Plastering Types: Internal and External

Plaster is the most taken-for-granted layer in an Indian building. It sits between the structure and the paint, it is applied by every contractor, and it rarely appears in the drawings beyond a note saying 12 mm thick. Yet plaster decides how flat the walls look under a cove light, how well the paint lasts, whether the external walls stay dry through a Surat or Mumbai monsoon, and whether hairline cracks appear along every column and beam within a year of handover.

Most plaster problems in Indian homes are not caused by choosing the wrong type. They are caused by the same handful of site errors: plastering on dry, dusty brickwork; skipping the mesh at the junction of concrete and masonry; applying one thick coat outside instead of two; leaving out the drip grooves under sills and chajjas; and stopping curing after two days. A good plaster type applied badly fails; an ordinary plaster applied carefully lasts decades.

This article explains the plaster types used inside and outside Indian buildings, from cement-sand and gypsum to lime, sand-faced and textured renders; their thicknesses, mix ratios and curing; the details that prevent cracks; and indicative October 2026 costs. It is written for homeowners who want to check a contractor's work and for students who want to understand why the rules exist. Structural cracks are a separate matter: any crack that is wide, growing or diagonal should be checked by a qualified structural engineer, not plastered over.

A short history of plaster in India

For most of India's building history, plaster meant lime. Lime mortars and plasters, often mixed with surkhi — powdered burnt brick that acts as a pozzolana and helps the lime set — protected brick and rubble walls in forts, temples, havelis and ordinary houses. Lime plaster is soft, breathable and slightly flexible, so it tolerates the small movements of thick masonry walls and lets moisture escape rather than trapping it. Regional traditions refined it into polished finishes: araish in Rajasthan, a lime plaster burnished to a marble-like sheen, and polished lime finishes in the south that were known in colonial records as chunam.

Portland cement changed the picture in the twentieth century. As reinforced concrete frames and brick infill became the standard Indian building system, cement-sand plaster became the default for both inside and outside: it is strong, fast, uses easily available materials and can be applied by any mason. Its weaknesses — shrinkage cracking, a hard, impermeable surface, and poor compatibility with old lime-built walls — were accepted as part of the trade. From the 2000s onwards, factory-made gypsum plasters and ready-mix dry plasters spread through Indian cities, along with AAC blocks whose flatter surfaces allow thinner coats. Today, gypsum is common on internal walls of apartments and offices, cement plaster remains standard outside, and lime is returning for heritage repair and as a feature finish.

How plaster works: substrate, coats and finish

Every plaster system has three parts. The substrate is the wall behind — brick, AAC block, concrete block, stone or RCC — and it decides how much the plaster must bond to, how much water it will suck out of fresh plaster, and how much it will move. The plaster coats build up the flat surface: one coat inside on reasonably true brickwork, two coats outside or on very uneven walls. The finish is the final surface — trowelled smooth for putty and paint, sand-faced for an external texture, or polished in decorative work. Bond depends on a clean, rough, damp-but-not-wet surface; strength and crack resistance depend on the mix, the sand and the curing.

Internal plaster types

Inside a building, plaster must give a flat, even, paintable surface, resist knocks, and accept fixings for curtains, cabinets and TVs. It does not face rain, so it can be thinner and, in the case of gypsum, need no water curing. Five internal types are common in Indian practice.

Cement-sand plaster

The standard internal plaster for decades: cement and sand, typically in a 1:6 ratio by volume for walls, applied in a single coat about 12 mm thick on reasonably true brickwork, or 15 mm on the rougher face of a wall. Ceilings get a thinner coat of about 6 mm in a richer mix, commonly 1:3 or 1:4, because a thick coat overhead is more likely to debond and fall. Cement plaster is strong and moisture-tolerant, so it is the right choice in bathrooms, kitchens and utility areas. Its weaknesses are shrinkage cracking if the mix is too rich or curing is poor, and the need for wall putty to achieve a smooth finish for emulsion paint.

Gypsum plaster

Factory-made gypsum plaster, covered by IS 2547, is mixed with water and applied directly to brick, block or concrete in one coat, typically about 10–13 mm on walls and less on concrete surfaces. It sets quickly, does not need water curing, shrinks very little, and can be finished to a smooth, flat surface that is ready for primer and paint without a full putty system. It is popular in apartments and offices because it shortens the programme. Its limits are clear: gypsum is softened by persistent moisture, so it is not used on external walls, in wet areas such as shower walls, or on walls with rising damp; cement plaster is used there instead.

