Damp Proof Course (DPC): Thickness, Mix Ratio, Materials and How It Is Laid

Key points

• IS 2212 asks for a concrete DPC of 1:2:4 mix with 10 mm stone, not less than 40 mm thick, given a waterproofing treatment.
• The DPC sits at least 150 mm above the finished ground or plinth protection and runs without a break, even under door openings.
• CPWD cures it for at least seven days, lets it dry, and then applies hot bitumen where the drawing asks for it.
• A failed DPC shows as a damp band with a salt tide mark low on ground-floor walls, rarely higher than about 1.5 m.

What is a damp proof course (DPC)?

A DPC is a barrier that water cannot pass through, built into a wall at a level where the wall leaves the ground. Bricks, stone and mortar are full of tiny connected pores. Water in damp soil moves up through those pores on its own, the same way oil climbs a lamp wick. This is called capillary action, and the dampness it carries up a wall is called rising damp.

Without a barrier, the water climbs until it can evaporate from the wall face, and the salts it carries stay behind as a white crust. IS 2212 calls this efflorescence. Over a few monsoons the plaster softens and falls, paint blisters, and switch boards fitted low on the wall start to give trouble.

The National Building Code of India 2016 treats a missing DPC as a maintenance problem in its own right. Part 12, Annex A, lists “lack of damp-proof course treatment in walls and particularly in sunken floors” among the common causes of trouble in floors.

Figure 1: Where the damp proof course sits in a wall at plinth level

Dimensions from IS 2212:1991, clauses 6.8.1.1 and 6.8.4.

Where is the DPC laid in a building?

At plinth level, in every wall. IS 2212 clause 6.8.4 says all walls in a building shall have a damp proof course at least 15 cm (150 mm) above the finished ground or plinth protection level, and preferably immediately below the underside of the ground floor. The same clause says it runs without a break along the whole length of the wall, even under door and other openings.

The 150 mm gap matters. Rain splashes the foot of the wall, and soil, paving or a road outside rises over the years. Once the outside level reaches the DPC, water walks round the barrier through the masonry and plaster. That is called bridging the DPC.

Clause 6.8.2 names three places a DPC may be needed, horizontal or vertical:

• below the lowest floor, to stop water entering from the soil;
• above ground level, to stop water rising up the wall, which is the plinth DPC most houses need;
• at openings, parapets and similar points, to keep rain water out of the structure.

IS 3067:1988, the code for damp-proofing and waterproofing of buildings, adds for damp-proofing above ground that the DPC must cover the full thickness of the wall excluding the plaster, and must not be set back from the face to leave room for pointing.

Where a floor is below the outside ground, as in a basement, clause 6.8.3 asks for a horizontal DPC under the floor joined by a vertical DPC on the outer walls to the DPC above ground. IS 3067 adds that basements are damp-proofed in the dry season, when subsoil water is lowest, and new ones from the outside with at least 600 mm of working space.

What thickness and mix ratio is used for DPC?

For an ordinary wall, 1:2:4 cement concrete at least 40 mm thick. That ratio means one part cement, two parts coarse sand and four parts graded stone by volume, the same mix site engineers take as M15. IS 2212 clause 6.8.1.1 sets out the concrete DPC in four lines: stone aggregate of 10 mm nominal size, a 1:2:4 mix, a layer not less than 4 cm thick, and a waterproofing treatment either brushed on the surface or mixed in as an integral waterproofing compound.

CPWD’s Delhi Analysis of Rates 2014 has two concrete DPC items, and their wording turns up in many building estimates.

Table 1: DPC thickness and mix in the Indian codes and CPWD items

CPWD pairs the stone size with the thickness: 12.5 mm stone in a 40 mm layer, 20 mm stone in a 50 mm layer. Each stone stays well under half the depth of the course, so the concrete can be tamped dense. Big stone in a thin layer leaves voids, and voids let water through.

DPC concrete is richer than the plain bed under a footing because it has to be dense, not just spread load. The common site ratios are compared in PCC vs RCC, and how added water affects density in the guide to the water cement ratio.

Which materials are used for a damp proof course?

