Paints and coatings

At a glance

For homeowners and small-project buyers

Paint specification reduces to three decisions: substrate, product category and finish. Substrate is either a cementitious wall (plaster, concrete), a ferrous surface (grille, railing, gate), or a timber surface (door, shutter, furniture). Each substrate needs its own primer sequence and its own topcoat category; a wall emulsion applied on a grille will peel within months, and an enamel meant for metal applied on a cementitious wall will chalk and discolour.

Product category covers emulsion, enamel, distemper, texture and special-effect coatings. For interior walls the default is an acrylic emulsion in matte for ceilings and bedrooms or silk finish for living areas and dining rooms. For exterior walls the default is an acrylic exterior emulsion with elastomeric additives such as Asian Apex or Birla Opus Ever Stay, warranted for five to ten years against blistering, peeling and chalking. For metal grilles, gates and railings the default is a synthetic enamel or, for better durability and UV stability, a polyurethane topcoat. For wood the choice is melamine for furniture, polyurethane for doors and structural millwork, or natural wax-oil finishes for traditional teak.

Finish is the gloss level: matte absorbs light and hides minor surface defects but shows fingerprints; silk and satin are the all-purpose default for living spaces and hide dirt well; semi-gloss and gloss finishes are wipeable and durable but ruthlessly show substrate imperfections.

Coverage on a typical two-coat system runs between 100 and 140 square feet per litre for a smooth interior wall with good surface preparation, and 80 to 100 square feet per litre for exterior walls because of higher absorption and texture. A 1200 square feet carpet-area house needs roughly 40 to 50 litres of interior emulsion, 8 to 12 litres of primer, 20 kilogrammes of putty and 10 to 15 litres of exterior emulsion to cover the external facade.

For a repaint, the surface preparation is more important than the product choice. Sand, wash, de-dust and patch all cracks before the first primer coat; applying fresh paint over loose flakes or dust guarantees peeling within a year regardless of the paint brand.

For contractors and site engineers

Paint specification on a commercial or institutional project is governed by substrate preparation, dry film thickness, adhesion, gloss retention, colour stability and VOC compliance. Substrate preparation under ASTM D4258 requires a clean, dry, sound surface free of laitance, efflorescence, loose particles and form-release agents; a substrate moisture content below 15 percent for cementitious walls under ASTM D4263 calcium chloride test or equivalent.

Dry film thickness under ASTM D7091 is the single most common point of failure in field-applied coatings. Manufacturer data sheets specify the minimum and maximum DFT per coat; a project specification should require DFT measurement at each coat and rejection of areas below eighty percent of the nominal value. Adhesion testing under ASTM D3359 cross-cut or ISO 2409 on representative panels should return a minimum classification of 4B or grade 1 for interior work and 5B or grade 0 for exterior and exposed work.

Gloss retention under ASTM D523 and ISO 2813 is measured at 60 degrees for semi-gloss and gloss paints and at 85 degrees for matte. Exterior paints should retain at least sixty percent of initial gloss after two years of Florida exposure or equivalent accelerated weathering under ASTM G155 xenon-arc or ASTM D4587 UV-B. Colour stability is expressed as delta-E CIE Lab, with commercial-grade exterior paints typically specified below 3.0 delta-E after 1000 hours of accelerated weathering.

VOC compliance varies by jurisdiction. The US EPA Method 24 test gives gram-per-litre VOC content; low-VOC paints under 50 g/l and zero-VOC paints under 5 g/l are specified for hospitals, schools and LEED-rated projects. In India the Ministry of Environment and the Bureau of Indian Standards reference the GRIHA and IGBC green building ratings, which adopt VOC thresholds aligned with international practice.

Film system selection is substrate-driven. On cementitious walls, a two-coat alkali-resistant primer under ISO 12944 Part 5 class C1 to C3 is followed by two topcoats of acrylic emulsion. On new mild-steel railings, a zinc-phosphate primer to ISO 12944 class C3 to C5 is followed by a polyurethane topcoat. On new timber, a wood stain and sealer followed by two or three PU coats with inter-coat sanding gives both colour development and film durability.

Governing standards referenced in this category are ASTM D4258 for surface preparation, ASTM D7091 for dry film thickness, ASTM D3359 for adhesion, ISO 2813 for gloss, ISO 12944 for corrosion protection by paint systems and the MPI Master Painters Institute architectural coatings standards.

Brands stocked in this category

The yard carries the brands listed below; availability varies by destination because freight economics favour nearest-mill sourcing. See the brands page for the full roster across every category.

Related articles

For application sequence on new cementitious walls see the blog article on paint, putty and primer sequence. For related finishing specifications see the category pages on cement and binders and adhesives and chemicals.

South India service footprint