Injection mortars † 19 mm diameter holes are bored from both sides
of a wall, at the appropriate level and no more than 230 mm apart
horizontally, to a depth equating to three-fifths of the wall
thickness. They should be inclined downwards at an angle of 20 to
30 °. The drill holes are flushed out with water, before injecting
mortar from the base of the hole and outwards. This can be
undertaken with a hand operated caulking gun. Special cement
mortars contain styrene butadiene resin (SDR) or epoxy resin and
must be mixed in accordance with the manufacturer's guidance.Notes relating to all applications of chemical dpcs:* Before commencing work, old plasterwork and rendered
undercoats are removed to expose the masonry. This should
be to a height of at least 300 mm above the last detectable
(moisture meter reading) signs of rising dampness (1 metre
min.).* If the wall is only accessible from one side and both sides
need treatment, a second deeper series of holes may be bored
from one side, to penetrate the inaccessible side.* On completion of work, all boreholes are made good with
cement mortar. Where dilute chemicals are used for the dpc,
the mortar is rammed the full length of the hole with a piece
of timber dowelling.* The chemicals are effective by bonding to, and lining the
masonry pores by curing and solvent evaporation.* The process is intended to provide an acceptable measure of
control over rising dampness. A limited amount of water
vapour may still rise, but this should be dispersed by
evaporation in a heated building.Refs.BS 6576: Code of practice for diagnosis of rising damp in walls of
buildings and installation of chemical damp-proof courses.
BRE Digest 245: Rising damp in walls: diagnosis and treatment.
BRE Digest 380: Damp-proof courses.
BRE Good Repair Guide 6: Treating rising damp in houses.Chemical Damp-Proof Courses for Remedial Work (2)