Proofing with silicones
WHY OUR NEW GENERATION
INJECTION CREAMS ARE BETTER THAN LIQUIDS AND STICKS?
The technical review below
summarises the problems of the last generation of liquid damp proofing
systems. Our New Generation Creams are infinitely better for the following
- no pressure used in placing
the cream in the hole, so no losses down cracks and crevices
- gradual spread of the
cream giving even distribution, unlike liquid short term squirt and
- no solvents to evaporate,
so no smell, no health hazards and nice slow spread
- not caustic and non-staining,
unlike the old water based DPC Fluids (Siliconates)
- no solid stick to push
into a ragged hole and a lot cheaper
with Silicone Creams call our experts on 01626 331351.
DOES CHEMICAL DAMP PROOFING
WORK - PRESSURE
INJECTION USING LIQUIDS
Unlike a physical damp-proof
course these injected liquid damp-proof courses do not form a 'discrete
impermeable plane', but more of a 'diffuse band'. When fluids are injected
into a heterogeneous substrate such as brick/mortar they do not totally
fill up the porous structures and neither do they completely push out
the water in front of the advancing injection fluid as is so often claimed.
Instead, the fluid tends to 'finger' within the substrate, a process
known as 'viscous fingering'. The fingers of the injected material form
when the fluid takes the lines of least resistance such as the larger
pores and cracks. Unfortunately, such pathways are not the most important
elements in the conductance of water up the wall. Furthermore, the damper
the substrate the greater this fingering is likely to be, especially
with solvent based systems since these are not miscible with the resident
moisture. Fingering is also increased by injection at high pressure.
Reduction of the phenomenon is obtained by low pressure injection or,
better still, by gravity diffusion of the DPC fluid.
with pressure injected damp proof courses call our experts on 01626
WHY PRESSURE INJECTION
CAN BE INCOMPLETE
The result of the damp-proofing
fluids forming fingers give rise to non-impregnated 'pools' within the
wall through which water can continue to rise. In the case of pressure
injection damp-proof courses, this suggests that it is unlikely that
the diffuse band of the damp-proofing agent will be totally complete.
The resultant chemical damp-proof course may therefore not stop rising
dampness by causing an immediate cutoff of rising water above the damp-proof
course like that effected by a physical damp-proof course. Instead,
a relatively rapid decline in the moisture gradient should occur above
the inserted chemical damp-proof course due to the 'control' exerted.
Thus, in practice, the rising ground water should be reduced to such
a level that, in association with specialist replastering, it should
no longer cause decorative spoiling or damage.
with pressure injected damp proof courses call our experts on 01626
AFFECTS LIQUID SYSTEMS?
The efficacy of the water
repellent damp-proofing systems can be affected where there are detergents
(surfactants) impregnated into the wall by, for example, past leakage
from sink waste pipes. A similar problem may occur when walls are sterilised
against dry rot infection by biocide formulations containing surfactants.
The overall effectiveness of a remedial damp-proof course can be investigated
by examining the relationship between the distribution of free moisture
(water due to rising dampness or other source of active water ingress)
and contaminant salts (chloride and nitrate). Where rising dampness
is still active capillary moisture will be found to the full height
of salts. The absence of capillary moisture in the presence of salts
arising from rising dampness indicates that drying back has occurred
and that the damp-proof course is effective. Intermediary stages are
also found which demonstrate different degrees of control of the rising
dampness. If chloride and nitrate are not detected in a sampled profile
it is possible that the ingress of moisture is due to recently developed
rising dampness or more likely through rainwater penetration, condensation,
plumbing defect or other sources.
with pressure 'salts' analysis call our experts on 01626 331351.
A CHEMICAL DAMP COURSE
When evaluating the efficacy
of remedial damp-proof courses care must be taken not to misinterpret
electrical moisture meter readings; high readings might not indicate
that the damp-proof course itself has failed. They may reflect a number
of possibilities including contaminated or inadequate plasterwork. Thus,
an accurate assessment of the efficacy of a damp-proof course can only
be undertaken by determining full moisture profiles linked with analysis
for contaminant salts. It is also important to give consideration to
the expected performance and limitations of the installed system as
NOTE: It is identified in
BS 6576:1985 that where timber suspended floors are encountered the
damp-proof course must be injected, where possible, below joist level;
this is to protect the embedded timbers from dampness and the risk of
fungal decay. However, given the likely efficacy of injection systems
the embedded joist ends could still remain in contact with damp masonry
even if above the injected damp-proof course and may therefore remain
at risk to fungal decay. It would be considered prudent that in all
cases where a damp-proof course is installed in relation to a timber
suspended floor, action is taken to protect any embedded timbers just
above and certainly below the injected damp-proof course to prevent
potential decay! Boron Gel, injected Boron Paste and the insertion of
a plastic membrane can all be used to protect vulnerable joist ends
and bearings. Do NOT bag joist ends in plastic - this can lead to serious
decay, due to condensation and lack of breathing.
with testing a damp proof courses call our experts on 01626 331351.
Learn from the UK's greatest
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Site written by: David
David Moore, B.A. (Hons.),
C.T.I.S., C.R.D.S. Technical Author
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