Hi guys, 

 

When checking a fire door with a one inch rebate around the frame, where am I measuring the gap between the door and the frame? From the inside, the gap above and side of the door is in excess of the 4mm but there is a less than 1mm gap between the door and the rebate on the other side so the door is effectively entirely sealed and im not sure how smoke could pass through. 

 

So, for fire doors with one inch rebates around the tops and sides, am I checking the door gaps between the door and frame or the door and the rebates? 

 

Cheers in advance

So the door leaf doesn't overlap the rebate and is like this?

Sorry Anthony, I'm not explaining it very well. Hopefully my drawing will help to explain. 

So from the inside of the room, if you look at the door, there are gaps between the door and the frame itself. From the outside of the room, because the door closes on to a rebate (approx 1inch), there are no gaps around the tops and sides at all, but a very small (1mm) gap between the rebate and the door. 

By my logic, whilst the gaps on the inside LOOK to be in excess, any smoke going through this would hit the rebate and not be able to travel further, so the gap the smoke could escape from is actually on the 1mm gap between the door and rebate. 

But all the fire door checking guides I've seen are very simplistic in that you measure simply between the door and frame - they don't mention rebates (that I can find). 

The gap should be measured at the point between the edge of the door leaf and the face of the door frame. Guidance in BS 8214: 2016 states that the gap should be between 2mm minimum and 4mm maximum for optimum fire resistance performance. 

For restricted spread of cold smoke the seal should fill the gap but without causing the door to catch or bind when self-closing.