POP punning

Plaster of Paris punning is a thin finishing layer of a few millimetres applied over cement plaster to create a smooth surface, often instead of wall putty. It is fast and smooth but brittle, and in humid conditions poorly applied POP can blister or flake. Many contractors now prefer two coats of acrylic or cement-based wall putty, which is more tolerant of damp, but POP punning remains common in some cities.

Lime plaster

Lime plaster is applied in several coats, traditionally with a lime-sand or lime-surkhi mix, and is covered by IS 2394. It is breathable and slightly flexible, so it is the correct choice for repairing old lime-built walls, where cement plaster traps moisture and accelerates decay. In new buildings it is mostly used as a feature finish. This site prices lime plaster at about ₹60–180 per sq ft applied, with specialist multi-coat work higher; it needs a skilled mason and careful curing.

Ready-mix and machine-applied plasters

Pre-blended dry plasters — cement-based or gypsum-based — arrive in bags with sand already graded and additives included, so the site only adds water. They give more consistent quality than site-batched mixes, which often suffer from dirty or poorly graded sand. On larger projects they can be sprayed by machine, which increases speed and uniformity. AAC block manufacturers often recommend their own thin-coat plasters or block-specific ready-mix products, applied with mesh at joints.

External plaster types

External plaster is a weather skin. It must shed driving rain, resist sun and heat cycles, avoid cracking where it meets concrete, and give a surface that holds paint or provides its own textured finish. In most Indian climates, and especially on coasts and in heavy-monsoon regions, it is applied in two coats with a waterproofing additive, to a total thickness of about 18–20 mm. One thick coat of the same total thickness is a common shortcut that tends to crack and debond.

Sand-faced plaster

The most common external finish in western India. After the finishing coat is laid and levelled, coarse sand is pressed or sprinkled into the surface and lightly sponged, leaving a uniform granular texture. It hides minor unevenness, sheds water reasonably well and takes paint, although the textured surface uses more paint than a smooth one. Its quality depends on clean, well-graded sand and consistent technique across the whole facade; patches done on different days by different masons often show.

Smooth (neat) finish

The finishing coat is trowelled smooth to receive exterior paint or texture coatings. It looks clean and modern but shows every wave and crack under raking light, so it needs a skilled mason and good curing. It is common on contemporary facades where the paint or a texture coat provides the finish.

Rough cast, pebble dash and textured renders

Rough cast or wet dash throws a wet mix containing small aggregate onto the base coat; pebble dash or dry dash presses clean pebbles or chips into a fresh finishing coat. Both give durable, rugged surfaces that shed rain and hide hairline cracks, and both were common on older bungalows and institutional buildings. Scraped and combed finishes and factory-made textured renders give a range of decorative surfaces. All of these are harder to repaint and to repair invisibly than plain plaster, so they suit buildings where the texture is the intended final look. External rendered finishes are covered in IS 2402.

The details that prevent cracks

Most plaster cracks in RCC-framed buildings appear in predictable places: along the line where a brick or block wall meets a concrete column or beam, at the corners of window and door openings, under long lintels, and in map-like patterns on large panels that were plastered too rich or cured too briefly. Concrete and masonry move differently with temperature, moisture and load, and the plaster bridging them cracks along the joint unless that joint is reinforced or deliberately expressed.

• Rake brick or block joints about 10–12 mm deep, brush the wall clean and wet it the day before, so it is damp but not running with water when plaster goes on.
• Hack smooth RCC surfaces or apply a bonding coat or spatterdash so plaster has a mechanical key.
• Fix galvanised mesh or metal lath about 300 mm wide — 150 mm each side — over every joint between RCC and masonry, and diagonal strips at the corners of openings.
• Fill chases for conduits and pipes with mortar and mesh them before plastering; a chase plastered directly almost always cracks.
• Apply external plaster in two coats, not one thick coat, with the base coat scratched for key.
• Form drip grooves under chajjas, sills and projections, and horizontal grooves at floor levels on tall facades.
• Use clean, well-graded plastering sand (IS 1542 gives the requirements), not silty or mixed sand.
• Cure cement plaster continuously for at least seven days and protect fresh work from direct sun and strong wind.
• Let the wall dry fully before putty and paint; painting a damp wall causes blistering and efflorescence.

