Electro-osmosis
The only current installers of electro-osmotic damp proof courses are
Wykamol/Lectros and Triton Chemicals ( Trimotic Damp-Proofing System)
and they state that an active electro-osmosis damp-proofing system
‘introduces a very small and perfectly safe electric current into the
wall just above ground level through a series of titanium anodes
inserted into the brickwork. Its effect is to repel the rising moisture
molecules down the walls and harmlessly back into the ground. As long as
this tiny positive charge is maintained, the protected walls remain dry
and totally free of damp. A series of small holes are drilled in the
outside masonry just above ground level, and tiny anodes inserted,
linked by a special connecting wire which is 'pointed' into the wall.
The finished result is virtually invisible and the disruption is
minimal.’
After drilling holes around the base of walls at intervals of around
400mm, titanium anodes are placed into the holes and connected in a ring
circuit by a cable which is bedded into a mortar joint. This ring
circuit is attached to the mains via a step-down transformer to deliver
a small positive charge and it is this charge which is intended to
reverse the upward flow of rising damp.
Removal of plaster affected by damp is still required in the usual way
by hacking of the plaster up to a height of one metre and then replacing
the plaster with a sand/cement render containing an integral
water-proofing agent. This dense waterproof render itself will be enough
to prevent any dampness from affecting the internal surfaces.
Previous systems may have failed mainly due to the failure of anodes by
electrolysis but this has been apparently overcome by the use of
platinised titanium which has greater resistance to physical or chemical
breakdown and the system now in use is promoted as being successful in
controlling rising damp and is widely promoted as a chemical-free form
of damp-proofing.
However the Building Research Establishment (BRE) has investigated
electro-osmotic damp-proofing and it has some reservations about its
effectiveness in controlling rising damp and they stated ‘that the
principle of electro-osmosis in which the movement of liquid through a
porous material will occur if an electrical potential is applied across
the porous material. This classical view of electro-osmosis considers
that the liquid moved is not subject to capillary forces but in the case
of rising damp there is substantial capillary pressure to overcome. It
has bee suggested that thousands of volts (rather than the few used in
practice) would be necessary to cause sufficient downward pressure to
overcome rising damp’
Electro-osmosis is the flow of an aqueous electrolyte solution in a
capillary system (a porous medium or a capillary tube) under the action
of an electric field. The flow arises from the action which the electric
field exerts on the electrical double layer at the interface between the
solution and the solid surface. The result is a shear steady flow which
is proportional to the electric field and depends on the zeta potential,
the potential difference between the fixed charges on the solid surface
and on the composition of the electrolyte solution.
The potential difference is usually around 300mV and the associated
electric field is extremely weak and research has shown that the flow
the flow produced by an electric field of this magnitude is generally
insignificant with the upward flux produced in capillary rise and
electro-osmosis is further suppressed in the presence of salts and is
likely to be unpredictable in masonry structures.
Unsurprisingly this form of damp-proofing has never been awarded a
British Board of Agrément Certificate (BBA) although it can still be
covered by long-term guarantees issued through Guarantee Protection
Trust and Construction Guarantee Scheme, both of which are acceptable to
mortgage providers.
If you need any more information about the effectiveness of
electro-osmotic damp-proofing then please call us on 020 8226 3101 or
e-mail
enquiries@dampbuster.co.uk