PCC vs RCC: Difference, Mix Ratio and Where Each Is Used in a House

What is the difference between PCC and RCC?

The difference is steel, and everything else follows from it. Concrete is very good at being squeezed and poor at being pulled. PCC is used where the concrete is only squeezed. RCC puts steel bars exactly where the concrete would be pulled, so the two materials share the work. The Indian code for both is the same document, IS 456:2000, Plain and Reinforced Concrete, Code of Practice, and it treats them differently on grade, cement content and cover.

Table 1: PCC vs RCC compared, as set out in IS 456:2000

The unit weights show how little the steel adds to the mass. IS 456 tells designers to take plain concrete at 24 kN per cubic metre and reinforced concrete at 25, a difference of roughly 100 kg in every cubic metre. Weights for the other materials on a site are in the guide to the unit weight of building materials.

Why does concrete need steel at all?

Because its pulling strength is a small fraction of its crushing strength. IS 456 gives a simple estimate in clause 6.2.2: the flexural strength of concrete, which is its strength when bent, is 0.7 × √fck, where fck is the cube strength. For M20 concrete that works out to about 3.1 N/mm². Its crushing strength is 20 N/mm². So the same concrete that holds 20 units when squeezed starts to crack at about a sixth of that when bent.

Picture a lintel over a door. The load from the wall above pushes it down in the middle. The top of the lintel gets squeezed together and the bottom gets stretched apart. Plain concrete would crack from the bottom and drop. Steel bars placed near the bottom face carry that stretch, and the concrete above carries the squeeze. That is why the main bars in a beam or slab sit low, close to the bottom face, with only the cover of concrete below them.

Even RCC cracks a little. The steel does not stop hairline cracks in the stretched face; it holds them tight. IS 456 clause 35.3.2 says crack width at the surface should not in general exceed 0.3 mm in members where cracking does no harm, and tighter limits apply where it does. A PCC member has no such control. Once it cracks through, the two pieces are on their own.

For slabs, the code sets a floor on how much steel goes in. Clause 26.5.2.1 asks for at least 0.12 percent of the slab’s cross-section when high strength deformed bars are used, and 0.15 percent with mild steel. For a 125 mm (5 inch) slab that is at least 150 mm² of steel in every metre of width. The same clause caps the bar diameter at one-eighth of the slab thickness. The bar itself, its grades and how to judge a good one are covered in the guide to TMT bars.

What mix ratio is used for PCC and RCC?

On Indian sites, mixes are still spoken of by volume: one part cement, then parts of sand, then parts of stone. The leaner the mix, the more stone and sand per bag of cement, and the lower the strength. IS 456:2000 itself writes nominal mixes by mass, as the maximum kilograms of total aggregate per 50 kg bag of cement, and it allows nominal mixes only up to M20 (clause 9.3). Anything stronger needs a designed mix proven with trial cubes.

Table 2: Common PCC and RCC mixes, with the IS 456 nominal-mix limit for each grade

The first column is how masons and contractors talk. The volume ratios are a working shorthand for the mass limits in the third column, not an exact match. How the two compare for M20, and how to turn any ratio into bags of cement and cubic metres of sand and stone, is worked through in the guide to building material calculation.

Exposure also decides the grade. IS 456 Table 5 sets a minimum grade, a minimum cement content and a maximum water-cement ratio for each of five exposure classes, and it sets them separately for plain and reinforced concrete. Reinforced concrete always gets the stricter numbers, because water and salt that reach the steel make it rust, and rust swells and splits the concrete from inside.

Table 3: Minimum grade, cement and water-cement ratio for PCC and RCC by exposure (IS 456:2000, Table 5)

Table 3 of the code says what each class means. Concrete protected from weather is mild. Concrete buried in ordinary, non-aggressive soil, or kept under water, is moderate. Exposure to severe rain, alternate wetting and drying, or a coastal environment is severe. Two exceptions sit beside the table. Clause 6.1.3 allows grades lower than Table 5 for plain concrete construction, lean concrete, simple foundations and foundations for masonry walls, which is why a 1:4:8 bed is acceptable under a footing. And clause 8.2.8 asks for at least M20 for plain concrete and M30 for reinforced concrete in sea water or directly along the coast. The water side of these limits, in litres per bag, is set out in the guide to the water cement ratio.

Why is PCC laid under a footing?

The PCC bed under a footing is not there for strength. It is a clean, flat working floor at the bottom of the pit. Before it goes in, the soil at the bottom of the trench is levelled and rammed; IS 1080:1985, the code for shallow foundations, asks for the bed of the pit to be thoroughly compacted by manual ramming before concrete is laid (clause 5.4). The PCC then does four jobs.

1. It gives a level surface to mark out the footing and set the steel on.
2. It keeps mud out of the fresh RCC, so the footing concrete is not weakened by soil mixed into its bottom layer.
3. It stops dry soil from sucking water out of the fresh footing concrete before it has set.
4. It gives the cover blocks something firm to sit on, so the bottom bars stay at their set height. IS 456 clause 26.4.2.2 asks for at least 50 mm of cover in footings.

