6 Aug 2011
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United Kingdom
I need to hang a Fire Door and it needs to comply with latest Fire regulations.

I am stuck with where to route for 10mm wide Intumescent Strip, if I route in the middle of the door, 3 Fire Door hinges will pass over the strip, which could cause smoke to pass through.

If I just miss the hinge, which is 30mm wide, and then route 10mm channel for the strip, this leaves only a 4mm wall towards the Fire side (Kitchen)

Question is is this likely to cause problem when it is this close to the fire side, if it is in the middle and hinges cover it, this may breach smoke barrier.
Please see my diagram to show you what I mean.

Please kindly let me know your best views.
With regards and thanks in advance.

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Another point I wish to make, would it be actually better to have it as close to fire side so that it reacts quickly and seals the door gaps more quicker than if it was in the center?
if you buy a fire door liner with a intumesent groove , the groove ends up middle of the hinges, so you have this hit and miss, building/ fire officers never seem to comment on it.
I suppose you could glue strip across the hinge to give continuity if you feel that would help you sleep at night.
It goes in the middle, and the slight gap over the hinges isn't anything to worry about. You can't guarantee which side the fire will start from.
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Thanks mate, both of you, this door is being required to prevent any fire/smoke breaking out in a kitchen which must be prevented from spreading into living areas and so an FD30 door is the minimum requirement just on a kitchen door. So I agree fire can break anywhere, but its prime purpose if to keep any kitchen fires at bay, which is where statistically more fires break out in private dwellings

Therefore before I run my router in the middle and ruin this door i definitely wanted to know if a break at the hinges (3 hinges would mean a total of 300mm break in smoke seal)

Or would it be better if I run the channel in the middle and then take it around the hinges where the hinges are?

Secondly, I have been advised to use 3 BS hinges for fire doors, not a problem, one at the top I have been told should be 6" from top, and the bottom most at 9" from bottom, however opinion is divided as to where the mid hinge should go, some say fit it in the middle as it is to stop the heavy door warping, others say it should be mounted 9" below the top hinge, for a fact that fire doors are heavy and they need to support heavy weight and top hinge bears most of the brunt of the weight, so another hinge (middle hinge) 9" close to top hinge is better.

I can see this point, where it may not be a fire door but just a heavy industrial door, but according to my opinion a center hinge is asked for to avoid warping, which may be more important in a fire door than an ordinary heavy door, I personally think it should be in the middle, as there is risk of someone saying was the door fitter pi55ed when he fitted the middle hinge? but what if I am wrong.

It will also need to be fitted with a self closing mechanism, I bought one that uses a chain.

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As long as the door frame is straight, then fitting the 3rd hinge in the middle is fine. If it's warped, then 9" from the top hinge will work better, it's nothing to do with the door.

Here's an alternative intumescent method though.
From memory, 10 mm doesn't meet current regs. - it needs to be 15 mm. You'll also need intumescent pads in the hinge positions.

FD30 = 15 mm strip
FD60 = 20 mm or 2 no. 10 mm strips
10mm seal should be OK according to this site with some serious information on Fire doors :
Following extract from above site
Fire Door Seals or Fire and Smoke Seals
Intumescent fire door seals should be fitted to the stiles and head of a fire-resisting doorset.
These seals are fitted into grooves cut into the door or the frame, or alternatively, can be surface mounted. As soon as the temperature in the vicinity of the strips exceeds 200°C, usually about 10-15 minutes after the start of a fire, the seal swells and seals the gaps between door and frame.

  • As smoke spread is an even greater threat to life and property than flames, particularly in the early stages of a fire, fire doors might also have to be fitted with a ‘cold smoke’ seal to prevent the ingress of smoke around the door edges (such fire doors would be specified as FDs fire doors). Exceptions apply where the leakage of smoke is essential for detecting a fire early.
    Combined smoke and intumescent seals are available.
Not all intumescent materials act in the same way. Low pressure seals expand in all directions but provide little help to the door in resisting distortion under fire. Some high pressure seals exert pressure mainly in one direction and provide some resistance to distortion of the door leaf under fire. A further type of intumescent material, available in different grades, acts in all directions and generates some pressure. Fire door seals activate at temperatures that are above human survival levels. The following is information on the type or size of intumescent fire door seal that should be used.

