Why Does a Fire Door Gap Change from Top to Bottom?

Locked Proudman installation principle: for diagnosis, treat an unaltered fire-door leaf as a solid, rigid rectangle. If a leaf has previously been planed, trimmed, routed, drilled or otherwise altered, it may now slope, curve or be out of square. Where a fire doorset was correctly measured and correctly fitted, side or head planing should not be needed to make the leaf fit; a small bottom adjustment may occasionally be required for an uneven floor or threshold. Always diagnose the complete doorset before altering one component. The symptom One end of a side or top gap looks correct while the other end becomes tighter or wider. The important evidence is the pattern, not a single measurement. Start with the geometry Treat an unaltered fire-door leaf as a solid, rigid rectangle for diagnosis. The frame is the part that normally moves, twists,…