intumescent fittings

[AnthonyB]

On behalf of a colleague on a type of fire door on a Middle Eastern new build:


"I've had a query regarding intumescent products on fire doors.
The doors reportedly have intumescent products inserted beneath the veneer on the edge of the door leaf.
It seems to me a large amount of the veneer would have to deteriorate before the intumescent product was actuated

Thoughts:
- If the white layer is intumescent mastic, the heat soak from the veneer would cause a considerable delay in expansion. If the veneer had to totally burn through (remembering that the face of the door, not the leading edge would be exposed to fire) I could see the door failing before the intumescent product came into play.
- If the intumescent layer expands before the veneer burns through, then the veneer would be forced off against the frame and imperfections in the fit would not be filled."

I'll try and add a picture later, the veneer layer appear quite thick.

Doors not BS certified or marked by a certification scheme as installed/made outside of the UK

[kurnal]

The people at envirograf may be able to advise on this as they make a product that sounds similar to your description

http://www.envirograf.com/acrobat/070.pdf

I am not sure how the intumescent material works, whether it pushes the hardwood edging off the door or whether
the smoke seal is pushed out of the groove allowing the intumescent material to pass through.

[Tom Sutton]

AB are we talking about lippings or veneer because one is about 6mm thick and the other 1mm thick. Also lippings are a tried and test method.

[AnthonyB]

From the photo it looks more like 6mm from the edge.

[Tom Sutton]

Well that is lipping and what you described is a standard construction. However if the doors are not certified then there is no way of checking without destroying the door also you cannot know which type of intumescent has been used.

If you require a more in depth information check out Architectural and Specialists Door Manufacturers Association and download the Best Practice Guide to Timber Fire Doors (Auntie LIn). http://www.asdma.com/bpg.html

[Phoenix]

If the veneer had to totally burn through (remembering that the face of the door, not the leading edge would be exposed to fire) I could see the door failing before the intumescent product came into play.

I cannot comment on other matters you mention but I would point out some faulty thinking in the small matter mentioned above. 

It is not the face of the door that is likely to fail to a fire, but it is the "leading edge" that may be exposed to fire and hot gases passing through a gap that is much more likely to lead to failure (at least in terms of integrity).  That, of course, is why intumescent strips are fitted at the edges where gaps are most likely to occur.

Stu

[AnthonyB]

A fair point - don't shoot the messenger though - I'm just cut & pasting! 

[Auntie LIn]

For what it's worth....
this concealed intumescent technology is a very specialised way of protecting door leaf edges - and usually only the long edges - heads being more vulnerable.   You need a careful balance of a lipping which is not too thick (6mm max is good - veneer if fabulous if you can get it to stick without activating the seal!).   You need enough seal to get close to the leaf edges but you also have to have enough timber on either side of the seal to allow the lipping to bond successfully to the door.   The adhesive that is used for bonding the lipping into position has to be one which softens on the application of heat - unlike most fr door adhesives which are required to stick like the proverbial.   The whole system relies very heavily on skilled manufacturing and accurate fit of the door.   It's no good making a decent fist of a door in the factory and then sending it out to site where some idiot planes 6mm+ off one of the lippings.   I have encountered instances where about 400mm of one whole lipping had been planed away to below the level of the seal.   You also find that the lippings are not so robust as those where exposed seals are used.   When the lipping gets knocked off and needs replacing, will the maintenance man a) notice that there was some stuff under the back of the lipping b) know what it was (you need a pressure-generating material such as Palusol or one of the graphite based seals for best effect) , c) replace it and d) know what adhesive to stick it back on with?

Unless you're working with experts in the field of fire doors avoid concealed intumescent details!