Material use for Damp Proof Coarse ( D.P.C. )
When the construction of a building is start, the main object is that it should remain dry and no moisture should travel through wall, roofs, floors etc. The material use for Damp proof coarse is provide so that dampness may not occur in the buildings.
The Material use for damp proof coarse generally, are classify into three types as list below :-
Metal sheets of Aluminium, Lead and Copper plastic sheets ( polythene sheets ), Bituminous felts, Hot bitumen, Bituminous sheets etc.
Mastic asphalt or combination of layers or materials.
Cement concrete layers, mortar layers, use of first class bricks, slates, stones etc.
Sheets of aluminium, lead and copper
These are use as membranes for damp proofing. These are lay over the walls throughout their thickness. Lead sheets are always lay with lime mortar due to the chemical reaction of cement with lead. Lead and aluminium sheets should be coat with asphalt. The thickness of the sheets should not be less than 3 mm.
Copper sheets are highly durable are provide good resistance to dampness and also against sliding action. The thickness of lead sheets should be such that the weight is not less than 20 kg per square meter of area.
Combination of sheets and bituminous felts
D.P.C. of Lead Core possesses properties such as economy, efficiency, easy laying and durability.
Hot asphalt or hot bitumen
It is heat and spread over the concrete bed or mortar. Its thickness should not be less than 3 mm. It is an excellent D.P.C. as it offers a tough surface, impervious in nature and indestructible.
Bituminous felt or Asphaltic felt
It is available in rolls of normal walls width and 6 mm in thickness. It is place over the layer of cement mortar lay on brick work. Full width overlap should be provide in case of crossing and angles and 10 cm in case of joints. It cannot withstand heavy loads.
Mastic asphalt or bituminous mastic
It is obtain by heating the asphalt with sand and mineral filler. It forms an excellent impervious layer for D.P.C. as the material is highly durable and reasonably elastic.
Granite, trap, slates etc. are lay in cement mortar in two coarse for forming an effective. D.P.C. The stones are place for the full width of wall. Joints should not be in the same vertical line.
Bricks which absorb water less than 9/2 % of their weight are suitable at place not subject to excessive dampness.
Cement concrete layer
It is provide at plinth level with mix ratio as 1:2:4. Cement concrete layer is suitable where dampness is not excessive. It is use as a horizontal main D.P.C. and its thickness should be at least 4 cm. Two coats of hot bitumen are apply over it.
It is use either as a bedding layer for taking up other damp proof courses or as a water proofing plaster. For bedding, the ratio is 1:3 ( cement mortar ) and little lime is add to increase the work ability. For the plaster work, it is prepare either by mixing 1 part of cement and 2 parts of sand, pulverized alum and soap water or 1:3 cement and sand with patented damp proofing material like pudlo, sika, dampro etc. After plastering in thickness varying from 2 to 4 cm, two coats of hot bitumen are apply.