North Kent College, Dartford

• Planned the job as four short visits over the build programme: low level frame bonds, high level frame bonds, roof network after all other roof works, and earth rods before groundworks completion. Total estimated site time was four days.
• Bonded the frame at 20 m centres around the perimeter by drilling 10 mm holes in the steelwork and fitting M10 bonding clamps with 25 x 3 mm aluminium tape tails, rolled up at high level for the roofers to leave out.
• Installed the 25 x 3 mm PVC coated aluminium air termination network once the roof was clipped out and bonded plant, flues, handrails and aerials into it with M10 clamps.
• Drove nine earth rods to an initial depth of 2.4 m with a 110 V percussion hammer, under a Willmott Dixon service avoidance plan: the main contractor CAT scanned and marked each rod position, witnessed the driving and photographed it for the record. Percussion tool use was logged to a 44 minute daily limit per operative for HAVS control.
• Tested each electrode with a calibrated digital earth tester and connected the down conductor tails through test clamps.

A steel frame system with nine driven rods delivered on four visits to suit the programme, with the frame carrying the lightning current and no external down tapes on the finished elevations. The system was tested on completion.