IS 2212 clause 5.3 lists four material groups for a DPC: bitumen felts, bituminous compounds, mortar or concrete, and stone slabs. On a house site the usual choice is concrete with a waterproofing treatment, because it uses the same cement, sand and stone already there.

Table 2: DPC materials and the Indian Standard behind each

An integral waterproofing compound is a powder or liquid mixed into the concrete. Under IS 2645 it passes only if it cuts the water passing through a test cylinder to less than half that of plain mortar and keeps 3-day and 7-day strength at no less than 90 percent of the plain mix. Its chloride content, which rusts steel, must be declared and may not exceed 2 percent of the product. The kinds of compound sold and where else they go in a house are covered in the guide to waterproofing chemicals.

Building mastic is a different product from the road and bridge-deck mix explained in the guide to mastic asphalt.

Plastic sheet is also laid as a DPC on some sites. It is not one of the material groups IS 2212 lists, so if your contractor proposes it, ask the engineer to specify it on the drawing.

Is the plinth beam the same as the DPC?

Sometimes, and the drawing decides. In load-bearing masonry houses built to the earthquake rules, the reinforced concrete band at plinth level does both jobs. The National Building Code 2016 (Part 6, Section 4) says that where a plinth band is provided, it doubles as the damp proof course. The difference between a plinth band and a plinth beam, and the steel that goes into each, is in the guide to plinth beam cost.

On an RCC framed house, the drawing either shows a separate DPC course laid on top of the plinth beam or treats the top of the beam itself as the DPC level. Ask which one yours shows. Either way, the 150 mm rule above finished ground still applies, and IS 2212 asks for a waterproofing treatment on any concrete DPC.

Do not swap one DPC type for another on site. The same NBC section treats a properly bonded concrete DPC as no break in the wall, but a membrane DPC such as felt can break the bond, and the wall’s effective height is then worked out differently. On a load-bearing wall that is the engineer’s call.

Masonry below the DPC stays damp for life, so IS 6041 does not allow AAC blocks there, as AAC blocks vs red bricks explains. Burnt clay bricks, stone or solid blocks go up to the DPC; the brick classes are in types of bricks.

How is a DPC laid on site?

The method below follows CPWD Specifications 2009, Volume 1, clause 4.4, with the additions from IS 3067 and IS 2212.

1. Bring the plinth masonry up to the DPC level on every wall. Clean and level the top so it is free from projections that could damage the course (IS 3067 clause 6.1.1).
2. Fix steel side shuttering on both faces, firm enough not to move or leak when the concrete is tamped. CPWD wants the DPC edges straight, even and vertical.
3. Mix the 1:2:4 concrete to a workable consistency. Add any waterproofing compound at the maker’s dose per 50 kg bag of cement, never more than 3 percent of the cement weight.
4. Lay the concrete in one continuous run and tamp it into a dense mass. Stop only at the point planned for the DPC to end. CPWD allows no construction joints in a DPC. Carry it across door openings and over the full width of the wall.
5. Remove the side forms. The faces should be smooth with no honeycombing, the stony gaps described in the guide to honeycombing in concrete. A honeycombed DPC has a built-in water path.
6. Cure the DPC for at least seven days, then let it dry out (CPWD clause 4.4.2).
7. Where hot bitumen is specified, clean the dry surface with brushes and then a cloth soaked in kerosene, and apply the hot bitumen evenly so no bare spots are left. CPWD’s specification heats penetration-grade bitumen to 160 °C, give or take 5 °C.
8. Where a horizontal DPC has to turn up a wall, as in a basement or a sunken floor, form a 1:4 cement mortar fillet of 75 mm radius at the corner first. IS 3067 asks for this fillet wherever a horizontal treatment continues up a vertical face.

A DPC is a small pour and easy to rush. The mistakes that cause trouble later are continuity mistakes: a break at a door, a joint where the day’s work stopped, a corner with no fillet.

Plinth, DPC and footing concrete on a house site is usually batched in a self-loading mixer such as the Tarle SLM 2200 or the AJAX ARGO 4500. If you are planning the pour, compare concrete mixer models and talk to a dealer near you.

What are the signs of a failed DPC or rising damp?

