RISING DAMP
Rising damp is the upward movement of ground water through the pores of a permeable masonry wall via a process called capillarity. Capillarity is the same process that enables the movement of water from tree roots to tree tops via intricately stacked hollow cells despite the counteractive force of gravity
Rising damp typically occurs if the built-in damp-proof course is bridged, for example by the render, plaster or pointing or by a change in ground level or a blockage at the base of a cavity wall structure. An original damp proof course can also fail due to damaged caused by structural movement or alteration
In such cases rising dampness may become a problem if it is likely to affect vulnerable materials or finishes that are in contact with the wall. For example if the dampness has potential to rot joist ends, skirting boards or the bottom of door frames or if it causes wall plaster or wall coverings to deteriorate or become stained. In such cases it is necessary to introduce a new damp proof course at the base of the walls, see DAMP PROOFING
PENETRATING DAMP
Penetrating damp is the term that describes the ingress of water into the living accommodation of the building through its walls. Water can soak into and through walls at levels that are both above and below ground.
Above ground, penetrating dampness is usually due to one or more building maintenance defect. For example penetrating damp may be the result of faulty junction between windows and walls or could be the combination of a leaking rainwater pipe and dilapidated pointing or frost damaged bricks, which has allowed dampness to soak completely through the wall. Fortunately once the defect is correctly identified, and the source of water ingress eliminated, the likelihood of further penetrating damp is minimised.
In below ground situations water ingress is usually due to penetration of groundwater, the degree of which may be intensified by the presence of positive water pressure if the water table is high and the drainage system around the outside of the building is poor. Waterproofing existing home basements requires the introduction of an internal tanking or lining system that prevents ingress of dampness into the living accommodation.
BASEMENT DRAINAGE
The key to successful basement waterproofing is effective drainage. Cellar drainage typically comprises a ‘ Natural Gravity Drain’ or a ‘Mechanical Sump & Pump Arrangement’, both of which are used in conjunction with falls or drainage channels.
Drains and soak-away systems can and do block up or back up, causing flooding, including escape of foul waste. Natural Gravity Drainage is only feasible, within the bounds of the property or at a point of exit from it, where 'internal drainage' is certified as being in the good working order and the connection of local drains into public drains or a soak-away includes protection against blockage or back-up potential. Otherwise a sump and pump system should always be used.
CONDENSATION
The air inside buildings often incorporates high moisture content due to the activity of the inhabitants in cooking, bathing, drying clothes etc. When this humid air cools its capacity to hold water vapour decreases and once a dew point is reached, the condensate is deposited onto surfaces having a lower temperature than the moisture laden air. This condensate is immediately obvious on non-porous surfaces such as glass and ceramics but is, initially, less noticeable on porous cold surfaces such as plasterboards, wall plaster and timber, which may simply absorb the moisture.
Condensation occurs most often in rooms where large amounts of moisture are produced, such as kitchens and bathrooms, and in unheated rooms into which the moist air has drifted. It often concentrates in areas where air movement is restricted, such as behind furniture or inside cupboards on outside walls allowing mould spores to germinate and musty odours to accumulate.
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