PCC in Building Construction: Full Form, Ratio, Thickness and Uses

PCC (plain cement concrete) is concrete of cement, sand and aggregate with no steel in it. In a building it is the lean bed under footings, plinth beams and ground floors, the foundation strip under brick walls and the bed of drains, usually in a 1:4:8, 1:3:6 or 1:2:4 mix. One m³ of 1:4:8 PCC takes about 3.4 bags of cement, 16.6 cft of sand and 33.2 cft of aggregate, the figures our cost engine uses.

Below: where PCC goes, the three common mixes with their materials per m³, thickness under footings, the IS 456 clauses that apply, PCC vs RCC, a worked house example and how PCC is measured in a BOQ.

What is PCC? Full form and meaning#

PCC stands for plain cement concrete: concrete without reinforcement. Site engineers also call a thin PCC bed lean concrete or blinding concrete. CPWD schedules call it cement concrete (CC): item 4.1 of the CPWD DSR 2023 is "cement concrete of specified grade excluding the cost of centering and shuttering - All work up to plinth level".

Plain concrete is strong in compression and weak in tension. So PCC goes where the load only presses down on it: a bed, a base or a filling. A member that has to bend or span needs steel, and then it is RCC.

Where is PCC used in building construction?#

Mostly at or below plinth level: under footings, plinth beams and ground floors, under brick wall foundations, and in drains.

The structural drawing or the specification names the mix and thickness for each location. If it does not, ask the engineer before you price or pour.

PCC ratio: 1:4:8, 1:3:6 and 1:2:4#

1:4:8 is the usual lean bed under footings and floors; 1:3:6 and 1:2:4 are richer mixes for where the drawing asks for M10 or M15. The ratio is cement : sand : aggregate by volume.

Quantities are per m³ of wet concrete, before handling waste. Round cement up to whole bags when you buy.

How these quantities are worked out#

The 1:4:8 row is our cost engine's own figure, used by the house construction cost calculator. The other two rows use the dry-volume method of our concrete calculator: dry materials are 1.54 times the wet volume, cement weighs 1,440 kg per m³ loose, and a bag is 50 kg.

• 1:3:6: 1.54 ÷ (1 + 3 + 6) = 0.154 m³ of cement × 1,440 = 221.76 kg = 4.44 bags. Sand 0.154 × 3 = 0.462 m³ (16.3 cft). Aggregate 0.154 × 6 = 0.924 m³ (32.6 cft).
• 1:2:4: 1.54 ÷ 7 = 0.22 m³ of cement × 1,440 = 316.8 kg = 6.34 bags. Sand 0.44 m³ (15.5 cft). Aggregate 0.88 m³ (31.1 cft).
• 1:4:8 check: the same working gives 1.54 ÷ 13 × 1,440 = 170.6 kg = 3.41 bags, with 16.7 cft of sand and 33.5 cft of aggregate, within 1% of the engine's figures.

"With each bag" is batching by volume. One 50 kg bag is 50 ÷ 1,440 = 0.0347 m³, about 1.226 cft, so 1:4:8 needs 4 × 1.226 = 4.90 cft of sand and 8 × 1.226 = 9.81 cft of aggregate per bag.

Aggregate size#

CPWD DSR 2023 lists 1:4:8 only with 40 mm graded aggregate (item 4.1.8). It lists 1:3:6 with 20 mm (4.1.5) or 40 mm (4.1.6) aggregate, and 1:2:4 with 20 mm (4.1.3) or 40 mm (4.1.4). Plain concrete above plinth, in copings, sills and similar items, is a separate DSR item (4.2). For grades M20 and above, see our concrete mix design guide.

What IS 456 says about PCC#

IS 456:2000 has no separate PCC chapter. Five provisions decide how lean the mix can be and how it is batched and cured. Clause numbers below are from the IS 456:2000 text.

• Clause 6.1.3: concrete of grades lower than those in Table 5 may be used for plain concrete constructions, lean concrete, simple foundations and foundations for masonry walls. That covers lean PCC beds under footings.
• Tables 3 and 5: concrete buried in non-aggressive soil is "moderate" exposure (Table 3). For plain concrete at that exposure, Table 5 lists a minimum grade of M15, at least 240 kg of cement per m³ and a water-cement ratio of at most 0.60; at mild exposure it sets no minimum grade. Where PCC is itself the finished element in wet ground, such as a drain bed, check the Table 5 grade with the engineer.
• Clause 9.3 and Table 9: nominal mixes may be used up to M20. Table 9 sets them by mass per 50 kg of cement: at most 625 kg of dry aggregate and 45 litres of water for M7.5, 480 kg and 34 litres for M10, and 330 kg and 32 litres for M15. The ratios 1:4:8, 1:3:6 and 1:2:4 are the site convention for those grades, not the code's wording.
• Clause 10.2.4: volume batching is allowed only where weigh-batching is not practical, with the bulk densities of the actual materials established and an allowance for bulking of sand.
• Clause 7.1 lists blinding concrete under "very low" workability, and clause 13.5.1 asks for moist curing for at least 7 days with ordinary Portland cement and at least 10 days with mineral admixtures or blended cements such as PPC, and 10 days in hot, dry weather.

