Water testing the Shockmat over Wolfin at the Telstra Exchange, 237 Castlereagh Street Sydney

Client: Telstra Transfield

Location: 3 Sydney CBD Telephone Exchanges

Task: To provide high integrity, durable waterproofing that will protect Telstra’s main telephone exchanges.

Andersal Site Supervisor: Eddie Issa

Special Challenge

  • Telstra had an extremely tight time frame for project commencement. As the waterproofing is protecting hundreds of millions of dollars of equipment, zero tolerance to water ingress is mandatory.
  • One roof had asbestos inbedded in 30 year old sheeting.
  • One roof had an old PVC membrane that had been repaired or replaced a number of times.
  • Each roof had antennae that need to be shut down to protect works from electromagnetic radiation.
  • Some antennas had to be relocated to effect waterproofing integrity.


  • We contracted Ross Mitchell & Associates to remove and dispose of the asbestos. Staff fully equipped with demolition “space suits” recovered, packed in plastic and taped the asbestos then transported it to the specialist tip area.
  • Andersal coordinated with Telstra staff to match their OH & S standards to switch off antennea when in close proximity to our trades people.
  • Andersal utilised 50 tonne cranes from Gillespies to lift materials to the 15-20 floors to the roof.
  • Andersal applied in total about 1600m2 of Wolfin S. This provided a fully bonded PVC membrane.
  • Andersal added shockmat to one roof to protect the membrane from other tradespeople.
  • Some antennea had to be relocated. Telstra staff did the relocation. Andersal staff sealed the old and new antennea locations.
  • Where practical the old membrane was removed, otherwise when plumbing or plant prevented it the new membrane was laid over the old, as Wolfin is impervious to most bitumen or other common products found at roof levels.