Reading the figure

• 1, brown: the bottom of the pit, levelled and rammed.
• 2, light grey: the PCC bed, projecting a little beyond the footing on every side.
• 3, mid grey: the RCC footing. The red line and dots are its bottom steel mesh.
• 4: the RCC column, with its vertical bars running down into the footing.
• 5, green: cover blocks holding the mesh at least 50 mm above the PCC.

Neither IS 456 nor IS 1080 fixes a thickness for this levelling bed. The structural drawing does. On Indian house drawings it is usually a thin layer of about 75 to 100 mm (3 to 4 inches), in 1:4:8 or 1:3:6, laid a little wider than the footing so the formwork has a base. If your drawing shows a different figure, follow the drawing. The blocks that hold the steel at its cover are explained in the guide to cover blocks.

The same thinking applies under a plinth beam. Where the beam is cast on a PCC bed, the bed forms its bottom face and no shuttering is needed underneath, which is one of the details worked through in the guide to plinth beam cost.

A whole footing can also be plain concrete. IS 1080 clause 4.8 allows unreinforced cement concrete foundations as long as the load spreads out from the column or wall at no flatter than 1 vertical to 1 horizontal, with an edge at least 150 mm thick. Where the footing has to be wider than that spread allows, the code says it should be reinforced. That is the point where PCC stops being enough and RCC takes over.

Where is PCC used in a house, and where is RCC used?

Walk up a typical framed house from the ground and the two alternate.

• PCC: the levelling bed under each footing; the sub-floor in the ground floor (CPWD Specifications 2009, in its anti-termite construction measures, asks for a dense cement concrete 1:3:6 sub-floor at least 75 mm thick over the sand filling); floor base and topping layers; the apron or plinth protection around the house; the thin concrete layer of the damp proof course at plinth level, often with a waterproofing compound added.
• RCC: the footings, the columns, the plinth beams that tie the columns at ground level, lintels over doors and windows, the roof and floor slabs, the staircase, sunshades and the water-tank slab.

CPWD’s own specification book draws the same line. Its sub-head 4 covers plain concrete work and its sub-head 5 covers reinforced cement concrete work, with separate rules for formwork, steel and testing. The compounds added to the damp proof course concrete are described in the guide to waterproofing chemicals.

The words also turn up outside a house. A “PCC road” and an “RCC road” are both concrete roads, one without steel and one with a steel mesh, and their layers and thicknesses are covered in the guide to CC road construction. A “PCC pole” on a power line is a different thing again: there PCC usually means prestressed cement concrete, made under IS 1678, where the steel wires are pulled tight before the concrete is cast around them.

How are PCC and RCC mixed and placed on site?

The mixing is the same for both; what changes is the care around it. PCC for a bed or a floor can be mixed in a small drum mixer and wheeled straight into place. RCC needs the steel tied, checked and propped on cover blocks before the first load arrives, and it needs proper compaction with a needle vibrator so the concrete fills every gap around the bars. Poorly compacted RCC leaves voids next to the steel, which is where rust starts.

For a house slab or a run of footings, many contractors now use a self-loading concrete mixer, a machine that loads its own sand and aggregate with a front bucket, mixes the batch in its drum and drives it to the pour. Models such as the AJAX ARGO 4500, the Tarle SLM 2200 and the CONMAT CSLM 2800 are built for this kind of work. Whether to batch on site or order ready-mix is a separate decision, compared in RMC vs site mix concrete.

If you are planning a pour, compare concrete mixer models and talk to a dealer about the batch size your site needs.

Both kinds of concrete need curing, and RCC is checked for strength with cubes cast at the pour. How those cubes are made and judged at 7 and 28 days is in the guide to the cube test of concrete.

When is plain concrete enough, and when must you use RCC?

A simple test works for most of a house. Ask what the concrete is resting on and what it is holding up.

• If it rests on firm ground along its whole length and only carries weight straight down into that ground, plain concrete can do the job. Beds, sub-floors, floor bases and plinth protection are like this.
• If it spans across a gap, sticks out past its support, or carries a column or a floor, it bends, and a bending member needs steel. Slabs, beams, lintels, sunshades, columns and most footings are like this.

Do not try to save money by leaving steel out of a member that bends. A plain concrete lintel or slab has nothing to hold it together once its stretched face cracks, and it can break through under load with little warning. The opposite mistake is cheaper but still wasteful: putting steel into a levelling bed or a floor base where it has no tension to carry.

The decision on grade, steel and sizes for any load-bearing member belongs to the structural engineer who signs the drawing. Use this guide to read that drawing, ask the right questions on site and order the right materials. More material topics are collected in the building materials guides.

The grades, cement contents, cover and steel limits on this page are from IS 456:2000, Plain and Reinforced Concrete, Code of Practice (with Amendments 1 and 2), clauses 6.1.3, 6.2.2, 8.2.8, 9.3, 19.2.1, 26.4.2.2, 26.5.2.1 and 35.3.2 and Tables 3, 5, 9 and 16. Foundation rules are from IS 1080:1985, Design and Construction of Shallow Foundations in Soils, clauses 4.8 and 5.4. The sub-floor rule and the split between plain and reinforced work are from CPWD Specifications 2009, Volume 1, sub-heads 2, 4 and 5. 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. Concrete grades, mixes and code limits on this page are as published in the Indian Standards named above; have a structural engineer set the grade, steel and cover for any load-bearing work.