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3mm gap for smoke sealed doors inclusive of brushes?


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I've got these to put on the door, and left a 3mm gap at the bottom so the brushes just touch the floor. However, whether they are poorly made or its

just debris on the floor, the brushes have been coming away in a few days. the brushes are 4mm, so theres a 1mm contact with the flooring.

Does the 3mm gap need to include the brush, and why are the brushes coming off so quickly - the plastic is still on the door, just the brush itself coming off.



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On the same subject of gaps round fire doors. Does the door stop side of the door still need to be 3-4 gap?. I'm currently up grading old fire doors and they have a decent leading edge on the lock side. I'm sure once this side meets the door stop it will be over 4mm but the side you can see is 4mm or lower. And can I use hard wood edging on the bottom to close my gap to 10mm? 


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Best practice guidance for timber based fire doors is that the door to frame gap and threshold gap should be in accordance with the door manufacturers installation instructions. Where the manufacturer is unknown the gap should be 2mm to 4mm and this includes at the leading edge too. For the threshold the gap should be 3mm where cold smoke protection is required or 10mm max where no smoke protection is required or where a threshold smoke seal is fitted.

When re-lipping door edges use hardwood such as White Oak, Dark Red Meranti or Sapele. Retained lipping thickness should be 6mm min and 18mm max. and sanded flush with no gaps where the lipping meets the door leaf.

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