Total length, external 550 ft. " " internal 520 ft. Length of high roofs 425 ft. " of nave from west door to screen 205 ft. " of choir and presbytery 169 ft. " of Lady Chapel 57 ft. " of transept, interior 177 ft. Width of nave with aisles 75 ft. 4 in. " " without aisles, between piers 29 ft. 6 in. to 31 ft. 6 in. " of presbytery 75 ft. to 78 ft. " of west front, exterior 105 ft. " of transept, interior 32 ft. to 33 ft. 6 in. " " exterior 54 ft. 4 in. " of Lady Chapel, interior 24 ft. Diameter of tower piers, east and west 16 ft. Distance between tower piers each way 24 ft. Height of tower piers 43 ft. " " arches 55 ft. " of tower 144 ft. Width of tower, east and west, exterior 47 ft. " " north and south, exterior 45 ft. Height of nave ceiling (from floor) 66 ft. 4 in. " of ridge of high roofs 96 ft. " of Lady Chapel vault 33 ft. Total internal area (about) 39,240 sq. ft. Height of floor above mean sea-level 340 ft. [13] These are the dimensions given by Lord Grimthorpe; the altitudes, except when otherwise stated, are measured from the level of the floor at the west doorways. [Illustration: GROUND-PLAN OF ST. ALBANS CATHEDRAL.]