Fire Door Threshold Gap

The gap between the door and the frame is extremely important and must be suitable for the intumescent seal fitted.

Fire door threshold gap.

In general the gap should not exceed 3mm along the 2 long edges and across top of the door leaf to facilitate checking of the gap on site a bwf fire door alliance scheme gap tester is available on request here. The gap between door and frame at the top and sides should be 2 4 mm and the threshold gap as per manufacturers instructions typically around 8 10 mm the certificate will include details of this. Bs9999 2008 recommends for fire doors with cold smoke control that the threshold gap should be either less than 3mm in height or should be fitted with a threshold seal. If a door is to work effectively in its normal role the door leaf must be free to move within the frame and in order to achieve this there must be a gap around the perimeter.

Underneath the fire door a gap of 8mm is traditionally acceptable although for fire doors that are required to limit spread of cold smoke only 3 mm is permissible with a threshold seal to be fitted if the gap is bigger. The artificial seal may be any material such as an impermeable sheet or tape by testing air infiltration with the artificial bottom seal in place any air that. It is through extensive testing of fire rated doorsets together with knowledge of the pressure regime within a fire test that a larger gap is permitted at the threshold of the door. Nothing must be cut at the top at all and the certification label must remain intact.

There is negative pressure at the threshold during test conditions and so cool air is drawn in underneath the door. When speaking with manufacturers however a common statement is that a fire doors gap of up to 8 mm underneath the door is permissible. Mind the gap fire door seals fire doors play a crucial role in restricting the spread of fire and smoke. How much can you cut off a fire door.

The ul 1784 test standard states in order to obtain information on the extent of air leakage at the ungasketed bottom gap of a test sample an artificial seal may be applied to the bottom 6 inches 152 4 mm of the test sample. Approved document f ventilation in domestic buildings a ventilation gap totalling 7600 mm is recommended at the threshold of the door to allow.