Most exterior painting failures in India are not caused by the paint. They are caused by doing the right steps in the wrong order, or skipping the boring ones.
Here is the sequence professional contractors follow, with the intervals that actually matter.
Before You Start: Weather and Timing
Check three things before opening anything.
No rain forecast for at least 24 hours after application. Surface temperature below 40 degrees Celsius, which means avoiding direct afternoon sun on the wall you are working on. Relative humidity below about 85 percent.
In most of India that means working October to March, and within a working day, following the shade around the building rather than painting whichever wall is convenient.
Step 1: Clean and Assess the Surface
Walk the whole elevation first and note what you find. Cracks and their widths. Flaking areas. Chalking. Algae or fungal growth. Damp patches. Loose or hollow plaster, which you can find by tapping.
Then wash. Water and a stiff brush for most surfaces, working bottom to top to prevent dirty streaks running down clean wall. Heavy chalking may need a pressure washer.
Treat any biological growth with a biocidal wash at this stage, not later.
Step 2: Repair Cracks and Damage
Remove all loose and flaking paint by scraping and wire brushing back to a firm edge. Feather the edges so the transition is not visible under paint.
Rake out cracks into a shallow V, dust them clean, and fill. Acrylic crack filler for static cracks under 1.5 mm. Flexible polyurethane sealant with mesh tape for moving joints. Polymer-modified mortar for larger repairs.
Cut out and re-plaster any hollow-sounding areas. Painting over hollow plaster just delays the problem by one season.
Step 3: Apply Exterior Putty (If Needed)
Putty is for levelling, not for sealing or bonding. It goes on only where the surface is uneven.
Use exterior grade, either acrylic or a water-resistant white cement putty. Interior putty outdoors will fail, usually within the first monsoon.
One to two thin coats, sanded between, rather than one thick one. Allow 6 to 8 hours between coats and let the final coat dry fully before sanding. Dust off thoroughly afterwards, because putty dust left on the surface ruins primer adhesion.
Step 4: Prime the Wall
Use an exterior alkali-resistant primer. On new plaster this is mandatory. On previously painted sound surfaces it is strongly recommended.
One full coat, applied at the specified thinning ratio, usually 30 to 50 percent water for exterior primers. Check the tin, because primer thinning ratios differ substantially from finish coats.
Allow 6 to 8 hours drying, or overnight in cooler weather.
The wall should look uniformly sealed after this, with no patchy absorption. If some areas still look thirsty, spot-prime them again.
Step 5: First Finish Coat
Stir the paint thoroughly before and periodically during use. Pigment settles, and an unstirred tin gives inconsistent colour.
Thin only to the specified ratio, typically 10 to 15 percent water for exterior emulsions. This is the number most often abused on site. Over-thinning reduces film thickness proportionally and is the leading cause of premature failure.
Work in manageable sections and maintain a wet edge. Cut in at edges and corners with a brush first, then roll the field. Always complete a full wall in one session rather than stopping halfway, or you will see a join line.
Step 6: Second Finish Coat
Wait the full recoat interval. For most exterior emulsions this is 4 to 6 hours. UVCLAAD Aura states 2 to 4 hours, which is faster than most.
Recoating too early traps solvent and moisture in the first coat and causes soft film, poor adhesion and sometimes visible patchiness.
Apply the second coat in the opposite direction to the first where practical. This improves coverage uniformity.
A third coat is needed when going from dark to light, on very porous surfaces, or with deep tinted shades that have lower hiding power.
Drying Intervals That Matter
| Stage | Minimum interval | Why |
|---|---|---|
| New plaster to painting | 21-28 days | Alkalinity must settle |
| After washing | 2-3 days | Wall must be dry through |
| Putty coat to next coat | 6-8 hours | Full set before sanding |
| Primer to first coat | 6-8 hours | Primer must cure |
| Between finish coats | 4-6 hours | Prevents soft film |
| Final coat to rain exposure | 24 hours | Initial water resistance |
| Full cure | 7 days | Complete film hardness |
Tools: Roller, Brush or Spray
Roller is the default for flat wall areas. Use a medium pile roller, 8 to 12 mm, for normal plaster and longer pile for textured surfaces. Fast, consistent, and wastage stays around 10 percent.
Brush for cutting in, corners, edges, grooves and detail. Slower but essential, and no elevation gets finished with a roller alone.
Spray is fastest on large plain elevations and gives an excellent finish. It also wastes 25 to 35 percent of your material as overspray and needs extensive masking. Worth it on big commercial jobs, rarely worth it on a house.
Common Mistakes
- Painting new plaster before it has cured
- Over-thinning to stretch material
- Skipping primer on a repaint
- Applying the second coat too early
- Painting a wall in direct afternoon sun, which dries the film before it levels
- Stopping mid-wall and resuming later, leaving a visible lap mark
- Not stirring the tin between refills
Frequently Asked Questions
What is the correct order for exterior painting?
Clean and assess, repair cracks and loose plaster, apply exterior putty where levelling is needed, apply alkali-resistant primer, then two full finish coats. Each stage needs its full drying interval before the next.
How long between coats of exterior paint?
Four to six hours for most exterior emulsions, though some products state two to four. Recoating earlier traps moisture in the first coat and produces a soft film with poor adhesion.
Can I paint exterior walls myself?
Ground-floor walls and boundary walls are realistic DIY projects. Anything requiring scaffolding is better left to professionals, both for safety and because access equipment usually costs more to hire than the labour saving is worth.
Roller or brush for exterior walls?
Use a medium pile roller for flat wall areas and a brush for cutting in at edges, corners and detail. Spray is faster on large plain elevations but wastes 25 to 35 percent of the paint as overspray.
Do I need putty on exterior walls?
Only where the surface is uneven and needs levelling. Putty does not seal or bond, so it never replaces primer. Always use exterior grade putty outdoors, as interior putty fails within the first monsoon.