Thickness, mix and timing at a glance

Thickness and mix ratios are guidance drawn from IS 1661 practice and common Indian specifications; the project's architect or engineer should confirm them for each wall type. A richer mix is not always better: excess cement increases shrinkage, which increases cracking. The figure below compares typical thicknesses.

Cement plaster or gypsum plaster inside?

This is the most common question homeowners ask during construction or renovation of an apartment. Both work well when applied correctly. Gypsum gives a flatter, quicker finish and avoids the curing wait, while cement plaster is more robust in damp conditions and is the only sensible choice in wet areas and on external walls. Many projects now use both: gypsum on dry internal walls and cement plaster in bathrooms, kitchens, balconies and outside.

Common plaster defects and their causes

When plaster fails, the cause is usually visible to a trained eye. Fine map cracking points to shrinkage — a rich mix, too much water or poor curing. A straight crack along a column or beam line points to a missing mesh strip. A hollow sound when the wall is tapped means the plaster has debonded from a dusty or smooth substrate. White salts on the surface are efflorescence, carried out by moisture from bricks, sand or water. Each needs a different remedy, and painting over any of them simply hides the problem for a season.

What plastering costs in 2026

Plaster is normally priced per square foot or square metre of wall area, either labour-only (the owner or main contractor supplies cement and sand) or with material. Rates vary considerably by city, wall height, access, wall condition and specification, so the figures below are indicative October 2026 ranges for material and labour, excluding scaffolding where noted, GST and any waterproofing system. Painting rates are separate and follow this site's painting guide: putty, primer and two coats of premium emulsion at about ₹20–30 per sq ft of paintable area.

As an example, a 1,000 sq ft carpet-area flat has roughly 3,000–3,300 sq ft of internal wall and ceiling surface. At ₹35–55 per sq ft, internal plastering would cost about ₹1.05–1.8 lakh, before putty and paint. The cheapest quotation is often the one that leaves out mesh, curing supervision, or the second external coat — the very items that decide whether the plaster cracks.

Where plastering is going

Plastering is changing in three directions. First, machine application and ready-mix plasters are spreading on large projects because they give consistent quality and reduce dependence on site-batched sand, which is increasingly scarce and variable as river-sand mining is restricted and manufactured sand becomes common. Second, more accurate walling — AAC blocks, precast panels and drywall partitions — allows much thinner coats, or none at all on dry partitions. Third, lime and clay plasters are returning as lower-carbon, breathable finishes for feature walls and heritage repair. None of these changes the basic rules: a clean, keyed substrate, the right material for the location, reinforcement at joints, details that shed water, and proper curing or drying.

Frequently asked questions

What is the standard thickness of internal plaster?

Typically 12 mm for internal brick walls with a reasonably true face and 15 mm on the rougher face, about 6 mm on RCC ceilings, and about 10–13 mm for gypsum plaster on walls. The project specification should state the thickness for each surface.

Which is better, gypsum plaster or cement plaster?

For dry internal walls, gypsum plaster gives a flatter finish faster and needs no water curing. For bathrooms, kitchens, balconies, damp walls and all external walls, cement plaster is the right choice. Many homes use gypsum on living and bedroom walls and cement plaster everywhere else.

Why is external plaster done in two coats?

Two thinner coats bond better, shrink less and crack less than one thick coat. The base coat fills irregularities and is scratched for key; the finishing coat gives a uniform surface and texture. In heavy-rain regions the two-coat system with a waterproofing additive is much more reliable.

How many days should plaster be cured?

Cement plaster should be kept moist for at least seven days, as recommended in IS 1661 practice, and protected from direct sun and strong wind. Gypsum plaster is not water-cured; it must be allowed to dry before priming and painting.

What is sand-faced plaster?

Sand-faced plaster is an external finish in which coarse sand is pressed into the fresh finishing coat to create a uniform granular texture. It is common in western India because it hides minor unevenness and sheds rain well.