In short: keep the mix stiff, do not add water to make it flow, and keep it moist for the full curing period.

PCC thickness under footings#

IS 456 does not fix a PCC thickness; the structural drawing does. Our examples take 100 mm under house footings (the foundation cost guide) and for the floor bed in our house cost engine, and the RCC construction cost calculator takes 75 mm under a raft.

The bed is usually a little wider than the footing, so the formwork and cover blocks sit on it. In the example below, a 1.60 m footing sits on a 1.80 m PCC bed: (1.80 − 1.60) ÷ 2 = 0.10 m of projection on each side.

PCC vs RCC#

PCC has no steel and only beds, levels or fills; RCC carries bending through its reinforcement.

Worked example: PCC for a small house#

11.24 m³ of 1:4:8 PCC, needing about 38.2 bags of cement, 1.87 brass of sand and 3.73 brass of aggregate. The dimensions are illustrative, not a design: the same 10 footing pads as our foundation cost guide (a 1,000 sq ft footprint, G+1), plus a 100 mm floor bed over 80 m² of ground-floor rooms.

Materials at the engine's 3.4 bags, 16.6 cft of sand and 33.2 cft of aggregate per m³:

One brass is 100 cft. Add your site's usual handling allowance for sand and aggregate when you order.

Cost check, using rates already on our site. At the CPWD DSR 2023 rate for item 4.1.8, ₹6,812.00 per m³ (Delhi, as quoted in our compound wall cost guide), 11.24 m³ comes to 11.24 × 6,812.00 = ₹76,566.88. That is a schedule benchmark, not a contractor's quote. The foundation cost guide prices the 3.24 m³ under the footings at its engine rate of ₹5,454.45 per m³: ₹17,672.42.

How is PCC measured in a BOQ?#

In cubic metres, to the dimensions on the drawing, under IS 1200 Part 2 (concrete works), with one item per mix and location. Our IS 1200 method of measurement guide covers Part 2's general rules. For PCC they come down to these:

• Volume = length × breadth × thickness from the drawing. Measure the drawing size, not the poured volume.
• Separate items for PCC below footings, under floors and below masonry, and for each mix and aggregate size. CPWD DSR prices 1:4:8, 1:3:6 and 1:2:4 as separate items.
• Formwork is extra. DSR item 4.1 excludes centering and shuttering. If the specification asks for edge shuttering, it is a separate item in m² under IS 1200 Part 5.

The worked example becomes two BOQ lines:

For a full set of foundation quantities measured from your own drawings, our desk prepares a BOQ from your drawings, with PCC, RCC, steel and shuttering measured item by item to IS 1200.

FAQs#

What is the full form of PCC in construction?#

Plain cement concrete: cement, sand, aggregate and water, with no reinforcement. It is also called lean concrete or blinding concrete when laid as a thin bed, and cement concrete (CC) in CPWD schedules.

What is the ratio of PCC under a footing?#

Usually 1:4:8 (cement : sand : aggregate), sometimes 1:3:6 where the drawing asks for M10. The structural drawing decides.

How much cement is needed for 1 m³ of PCC 1:4:8?#

About 3.4 bags of 50 kg (170 kg), with 16.6 cft of sand and 33.2 cft of aggregate, in our cost engine. For 1:3:6 it is about 4.44 bags, and for 1:2:4 about 6.34 bags.

What is the thickness of PCC under a footing?#

IS 456 does not fix it; the structural drawing does. Our examples use 100 mm under house footings and floor beds and 75 mm under a raft, with the bed a little wider than the footing.

Is PCC M7.5 or M10?#

It depends on the mix: 1:4:8 is commonly equated with M7.5, 1:3:6 with M10 and 1:2:4 with M15. IS 456 Table 9 defines these nominal grades by aggregate mass and water per 50 kg of cement, not by volume ratios.

What is the difference between PCC and RCC?#

PCC has no steel and only beds, levels or fills. RCC has reinforcement, so it can bend and span: footings, columns, beams and slabs. In a BOQ, PCC is one concrete item in m³; RCC also has steel in kg and formwork in m².