t tested with the fire door and rarely has the right stop or seal groove, so plan to fit an FD30 lining at the same time.

Can I paint a 44mm fire door?

Yes. Primed doors are made for it, and unfinished timber can be painted or sealed too. Keep paint off the intumescent strips, the smoke seals and the certification label.

How soon should I seal an unfinished oak door?

Before it goes into use, once any trimming is done. Seal all six faces, top and bottom edges included, and steer clear of wire wool between coats, because it reacts with the tannin in oak and leaves dark marks.

Does a 44mm fire door need a self-closer?

Only where the door schedule or your fire risk assessment calls for one, which is common on escape routes and in shared buildings. Check with building control before you leave one off.