DAMP PROOFING

REASON FOR DAMPNESS IN EXISTING BUILDINGS

REQUIREMENTS OF AN IDEAL DAMP PROOFING MATERIAL

• IMPERVIOUS

• DURABLE, IDEALLY FOR THE ENTIRE BUILDING LIFE.

• STEADY

• RESIST ANY LOAD SAFELY

• FLEXIBLE

• DIMENSIONALLY STABLE

• CHEAP

• SALT FREE

GENERAL PRINCIPLES OF WATER PROOFING COURSE (OR DPC)

• DAMP PROOFING COURSE MAY BE VERTICAL OR HORIZONTAL

• HORIZONTAL DPC SHOULD COVER THE FULL THICKNESS OF THE WALL

• THE HORIZONTAL DPC SHOULD BE LAID CONTINUOUSLY AT JUNCTIONS

AND CORNERS

• MORTAR BED BELOW DPC SHOULD BE LEVELLED, EVEN AND WITH NO

PROJECTIONS, TO AVOID DAMAGE OF DPC

• DPC SHOULD BE LAID TO MAKE A CONTINUOUS PROTECTION

• DPC SHOULD NOT BE KEPT EXPOSED ON THE WALL SURFACE TO AVOID

DAMAGE

• A CEMENT CONCRETE FILLET OF 75MM RADIUS SHOULD BE PROVIDED

AT THE JUCTION WHEN THE HORIZONTAL DPC CONTINUES VERTICALLY

ON THE WALL.

IF THE LEVEL OF THE GROUND FLOOR IS AT THE SAME LEVEL AS THE GROUND SURFACE, THE DAMP PROOFING COURSE AND THE DAMP PROOFING MEMBRANE SHOULD BE CONTINUOUS AND STEPPED VERTICALLY AS SHOWN IN THE FIGURE.

IT SHOULD BE FLEXIBLE AND AT THE JUNCTION IT SHOULD BE FILLET AT 75 MM RADIUS AS SHOWN.

METHODS OF WATER PROOFINGDAMP PROOFING OF AN EXTERNAL WALL

IF TWO FLOORS ARE AT DIFFERENT LEVELS, DIVIDED BY AN INTERNAL WALL, THE DAMP PROOFING COURSE ON THE INTERNAL WALL SHOULD BE AT THE LEVEL OF THE LOWER FLOOR.

THE BASIC PRINCIPAL OF STEPPING IT WITH THE DAMP PROOFING MEMBRANE ON THE FLOOR MUST ALSO BE APPLIED.AN ADDITIONAL VERTICAL DAMP PROOFING MEMBRANE MUST BE APPLIED TO PREVENT MOISTURE FROM ENTERING THROUGH THE STAGGERED FLOOR LEVELS.

DAMP PROOFING OF AN INTERNAL WALL

DAMP PROOFING THROUGH AIR DRAIN

THIS METHOD IS USED TO PREVENT MOISTURE FROM ENTERING THE WALLS THROUGH THE ADJACENT GROUND.A HOLLOW CHAMBER OF AIR IS CONSTRUCTED PARALLEL TO THE EXTERNAL WALL. THE WIDTH MAY BE 200-300 MM .THE CHAMBER IS CLOSED ON THE TOP BY RCC OR STONE TOP WITH GRATED OPENINGS AT REGULAR INTERVALS. THE VERTICAL AND HORIZONTAL DAMP PROOFING COURSES MAY BE PROVIDED AS SHOWN.

DAMP PROOFING OF BASEMENTS THROUGH ASPHALT TANKING

IMPORTANT FACTORS TO KEEP IN MIND:• LAYER OF ASPHALT MUST BE

CONTINUOUS• VERTICAL ASPHALT LAYER MAY

END IN A HORIZONTAL DPC• VERTICAL DPC SHOULD BE TAKEN

150 MM ABOVE THE GROUND LEVEL

• HORIZONTAL ASPHALT: 30MM THK.

• VERTICAL ASPHALT LAYER : 20 MM THK., BOTH IN 3 COATS

• SEQUENCE OF CONSTRUCTION: INNER WALL, ASPHALT LAYER, PROTECTIVE WALL.

DAMP PROOFING OF STEPPED GROUND

FOR A SLOPED SITE, THE DAMP PROOF COURSE SHOULD BE STEPPED SUCH THAT IT REMAINS AT A MINIMUM VERTICAL DISTANCE OF 150 MM FROM THE GROUND.

