Damp Proofing
Water penetration and the resulting problems of dampness are the foremost cause of deterioration in all buildings. The presence of excess moisture encourages the growth of mould, wood and brick-rotting fungi, which can invade a house with such vigour that they literally eat away the structure. To counteract this, the Building Regulations require that dwellings are designed with prevention in mind and British Standard 8215: 'Design & Installation of Damp Proof Courses in Masonry Construction' sets out the key criteria. There are also essential references contained in BS 8102 'Protection Against Water from the Ground', BS 5628 (Part 3, s3) 'Movement Joints' and 'Exclusion of Moisture'.
The principal considerations when choosing materials for a damp-proof course (DPC) are durability, resistance to stress, pliability and compatibility. The DPC must act as an effective barrier, stopping water from rising up out of the ground and through the brickwork. There are two main types of established DPC membrane material: PVC and bitumen. The latter is more expensive and usually only specified when the circumstances demand extra protection. The installation height of all DPCs is required to be 150mm above the finished ground level. It is therefore important to decide exactly where the ground level will be, once the garden and any paving have been established, because levels are likely to differ from their current height.
The other significant factor is that the effectiveness of a DPC can be compromised by careless workmanship when building the walls both below and above ground level. If excess mortar and other building debris are allowed to rest in the cavity, they can provide a bridge which moisture will use to traverse the DPC and continue its journey up the walls. By keeping mortar lines neat and cavity floors clear of building debris, you will be helping to maintain the efficiency of the DPC installation and reduce the chance of damp penetration for years to come.
