This structure was completely below ground with raised entrances level with the surface and was roughly aligned east to west. Both entrances were 45cm above the chamber roof and capped with corrugated iron and concrete. The concrete covers each sat on a lip that was 5cm deep at the sides and entrance. The eastern entrance measured 6.7m long by 1m wide and had eleven steps leading down to a corridor that was 70cm wide. The west entrance measured 6.65m long by 1m wide and was blocked with earth and rubble, making it impossible to ascertain the number of steps. Both corridors terminated in an 87cm-deep recess with a centrally positioned 10cm-diameter exhaust vent. Both had poured concrete floors with five 60cm by 46cm concrete slabs set into them.
The central chamber was identical to shelters F1-F7 and F9 in terms of measurements and fittings. <1>