Type of fire door
Intumescent Seals
Intumescent Fire and Smoke Seals

30/30 Single action door

30/30 Double action door

10mm x 4mm

(Both sides and top)

10mm x 4mm

(Both sides and top)

30/30 Double pairs of doors
10mm x 4mm on one centre stile

10mm x 4mm on other stile, heads and back edges

60/60 Single action door

60/60 Double action door

20mm x 4mm

(Both sides and top)

20mm x 4mm

(Both sides and top)

60/60 Double pair of doors
20mm x 4mm on one centre stile

20mm x 4mm on other stile, heads and back edges

Most modern fire door seals combine the intumescent and cold smoke elements in one seal.

Grooves should be made slightly wider than the seals to allow for the pre-painting and shrinkage of timber.

Note: – It is advisable to ask fire door manufacturers what type of seal to use.
I am afraid, I just conducted a simple experiment, where I rebated a small section 4mm deep by 40mm in length in a piece of timber, and inserted a 40mm length of Intumescent strip with cold draft brush, this brush keeps the cold draft at bay and also provides initial seal before the heat reacts with the intumescent strip in the channel.

If a fire was to break out, large amount of smoke would spew first, the draft brush strip would take care of most of it up to a certain length of time, then as the heat strikes the brush, these are made of some plastic or nylon material which starts to melt and shrink, creating a big gap, and then becomes molten mess, in the mean time I counted like 100 seconds and continued applying the heat from a 2kw heat gun, not a flame one, to the seal which i held in one piece of wood representing door and screwed another on top about 3.5mm gap, to represent a 3 -4 mm gap, as recommended by fire doors, so this means whilst the brush vanished into a molten substance, shrunk, opening up the gap, that would allow lethal smoke to penetrate through, before the intumescent strip starts to react to heat, which would take another 100 to 120 seconds, before it expands sufficiently to seal this gap.

Not sure if these things really do as claimed or are we being bothered unnecessarily, of course a mains powered heat detector with battery backup fitted in the kitchen and linked to other detectors in each room and corridor would have gone long before and occupants would have escaped well before any of these seals even starts to react.

I think I need to spend more time on decent linked heat detector, much more than this Fire Door. Sure the Firemen would be wearing breathing apparatus and eventually they will need to break the door down to put the fire out.

By the time I finished with my experiment, the wood had darkened a bit, changed from cream colour to light brown, not charred . I was constantly directing heat at the gap. It smelt like wood is getting really hot and and about to cinder.
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I am stuck with where to rout for 10mm wide Intumescent Strip

On mine, the groove for the intumescent + fur strip is in the door lining, not the door. They are delivered like that. The linings have pink fire foam sealing the lining to the wall (there is a gap size limit, I don't remember it) and covered by the architrave. I believe a gun applied seal can also be used.

There is a door stop on the lining, which the door meets. Mine are quite a good fit so might stop more hot gases than the gap in your experiment.

I don't know how the temperature at which the pile melts, compare to the temperature at which the intumescent strip swells.
Of course, the brush or cold draft fur strip is made of hundreds of tiny hairlike nylon bristols and designed to melt, so that after it melts away it opens up the access for the intumescent material to start popping out of the slot into which this fur strip is held in. That makes sense, but there is this problem of about 100 seconds where the gap between the door frame and the door is completely open and this can allow some smoke to escape.
i wouldnt worry about the 100 seconds smokes gonna go under door as well which ever way you look at the fire door is to give you time to escape not to contain fire
plus if your worry about hinge gap use intumescent paint on frame works faster than the strips
I wish I had known this, would have saved me a lot of hassle, I am still at it, the frame is not 100% square, that means getting the gaps right and parallel is not a trial and error, its got be shaped and cut right the first time, with equal gaps of 3 to 4 mm all around except underneath with maximum of 4 mm.

Another problem I have is the door manufacturer recommends maximum trimming of 6mm from the bottom edge whilst the floor tiles added after the original frame was bolted in years ago means the door needs a larger trim of about 12mm and Howden doors do not allow any more than 6mm from the bottom and none from the top, and sides only 4mm. Pain in the back side will kill me before fire does!
you can take 12mm of the bottom with no problems the 6mm is normaly just for sides
But is that paint just going to turn a non FD, into an FD, that would still require the intumescent strip anyway.

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