Clearance around a fire door.

[ProDave]

Simple question:  How much clearance is needed around an internal fire door for the intumescent seal?

 

More detail.  This is the door between our utility room and the garage. when I hung the door, it has always been a bit tight on the intumescent strip, needing a good slam to shut it.  I doubt it would have closed with a door closer.  So I was always planning to plane the door a bit.

 

Now in the last few days the utility room has been plastered, and now with the humidity of the wet plaster that door now won't shut.

 

So time to plane it.

 

But the question is simply, does the door need to "brush" on the intumescent strip as it closes, or is the theory that the strip expands with heat to seal the gap.  If so what gap is allowed?

 

I'm worried about planing the door now and when it shrinks back to size being too loose.

[MikeSharp01]

How thick is the i strip and is it encased in plastic. They expand a good deal. Iirc the size of the gap and the width of the seal are controlled by the fire rating. The smaller you get the gap the longer the rating for a given width broadly, a few mm should not be a problem. 

[MikeSharp01]

Yep this link sort of explains - well the PDF does.

https://www.promat.co.uk/en/products/promaseal-expansion-joint

[ProDave]

15 minutes ago, MikeSharp01 said:

Yep this link sort of explains - well the PDF does.

https://www.promat.co.uk/en/products/promaseal-expansion-joint

It looks nothing like that.

 

It's a fire door, door frame and intumescent strip all from Howdens.  the strip sits in a groove in the door frame and the bit in the groove is plastic, but the bit that "presents" itself sticking out of the groove is a bit like a brush strip.

 

I want the door to close easily (so a door close will shut it without problem) but I don't want there to be too much gap that BC fail it because it is not fire proof. 

 

So does the door have to touch the strip, or just come close?

[PeterW]

So that is a full brush smoke seal,  not an intumescent strip. 

 

2p piece all round is ideal but an intumescent strip will expand to 6-8mm at least anyway In the event of a fire.   

[ProDave]

8 minutes ago, PeterW said:

So that is a full brush smoke seal,  not an intumescent strip. 

 

2p piece all round is ideal but an intumescent strip will expand to 6-8mm at least anyway In the event of a fire.   

It was sold to me by Howdens as an "Intumescent strip"  Are you saying it is not?

 

I think it is this one https://www.howdens.com/hardware/screws-and-ironmongery/door-furniture/door-closers/intumescent-fire-strip-21m-obj-sku-family-its0005

 

So the bottom line is I can plane the door so it almost touches the strip and the strip will expand to fill the gap in a fire?

[PeterW]

That’s a fire and smoke strip - they do a fire strip which is just the plastic without the brush. 

[Bitpipe]

Mine came from Howdens but is fire only - looks like this ...

[carlb40]

3mm is standard top and the sides, i think it's either 4 or 5mm for the bottom of the door.  Be careful planing a fire door, most now state that planing a fire door voids the warranty.  Personally i would leave the door for a few weeks to see what happens with it before planing it.