A band of damp across the bottom of ground-floor walls, with a white salt line at its upper edge. That line is the tide mark. Wikipedia’s article on structural damp notes that rising damp has been seen as high as 5 m, but usually rises much less and rarely above 1.5 m. The tide mark forms because salts carried up from the ground, mostly nitrates and chlorides, are left behind where the water evaporates. Since the water comes from wet ground, rising damp is rare on floors above the ground floor.

The same article warns that rising damp is often misdiagnosed. A wall stain can just as easily come from a leaking pipe, rain getting in, or condensation. Check before you pay for a cure.

Table 3: Reading damp on a wall: symptom, likely cause and what to check

A good DPC also fails when the house around it changes. It gets bridged when:

• the road, courtyard or garden outside is raised over the years until it is level with the DPC;
• outside plaster is carried down across the DPC to the ground, giving water a path round it;
• a ramp, platform or flower bed is built against the wall above the DPC line;
• the DPC was set back from the face for pointing, or stopped short of the full wall width.

The problem is old. An 1872 entry in the British Medical Journal, quoted in the same Wikipedia article, complained that damp courses were built too near the ground line, so rain splashed above them and rising ground soon hid them.

Can rising damp be fixed after the house is built?

Often, and the first fix costs the least. If the DPC is there but bridged, remove the bridge: lower the soil or paving outside to at least 150 mm below the DPC, slope the plinth protection away, cut the outside plaster back to just above the DPC line, and lead downpipes and taps away from the wall. Let the wall dry before replastering; Wikipedia notes that salt deposits stay even after the water has been dealt with.

If the house has no DPC at all, chemical damp-proof courses are sold that are injected into the base of the wall. That is specialist work, worth paying for only once the cause is confirmed, because a plumbing leak treated as rising damp will not stop.

The cheapest treatment is the one built in at the plinth, which is why the guide to low cost house construction lists plinth waterproofing among the things never worth cutting.

How is a DPC measured on a building estimate?

In square metres of area, with the thickness written into the item. CPWD Specifications 2009 clause 4.4.5 measures the length and breadth correct to a centimetre, works out the area in square metres to two decimal places, and checks that the depth is nowhere less than the thickness specified.

For example, a 230 mm (9 inch) wall 10 m long needs 0.23 × 10 = 2.30 m² of DPC. At 40 mm thick that is 2.30 × 0.04 = 0.092 m³ of concrete. Cement, sand and stone for that volume can be worked out with the method in the guide to building material calculation.

Read the item wording. Under clause 4.4.6, the DPC rate covers the concrete, laying and curing; the hot bitumen coat and the waterproofing compound are paid separately unless the item says otherwise, the compound per 50 kg bag of cement. A quote that just says “DPC” may leave out both.

A DPC is one of the cheapest items in a house and one of the hardest to add later. Get the thickness, mix, waterproofing and 150 mm height on the drawing before the plinth goes up. More topics are in the building materials guides.

The DPC rules on this page are from IS 2212:1991, Code of Practice for Brickwork, clauses 3, 5.3 and 6.8; IS 3067:1988, Code of Practice for General Design Details and Preparatory Work for Damp-Proofing and Water-Proofing of Buildings, clauses 2.1, 3.1 and 6.1; IS 1609:1991, Damp-Proofing Treatment Using Bitumen Felts; IS 2645:2003, Integral Waterproofing Compounds for Cement Mortar and Concrete, clause 3; CPWD Specifications 2009, Volume 1, clause 4.4, and CPWD Delhi Analysis of Rates 2014, items 4.10 to 4.13; and the National Building Code of India 2016, Part 6 Section 4 and Part 12 Annex A. The rising damp heights and the 1872 quote are from Wikipedia’s article on structural damp. All were read in October 2026.

Prices, specifications and features are indicative, vary by variant, location and date, and should always be confirmed with the official OEM or authorised dealer before any purchase decision. DesiMachines is not liable for decisions taken on the basis of information that may have changed after publication. Thicknesses, mixes and code limits on this page are as published in the Indian Standards and CPWD documents named above; follow your structural engineer’s drawing for the DPC detail on your own building.