Under door seal for Flat fire door

[whitedragon101]

We are just changing the doors on our flat.  An FD30s fire door is required for our front door.  The building is 12 stories we are on the 5th.  The door opens onto a landing with 4 other flats.  There is a stay put policy for fire.  There are 2 doors at opposite ends of the landing which lead to the two separate stair wells.  I am having an FD30 fire door with intumescent strips with brush smoke seals to the top and sides.  The bottom however is over carpet.

1)  Do I need to smoke seal the bottom of the door?
2)  If so is a adding wooden block under the door (instead of a carpet gripper ) that leaves only a 3mm gap sufficient protection?
3)  If the answer to 2 is no would adding an intumescent brush strip recessed into the wooden block provide sufficient protection?

Many thanks

[Fishy]

Not normally, but check the installation instructions and fire certification for the door that you're having installed - this should be followed scrupulously.  BS 8214 (Timber-based fire door assemblies ? Code of practice) has the following general guidance:

"....9.5.3 Under-door (threshold) gaps for fire resistance

Under-door (threshold) gaps should be in accordance with the fire door manufacturer?s installation instructions for the particular design.
NOTE 1 Gaps larger than those approved are likely to compromise the fire resistance performance of the door assembly.

The door should be able to open freely over its entire opening angle without damaging the seal or catching on the floor.

NOTE 2 Further guidance on threshold gaps is given in the ASDMA publication Guidance and recommendations for the coordination of bespoke doorsets..."