44 or 38?

[K Lard]

When I have been making an assessment of existing fire resisting doors when there is no supporting documentation or markings, one of the features that I have been looking for is that they are at least 44 mm thick. This is supported by BS 8214 1990 and is also mentioned in the flats guide, albeit in connection with upgrading doors. I have come across a document published by a fire authority which states that the minimum thickness in identifying a fire resisting door is 38 mm. Any one know where this figure comes from? The link to the document is http://www3.hants.gov.uk/fs-firedoorchecksandadvice.doc

[wee brian]

I'd have gone 44. There probably are 38mm FD30s out there but most 38mm doors won't be FR

[JT]

There's 35mm FD30 doors. https://www.howdens.com/media/library/pdf/2513.pdf

Shouldn't common sense and competency prevail, and not stick to a certain thickness.
I would be more concerned with the location, occupancy, fire loading etc as determining factors over a 30 minute furnace test.
Will the door effectively serve its purpose.

[wee brian]

Yes all of that. But when you're looking at a door and wondering if its a fire door then the thickness is a good clue.

[JT]

It's a clue, and only that. The weight and strength in flexion give a more indicative idea.
The only real way to know is invasive. That's fine if you've got several critical doors.

You could always employ a fire door inspector.....

[Fishy]

...The weight and strength in flexion give a more indicative idea...

Trust me - no they don't...

http://www.crisis-response.com/forum/index.php?topic=6744.0

 

[JT]

Always happy to learn. For me I've always been satisfied by checking weight and strength of door.
Can normally tell if hollow/egg shell construction.

How would you suggest checking as I couldn't see a formal test in your link?

[colin todd]

Probably, the burning rate of timber is slower in Hampshire, so you can have thinner doors.  I think it is something to do with slow pace of life.  Anyway, if the FRS say it is ok, they must be right cos they know everything there is to know about fire.  I once nearly bought a house in Hampshire, but it was too close to the road for the cats and somehow I didnt like the idea of living in Hampshire rather than Surrey.  The house backed onto the largest single field in Hampshire; in Scotland farmers have bigger postage stamps.

[kurnal]

Well Colin I'm baffled to see your point. Perhaps it's time we set up a pseuds corner ?

[kurnal]

There's 35mm FD30 doors. https://www.howdens.com/media/library/pdf/2513.pdf

Shouldn't common sense and competency prevail, and not stick to a certain thickness.
I would be more concerned with the location, occupancy, fire loading etc as determining factors over a 30 minute furnace test.
Will the door effectively serve its purpose.

Exactly right. Let's not forget that standards and test methodology changed many times over the years and that generally in the UK such changes are not applied retrospectively as this would create a huge financial burden on the economy. If it's still fit for purpose  and in good condition then an older door installed to older standards is still acceptable subject to the fire risk assessment.

[colin todd]

Whats a pseud?

[kurnal]

You have never read private eye?

[colin todd]

No, never. 

[Fishy]

Always happy to learn. For me I've always been satisfied by checking weight and strength of door.
Can normally tell if hollow/egg shell construction.

How would you suggest checking as I couldn't see a formal test in your link?

When fire tested, doors don't tend to fail by burning through - they most often fail because they distort out of the frame so you get erosion and big gaps around the edges.  Thicker timber doors bow less, but apparently  'stronger' doors might bow more!  This is one of the reasons why keeping the basic construction the same but going from 44mm to 54mm will often give you a 100% increase in F/R - blindingly obvious that if burn-through was the main issue that extra 10mm would only give you an extra 20% or so, not double.  It's also why reducing thickness from 44mm to 38mm might have a  far greater effect on the fire resistance than the 6mm difference would suggest!  As another example - steel doors, can be very strong & will never burn through but might only give you a few minutes F/R because they can distort significantly and quickly - producing gaps you could put your fist through within 10 - 15 mins.  That's why the locking/latching mechanism is so important on some configurations of steel fire doors (& it's why they're often three-point latched).

We won't go through the "...but does it really matter..." debate (that's been done on other threads), but the answer is look at the standards (e.g. BS 8214) & if you make such judgements regularly then some relevant training and possibly formal qualifications would probably be in order.  We've seen some clients starting to insist upon Fire Door Inspection Scheme membership, for example.

[JT]

I was with you on the first paragraph, I could see your logic.
I would disagree with stronger doors bowing more from my experience. But would appreciate to see some data on this if you have it?

Second paragraph "fire door inspection scheme membership", that might sum up why we disagree.