WHAT IS Damp Proof Course?
Damp-proof course (DPC) means a continuous layer of impervious material placed in a masonry wall or pier, or between a wall or pier and a floor, to prevent the upward or downward migration of water.
DPC is a horizontal barrier in a wall designed to resist moisture rising through the structure by capillary action - a phenomenon known as rising damp. A damp-proof membrane (DPM) performs a similar function for a solid floor.
Moisture resistance is not necessarily absolute: it is usually defined by a specific test method, limits, and engineering tolerances.
MATERIAL USED FOR DPC?
- Embossed black polyethylene film of high impact resistance.
- Polyethylene coated metal.
- Bitumen impregnated materials.
- Termite shields (with no penetrations) continuous through the wall or pier.
Common DEFECTS found
- Inappropriate, damaged, inadequately installed, or no DPC are the main factors for rising damp or DPC failure, together with this, the following issues can exaggerate any defects with the DPC.
- Rotting wood, peeling paint and salt deposits are evidence of rising damp.
- Moisture ingress above the DPC/flashing which is not fully discharged from the wall cavity.
- Overly porous masonry construction exposed to high rainfall (exacerbated by inadequate or no eaves overhang) allowing moisture penetration that exceeds the capacity of the discharge system, i.e. flashing, DPC and weep holes.
- A damaged DPC or the DPC no longer copes with changing conditions such as a rise in ground level.
- Inadequate sub-floor ventilation, lack of ventilation in the sub-floor results in a build-up of humidity and means only minimal evaporation from the soil and base walls occurs.
- Sub-floor obstructions, any debris in the sub-floor can obstruct the flow of ventilation and may contribute to dampness.
- Poor drainage and/or damaged guttering and pipes, water may be directed underneath the house by way of poor drainage, the build-up of garden beds and sloping grounds.
- Some DPC materials may contain asbestos fibres. This was more commonly found in the older, grey sealants as well as flexible tar boards.
- Other possibly hazardous materials include the use of lead sheets as a DPC material.
Call Northern House Inspections Melbourne today on 0481 299 682 or fill out our Instant Quote form and allow Mike who uses state of the art moisture meters and thermal camera to check for any rising damp issues which could affect your new home purchase. These problems can be identified before you negotiate your purchase price to account for any remedial works required to get your new home healthy again.