Attention Body Corporates

Waterproofing Corrosion Alert.

Recently we attended a service call to check a faulty booster and while inspecting the system we found the following antenna mount rusted away. 

Rusty LA Roof Mount

This system had been installed approximately 5 years ago on a 4 storeys building 500 metres from the beach. The masting equipment was of good quality and showed the expected amount of corrosion except for the mount. The mount was hot dip galvanised and should have had almost no corrosion. The base plate was fine yet the centre mounting flange was rusted through.

On further inspection it became obvious that the cause was the waterproofing that had been applied to the mounting plate after the aerial mount had been installed.  The waterproofing had been applied up the sides of the vertical section of the plate and as a result had formed a water trap which filled with salty water.  The part of the mount was sitting in saltwater continuously which caused it to rust away rapidly despite the galvanising.

I have attached a photo of a recent roof mount installed in conjunction with the water proofer showing the waterproofing done so that it covers the plate but not up the vertical section.


The danger here is that had we not been on site for a different problem and had we not been thorough enough to check the mount (the rust was hidden by the waterproofing) this mast would have collapsed, likely breaking the antenna and mast, perforating the waterproof roof membrane and resultant emergency phone calls. (Murphy’s law says this would happen on a Friday afternoon or Sunday)

We would therefore suggest the following:

  1. Alert water proofers to only waterproof the base of the antenna  mount, attaching a copy of these photos to clarify the point.
  2. Buildings with this flat roof design that have been re- waterproofed in recent years could be inspected,the mount photographed and any remedial work recommended.


We would be happy to inspect, photograph and report at no charge if this would be of assistance.

I hope this information is of use to you and look forward to being of service in the future.

We have added the closer inspection of the mounts on this type of installation to our checklist and should we encounter this corrosion problem on one of your buildings we will forward a photo and report in addition to any other work being done at the time.