Why Cavity Cleaning is Important for Damp-Proofing?
The amount of rubble which accumulates between the internal and external walls can be surprising.
Without cleaning this out, damp-proofing is much less effective as water still has a “bridge” to travel through – this is how the water gets from outside to inside!
When the original bricks were laid, the visible joints (internal wall and external) were finished cleanly. However the joints on the cavity side of the wall were not always cleared, leaving overhanging mortar which over years has broken off and fallen into the bottom of the cavity between the walls. By thoroughly cleaning this out, the damp-course membrane which is inserted into the wall can now be effective.
Without cavity cleaning, the silicone method of damp-proofing is less effective as water still has a bridge to travel through.