Issue 44 winter 24 - Journal - Page 86
• Replacement of the masonry leaving a cavity between
the steel frame and external cladding providing this is not
visually evident
Benefits of ICCP
• It is a less invasive method than traditional repair work
• ICCP is generally more cost effective and is faster to
implement
This method provides an adequate repair with a designlife expectancy dependent on the preparation of the
steelwork and the choice of paint system.
• The inert catalytic anodes are not consumed and have
a high design life in comparison to sacrificial cathodic
protection
• The cathodic protection current can be pushed through
higher resistivity electrolytes (concrete, stone, mortar etc)
by the higher drive voltages available from the power supply
Case Study
Project Freemason’s Hall
Client United Grand Lodge of England
Main Contractor Szerelmey Restoration
The Freemason’s Hall in London is the headquarters of
the United Grand Lodge of England and the Supreme
Grand Chapter of Royal Arch Masons of England and has
been a masonic meeting place since 1775. The current
building, which is Grade II* is the third building on the site
and was built between 1927 and 1933 to the designs of
architects Henry Victor Ashley and F Winton Newman.
The building is in the Art Deco style and was built as a
memorial to the 3,225 Freemasons who died on active
service during WWI. The building has been used frequently as a filming location for popular TV series and films.
Considerations with ICCP
ICCP requires highly specialised skills and only works
effectively if the protective current passes consistently to
the steel via a mortar, concrete or stone connection.
Unfortunately, the quality and consistency of mortar
in- fill in early steel framed buildings is highly variable.
There is another risk with CP - Failure to ensure electrical
continuity of all metallic elements in a building is an
important issue as it can lead to the accelerated corrosion
of any discontinuous metallic elements.
Other considerations are the costs associated with the
ongoing monitoring. Although these are relatively
modest, they are a cost none-the-less. There is also a need
to slightly widen the joints. On balance widening joints is
preferable to cutting out dozens of blocks to reach the
rust, but it is still a negative impact.
Acting as Main Contractor, Szerelmey Restoration
delivered the first of a number of phases of restoration
works to the substantial building. Like many buildings of
this particular era, there were signs of “Regent Street”
disease across the façade. Works included cleaning and
restoring the stonework to the main tower and undertaking the biggest cathodic protection scheme delivered to
date. We also managed the installation of cathodic protection incorporating concrete repairs to the tower. Other
works involved asphalt repairs to the high level roofs and
repairs and decoration to the crittal windows.
The external cladding is also a consideration; terracotta,
faience and glazed bricks can act as an insulator and make
it difficult to distribute protective currents.
Traditional Treatment
This involves the removal of damaged masonry followed
by the removal of the corrosive material and then
application of a suitable coating prior to reinstatement of
the masonry. In cases where extensive corrosion problems
are present and the masonry is displaced or damaged,
traditional methods of repair are generally the only option.
In instances where a mason needs to do lots of repair like
this to address the problem, regardless of the long-term
solution, cathodic protection is unlikely to be the right
course of action. Generally speaking CP is best used as a
“catch it early” solution as the cause can be addressed and
much of the original fabric retained.
To address this, the team is currently preparing areas of
the front façade of the building for cathodic protection.
Works have commenced on concrete remedials and
additional repairs to the façade and roof.
Traditional Repair Methods
Once the corroded area is revealed the following method
may be used:
• Grit blasting the corroded steel
• Application of a corrosion inhibiting paint/coating
system such as a zinc rich two part epoxy
• Where appropriate, the addition of DPC’s, particularly
if a cavity cannot be achieved between the steel and
external ashlar masonry
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Conservation & Heritage Journal
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