THE DAMP PROOF COURSE MAY BE OF ANY SUITABLE, FLEXIBLE MATERIAL SUCH AS BITUMINOUS FELTS ETC.

DAMP PROOFING OF PARAPET WALLS

PROVISION OF COPING ON TOP OF THE WALL SURFACE, PREVENTS THE ENTRY OF DAMP FROM THE TOP SURFACE OF THE WALL.

COPING MAY BE PROVIDED BYMEANS OF:• STONE• PCC• METAL FLASHING• MOULDED RCC PARAPETALL FORMS OF COPING MUST BE SLOPED IN ORDER TO PREVENT WATER STAGNATING ON THE TOP SURFACE

DAMP PROOFING OF CAVITY WALLS

TWO PARALLEL WALLS SEPERATED BY AIR GAP EXCEPT AT WALL TIES WHICH ARE OF IMPERVIOUS MATERIAL

THE METHOD OF DAMP PROOFING IS SIMILAR TO NORMAL SINGLE LEAFWALLS, EXCEPT THAT THE TWO LEAFS OF THE CAVITY WALLS HAVE SEPARATE DPC COURSES

DAMP PROOFING OF FLAT ROOF

WATER PROOFING OF FLAT ROOFS MAY BE DONE BY ANY OF THE FOUR METHODS:

• FINISHING

• BEDDING CONCRETE AND FLOORING

• MASTIC ASPHALT AND JUTE CLOTH

• USE OF WATER PROOFING COMPOUND

FINISHING

FOR BUILDINGS OF CHEAP CONSTRUCTION, THE FINISHING OFROOF SURFACE IS DONE AT THE TIME OF LAYING THE CEMENT CONCRETE. THE FINISHING OF FLAT ROOF IS CARRIED OUT IN CEMENT MORTAR OF PROPORTION 1:4

BEDDING CONCRETE AND FLOORING

THE RCC SLAB SURFACE IS KEPT ROUGH AND ON THIS SURFACE, A 100 MM LAYER OF CONCRETE IS LAID.

THE CONCRETE MAY BE CEMENT CONCRETE OR LIME CONCRETE. THE SURFACE OF THE CONCRETE IS FINISHED BY A LAYER OF SUITABLE FLOORING SUCH AS TILES, TERRAZO, IPS ETC.

A CONVEX JOINT IS PROVIDED AT THE JUNCTION TO PREVENT STAGNATION AT JOINTS.

MASTIC ASPHALT AND JUTE CLOTH A LAYER OF HOT MASTIC ASPHALT IS LAID ON THE ROOF SURFACE. A JUTE CLOTH IS THEN LAID ON TOP OF THIS LAYER. THEN ONE MORE LAYER OF MASTIC ASPHALT IS LAID SO THAT THE JUTE CLOTH IS SANDWICHED IN BETWEEN THE ASPHALT. SAND IS THEN SPRINKLED OVER THIS SURFACE.FOR BETTER GRIP A LEAD SHEET IS INSETED AT THE JUNSTION AS SHOWN.

USE OF WATERPROOFING COMPOUND

SOME WATER PROOFING COMPOUNDS LIKE IMPERMO ETC, AVAILABLE IN THE MARKET MAY BE ADDED TO THE CEMENT DURING CONSTRUCTION.IT PREVENTS SEEPAGE, LEAKAGE AND DAMP DUE TO CAPILLARY ACTION OF THE MOISTURE IN CEMENT, MORTAR AND CONCRETE.ONLY ABOUT 2% OF THE WATERPROOFING COMPOUND MAY BE ADDED TO THE CEMENT BY HAND THOUROUGHLY BEFORE MIXING IT WITH AGGREGATES.

DAMP PROOFING OF CURVED ROOF

IN A PITCHED ROOF, A TROUGH, KNOWN AS A GUTTER IS PROFIDED AT THE END OF THE SLOPE. THE GUTTER RUNS ALONG THE FULL LENGTH OF THE ROOF.

AT SUITABLE POINTS ALONG THIS LENGTH, OUTLET POINTS ARE PROVIDED WHERE RAIN WATER PIPES ARE CONNECTED TO TAKE THE WATER DOWN.

THE RAIN WATER PIPES ,MAY BE MADE OF COPPER, LEAD, MILD STEEL, CAST IRON OR ASBESTOS CEMENT.