The construction of the building should be dam proof. The chief cause of dampness is absorption of moisture by the material (brick, mortar, and stone).
Either account of bad workmanship or by use of defective materials moisture [‘hay find its way inside the space either through walls, floors or roofs.
Its presence will indicate the material have been porous and likely to deteriorate. It may also entrap in masonry.
Signs of dampness –
(ii) Weathering of materials-metal rusting.
(iii) Pealing of plastering/pointing-last deteriorating and crumbling.
(iv) Efflorescence appearing on brickwork or plaster work.
(v) Growth of Vegetarians.
(vi) Electrical fittings deteriorated.
(vii) Carpets get damaged Rubber linoleum losing adhesion to the floor,
(viii) Creates unhealthy conditions to occupants.
(ix) Strains on wall papers and paint work. Paint work blistering, swelling or showing yellow oily ruin, distemper flaking.
(x) Wood/wall board warping and bucking.
(xi) Plywood coming apart.
(xii) It promotes growth of termite.
Causes of Dampness
(i) Moisture rising from soils, soften magesile composition floor.
(ii) Bath water penetration.
(iii) Exposed tops of parapet and compound walls.
(iv) Defective materials and construction.
(v) Level of site.
(vi) Drain ability of soil.
(vii) Kitchen, bath room down water pipes and leakage in drainage, cement facing/pulled away from the wall
(viii) Dampness rising through the foundation walls.
(ix) Splashing rain water which rebounds after hitting the water surface.
(x) Sloped roof rain water may percolate through defective roof.
(xi) Inadequate roof slope for flat roof.
(xii) Damp proof course at ground floor level being nonexistent, fractured or perished. Made ineffective by soil, coal, etc., piled against the wall above its level.
‘(xiii) The air bricks ventilating a joist floor being blocked up in sufficient number or wrongly positioned.
(xiv) Ground moisture rising through a solid concrete floor which has no water proof membrane.
(xv) Trees and shrubs close to the building
(xvi) In basement, a leaking drain pipe, the absence of a damp proof course at basement floor level.
(xvii) Cracks in brickwork or missionary.
(xviii) Defective pointing of the brickwork.
(xix) The exterior wall too thin for an exposed situation
(xx) The wall cavity bridged by plaster lodged on the wall tiles or debries collected at the bottom.
(xxi) The damp proof courses above the lintel and down the sides of windows/ doors openings absent, fractured or perished.
(xxii) A perished mastic or cement filling between window or door frame and the wall
(xxiii) A defective sill which requires, re pointing or the renewal of the mastic or cement between the sill and the window/door frame.
(xxiv) The absence of a throat on the underside of a window sill.
(xx) Horizontal projections from the walls (e.g.. ledges moulding which are not protected by slopping cement fillet or a metal flashing.
(xxvi) Flashings which have slipped or developed pin holes (especially round chimney stacks).
(xxvii) Cracks or pin holes in the asphalt or metal covering of a flat roof.
(xxviii) A cracked or dislodged roof tile or slate.
(xxix) The absence of a damp proof course in a chimney stack or parapet at roof level.
(xxx) Persistent splashing against the foot of a wall by an overflowing warning pipe.
(xxxi) A fire place blocked up without a Vent but with the top of the left open.
(xxxii) Condensation within a flue caused by a slow burning fire
Remedial measures of preventing dampness depends upon where dampness is there-
(i) For damp arising out of subsoil water. The measures are-
(a) Reduction of subsoil water by provision of relief well and pumping points.
(b) Opening of joints for evaporating of moisture.
(c) Providing an effective damp proof course (Walls, floors basement). A horizontal damp proof course is built into walls at a height of 15 cm or more above the level of soil.
It may consist of Tar (Bituminous) felt, slate sheet, copper sheet, and lead or optic asphalt. It must cover the entire width and length of every wall including steeper walls. Walls with a base of granite or three rows of bricks do not require further damp proof course.
Solid floors are built level with a damp proof course. Timber floors are built with their joists above the damp proof course. Damp proof course is also required in chimney stack where they adjoin the roof. Object is to form a barrier against rising damp. Precautions –
A uniform thickness to be provided.
Construction joints should be minimum.
Full thickness of wall must be covered.
When damp proof course is provided at plinth level it should not be carried across the door & Verandah openings,
Before laying bituminous coating the surface of the cement mortar or concrete should be allowed to dry.
Proper overlapping should be provided in damp proof course at corners or of walls.
In damp proof course at junctions of walls flexible material should always be used.
(ii) For checking damp through walls surface treatment is suitable.
(iii) For damp from leaking roof-Repairing of the junctions of roof surface with other parts of the building.
New damp proof course may be inserted below parapet water proof roof.
(iv) General use of cement plaster with water proofing compound to prevent dampness entering through the brick wall surface.
It is done to prevent entry of dampness through joints of stone/brick masonry. Proper drainage of rain water. Change the filling materials from floor use, damp proof materials.
(vi) Conditions of service fittings
(vii) Drainage of terrace of pitch roof
(viii) Growth of vegetarian.
(ix) Structural defects.
(x) Guniting – Depositing an impervious layer of rich cement mortar over the surface to be water proofed.
(xi) Cavity wall construction.