Guide
New wall vs repaint
How painting new plaster differs from repainting an existing surface.
Answer
Does new plaster need different treatment from a repaint?
Explanation
New work
The questions are about the plaster itself: whether it has cured, how porous it is, and what the product system requires on a bare surface.
Detail
Repainting
The questions are about what is already there. Is the existing coating sound, chalking, peeling or damp? A coating applied over a failing surface fails with it, regardless of the product quality.
Detail
What to record
Use the surface condition check on the tools page and send photographs. What you can see is more useful than a general description.
Questions
Also asked
How do I know if the existing coating is sound?
Rub it — a powdery residue suggests chalking. Look for lifting edges, flaking and staining. Photographs of any doubtful area are the practical way to raise it.
Next
Ready to plan it?
Measure the walls, estimate each layer and build a paint list to send as one structured requirement.
New plaster needs time
Fresh plaster is alkaline and wet, and both matter. Painting too early is the most common cause of a finish that fails within a year on new construction.
- Curing time. New plaster typically needs several weeks to dry and for alkalinity to fall. The exact period depends on thickness, weather and ventilation — and in a Goan monsoon it is longer, not shorter.
- Alkali attack. Paint applied over high-alkalinity plaster can discolour, blister or lose adhesion. An alkali-resistant primer manages this where waiting is not possible.
- Trapped moisture. Sealing a wall that is still drying traps water behind the film. It emerges later as blistering or peeling, usually in patches that follow the damp.
Repainting is about what is already there
On an existing wall the paint is rarely the problem. The question is what the old surface is doing.
| What you find | What it means | Before painting |
|---|---|---|
| Chalky powder on your hand | Old coating has broken down under UV | Wash back, prime |
| Flaking or peeling | Adhesion lost, often from moisture behind | Remove all loose material, find the moisture |
| Green or black patches | Algae or fungal growth, common on shaded walls | Treat, do not paint over |
| Bubbling | Moisture behind the film | Source first. Paint will not hold |
| Sound, clean, slightly dull | Nothing wrong | Clean, spot prime, repaint |
| Oil-based or enamel underneath | Emulsion may not adhere | Abrade and use a suitable primer |