A damp proof course ( dpc ) is a physical barrier inserted into the fabric of a building to stop water passing from one place to another. This can be on a horizontal plane, stopping water rising up from the ground by being sucked up by the dry masonry above, or vertically to stop water passing from the outside of a building, though the masonry, to the inside. Dpc's have taken many forms through the ages and one of the earliest forms was to use a layer of slate in the construction. Slate is still used but the less expensive plastic version ( below right ) is now more widely used. Technical specification of dpc Water vapour permeability 0.28 gm2 day-1 Bs3177 Water vapour transmission 733 mnsg-1 Water absorption 0.22% Bs2782 : 430a Resistance to leakage at joints Pass Moat 27 : 5.2.1 Tensile strength of joint Unaged : 300 n Heat aged : 290 n Water soak : 257 n Moat 27 : 5.2.2/3/4 Cold flex temperature −60¡ãc Bs2782 : 320a Tensile strength L : 12.9 nmm-2 T : 11.2 nmm-2 Bs2782 : 320a Elongation at break L : 415% T : 582% Bs2782 : 320a Tear strength L : 122 nmm-1 T : 96 nmm-1 Bba method Low temperature flexibility L :