PHYSICAL DAMP COURSING
BRE Digest 245 states that a physical damp-proof course is the only
fully reliable and permanent method of retro-fitting a d.p.c. but it is
a time consuming and labour intensive process and consequently very
expensive compared to other forms of damp-proofing.
An early method of physical damp-proofing was simply the replacement of
bricks with Class B engineering bricks at the appropriate height,
typically 150mm above ground level, but this method is only suitable for
short runs and if longer sections of wall are need then diamond tipped
chainsaws are used to cut a section through the full thickness of the
wall, including the internal and external finishes, to from a gap in the
brickwork wide enough to allow the insertion on the damp-proof course
which is then sandwiched in a dense mortar above and below it. The
damp-proof membrane is overlapped with the neighbouring section of DPC
membrane to ensure a watertight finish. Slate wedges are placed
approximately 100mm -125mm centres, from both sides of the wall, and
staggered. These are driven home in order to compress the mortar as well
as providing adequate structural support for the wall. The slate wedges
are then trimmed and made flush with the external brickwork and internal
walls. The mortar joint can then be re-pointed in the normal way and the
internal surface should be made good and skirting boards etc replaced.
To prevent any structural instability the cutting can only be done in
short lengths, usually around one metre and alternated in a similar way
to carrying out underpinning. The damp-proof membrane is usually copper
or bitumous felt and both of these are sufficient to prevent rising
dampness from the ground. There is also a system of forcing ribbed
stainless steel sheets into the groove using a pneumatic hammer to push
the steel through the full thickness of the wall.
The lifespan of a physical damp course is far longer than any form of
chemical damp-proofing, electro-osmotic damp-proofing or evaporative
siphon damp control systems and it creates a total barrier against
rising damp with firms who fit physical damp-proof courses offering 50
year guarantees against the recurrence of rising dampness from the
ground.
If you need any more information about the installation of physical
damp-course then please call us on 020 8226 3101 or e-mail
enquiries@dampbuster.co.uk