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What gap under fire door

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When renovating a 3 storey house and putting in fire doors can a gap be left at the bottom of the door to allow for floor coverings to be added as I do not want to decide whether to have carpet or Karndean type flooring. I have been told that carpet or whatever has to be installed for the doors to pass Building Regs!

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The gap at the bottom of the fire door is important. If the gap is too large, the issue is 1) That cold-smoke may spread from the fire side and 2) That cold air from the non fire side may be drawn under the door and feed the fire to aid its development.

The maximum gap allowed for a fire door is generally 10mm between the door bottom edge and the floor covering. The maximum gap for a fire door with smoke protection is 3mm but if this is not possible a gap of up to 10mm is permissible with the use of a smoke seal to seal the gap at the door bottom edge.

The easiest way to achieve the above is to use a hardwood threshold strip, that way you can get a consistent gap as well as avoid the door sticking on the carpet and failing to self-close.

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The fire safety issue is that the gaps specified by Neil has to be there when the work is completed and the floor coverings are fitted. As for the Building Control Office/Authorised Inspector, issuing a completion certificate, you will have to speak to them.

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Guest Novice

The gap under fire doors is becoming a bigger problem as we move to new buildings with underfloor heating in the floor screed. To reduce costs and increase profits contractors are reducing the depth of the finishing screed and in a recent inspection I found gaps of up to 32mm between the bottom of a fire door and the finished floor covering!

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Guest Kay

Please can I ask guidance on the following. I am a tenant in a housing association flat. There is a 1 inch gap (highest point) under my front external fire door and no fire strip. I moved into the property in May 2018. Following the joiner attending 2 weeks ago after me advising the association of there being no fire strip and the gap underneath, over 4 weeks ago, the housing association have told me I am getting a full upgrade. I asked what this meant and was told they are putting a letter plate on/adding hinges/A drop seal and cold smoke seals. I am worried about the gap under the door and they have said it will confirm to standards required for a fire door. Please can anyone with this kind of knowledge advise me? 

 

20181117_150517.jpg

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Maximum gap under a timber based fire door should be 8mm to 10mm. If the gap is more than that then a threshold plate is required to reduce the gap to 10mm or below. Where the door is required to restrict spread of cold smoke (which will be the case with a flat entrance door) the maximum gap should be 3mm. Where the 3mm max gap cannot be achieved a threshold smoke seal should be fitted.

Therefore the upgrading contractor should reduce the gap to 10mm before fitting a threshold smoke seal. 

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Neil assuming the floor is not level and you if you fit a threshold plate to the floor would this not create a tripping hazard or could you make a bespoke one out of hardwood with a chamfer on each side?

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Hi Tom,

Clearly, using hardwood for the threshold plate allows you to 'plane-in' to achieve a better degree of gap accuracy. Other aluminium threshold plates are available and compliant to Part M Access Regulations.

It is advisable to risk assess TRIP hazard vs SMOKE hazard before fitting a threshold plate to the floor.

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